VERE HS Mur % yeh ey Pik y hw THE UNIVERSITY OF ILLINOIS LIBRARY , ool ot Corea we =) f*BGey . = 2 UNIVERSITY LIBRARY UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN The person charging this material is responsible for its renewal or return to the library on or before the due date. The minimum fee for a lost item is $125.00, $300.00 for bound journals. Theft, mutilation, and underlining of books are reasons for disciplinary action and may result in dismissal from the University. Please note: self-stick notes may result in torn pages and lift some inks. Renew via the Telephone Center at 217-333-8400, 846-262-1510 (toll-free) or circlib @uiuc.edu. Renew online by choosing the My Account option at: http://www.library.uiuc.edu/catalog/ JUL 1 2 203 Digitized by the Internet Archive In 2011 with funding from University of Illinois Urbana-Champaign htto://www.archive.org/details/reportuponunited0Swhee JNA reyen ures HELIOTYPE Peres DABARBBAS , ENGINEER DEPARTMENT, UNITED STATES ARMY. KO > oie ‘ "Wvvewwver REPORT GEOGRAPHICAL AND GEOLOGICAL EXPLORATIONS AND SURVEYS WEST OF THE ONE HUNDREDTH MERIDIAN, IN CHARGE OF FIRST LIEUT. GEO. M. WHEELER, CORPS OF ENGINEERS, U.S. ARMY, UNDER THE DIRECTION OF BRIG. GEN. A. A. HUMPHREYS, CHIEF OF ENGINEERS, U.S. ARMY. PUBLISHED BY AUTHORITY OF HON. WM. W. BELKNAP, SECRETARY OF WAR, IN ACCORDANCE WITH ACTS OF CONGRESS OF JUNE 23, 1874, AND FEBRUARY 15, 1875. IN SIX VOLUMES, ACCOMPANIED BY ONE TOPOGRAPHICAL AND ONE GEOLOGICAL ATLAS. PARTS I, Il, III, IV, V. VOL. II].—GEOLOGY. WASHINGTON: GOVERNMEN! PRINTING OFFIOR. 1875. F 5, 31 Ce YVEV\ | TABLE OF CONTENTS. PART I. — wav eas 2 NUM YSIS ILLVER TO LITTLE COLORADO RIVER. -.-- ------------ ---- +--+: Section III.—From Litt_e CoLtorapo River To Camp APACHE, ARIZONA. -- .----. -------- Section IV.—From Camp APACHE, ARIZONA, TO GILA RIVER, ..--.--------------- eecte. 4: PART III. GEOLOGY OF PORTIONS oF Urau, NEVADA, ARIZONA, AND NEW MEXICO, EXPLORED AND SURVEYED IN 1872 AND 1873. By Assistant E. E. HOWELL. Cuapter VIII.—TuHE Bastin RaNGE System Or SOUTHWESTERN UTAI....- -.-..-----+----------- Section I.—MOUNTAIN RANGES; THEIR GEOLOGICAL STRUCTURE, AGE, THICKNESS, AND CHARACTER OF STRATA - .... .-.2 +--- 20---- conan ewe acne see en noncesce SEcTION II.—VALLEYS; THEIR RELATION TO GEOLOGICAL STRUCTURES; LAKES, ANCIENT AND MODERN; RIVERS; WATER SUPPLY -.-.-.----.--------- = esooe arReeee SECTION III.—VoLCANIC PHENOMENA. LITHOLOGICAL CHARACTER AND DISTRIBUTION OF VOLCANIC ROCKS AND MODE OF OCCURRENCE. THERMAL SPRINGS,.-------- BEeGRION LV.—PCONOMIC (GEOLOGY :.-—.< 22.20 -s-0 scensncceacenslacjens Sfeeceacusmes aeeeapee 55 3G 209 215 216 231 231 248 253 257 ERRATA. Page 43, 12th line, omit “s” in “Plateaus,” and add “s” to “lie.” Page 44, 15th line, for “ hefore ” read “after.” : Page 95, 6th line from bottom, insert “clay” after “Subaqueous.” Page 103, 22d line, for “Anodae” read ‘‘Anodonta.” Pages 109 and 116, middle, for “San Francisco” read ‘‘ Colorado.” Page 172, 6th line, for ‘‘ Cordillera” read “Basin Range.” Page 173, middle, for “New Mexico” read “ Dakota.” Page 180, 2d line from bottom, for “ bought” read “ brought.” Page 182, 3d line from bottom, for “lobe” read “to be.” Page 239, 8th line, after “lava,” insert ‘“(No. 4 of section).” Page 510, 2d line, for “crust” read “crest.” _ Page 512, 7th line, for “ northward” read “ westward.” . | ae frm VEY I TABLE OF CONTENTS. LETTER OF TRANSMITTAL..---- 6 EA ee eee eee aa BSE SSE emote eemeinmaec DOeet EL OCoe PART I. REPORT UPON THE GEOLOGY OF PORTIONS OF NEVADA, UTAH, CALIFORNIA, AND ARIZONA, EXAM- INED IN THE YEARS 1871 anp 1872. By Assistant G. K. GILBERT, A. M. GHAUTERU— OROLOG Yes. 22 225 sees oan see As eae ee: Geer reese Section JI.—THE Basin RANGE SYSTEM .----- eeeeaneameisse Shs CO QaREOOE Section II.—THE CoLorapo PLATEAU SYSTEM...---- Gee eee comer ase ee eet eeeeee ais SEcTIon JII.—THE BoRDER LAND BETWEEN THE Basin RANGE SYSTEM AND THE PLATEAU... Section IV.—GENERAL CONSIDERATIONS..-.-.----- eae fsbo. oe soon - se eete ree seen Craprer Il.—Vatrnys; CANONS, AND EROSIONS: .--<2< 225- sccsce enon 2-23 se ces cow nas ohne vacen- CHAPTER UL HiT GEACTAR POOH) sc. t(D nl eo 4 > 54 \-- bapt s a at zu ’ t ects ; phe, d td ptt F t* *.tig ae ; P Bist ae tee DROS erg! Peis ‘ 21 © sek Pe eh Wa : \ Peers cer ee, = 3 3 Bs oF, nhs wary’ ays on ‘a " >> fr. =a 7, Xl y's ie iY Ve “ q < 4 ak wae aa 0) Rs rita: ae 7 Ves eet p oe tive ts adage Pa ai we 5 iT 1 pennies bats -~ — , Bete tetany S : j A : See Me ee 2 = pet . bs i: J ce i>, 4 , ’ Unrrep States ENGINEER OFFICE, GEOGRAPHICAL EXPLORATIONS AND SURVEYS, West oF THE ONE HUNDREDTH MerIDIAN, Washington, D. C., November 11, 1874. Geyer: I have the honor to forward herewith reports upon geologi- cal data gathered by parties of the survey under my charge for publication, in accordance with the act of Congress, approved June 23, 1874. (See Statutes at Large, Forty-third Congress, First Session, page 224.) This volume is one of the series of six heretofore proposed for the elab- oration of the detailed results of the survey. The geological assistants have usually been members of the field par- ties, organized to embrace representatives of the several branches of the work, except during occasions incident to a divergence from the routes of travel necessary to carry on the main or topographical branch. The obstacles attendant upon researches amid the mountain intricacies, rigid plateau contours, and desert-wastes encountered, have largely added to their undertakings, while their reports will attest the manner in which they have prosecuted the arduous duties intrusted to them. The nature of the survey has necessarily made geological and other scientific inquiry subsidiary to the main object of the work, which, in view of the great area covered by the survey, consists in the determination of positions and the delineation of the surface of the region occupied. Hence the geologists have not had the same facilities they would have had in parties organized especially for geological work ; but notwithstanding these deficiencies and the difficulties they entailed, it is believed that these reports extend and connect our geological information over a wide field, embracing areas in several important basins of drainage of six different States and Territories, including portions of the plateau region, and several prominent mountain ranges heretofore conjecturally known, and will not be without their important values and acceptable as a worthy contribution to our geological knowledge of the territorial domain west of the Mississippi River. 1B “ee 14 GEOLOGY. It is believed that the geological matter here presented, when supple- mented, as it soon will be, by a series of geological maps and paleontologi- cal reports, will answer all the present needs of the Government and of the industries of these partially inhabited areas, in which, for years to come, geological or other scientific examinations will find but few localities where sectional industrial interests may be healthfully promoted with economy to them or to the Government. The time consumed in office labor, as compared with that in the field, has been somewhat inadequate, yet the results appear in the systematic rather than the itinerary form, which it is hoped will prove advantageous to all the purposes to which they may be applied. Fossil and other geological specimens have been collected from a wide-- spread range, including many well-prospected localities, and their number is large. Their examination will lead to an extended report upon the paleontology of the area embraced by the survey affording a large number of new forms of the extinct fauna of that region, identifying with certainty geological relations heretofore vague, and defining horizons newly discovered. They have been placed in the hands of Prof. C. A. White, of Bowdoin College, a preliminary examination having been: made by Prof. F. B. Meek, a portion of the results of which are incorporated herein. 'The report upon these col- lections will form the bulk of Vol. IV of the series. This volume will also embrace, in addition, reports, if they be submitted in time, upon the ver- tebrate collections of 1874. The collection of rock-specimens, especially of volcanic varieties, is large and well worthy of special examination for additional evidence, bear ing upon lithological characteristics. The practical or economic features of the accompanying reports will appeal to those interested in the mineral and agricultural industries con- stantly advancing into these untrodden fields, and that of Dr. Loew, who has, with patient labor, made chemical investigations and analyses in min- eral waters, plants, soils, &c., forms an interesting feature of the volume. Mr. G. K. Gilbert, A. M., geological assistant during three field seasons, contributes more largely than any other to this volume, and besides his LETTER OF TRANSMITTAL. 15 purely professional labors, has aided to give form to the work of the geological parties. Mr. EK. KE. Howell, geological assistant in the years 1872~73, presents his individual contribution. ; The report of Prof. John J. Stevenson, an assistant with the Colorado party under Lieutenant Marshall in 1873, relates to territory somewhat disconnected from the areas occupied by the others, and treats its subjects in the same systematic manner. Mr. A. R. Marvine, occupying the position of astronomical assistant in 1871, while on the march to the southward, examined areas contiguous to his route so far as circumstances would permit. Considering the character and scope of the results from the labors of the geological assistants, the comparative increase of expense attendant upon attaching them to the several parties seems to have been justified, and the advantages of affording opportunities for examinations in this cognate scientific branch are made manifest. Very respectfully, your obedient servant, Geo. M. WHEELER, First Lieutenant Corps of Engineers, in Charge. Brig. Gen. A. A. Humpureys, Chief of Engineers, United States Army. Norre.—Owing to an omission in the act making appropriation for the publication of the survey reports, the MS. for this volume has been delayed until this date; and meanwhile Dr. Loew has returned from the field and prepared a report upon the mineral springs, of which specimens were col- lected during the field season of 1874; also a report upon the composition of coal from different localities in New Mexico and Colorado. As both are germane to the subject-matter of his report for 1873, they have been in- corporated therewith, not being of sufficient length to justify publication in separate form. Gro. M. WHEELER, Tneutenant of Engineers, in Charge. Unirep Srates EncGinrrer OFFIce, Washington, February 10, 1875. PACES EE. REPORT ON « THE GEOLOGY OF PORTIONS OF NEVADA, UTAH, CALIFORNIA, AND ARIZONA. EXAMINED IN THE YEARS 1871 AND 1872. BY G. K. GILBERT, A. M. COMPRISING CuarTtrr I—OROLOGY ; II. VALLEYS, CANONS, EROSION; JII.—THE GLACIAL EPOCH; IV.—WATER-SUPPLY; V.—VOLCANIC ROCKS AND MOUNTAINS; anp VI—THE STRATIFIED ROCKS. 2ws 17-18 . ae , > ; q sf - ce « , ‘ - r é F i ‘ ’ c ay . c t : i A . - * ‘ ‘ > . = ‘ 4 -s - , < = Bins ac v 2 ? : zy ¥ ee ‘ a! v. “hy . >| 2 } ' a an yoni Aa iptedtiay G.th Re, Faas Po SPR: Oe nh} ne el ios - 4 . } ' - + ; beg : ° ; . 7 ‘ f ef ; be hee bes 7 i a ' te ts 5 F Pi ’ + a errs > teat (pags pdt pide thee ’ Lo oo Bais. CP ee. ‘ ‘ - Sia ¥ ee bee ddtreh’s NED +48 eee § bluoite ; - fe Apeat ean awe x gow glahiv id het TE Dot : TSH ise. Baghtae ais (|: : lel ae t bee erte ome Savant a spate. bien a asthe Ie fis dg? gf hotesintn - Fic. 2.—Section of west front of Oquirrh range at Ophir City. Scale, 1-72000. Base line = level of Great Sa't Lake. a. Ophir City. s. Silurian. c. Carboniferons. THE BASIN RANGE SYSTEM. 27 The Thomas range, like the Onaqui, is a simple uplift, presenting throughout its extent a bold escarpment to the east, while at the west its slope is that of its strata, which dip beneath the desert. At Dugway Pass, where we crossed it, its rocks are calcareous, but were not found to contain fossils. There is reason, however, to surmise, from strati- graphical data, that they belong to the Silurian series. A short dis- tance north of the pass is an out- flow of gray trachyte, and south of it the range is entirely buried be- neath a similar lava. Between this and the House range, but nearer the former, are two low ridges par- allel to the first, of like condition and dip, and similarly accompa- nied by volcanic eruptions. In the northern portion of the House range its strata dip to the west and the eastern face is pre- cipitous. The first of the sections given was made at Fish Spring, near the northern end of the range, and the second two miles farther south; the same general structure continues for twenty miles, to Dry Pass, where there is an abrupt change of dip from west to east. The third section was made at Dome Pass, ten miles farther south, > ‘ulejOnoW Woon ‘yp ‘suradg odojeq *qS0A\ OY} WOJ, U9es sv ‘oduUvI OSNOFT OY} JO MIvAStTIG—'9 “DI,T ‘QUO}SOUNIT ULIINTIS “77 ‘oyizjavnb uring “bb ‘sseg Aig ‘q ‘Sujidg ysig ‘9 -YV puv uoury omog ‘a “ONV'T FCG Jvorp Jo [eAsl = oull oseq “Q00GL-T ‘woURHoMog 4v pue Sardy ysty Jo yynos sopror omg ‘Suyadg ystq 4u ‘osuvs osnozy oy} Jo smorjoag ‘g ‘pe ‘SOL ‘arog So = Se == <<< === fre Lorre a aS ee a and represents the general character of the range for twenty miles south of Dry Pass. But the rocks met with in going south are successively newer, owing to a southward dip, there combined with the easterly. By reference 28 GEOLOGY. to the sketch—Fig. 6— these peculiarities will be more readily understood. It represents the range as it might be seen from a remote position at the west. The dip of the portion at the left of Dry Pass is toward the observer. At Seale, 1-72000. Base line = level of Great Salt, Lake. a, Sevier Lake. Fic. 7.—Section of Beaver Creek Range. the right it is in the opposite direction, and a bold escarpment is presented over the whole face. In this escarpment the most northerly rocks (those nearest to Dry Pass) are quartzite, consti- tuting the base of the series. These gradually descend to the south, and finally disappear, being replaced upon the crest of the ridge by a massive gray limestone 1,000 feet in thickness, which constitutes the walls of Dome Cafion. The limestone is in turn covered by a series of calcareous shales not less than 200 feet thick, in which were found numerous trilobites, indicating the position of the series in the Silurian system; and these are covered by a second limestone. Finally, a second cross fault brings the quartzite once more to the surface, and the limestone above it is lifted, in Notch Mountain, to its greatest altitude. The Beaver Creek range on the opposite—2. e., eastern—side of Sevier lake, agrees with the southern portion of the House range in dip, and presents the lower portion of the stratigraphic series exhibited in that range. Its western base along the entire eastern shore of the lake is of quartzite, and its crest of massive gray and black limestones. Its strata, for the most part, maintain their easterly dip, so as to pass beneath the gravels of the Sevier desert; but at one point, near the sink of Beaver Creek, there is for a short distance at its eastern base a ridge with opposed dip, presenting an escarpment toward the east, and making with the principal mass a synclinal fold. Farther south it is continuous with the Picacho range, the structure of which is less simple. In the North Star mining districts a cross-section reveals an arrangement of strata suggesting a combined anticlinal and syn- clinal structure. If this surmise is correct the granite would appear to be in this case an axial rock, but at other points in the neigh- borhood it was observed in dikes intersecting the limestones which consti- tute the principal mass of the range, and it is noteworthy that, while the THE BASIN RANGE SYSTEM. 29 calcareous rocks immediately associated with the granite are highly crystal- line marbles, without determinable stratification, they are in other localities, not remote, so little altered as to be fossiliferous. My own observations were too brief to suffice for the determination of the re- lations of a system of rocks so greatly disturbed, but I am disposed to consider the axis at the west of the range as synclinal, and thus adopt a view held by Mr. J. E. Clayton, who has enjoyed facilities for a more thorough examination. I visited the Mineral range only at the southern end. There it consists of somewhat metamorphosed sedi- ments—limestone at base, succeeded by quartzite, quartzose schists, and finally, a second series of limestones. In the upper limestones are found a few fossils, referable probably to the Jura. This rock-system terminates ab- ruptly a few miles from the southern end of the range, and is replaced by a section composed almost entirely of granite. At the Granite mining district, five miles north of Adamsville, the section at the eastern base of the range consists of a white crystalline marble, with traces of a westerly dip, overlaid by granite, which extends un- broken, so far as can be judged by the distant view, to the summit of the range, and indeed to the opposite base. Along the line of contact between the marble and granite is a great vein of quartz, dipping 54° to the west. Par- allel to it, and alternating with bands of marble, are two somewhat similar veins, which serve to confirm the im- pression that their direction indicates the dip, not merely of the contact, but of the beds of limestone from which the marble has been formed. The crest of the range from this point nearly to its northern extremity has the ry OUT LG YVary Jo [oAP] = oul oseg “ONOSL-T ‘ETVIG “JolaysIp Sururus opravsry oy} 4v oSura [vaouipy JO uoljoag—'g “NIT * 981 ayru Duy peculiar ragged outline of a granitic ridge, but at the extremity there are reported other beds of limestone, in which the mining operations of the Antelope district are conducted. 30 GEOLOGY. The Snake range, on the borders of Utah and Nevada, is the most easterly of the high series that intervene between the desert depressions of Great Salt Lake at the east and the Humboldt sink at the west: it over- looks all the ranges of Utah to the Wahsatch. Its axis, which is exposed for nearly the whole length, consists of quartzite and limestone, with a limited amount of crystalline schists and granite. In the neighborhood of Clifton mining district, the most northerly point visited, rhyolitic lavas and syenite make up a great portion of the surface, but limestone masses are visible toward the eastern flank of the range, with eastward dip. At Uiyabi Pass there are slight exposures of limestone and sandstone, which indicate an anticlinal structure; but a few miles south the mountain rises rapidly in a single mass of westward-dipping strata. These are quickly replaced upon the crest of the ridge by granite, which constitutes the high peaks imme- diately east of Deep Creek Valley. The western base, however, at that point shows stratified rocks with the same dip. South of Pleasant Valley a portion of the range, locally known as Kern Mountains, has been greatly disturbed, and perhaps presents a reverse dip; but the interruption is only a few miles in-extent, and beyond, in the main Snake range, the westerly dip is resumed, and continues for thirty miles, to Sacramento pass, a few miles north of Wheeler’s Peak, the highest summit of the range. The peak appears to be the center of a fractured quaquaversal, the rocks upon its flanks dipping from it, not merely to the east and west, but to the north and south. The quartzite of its crest is covered at the north by the lime- stone of the Sacramento mining district, and at the south by heavy lime- stone beds; the base, at least, of the series belonging to the Silurian system. The mountain is deeply scored by caiions heading near the peak, and in the debris brought down through these on the western side Mr. Howell found granite boulders, but the portion of the range from which they were derived was not visible from any of our lines of examination. In that part of the range between the Sacramento district and the Kern Mountains, where the structure is most regular, the principal mass of the mountain consists of strata inclined to the west, but there are at the eastern base a few hundred feet of rocks with opposed inclination. The next range at the west is the Schell Creek. Where we first THE BASIN RANGE SYSTEM. oe touched it, near Schellbourne, it is flooded with rhyolitic lavas, and the structure of its sedimentary beds is not readily apparent; but both north and south of this point they appear in great inclined masses, which present escarpments to the east. In Ruby Hill Camion, quartzites are shown at the eastern base, and \ these are overlaid by several thousand feet of limestones, intersected by dikes of quartz-por- phyry, and so far metamorphosed that their lines of bedding are obscured. Farther south, at White’s Peak, where the crest of the range was climbed, the quartzites have risen so far as to constitute the upper ridge, and display a thick- guojsawyy ness, together with their associated schists, of over 11,000 feet. This entire series, together with the superimposed limestones, is tilted in AO one mass to the west, and the superior and less durable limestone beds have been so far eroded gIwog “yrog So7ITM 4e eSuva yoouy [JoWog Fo uoyoIg—G “Ol EZ, my.coly g GZ Spu' LEE auojs puny as to remain merely as secondary ridges or foot- hills to the west of the quartzite. Southward, the latter maintains its ascendency for ten or fifteen miles, and then gradually sinks to the south, and is once more replaced by the su- perior limestone. Paleontological data are by no means full, but by the aid of some collec- tions made by Mr. J. E. Clayton, at Rubyville and Schellbourne, the conclusion is ventured that the base of the series, including the entire quartzite series and the lower portion of the limestone, may be set down as Lower Silurian; “000GLT oull estg while the upper limestones are as recent as De- vonian, and perhaps Carboniferous. ; The Spring Mountain range in Southern Nevada is continuous for a great distance, and was intersected at two points. The section given was «ONL ITVS YLOTH JO [OA] * The symbols for limestone, &c., given with this cut, are adhered to in the other mountain sections of this ehapter. 32 GEOLOGY. observed just north of the pass by which the Los Angeles and Salt Lake road crosses the range.. The strata. appear to be conformable throughout, a, camp Fic. 10.—East front of Spring Mountain range at Cottonwood Creek. Scale, 1-72000. Base line = sea level. ¢, cross-stratified sandstone. on Cottonwood Creek, and but little altered. They are in chief part fossiliferous limestones of Carboniferous age, but comprise several bands of sandstone, one of which constitutes the princi- pal escarpment toward the east. At Olcott Peak, ten miles farther south, the rocks are almost exclusively lime- stone; and, while they were found to contain Lower Car- boniferous fossils, were not definitely codrdinated with those shown in the section. An abrupt change of structure occurs at the pass already alluded to, and, while that at the north is tolerably uniform, so that the section given applies for a distance of ten miles along the range, im- mediately south of the pass the rocks have been sub- jected to a greater amount of disturbance. Fifteen miles farther south, near Ivanpah, the rocks are chiefly lime- stone, of which the age was not determined, and they present opposed dips on opposite sides of the range, the interval being occupied by a mass of granite. The latter rock forms a belt, intersecting the range obliquely from northwest to southeast, and for a few miles south of Ivan- pah constitutes the eastern face of the mountain. The western mass of limestone, however, rises far above it, presenting the precipitous face upon which the imagina- tion of early prospectors read the mystic +ILD.* The northern section of the range will be given in detail in the chapter on the stratified rocks. Bare Mountain stands east of the Amargosa desert, near its northern end, and presents for a distance of ten miles, nearly its whole extent, a bold escarpment toward. the desert. We were unable to visit it, but its entire destitution of vegeta- *A fortuitous arrangement of stains or lichens suggests at a distance rude letters, several hundred feet in height, and gave rise to a fable that early Jesuit explorers had painted a sign to guide them back to arich mine. Some capital has been made of the story in the prospectus of a mining company. THE BASIN RANGE SYSTEM. 33 tion, and the precipitous character of its face, enabled me to sketch its structure from a distance. The accompanying diagram represents the south- western face of the ridge, and shows the dip of the strata longitudinally, _ as modified by transverse faults. The transverse dip of the rocks is to the northeast, or from the face represented in thesketch. In the diagram the topo- graphical reliefs are omitted, that they might not be confused with the geologi- cal features, but the contrasts of strata and the faults are no more. strongly drawn than they appeared in nature on the naked face of the mountain. It was extremely tantalizing to see there not less than 8,000 feet of bedded rocks so beautifully displayed, and yet be ‘q1eseq] VsOsIvULY ‘uouvg Aivpunog ye osuri vsosiemy jo uoyo0g9—ZT ‘DIT unable to examine a single stratum. The plain upon which we stood was composed of their débris, but its sand- stone and limestone pebbles could not be referred to their parent beds. A section of the Amargosa range was obtained at Boundary Canon. It is there composed entirely of altered sedimentary rocks, limestones, schists, and quartzites, and, so far as can be seen to the north and south, its crest “AOTIVA TIVE “T ‘[OAQ|-vas—vul] Oseq ‘QQDSL-T ‘eTvog “q1080p TsoSuvury 949 Surory ‘arezunoyy orvg Jo 4uoay ysoar Jo mvisviq—' Tl ‘oy “is similarly constituted. A few miles north of the point of section, however, it sis flanked both east and west by rhyo- litic beds, and these, too, form foot-hills, on the east side at least, toward the south. The strata are greatly disturbed ‘onoAyy “D We and dislocated, but are not arranged in systematic folds. Fractures not only longitudinal, but transverse, divide the rock into a ereat number of 3Wws 34 comparatively small masses. GEOLOGY. The caiion, by which we descended from the summit of the range to Death Valley, winding among these, rarely reveals the same arrangement on its opposite walls. A very slight change in the Scale, 1-72000. Base line D. Death Valley. S. Saratoga Springs. Fic. 13.—Section of Funeral Mountains at Saratoga Springs. A, Amargosa Desert. sea-level. Tic. 14. Section of the Inyo range near Deep Spring Valley. Scale, 1-72000. Base line=sea-level. position of the section would affect its details in great amount, but the confusion of strata represented is typical of the range, so far as it was seen. Only imperfect fossils were found, but these sufficed, with stratigraphical data, to connect the rock series with Silurian beds observed farther at the east. The Panamint range, on the opposite side of Death Valley, appeared from the distant view to be similarly con- stituted. Another section of very different character was obtained from the same (Amargosa) line of upheaval, fifty miles farther south, where the title of Funeral Mountains maintains. Theirextremesouth- ern end at Saratoga Springs shows a sys- tem of hornblende rocks and slates, without fossils, between which and the northern series no connection wasestablished. They are perfectly conformable, and dip in a single body to the east. The Inyo range, lying next the Sierra Nevada, to which, in the grandeur of its proportions, it is a fit neighbor, is too im- portant and complex to be characterized’ from our meager data. Buta single sec- tion was obtained, and that at the com- paratively low pass between Piper’s ranch and Big Pine, California. At this point the range is double, so as to include an undrained hollow—Deep Spring Valley—ten miles long and five broad, that might contain a lake a thousand feet deep, without overflowing. Where THE BASIN RANGE SYSTEM. 3D we crossed the eastern ridge, it consists of granite, in part a protogine with imbedded bowlders of dark, micaceous granite, and in part a syenitic granite. Farther south, near Deep Spring, gneissic rocks were observed, associated with the granite. In the western branch are dislocated and somewhat altered limestones, sandstones, and slates, as shown in the accompanying section. No fossils were found. The axis of the Black and Colorado Mountains, in north- western Arizona, is of granitoid rocks and highly crystalline schists. These are in great measure concealed by extensive eruptions of trachyte and rhyolite, which determine the bold scenery of the range. At the north, the Colorado River inter- sects two spurs, giving rise to Black and Bowlder canons. A few miles farther up, by Virgin Cafin, it crosses also a spur of the Virgin range. The materials and structures exhibited in these three sections are very closely related; that of Bowlder Canon, represented in the diagram, being most clearly made out. The nucleus there is of syenite, against which rest pli- cated crystalline schists; and over the whole are successive massive layers of trachyte, flanked at the east by basalt. The syenite is remarkably homogeneous in character, and there is nothing to indicate its origin, whether from fusion or metamorphism; but throughout its observed contact with the schistose rocks itis the inferior member. In Virgin Caton no granitoid nucleus is apparent, the entire exposure being gneissic, with a general anticlinal structure, modified by con- siderable minor plication. The overlying lavas were seen only in the distance; but, as judged by their habit, belong to the group of trachytes. In Black Canon the visible nucleus is a tolerably homogeneous rock, resembling pegmatite, but probably metamorphic in its origin. It is a comparatively inconspicuous feature, the greater part of the walls of the canton ay ATOVLY, "77 “qyestg “¢ 0006L-1 ‘aTvog *PAO[-VoS=ouIT osrg WY PLL sf + YE. OLE ing as ask are ire fer oe Tipe Mis Koken eA i heta ly L L ‘MOULD Jap{Aog Jo T]VA TWaoU Jo uoyoag—s] ‘OTT ‘aytuadg ‘8 <— 487 ‘aston ‘bb being composed of red, purplish, and brown trachyte, in beds of great ae ness, and in many places brecciated with fragments of similar character to the matrix, as well as with bowlders of gneiss and other schistose rocks. 36 GEOLOGY. In the Black Hills, north of Prescott, Arizona, a series of crystalline rocks similar to those of Bowlder Caion, are overlaid by unaltered sediments belonging to the Carboniferous series. The latter are unconformable, and appear to have been deposited after the principal upheaval of the schistose ridge; but from a later uplift have been them- selves somewhat tilted. The phenomena could not be very thoroughly observed, on account of the numerous eruptions of the trachyte and basalt in the neighborhood of the line of — section. A section obtained by Mr. Marvine at a point farther 20°H i ; Nv Scale,1-200000. g. Granite and schists. }. Basalt. . Black Hills. V. Verde south, and given in his report, is incomplete for the same reason. The axial rocks of the Toquima range were seen only in the neighborhood of Belmont, Nevada, where they are exposed for a distance of five to ten miles, the area being limited both north and south by a heavy mantle of rhyolite. The com- ponent rocks are granite and argillaceous slate, the latter somewhat metamorphosed, but not to such an extent as to A, Aubroy Cliff. entirely destroy its fossils, which are of Silurian forms. The boundary between the two, crosses the range obliquely from southeast to northwest, and is tortuous in detail. The granite. River. apparently intrudes in irregular bodies in the mass of the shale, which, in a general way, rests against the granite, and is inclined at a high angle. The shale contains some inter- calated beds of limestone and sandstone, and has an apparent thickness of four or five thousand feet, but there is so much plication observable as to render it probable that some redupli- cation has taken place. It lies to the north and east of the granite and contains the metalliferous veins of the Philadel- phia mining district. The granite forms the eastern face of the mountain, from Belmont south for not less than five miles. Fic. 16.—Section of Verde Valley. It was examined at few points, but appeared, while present- ing considerable variety, to be characterized by an unusually large percent- age of quartz, the yellow color of which imparts its hue to the general mass. Its eruptive character is intimated, not merely by its intrusion THE BASIN RANGE SYSTEM. au between bodies of slate, but by the presence in its mass of huge bowlders of gneiss, as well as of dissimilar granite. The axis of the Reveille range is covered by volcanic material through- out nearly its whole extent. So far as my own observation revealed, it is to be seen at but two points. The first of these is at Reveille, where for a few miles the crest and eastern face to the foot-hills are of limestone and quartzite, so dislocated that their sequence is hard to establish, but agree- ing in a westerly dip. Sixty miles farther south the sedimentary rocks are again exposed, forming a simple monoclinal, with westerly dip at a high angle, and with unusual continuity of strata along the strike. Fic. 17.—Section of Mount Worthington. Scale, 1-72000. Base line—level of : Great Salt Lake. Worthington Mountain, in Eastern Nevada, stands by itself, is fifteen miles long, and is remarkably acute in its cross-section. The strata are neatly horizontal, but incline slightly to the east, and pass completely through, so as to appear on both sides. Its northern end, according to Mr. _C. R. Ogden, who visited it, is flanked on the east by beds of rhyolite, associated with which are the Freiberg silver mines. At the southern end the limestones of its section are uncovered, and spring abruptly from the talus of gravel. I can conceive of no erosion that should have left this thin segment as the remnant of an inclined table or of a fold. Its narrowness, its straightness, and its isolation, mark it as a mass of strata thrust upward between two faults—strata, of which the companion parts lie beneath the débris at its foot. Lithologically it consists principally of limestone, inter- spersed with some sandstone, and containing abundant fossils, which are probably referable to the Silurian. Our collections were, however, Eeomoy ed, and the reference is made merely from memory. The portion of the Pahranagat range, which lies north of the pass at Logan Spring, consists of a principal and tolerably continuous mass of strata, forming the crest of the ridge, flanked at the east by a great number of irregularly disposed bodies, all of which have the same westerly dip, and 38 GEOLOGY. are separated from each other by faults, along which the downfall has been uniformly on the eastern side. While the trend of the main range is with Base line=level of Great Salt Lake. Scale, 1-72000. Q. Quartz Peak. S, Sanders Canon. 15.—Section of the Pahranagat range at Silver Cation. Tic. the meridian, a line of hills, consisting of similar faulted rock masses, extends northeasterly to the next general line of upheaval, where they culminate in Fossil Butte. These, as well as the immediate foot-hills of the range, are composed of westerly dipping strata. At Logan Pass, the axis of the range is hidden by rhyolitic outflows for a few miles, and south of it the strata re-appear in a single monoclinal with an easterly dip. The crest of the range in the vicinity of Silver Canon is of vitreous sandstone that overlies a limestone series of great thickness, in the upper part of which are the chief metalliferous veins of the Pahranagat district. The Timpahute range lies next west of the Pahra- nagat, and is its close counterpart in point of structure. In its northern portion the dip is westward, and a series of ridges, en echelon, stretch northeast to the north ex- tremity of the latter range. The main ridge, however, is comparatively low, and is even surpassed in size by the first parallel ridge at the east. In its southern por- tion the rocks incline to the east, and are divided by a series of vertical faults, the effect of which, as shown by the diagram, is to reduplicate the several beds upon the surface and increase the lateral extent of their outcrops. The quartzites at the west, and the limestones at the east, by their superior hardness, maintain parallel ridges, while the intervening shales have been denuded so as to form a valley within the range. Vertical faults within these shales contain the galena veins that have been East —— Tra. 19.—Section of Timpahute range at the Groom mining camp. Seale, 1-72000. Base line=level of Great Salt Lake. Mines at mined by the proprietors of Groom district As in the Pahranagat range, THE BASIN RANGE SYSTEM. 39 the point at which the dip changes has been the seat of volcanic activity, one result of which has been the uprearing of Timpahute peak, the loftiest summit of the range. I'1G. 20.—Chart of monoclinal ridges in Southern Ne- vada. 1inch=12miles. - The long and cross lines show direction of strike and dip. In the Timpabute range, a=—Timpahute peak, and f=Groom miningcamp. In the Pahranagat range, e=Quartz peak, and b=Logan pass. Inthe Hyko range, d—Fossil Butte. The features exhibited by these two ranges appear to me of great interest. Taken with the Hyko Hills at the east, they constitute a group most closely related in structure. The accompany- ing diagram (Fig. 20) represents merely the positions and strike of the upheaved masses. North of the dotted line a, }, ¢, all the strata dip to the west, and their several masses are separated by faults along which the downfall is inva- Fia. 21.—Chart of Monoclinal ridges in Western Utah. 1 inch=30 miles. B. Beaver Creek range. C. Cedar range. H. House range. O. Onaqui range. TJ. Thomas range. riably to the east. South of the dotted line the reverse is true; the dip is eastward, and the dowuthrow westward. There are no folds. There are 40 GEOLOGY. three main ridges, or maxima of elevation, about fifteen miles apart, and persistent through both phases of dip. In the lines of these maxima there are volcanic outflows, at a, b, and ¢., where the dip is reversed. The most patent immediate deductions from these phenomena are that the ridges are due to forces uniform in kind, and probably synchronous in action through the whole group, and that the directions in which the forces acted have horizontal components, opposite phases of which are exhibited in the areas of opposite dip. The further conclusions that the forces were deep-seated, that the parallel main-ridges recur with subequal interval, and that the volcanic eruptions are associated phenomena, are suggested; but, as their application is much broader, so, too, their demonstration depends on a greater array of facts. The systematic uniformity shown by this group of ridges does not stand alone. Another illustration, and one on a grander scale, is to be found in Western Utah. The strata of the Onaqui and Stansbury ranges, of Cedar and McDowell Mountains, Granite Mountain, of the Thomas range, and two small ridges west of it, and of the north part of the House range, dip to the west. South of Dry Pass (below the dotted line in the diagram) the case is reversed, and the continuation of the House range, the Beaver Creek range, and a number of small ridges known as the Confusion range, show an easterly dip. Structure of Ridges—In the great majority of the ranges I have just described, and in an equally large porportion of others, in regard to which my observations were too cursory to warrant individual mention in this connection, the beds exhibit in cross-section but a single direction of dip. Kither (Figs. 5, 7, 9, and 13) the strata in a single body incline from the crest to one base of the range, or (Figs. 1, 3, 4, 18, and 19) they are divided by a system of faults, trending parallel to the range, into several bodies, which dip in one common direction. In these cases the ranges may be called simple and compound monoclinals. Next in frequency are sections in which (Fig. 97) there appear at the base of the monoclinal escarpment strata dipping in the opposite direc- tion. Pure anticlinals (Figs. 2 and 15) are exceedingly rare, but in a number y vst iene ydkelieets ima iat oi hea ot) tat a meh ahee phctot Vis : ive tee Koh tthe rata be yen) oll %, ei tilg : i setlesitipeln ina eee 10. Sue = + eerestia ame) Bipinde x 2. Lat eee we a : i é = 1. ee? ir c re bined TTPO SS. Age i ta we ne! - : At S. re Vatt rm pies 4 : E - tesus bey 1 Ao eat es ‘ ; Pica Wis feo tcare ks - % ‘tice Ge - my j Th 8 ot ton _ : Trial 2s f wate, ate : ‘ _ he ™ ar ane cami ‘ . ¥ — a ‘ : i “oj Md ER 54 i wer ITY 6 ne = = oo = 29% ee | wt orn aad Te ety Rete ae esd siege ti : it ‘ 3 i avec Ta 4Ae a > . i L. ~ : ‘ii! 5 at i " . * . 7 7 ar 4 +: 7h ‘ ei Pie twa sie" de &» 3 hare i2 Tee eee TS un, Aad 03 HRs barack re Tater y Sate aks Sigtes sou ratte lier i! foe Siler el igh ices x oa * riba. Se “if ripe is a inthe beaters! ern we eT, ere sel taped again San) hill Kiet ati) a bea oltre pane ha apie + lane, pent, apis | Siseeee ois pele “Laat ‘ ' rn eH al et THE BASIN RANGE SYSTEM. AL of instances greatly shattered and dislocated rock-masses assume a quasi- anticlinal form, (Fig. 12.) Anticlinals and synclinals also occur as sub- sidiary features within some ranges, (Fig. 14.) A few most remarkable ranges present escarpments on both faces, (Fig. 17.) The labors of the Pennsylvania geologists have rendered so familiar the structure of the Appalachians, that it has been by many accepted as typical of all mountains, and a comparison will facilitate an understanding of the basin ranges. Indeed, I entered the field with the expectation of finding in the ridges of Nevada a like structure, and it was only with the accumulation of difficulties that I reluctantly abandoned the idea. It is im- possible, by any hypothetical denudation, to formulate the basin ranges as remnants of a system of anticlinal and synclinal folds. The simple mono- clinal may indeed be explained as the side of an anticlinal, by the harsh assumption that the remaining parts have been removed below the level of the adjacent valley, but the explanation will not apply to the compound monoclinal, (Figs. 18 and 19,) nor is the erosion conceivable that would carve Worthington Mountain (Fig. 17) from an anticlinal. The question, what is, then, the general structure of the basin ranges ? admits of less dogmatism; but if it cannot be completely answered, some light, at least, may be thrown on it. To begin with the simplest generalization, the ranges are a system; not indeed formed at the same time, but exhibiting certain common charac- ters, over a great area. They are parallel; they recur with some regularity of interval; they are of moderate dimensions. Second. The ridges of the system occupy loci of upheaval, and are not mere residua of denudation; the valleys of the system are not valleys of erosion, but mere intervals between lines of maximum uplift. Within the ranges there are indeed eroded valleys, and the details of relief show the inequality of erosion due to unequal resistance, but there is not on a grand scale that close dependence of form on durability that must maintain were the great features of the country carved by denuding agents. An easy illustration of this is afforded by the southern portion of the Timpahute range, (see Fig. 19.) The range terminates near the line of section, and is 42 GEOLOGY. surrounded at the east, south, and west by a gravel plain. The valley in the range, due to the occurrence of soft shales between harder beds, opens to the south, and is deepening very slowly, because it is little elevated above the plain. If the depression occupied by the gravels of the plain had itself been not only emptied, but excavated, it is inconceivable that the shale in the mountain should have escaped deep erosion. Furthermore, ridge lines are more persistent than structures. In the same continuous ridge are monoclinals with opposed dip, as in the Timpahute, Pahranagat, and House ranges—or monoclinal and anticlinal, as in the Spring Mountain and Snake ranges. The section at Ivanpah is peculiarly in point. The mountain there shows an axis of granite, flanked on each side by limestone, but the trend of the anticlinal is oblique to that of the range and it quickly runs out, the granite giving place at the north to the eastern mass of lime- stone, which rises and, as an eastward dipping monoclinal, constitutes the entire range, while the western limestone mass becomes, in the same man- ner, supreme at the south. And, finally, the character of the ridges, as main lines of structure, is indicated by the association of volcanic phenomena, as will appear when, in another chapter, the distribution of the lavas is described. Third. The movements of the strata by which ridges have been pro- duced have been in chief part vertical along planes of fracture, and have not involved great horizontal compression. There are some notable local exceptions to this, but considering the prevalence of faulted monoclinals, which demand no horizontal motion, the existence of the feature as a dis- tinctive one need not be questioned. Fourth. We may say, without fairly entering the field of speculation, that the forces which have been concerned in the upheaval of the basin ranges have been uniform in kind over large areas; that whatever may have been their ultimate sources and directions, they have manifested them- selves at the surface as simple agents of uplift, acting in vertical, or nearly vertical, planes, and that their Joci are below the immediate surface of the earth’s crust. THE COLORADO PLATEAU SYSTEM. 43 SECTION II. THE COLORADO PLATEAU SYSTEM. The province of plateaus is characterized by a system of tabular reliefs, consisting of strata little disturbed. What falls within our field is but a portion of a large area known as the Colorado Plateaus or Colorado Plateau System. It derives its name from its partial coincidence with the hydro- graphical basin of the upper portion of the Colorado of the West, but the two are far from identical. On one hand, the chief tributaries of the Colo- rado—the Grand, the Green, and the San Juan—rise beyond the Plateau region ; and, on the other, the waters of a part of the system find their way, as the Sevier River, to the Great Basin; while the Rio Virgen, which rises among the Plateaus, passes into the province of the Ranges before reaching the Colorado. The Colorado Plateaus lie between the Rocky Mountain System and the Basin Range System at the east and west, and stretches northward to the Uintahs. Of the political divisions, it includes Southeastern Utah, North- eastern Arizona, and adjacent portions of Colorado and New: Mexico. The simplicity of its structure, the thoroughness of its drainage, which rarely permits detritus to accumulate in its valleys, its barrenness, and the wonderful natural sections exposed in its cafions, conspire to render it indeed “the paradise of the geologist.” There he can trace the slow lithological mutations of strata continuously visible for hundreds of miles; can examine, in visible contact, the strata of nearly the entire geological series, and detect every nonconformity, however slight, and can study the simpler initiatory phases of an embryo mountain system. To the reports of Professor Marcou, who accompanied the expedition of Lieutenant Whipple in 185354, and of Dr. Newberry, the geologist of Lieutenant Ives’s expedition in 1858, we owe our first knowledge of the geology of the Plateaus. In the following year, Dr. Newberry, with Cap- tain Macomb, traversed the region east of the Upper Colorado, as far north as the junction of the Green and Grand; and since 1868, Mr. J. W. Powell has been engaged in the geological exploration of the Colorado and its west- 44 GEOLOGY. ern tributaries, including the Green. The reports of these gentlemen, though in so great an area they leave some fields untouched, will make known, when they shall have been published, all that is most important of the Pla- teaus. Our own explorations have pertained to the western margin of the sys- tem, and a belt within the margin from twenty-five to one hundred and twenty-five miles broad. i At the south we intersected routes of Professors Newberry and Marcou, and at the north visited numerous fields of the labors of Mr. Powell. So far as our own explorations have shown, the strata composing the tables range from the fresh-water beds considered as Eocene Tertiary to the Tonto group, a Paleozoic series, which underlies the recognized Carbonif- erous rocks of the Grand Canon of the Colorado. In the most southerly section the entire series is conformable, but at the northwest there is evidence of a disturbance before the deposition of the Cretaceous. The areas drained severally by the Sevier River, and by those tributa- ries of the Colorado which rise in Southern Utah, are geologically and topo- graphically, as well as hydrographically, somewhat distinct. The general dip of the strata throughout both regions is at a low angle to the north. The main forks of the Sevier rise upon the extreme southern edge of the Tertiary. strata, and flow northward almost entirely upon them, until, pass- ing through the Canon range, they empty into a desert valley of the Range System. The tributaries of the Colorado, on the contrary, rising along the same line, descend through the successive beds to the Grand Canon, which tray- erses Paleozoic rocks, and exhibit on their banks a complete section. The country which they cross is divided into a series of great terraces, by lines of cliffs trending east and west, facing south, and composed severally of the harder strata of the geological series. A system of faults, having a gen- eral north and south direction, traverses the entire region, and is*a very important element in the determination of the topography. In the Sevier country the faults and volcanic outflows have created all the geographical features. At the south, where the system of terraces is intersected at nearly THE COLORADO PLATEAU SYSTEM. 45 right angles by that of faults, it results that the country is divided into a great number of minor tables. The lines of cliffs, determined by the occur- rence of harder and more massive strata, are modified not only by the intersecting faults, which have great local effect upon the rate and manner of denudation, but by changes in the constitution of the beds which give rise to them. Beginning with the uppermost, the principal lines are as fol- lows : First, the fresh-water limestones, referred to the Tertiary, form a series of pink and white cliffs, culminating southward in two principal points, ter- minating the two tables, for which Professor Powell proposes to use the Indian titles, Pownsagunt and Markagunt. The next cliff consists of the calcareous sandstone at the top of the Cretaceous System, and has a pale greenish-yellow color. On the head- waters of the Kanab and Virgen it is inconspicuous, as compared with those adjacent to it, but derives great interest from the coal it bears. The third escarpment is made up principally of massive, ochreous and cream-colored sandstone, referable to the Triassic system, but is capped by a few feet of limestone, in which are Jurassic fossils. At Steamboat Mount- ain it unites with the red cliff below it, but on the Upper Virgen forms a distinct line, through which the Hast Fork passes in the cation below the town of Mount Carmel. The great fault of Long Valley, to which further allusion will be made below, here interrupts it, and it re-appears as.a bluff overlooking Long Valley from the east. Turning abruptly near Mount Carmel, it resumes its westerly course a few miles north of its former line of direction, and, crossing Kanab Creek ten or twelve miles above Kanab, continues a bold bluff in the rear of, and parallel to, the Vermilion Cliffs, as far, at least, as Paria Creek. ; The Vermilion Cliff, which comes next in order, has been further traced, and is a conspicuous feature of the topography of the country. The rocks which compose it are massive, cross-stratified sandstones, banded in buff ‘and red, but ordinarily stained superficially to a bright vermilion. From Steamboat Mountain, near Little Zion, this cliff was traced north of Rockville and Shunesburg, at which latter place it is cut by a cafion of the east fork of the Virgin, and thence, southeast to Pipe Spring. At this 46 GEOLOGY. point it is intersected by the same fault which deflected the Gray Cliff at Long Valley, and is itself carried northward a distance of three or four miles, when it resumes its easterly course, past the town of Kanab and Johnson’s Settlement, to Paria Creek, four miles above the town of Paria. Here it turns abruptly southward, and follows for forty miles the most east- erly fault of the Kaibab Plateau. In the southern part of this course it is the east wall of House Rock Valley, and it terminates that valley by turn- ing sharply to the east. At Jacob’s Pool, it swings to the northeast, and soon reaches the mouth of the Paria, where it crosses the Colorado, and once more assumes a southerly course. Beyond this point our explorations did not follow it, but it was seen by Mr. Marvine upon the eastern bank of the Colorado Chiquito, and there can be little uncertainty as to its general course in the interval. The next bench, named by Professor Powell the Shinarump Mesa, is of minor importance, and for the most part projects but a short distance from the base of the Vermilion Cliff. It is most strongly marked between Virgin City and Kanab, where it forms a chocolate-colored escarpment from 200 to 500 feet in height. From Virgin City it was traced by Mr. Howell to a point on the Virgin River, twenty miles below the town of Saint George. East of Kanab it was seen, with diminishing propor tions, as far as Navajo Wells, and it must extend nearly to the Paria in that direction. From House Rock Spring to Jacob’s Pool the conglome- rate which caps it is absent, and the cliff is lost, but it re-appears in the neighborhood of Rocker Creek. Thence it holds its place to the mouth of the Paria, and is continued as far as our view commanded south of the Colorado. It was noted by Mr. Marvine on the east bank of the Colorado Chiquito. Below this is the most important bench of all, capped by the upper lime- stone of the Carboniferous. Its extreme breadth, measured from the mouth of Paria Creek southwest to Aubrey Valley, is one hundred and thirty miles, and its length in a right line is more than three hundred miles. Through it the Colorado has cut Marble Caiion, and the greater part of Grand Canon. Upon it stand the peaks of San Francisco, Bill Williams, Floyd, Sitgreaves, and Kendrick, and the Mogollon, the Uinkaret, the Sheavwits, and other THE COLORADO PLATEAU SYSTEM. 47 volcanic mountains. South of San Francisco Mountain the names ‘Black Mesa” and “ Mogol- lon Mesa” have been indefinitely applied, and north of the Colorado, portions definitely limit- ed have been designated by Professor Powell, the Sheavwits, Kanab, and Kaibab Plateaus. For the portion south of the Colorado, bordering on that river from Diamond Creek to Paria Creek, and limited at the east by the Shin- arump Cliff, I shall employ the title, Colorado Plateau ; and for the cliffs which limit it at the south, I propose the title of Aubrey, since the Aubrey sandstone is their most conspicu- ‘TIvqUNOy Osta *[PAO[-VOS = OUI[-aSVg “payeIeSHexo o[vos [ROAOA “YI YUl_ of} 0F YUO Loaquy oy} woay wo01y9aG—-ZG “OT ous stratigraphic member. From the vicinity of Camp Apache to the Colorado at Diamond Creek, two hundred and forty miles, their line is continuous, and wonderfully direct in its ‘opra0[oH oy JO moury purty ‘9 general course, though, in places, deeply sinuate in detail. Beyond the river it holds its north- westerly course to the mouth of the Grand Cafion, and then turns north, becoming the upper member of the double cliff caused by the Grand Wash fault. Finally, the Red Wall limestone, south- west of Aubrey Valley, forms a series of low escarpments, of which the Music Mountain, of Lieutenant Ives’s map, is a promontory.* They are seen, at intervals, to Camp Apache, but are . 80 interrupted by the disturbances of the adja- *A regular alternation of hard and soft strata, producing parallel and equidistant lines across the face of the headland, suggested a musical staff, and led Lieutenant Ives to distinguish it with a name. As it is not distinguished by its size, it has been overlooked by frontiersmen, and the name caught from his map has been applied to a conspicuous crest ten miles further west. This later usage has been followed by Lieutenant Wheeler. SNSSN SSN AGN ANS POA “I BIO AeIVN yp Pug voy, -4 “ByO dumaeasyg +g “uv ug oO Aerquy “7 ‘BG ‘BUT Ul Sv OMILS OT} $10}}9'T “OQOOOPE-T :ZIA ‘o[vos [eJUOZIIOY Puv [VOTJIOA OILS OT} TATA UA\vAp GE UOIJOeS Jo MOIOG—'sZ “DIT 48 GEOLOGY. cent Basin Range System, and modified by variations in the lithologi- cal succession on which they depend, that they have no topographical continuity. The relations of all these mesas, except the lowest, are illustrated by the upper diagram, Fig. 22, which gives a profile and section from the Pink Cliffs at the head of Kanab Creek, Utah, one hundred and seventy miles, to the Black Hills, near Prescott, Arizona. The vertical scale is of necessity greatly exaggerated. In the lower sketch a portion of the same is given with the same vertical and horizontal scale. Two great water- sheds are intersected by the line of the diagram. The Pink Cliff separates the Sevier River of the Great Basin from Kanab and Paria Creeks, tributa- ries of the Colorado. The Aubrey Cliff divides the waters of the Colorado Chiquito from those of the Gila. Faults —The term “fault,” as it has been used in preceding paragraphs has a somewhat more extended meaning than the one usually given to it, and must be understood to include all cases in which rock-masses, once adjacent, have been separated by vertical movement without great disturb- ‘ance otherwise, whether the movement produced a fracture, simple or com- pound, or merely a flexure. In the field under consideration there are numerous instances in which the same fault affords, in different places, exam- ples of fracture and of flexure. The accompanying diagrams, as well as those given below to illustrate the Sevier Valley fault, will serve to indicate the range of variation. Fic. 24.—Ideal sections of faults. a and bd, fractured faults ;-¢,a folded fault or monoclinal fold. In their distribution the faults are in two ways systematic. First, they exhibit parallelism, not universal, but widely extended. Throughout the basin of the Upper Sevier, their direction ranges from north 10° east to north 30° east, and the faults, recurring with subequal intervals, have given rise to the series of parallel ridges which constitute the main features of the topography. Farther south, on the borders of Utah and Arizona, their trend THE COLORADO PLATEAU SYSTEM. 49 is more nearly north and south.* The second element of uniformity is in the direction of motion along the vertical plane. With few exceptions, throughout the region of the Upper Sevier, the eastern wall has been lifted, (or the western dropped,) and, as a concomitant feature, the strata have received an easterly dip. Wherever, between Salina and Panquitch, the mantle of lava permits the inspection of the underlying strata, their escarp- ments are found facing the west, and their inclinations directed to the east. The average amount of vertical displacement in this region along the lines of fault is not less than 2,000 feet. Farther south it diminishes some- what, and at the extreme southern edge of the plateau, in the neighborhood of the San Francisco and Mogollon Mountains, the disturbances have been slight. There is reason to believe that the several faults can be traced for great distances. One of them, the Sevier Valley fault, it was our fortune to examine at so many points as to be able to define its course for a dis- tance of two hundred and twenty-five miles, without including either end. The most northerly point at which a cross-section was obtained is the north end of Sam Pitch Valley. Its profile there exhibits, first a simple bluff, and then a duplex flexure involving several minor faults. With great variation of detail, these continue along the eastern margin of Sam Pitch Valley to Manti and Salina From the latter place to Glencove the convex fold is partly removed, so that its front consists of a bluff escarpment overlooking a narrow ridge of ‘highly inclined rock at its base, while the reverse fold is concealed beneath the detritus of the valley. From this point to Panquitch, a distance of sixty-five miles, the ridge, to which the fault gives rise, con- tinues unbroken, but is so completely covered with volcanic rocks that the presence of the sedimentary cannot be predicated from direct observation. At Panquitch the dislocation is by a simple fracture, and this character maintains as far as the divide between the Sevier and Virgen, where it * Exceptional to the general parallelism are some instances in which faults have forked, and their branches have become quite divergent. tSince this chapter was written, Mr. Howell has made some examinations near the town of Salina, which lead him to conclude that the Sevier fault terminates there, and that the fault which walls the Sam Pitch Valley is the prolongation of one which, southward, bears more to the east. His investiga- tions, however, although fuller than mine, do not entirely explain the structure at Salina, and for this reason I let my description stand, save as qualified by this note. 4ws 50 GEOLOGY. changes to a flexure, and so continues to the town of Glendale, at the head of Long Valley. East of Long Valley, from Glendale to Mount Carmel, it consists in part of a simple, and in part of a complex fracture, and beyond Fic. 25.—Thirteen sections of the Sevier fault,in order from north to south. The localitiesare: a, north of Springtown, Sam Pitch Valley; b, Springtown; c, Ephraim City; d, Manti; e, south of Manti, f, north of Salina, Sevier Valley ; g, Glencove; h, twenty miles south of Panquitch; i, Upper Kanab; /j. Glendale, Long Valley ; k, Mount Carmel; 1, near Moccasin Settlement; m, Pipe Spring, Arizona; 1. Trachyte; 2, Tertiary ; 3, Cretaceous; 4, Jurassic; 5, 6, and 7, Triassic ; 8, Carboniferous. the latter place, owing to the yielding nature of the material which here constitutes its margins, its structure is not evident, but its existence was traced continuously to Pipe Spring, Arizona. It is this fault which occasions the deflections in the cliff lines to which reference has already been made. THE COLORADO PLATEAU SYSTEM. 51 It is to be observed, that while the several escarpments at the east of the dislocation are carried further north than at the west, this is not due to any horizontal £8 displacement along the line of fault, but merely to S. the fact that the eastern portions, being lifted higher Ss - than the western, became subject to different conditions of denudation. Another phase of the system involved in the arrangement of the faults is exhibited in their symmetry with reference to the Kaibab Plateau. That table has been uplifted bodily between parallel meridional faults, and all faults west of it have a westward throw, while 0 Siaqaoy ut zany opr. Golo FNoge [VoOA “PLOF VIN off 07 oSuvr uls1A oy} wrosy W01}0AGS—"9g “DIT echeeeteferlee leet tee 4 $ uour Z IT, W * nvogerg qeqiey Sy fyoorg qvur the only one at the east that our exploration intersected CimN . . ° \ has an eastward throw.* This is well shown in the accompanying section, Fig. 26, which crosses the sys- tN : L N tem, in an easterly direction; from the Virgin range, LL fyseA, pursry yr oprr0jop ‘44 ro So So 2 i=) ° a = linea near the mouth of the Grand Caiion of the Colorado, = caigeN . Ld a L past the mouth of Paria Creek, a distance of one hun- 2 ciaaN - : > : 5 rE dred and sixty miles. The dislocations west of the 3 eal JN : Z & & Kaibab Plateau are the southward prolongation of the me Piva nals ot nw system manifested in the Sevier Basin. eHe fc . ° . . 5 5 2 i There are some special considerations, that will 5 = = tia) ae AR : Se warrant a brief individual mention of the several *& 2 . . . . . ° S Sg details of this section, with fuller illustration. e Ss . ee * . -- 6 The Paria fold was visited at but one point—that q E where Paria Creek enters the Colorado. The Colo- qe nye a rado here has a southwesterly course, and, at its inter- 58 uf . . et af section with the fold, passes from Triassic to Carbon- wee _iferous rocks. On both sides of the river the fold 2 is . . ts produces conspicuous topographical features. At the Bb | ae<4 . ~e @ “In the Geology of the Colorado Expedition, (p. 95,) Dr. Newberry = i describes.a partially flexed dislocation, near Fort Wingate, N. Mex., with 3 en _2 throw of 2,000 feet to the west. This, and his account (p. 93,) of an S < anticlinal at Old Fort Defiance, constitute the earliest notices of any mem- 3 ay oI bers of the system of disturbances within the Plateau area. 52 GEOLOGY. north, Paria Creek, for some miles, at least, has opened a cafon along the line of fault, and removed the greater portion of the inclined strata down to near the base of the Trias. It is especially noteworthy that what of the flexed sandstone remains belongs to the lower or synclinal side of the fold, (see Fig. 27,) indicating that the line of erosion, if determined by the : Last ———>— Fig. 28.—Section of Paria fold south of the Colorado River. Scale, 1-40000. P, Paria Creek; C, Colorado River; 1, Trias sandstone; 2, Shinarump conglomerate ; 3, Aubrey limestone. fault, was due to the fracture of the sandstone along the anticlinal flexure, and not to the channel afforded by the synclinal trough adjacent to it. South of the river the survival of the synclinal flexure is even more remark- able, for it marks the limit of the denudation of the Trias for many miles, (see Figs. 26 and 28.) The upturned sandstone beds rise higher than their horizontal prolongation, and constitute a persistent rim or parapet along the edge of the Triassic Plateau. It will be observed that the strata for some distance west of the fold are inclined to the east, and at the east are nearly horizontal, so that they include a gentle synclinal. An equally gentle and broad synclinal was noted by Dr. Newberry on the Colorado Chiquito, about one hundred miles distant, (Geology of Ives’s Expedition, p. 77,) and in the line of direction, south 15° east, given by the Paria fold, and the presumption is strong that the two coincide. The Kaibab Plateau was seen continuously from the Colorado River north to the neighborhood of Paria settlement, where its easterly fold inter- sects Paria Creek. At that point the fold is quite abrupt, and denudation THE COLORADO PLATEAU SYSTEM. 53 has left the inclined Triassic sandstone in an acute ridge, precisely similar to the one which marks the Paria fold south of the Colorado. The section (Fig. 29 a) cuts a few miles north of this, and shows the relation of the drainage lines to the flexed Valley lies in the mo- noclinal between them. Further south the valley - grows slowly broader, and finally opens into a broad plain, floored by the Car- TEEN ZZ —<—___§ spf boniferous, and stretching to the Colorado. Ten miles south of the cross- line represented in Fig. 29b, the line of fault, on the eastern side of the plateau, forks, producing the general structure shown in Fig. 29 ¢. The total displacement at the same time increases, and the folds are finally replaced by fractures near the Colorado. TITTTIT LITT TT 7 rs strata. The western fold _ | Pomither 2's & is either absent or very $2 | : : . Seis a o slight at this point, and S~ 7 ol the plateau is an unsym- FF. @ : * ye mB S metricanticlinal. Twenty Sees no. miles further south, where 3 2 2 the next section of the £2 plateau was obtained, it = 5 2 28 hasitstypical profile. The Sue . i=} cherty limestone atthe top £2 = of the Carboniferous is its 3% 8 ; oe floor, and descends in un- * ;, Me aes ruptured folds tothe plains = ® 09 on either side, (Fig. 290.) =~ At the east the marls and == ba sandstones of the Trias 23 a oP > overlie it,and House Rock 2 2 ee = 3 eae=s = =a £8 2y ° SG = ke) a= or 2% Fh = Fe "Son 8 Sci yooy osnoy rvou ‘gq {quomopyjog viaeg Jo Yy10U sol AVoJ & ‘Dv LEPTITITFITI IZ IIIT ZT 7 TITTTTITT7 54 GEOLOGY. Along Kanab Canon, apparently the cause of its general rectilinear course, is a simple folded fault, of about 200 feet drop. The two faults next in order I did not visit, but they have been laid down on our map by Mr. Thompson, of the topographical order, and beyond it the Paleozoic strata rest against the i 2 corps. On the direct line between the Hurricane fault os 2 and the mouth of the Grand Cation we made no survey, ‘ = but, from the absence of faults along the Grand Canon Y ae in that neighborhood, it is to be presumed that no con- ig E © siderable dislocations are omitted from the section. z 5 At the mouth of the Grand Cafion occurs the most . E profound dislocation of all. The lower wall of the sepa- Z 5 rated rocks is beyond the possibility of examination; but i a from an inspection of the dip, as given in the accom- 2 .-2 panying section, it will be seen that the vertical displace- ment cannot be less than 5,000 feet, and is probably Z 2 twice as great. Another fault succeeds this in close = S uplifted crystalline rocks of the Virgin range, which terminate in this direction the Plateau System. A number of scattered observations of faults, whose precise relation to the system was not established, need not be recorded; but I will describe in this place a Base line=sea level. Aubrey group; 2, Red Wall group; 3, Tonto group; 4, Archean. single one, to which I shall have future occasion to refer. ‘It was observed at the mouth of Diamond Creek, and may possibly be found identical or confluent with the Hurricane fault. It trends north 25° east, and coincides -- with the course of the Colorado immediately above the river level. 1 southward bend at which Diamond Creek enters, as well as with the valley through which the Colorado is Aubrey Cliff here approached from the south. The observed sec- tions all exhibit dislocation of about 600 feet, by frac- ture, (Fig. 31.) , The direction given to planes of fracture in the sketches of faults pre- Tia. 30.—Section of the Grand Wash fault as exhibited by the gorges of the Colorado. sented in the preceding pages are, for the most part, hypothetical. Lines THE COLORADO PLATEAU SYSTEM. 5D of fracture are apt to be covered by débris, so that they cannot readily be noted with precision, but in a number of instances, especially along the cations of the Colorado, I was enabled to see them perfectly revealed, and in every such case I found their planes vertical. In the case of the folds the vertical movement was possibly, or even probably, accompanied by some Sy / pl Ny aI LONG ——— Fig. 31.—(a-d.) Sections of Diamond Creek fault: a, at the mouth of Diamond Creek; 8, c, and d, at points on the Dry Cation which join that of Diamond Creek near its mouth. Scale, 1-72000. Base line=sea level. D, Diamond Creek: C, Dry Cation. horizontal movement of the strata, resulting in a slight diminution of the transverse diameter of the faulted region, but it is impossible, in the light of the convertibility of folded and fractured faults, to suppose that the verti- cal movements have been caused by lateral pressure applied to the strata in 56 GEOLOGY. which they are manifested. Whatever the place and mode of the remote cause, the immediate acts vertically and from some position beneath the strata we are able to examine. The flexures of strata in the folded faults are not accompanied by metamorphism; no lithological differences were detected between the dis- turbed and undisturbed portions of the strata. The amount of flexure sustained without fracture at any point we might assume, a priori, to depend on the nature of the rocks and the rate of movement. As a matter of fact, the most perfect arches are found in limestones and very calcareous sandstones, but they are not abruptly bent without partial rupture. Along the margins of the Kaibab Plateau, which afford the best examples, the Upper Carboniferous limestone has a convex curvature of from two to three miles’ radius. In the massive sandstones (freestones) of the Trias, I saw but a single instance of anticlinal curva- ture—at the north end of the Kaibab Plateau—and in that the convex- ity, though sufficient to demonstrate their flexibility, is very slight. In the synclinal curves of the Paria and East Kaibab folds, the sandstone is seamed throughout, as though it had been crushed and re-united, like the bars of ice in Professor Tyndall’s celebrated experiments on regelation. In the Sevier Valley fault, the rigidity of the Triassic sandstones appears to have determined the fracture along Long Valley, while the overlying Cretaceous shales were bent. In Figure 25, I have drawn what I imagine to be the re- lation of the two beds, although it is impossible to prove it by ocular dem- onstration. I see no reason why, regarding the phenomena as the results of a slow-acting force, we may not suppose that in depth, as well as longi- tudinally, the relation and alternation of fractures and flexures will depend on the nature and condition of the beds affected. That we must regard the phenomena as of slow production, no one can doubt, who considers that they include the curvature, through an are of fifteen or twenty degrees, of a massive sandstone 1,000 feet thick. RECAPITULATION OF FACTS IN REGARD TO THE COLORADO PLATEAU SYSTEM. The Colorado Plateau is subdivided in the area examined by a system of trausverse—east and west—cliffs, marking limits of successive strata. BORDER LAND BETWEEN RANGES AND PLATEAUS. 57 It is further subdivided by longitudinal—north and south—cliffs, pro- duced by faults. These faults are of great longitudinal extent, and of vertical, or nearly vertical, throw. They are manifested indifferently by fractures and by flexures of the visible strata. They exhibit system: By general parallelism with subequal intervals ; By uniformity in direction of throw through broad areas ; By symmetrical disposition about the Kaibab Plateau. The force or forces that have produced them are hence believed to be deep-seated, and uniform in kind and phase over large areas. SECTION. IIT. THE BORDER LAND BETWEEN THE RANGES AND THE PLATEAUS. Broad as is the distinction between the two provinces we have de- scribed, it is no easy task to define their common boundary, for here, as everywhere in nature, there is an interlocking of characteristics along the borders, and features regarded at first as crucial lose their significance with the extension of observation. If we begin our examination in the latitude of Provo, Utah, we find in the Wahsatch Mountains a perfect boundary. The country at the east is tabular, and composed of little disturbed strata of Cretaceous and Tertiary deposition, beneath which are buried disturbed strata of greater age, and at the west are narrow mountain ridges of greatly disturbed Pre-cretaceous strata, alternating with desert valleys. The sea in which were accumulated the Cretaceous sediments was limited by this Great Range. The topographical distinction of plateau and ridge, that arrests the attention of every observer, is thus coupled with a great fact of geological history, and it is easy to conceive that in mapping the plateau, we shall map the shore of the Cretaceous sea—that the presence or absence of Cretaceous rocks will guide us in assigning limits to the plateau at other points. If, however, we next examine the margin in the vicinity of Prescott, Arizona, a new element is introduced. The distinction of table and ridge is equally pronounced; but the boundary, instead of a mountain range, is the valley LAST oe aa, Pre-cretaceous rocks ; b, Post-jurassic rocks; O, Cedar Valley; ZL, Lake range; U, Utah Valley; WW, Wahsatch range. Scale, 1-405600. Base line= sea-level. IG. 32.—Generalized section of the Cretaceous shore, near Provo, Utah. GEOLOGY. of the Rio Verde, and the same Carboniferous strata that con- stitute the table at the northeast, re-appear, with some inclina- tion, in the first mountain ridge. The limit of the plateau now coincides with the limit of a great Post-carboniferous disturbance, that may or may not have preceded the Cretaceous period, and has no ascertainable relation to the Cretaceous sea. The consideration of the phenomena presented in these and other localities, leads to the conclusion that the Plateau is not a unit in history and origin, and that the only criterion by which it can be distinguished from the Range country, is the original superficial one of table and ridge. The plateau area has in part been longer and later submerged than adjacent regions, and in part exempted from the action of forces that threw up mountain ridges along its borders. It has not, however, been entirely exempt, and, differing from the Basin Range region only in the degree of disturbance, has not an absolute boundary. With this preliminary understanding, we will pass in rapid review the border land between the two provinces. In the statement above, that the Wahsatch marks locally the shore of the Cretaceous sea, the story is but half told. The Cretaceous and Tertiary deposits, which rest against its eastern flank, and which have no counterpart in Utah Valley, are many thousand feet higher than that valley. In explanation of this, we cannot suppose for a moment that the mountain was an impassable barrier to the ancient sea. Not only is the local drainage of the plateau now directly across the range—via the deep gorges of Provo River and Spanish Fork—to Utah Valley, but the ancient Wahsatch ridge terminates abruptly southward in Mount Nebo, and leaves open communication between Utah Valley and the Tertiary basin. The plain mean ing of the absence of the later strata in that valley and the great area west of it, is that these regions were above water at the time of their deposition. The Wahsatch and the country immediately east of it have been elevated, relatively to the BORDER LAND BETWEEN RANGES AND PLATEAUS. 59 . adjacent portion of the Great Basin, not less than 4,000 feet since the drainage of the great Tertiary lake. Concurrent with this general elevation, the plateau has been ridged by the formation of the system of faults described in the last section, and the lines of these later disturbances not merely run parallel to those of the Jurassic upheaval, but in places actually coincide with them. The Wahsatch range affords a case in point. South of Mount Nebo it is prolonged, with reduced proportions, as far as Gunnison; but the constituent strata are Tertiary instead of Paleozoic. The first elevation of the main range has been ascertained by King to have oceurred at the close of the Jurassic period,* and we here find evidence that it was again lifted after the deposition of the lacustrine strata of the Eocene. Another example is afforded by the Pahvan range, which may, perhaps, be con- sidered a southward extension of the Oquirrh. South of the great bend of the Sevier River it begins to show Tertiary (and perhaps Mesozoic) strata on its eastern flank, and near Holden, Fillmore, and Corn Creek they form the entire range, except the western foot-hills, resting unconformably upon Paleozoic rocks that were greatly tilted and eroded before ‘ol0z0a[eq ‘a f4snovovjor_ ‘q { Aretsay, ‘v ‘OYVT IVS WOT JO [OAe—oul] ost "QOOPPI-T ‘olwog “YRxH ‘orow]T, savou ‘osurr uvayeg Jo woyoog—eg “O1T their deposition. From Fillmore south their dip is uniformly eastward, correspondent to that exhibited in the successive parallel ridges at the east, until, a little beyond Corn Creek, they are lost to view beneath the great lava-field of the Sevier. The range is at this point the most westerly of the ridges bearing Tertiary deposits, but in the vicinity of Cedar City, where it re-appears from under the lava, the Tertiary passes beyond it to the Iron Mountain and Pine Valley Ranges. Throughout this region, from Mount Nebo to the Arizona line, there is a graduated mingling of characters, completely bridg- ing over the interval from the plateaus on one side to the ranges on the other. *Geology of the Fortieth Parallel, vol. iii, p. 3. 60 GEOLOGY. In Arizona the change is more abrupt. The plateau edge is a mesa of Carboniferous limestone, (chiefly the Aubrey limestone, but in part the Red Wall,) and the nearest Basin Range bears on its flanks these beds (or the Tonto sandstone) inclined toward the plateau. The valleys between are for the most part monoclinals, floored by the Tonto group, and contain the headwaters of Bill Williams Fork of the Colorado, and of the Verde and Tonto Creek, tributaries of the Salt River. The Grand Wash and the pro- longation of the same valley south of the Colorado occupy a pseudo- monoclinal formed by one of the great north and south faults, (Fig. 30.) About Camp Apache is an exceptional tract, drained by the upper tribu- taries of the Salt River—the White Mountains, Carrizo, and Cibicu—be- longing properly to the plateau, but deeply scored in every direction by canons, resulting from local conditions of denudation, wrought by lava- flows, an account of which is given in the report of Mr. Marvine. In brief, we may say that, as the Basin Ranges and Plateaus defy abso- lute definition, their common boundary must be left indefinite, and that the Jurassic and Tertiary systems of upheaval, coinciding in character and trend, can be locally discriminated only in the presence of intervening de- posits. SECTION IV. GENERAL CONSIDERATIONS. It remains to colligate the phenomena of the two provinces, and con- sider their relation to the general study of orology. We have already been led to conclude that the forces which have pro- duced the Basin Ranges were uniform in character over large areas, and in horizontal direction over minor, but still considerable, areas; that they have produced parallel ranges by nearly vertical upheaval; and that they were deep-seated. We have reached the same conclusions in regard to the forces which have produced the conjoint system of faults and ridges in the Colorado Plateau. We have also seen that the loci of the latter forces are in part coincident with those of the former. Anda single short step brings us to GENERAL CONSIDERATIONS. 61 the important conclusion that the forces were identical, (except in time and distribution;) that the whole phenomena belong to one great system of mountain formation, of which the ranges exemplify advanced, and the plateau faults the initial, stages. If this be granted, as I think it must, then it is impossible to overestimate the advantages of this field for the study of what may be called the embryology of mountain building. In it can be found differentiated the simplest initiatory phenomena, not obscured, but rather exposed, by denudation, and the process can be followed from step to step, until the complicated results of successive dislocations and erosions baffle analysis. The field is a broad one and its study has but begun; but with its progress I conceive there will accrue to the science of orographic geology a more valuable body of geological data than has been added since the Messrs. Rogers developed the structure of the Appalachians. Of late years the most important contributions have come from the physicists, and in their scales have been weighed the old theories of geologists. Here will be an opportunity to compare the speculations of the physicists with new geological data. The Appalachian mountain system, as the best studied great system— at least of those which exhibit unity of structure—has formed the geological basis of many theoretical structures, although, as Professor Whitney has pointed out, it is rather exceptional than typical in its character. The sys- tem we have described resembles it in the absence of any great central axis and in the general tendency to uniformity throughout, but differs widely in other respects. In the Appalachians corrugation has been produced com- monly by folding, exceptionally by faulting; in the Basin Ranges, com- monly by faulting, exceptionally by flexure. The regular alternation of curved synclinals and anticlinals is contrasted with rigid bodies of inclined strata, bounded by parallel faults. ‘The former demand the assumption of great horizontal diminution of the space covered by the disturbed strata, and suggest lateral pressure as the immediate force concerned; the latter involve little horizontal diminution, and suggest the application of vertical pressure from below. Almost no eruptive rocks occur with the former; massive eruptions and volcanoes abound among the latter, and are intimately associated with them. 62 GEOLOGY. To attempt the reconciliation of these antithetical phenomena is pre- mature, before the characters of the Basin Ranges shall have received more thorough study than has been possible for us; and I do not desire to under- take here a discussion of theoretical orology, but I cannot forbear a brief suggestion before leaving the subject. It is, that in the case of the Appalachians the primary phenomena are superficial; and in that of the Basin Ranges they are deep-seated, the superficial being secondary; that such a force as has crowded together the strata of the Appalachians—what- ever may have been its source—has acted in the Ranges on some portion of the earth’s crust beneath the immediate surface ; and the upper strata, by continually adapting themselves, under gravity, to the inequalities of the lower, have assumed the forms we see. Such a hypothesis, assigning to subterranean determination the position and direction of lines of uplift in the Range System, and leaving the character of the superficial phenomena to depend on the character and condition of the superficial materials, accords well with many of the observed facts, and especially with the persistence of ridges where structures are changed. It supposes that a ridge, created below, and slowly upheaving the superposed strata, would find them at one point coherent and flexible, and there produce an anticlinal; at another hard and rigid, and there uplift a fractured monoclinal; at a third seamed and incoherent, and there produce a pseudo-anticlinal, like that of the Amargosa Range. OHA PTR = [T,. VALLEYS. CANONS. EROSION. In the region of the Basin Ranges the valleys are residual; the mountains were uplifted in parallel lines, and the intervening troughs remained as valleys. In the typical- Plateau country the reverse holds good; the valleys have been formed by erosion, and the tables are residual. Transporting agencies are still deepening the latter valleys, but have for a long time been engaged in filling the former. Their general classification thus corresponds very nearly with that of the mountains, and it will be convenient to describe them in the same order. There is no evidence that the Range country has been beneath the ocean since the close of the Jurassic period, though it is impossible to say that the sea has not had access to some of its valleys since that time. Then began such of its ranges as had not earlier appeared, and since then they have been subjected to the unceasing play of atmospheric erosive agents, wearing away their summits, furrowing their flanks, and conveying their substance to the intervening valleys. A part of the eroded material— possibly the larger part—has been transported beyond the limits of the Range System, and contributed to the Cretaceous and Tertiary sediments at the east and west. Of the detritus that remained in the valleys, a portion may have been spread by the waters of estuaries connected with the Cretaceous sea, a portion was received by local bodies of fresh water, and the remainder has received such subaerial distribution as is now prevalent over the major part of the area. What may have been the original altitude of the ranges we have no means of knowing, but there is evidence, along the margin of the system, that their elevation was not all accomplished at once, and it is not impossible that progressive elevation and denudation, as they have opposed, have also measurably counterbalanced each other. Volcanic rocks have made important contributions to the filling of the val- 63 64 GEOLOGY. leys, both directly by floods of lava, and indirectly by their detritus; and they have been thrown as barriers across valleys, partitioning them off into minor basins. ab. Mountain foot-slope. aa. Alkali flat or playa. Fic. 34.—General section of an undrained valley. a. Arroyo. ab, oot-slope. Fa. 35.—General section of « drained valley. In this way the valleys have become floored by detritus of great and unprobed depth as universally as they are walled by mountain ridges. Under the existing climate, many valleys and groups of valleys are undrained. In the most arid the meager rain-fall sinks into the porous soil, from which it is slowly evaporated by permeating air. On rare occasions a surplus of water accumulates in the lowest depression, and there evaporates on the surface, depositing its fine sediment and dissolved minerals, and producing a level, lake-like plain, the familiar ‘alkali flat,” smooth and hard, if mechanical sediments prevail, but often pulveru- lent or pasty from the presence of efflorescent or hygro- scopic salts. In more humid basins permanent streams are maintained, and the evaporation plain is replaced by a lake, beneath which the fine sediments are de- posited, and in which the soluble salts are concentrated. The best watered regions send rivers to the ocean. Of the undrained valleys the cross-profile is broadly U-shaped. From the base of the mountain on either side stretches a long talus, or foot-slope, comparatively steep at first, but gradually losing its inclination, and finally merging in the evaporation plain. From the drained valleys the plain is absent and the foot-slopes meet in V-form. The débris of the mountain is brought to its margin in gorges or caiions, from the mouths of which it is spread in broad, low talus-cones, which make up the foot-slope. The stream that flows from the caion, whether transient or perennial, distributes the detritus over the cone by shifting its bed from time to time as the sediments clog it. As the cafion wears deeper at its mouth, and the stream discharges at a lower level, the upper portion of the cone is excavated and a new one VALLEYS. CANONS. EROSION. 65 modeled with lower apex and lower grade. In a general way, the coarsest material remains nearest the mountain, and the finer is farther removed, but the sorting is very imperfect, and heterogeneity is a characteristic of the gravels. Where limestone abounds in the constituent pebbles, they are commonly cemented, a little below the surface, into a firm conglomerate. The principal deserts of the province are relatively depressed regions, marked by excessive accumulations of detritus, which have so filled the valleys as to connect them in a continuous plain, beneath which the minor ranges are completely buried, and through which the peaks of the more lofty jut as islands. In the Colorado desert, Mr. Blake and Dr. Newberry found abundant evidence of the agency of lacustrine waters in the formation of the plain,* and the Gila Desert, which communicates with it, is floored by a nearly level plain of gravel and sand, from which the insular ridges—“ lost mountains ”—spring with an abruptness that testifies to wave action along their bases. No persistent mountain chain divides the latter plain from the ocean, and it rises but little above the sea level. There can be little doubt that it has been covered at some time since the creation of the mountain system by the waters of an estuary, and that the ocean level has been the efficient barrier to the further transportation of the detritus here accumu- lated; but of its chronology nothing definite is at present known. The Great Salt Lake desert occupies a depressed portion of the Range area, due to broad, general undulations, that have no discernible relation to the orographic corrugation of the surface, except that they co-exist, as do a long ground swell and the wavelets of a rising breeze. East and west of the desert the ascents culminate in the Wahsatch and Humboldt Mountains. Northward a general elevation of the ranges and intervening valleys along parallels 43° and 43° 30’ separates the plain of the Upper Snake River. One hundred and fifty miles farther south a similar line of uplands, includ- ing the Onaqui, Thomas, House, and other ranges, divides the Salt Lake from the Sevier desert. The lowest part of the included depression has been filled with a sea of detritus, until some of its ranges are completely submerged and others protrude only insular buttes to mark where they are * Pac. R. R. Repts., vol. v, Geol. Rept., by W. P. Blake, p. 235. Colorado Expedition, Geol. Rept., by J. 8. Newberry, p. 17. . 5ws 66 GEOLOGY. sunk. If these hidden mountains rise as high above their bases as do their neighbors on the rim of the basin, we may, by comparing summits with summits, learn something of the relative depression of the rocky bottom of the basin below its margin; and it would appear, judged in this manner, to be not less than 4,000 feet. And, on the same supposition, the desert sedi- ments, which, before burying the mountain ridges, have filled the inter- mediate valleys, may have a maximum thickness of 5,000 or 6,000 feet. Their upper surface, water-laid and smooth, is the broad floor of the desert, from which arms stretch north and south, between the fringing mountains. In longitude the plain measures a little over a hundred miles, and in lati- tude a little less. Its general level is about 4,200 feet above the ocean, and Great Salt Lake probably occupies its greatest depression, though lying close to its eastern border. Its surface material is a fine, adhesive, abso- lutely sterile clay, charged with chloride of sodium and other soluble salts, the deposit from the last expansion of the waters of the lake, an expansion so recent that the beach-lines formed at its culmination and during its slow subsidence are perfectly preserved on the shores of the desert. In another chapter these phenomena will receive fuller description, and attention will be called to their relation to the glacial epoch. The eccentric position of the lake is evidence of the novelty of the present relation of altitudes of different portions of the plain, which is far from an equilibrium. Nearly the whole present increment to the desert floor comes from beyond the Wahsatch Mountains, and is deposited in the deltas of the Jordan, Weber, and Bear rivers, on the eastern margin of the lake. Since the lake has no outlet, but parts with its surplus by evapora- tion, its area rather than its level tends to constancy; and, as the eastern shore increases, the water will rise, pari passu, and encroach on the western. The continuation of this process, if there is no counter influence, such as a secular depression of the lake basin, will push the water, in a few thousand years, to the western side of the desert. The Sevier Desert is of comparatively small extent, and is less sterile and arid. The Sevier River runs completely across it from northeast to southwest, and carries enough water to maintain a lake with one-tenth the evaporation surface of Great Salt Lake. The eastern portion of the plain VALLEYS. CANONS. EROSION. 67 is floored with basalt, in the hollows of which are a number of fresh and brackish lakes. The altitude of its general surface above the ocean is 5,000 feet, and of Sevier Lake, which occupies its greatest depression, 4,600 feet. The water of the lake is charged with salt, but in less degree than that of Great Salt Lake. No living thing was seen in it save Artemia, but the larva cases of dipterous insects floated on the surface and lay heaped upon the beach. Along the storm line, too, are dead fishes and fluviatile shells, and beaver-gnawed willows, all of which have floated from the river. The odor of these decaying organisms, though very like the ‘‘ perfume of the sea,” is over strong, and renders the shore as repulsive as it is desolate. A portion of the valleys of the Plateau country, and especially those of the upper Sevier, are, like the troughs of the Range region, structural, and lie between the monoclinal ridges produced by the system of faults described in the last chapter ; the remainder are valleys of erosion, and include the canons for which the region is renowned. The cations of the Colorado and of its tributaries, and the country which they intersect, are unsurpassed as a field for the study of river de- nudation. Not merely do they exhibit the grandest and most impressive results, but they show the agent by which they have been wrought, still in vigorous activity; and the conditions that have guided denudation and de- termined the resultant forms, are there so little complicated that they may be differentiated and analyzed. At the mouth of Paria Creek, the Colorado leaves the sandstones of the Trias, through which it has meandered for many miles in a narrow caion, emerges for a short space into full sunlight, while it crosses the marls at the base of that formation, and then begins its descent into the Carboniferous and underlying rocks, which wall it in through Marble and Grand Canons. In these gorges the river has no flood-plain. It is a well recognized fact in the natural history of rivers that their first work of erosion, where they have rapid fall, is upon their beds, and that it is only when they have so far reduced their grades as to greatly diminish their transporting and cut- ting power, that they begin wearing their banks and widening their chan- nels, so as to render flood-plains possible. The Colorado is here devoted to the deepening of its valley, and occupies its whole width from wall to 68 GEOLOGY. wall so completely that where the shore is of massive rock it is often diffi- cult to find foot-hold at the water’s edge. Were the entire wall from top to base of durable rock the chasm would indeed be as gloomily abysmal as it has been sometimes represented,* but there is an alternation of hard and soft strata, that serves to terrace the cliffs on a grand scale. In every profile of the canton the positions of the hard, massive beds are marked by precipices, and of the soft by slopes. With infinite slowness the latter are disintegrated by the action of the weather, the former are undermined, and the upper cliffs are caused to recede from the margin of the river. The stream in descending through the strata is walled at its edge alternately by cliffs and slopes, and each cliff begins its recession when the river, in deep- ening its channel, cuts below it into the softer strata. Where the cations are deepest and oldest, there they are broadest at top; and the recession of the uppermost terrace measures the same interval of time as does the depth of the cutting at the same place. In each of the accompanying sections of the cafion the widths and depths are given in the same scale, so as to present, as nearly as possible, the true proportions of the chasms. In Figure 36 the canon proper is con- tained by the Aubrey limestone, and is a simple sluice, seven or eight hun- dred feet deep, with vertical walls. While the river has been cutting this narrow slot in the hard limestone, atmospheric denudation, working on the Trias marls, and undermining the Trias sandstone, (1,) has driven back the escarpment of the latter four miles from one brink, and still farther from the other. So soon as the limestone is passed, and the gypsiferous sand- stone of the Aubrey reached, the undermining process begins at a lower level and the gorge opens to the form represented in Figure 37 and Plate IT. At Kanab Creek, Figure 38, the Aubrey limestone has receded so far as to be visible from the water only at angles of the caton, and the immediate *The difficulty of presenting in a sketch the proper relation of vertical and horizontal spaces, in illustration of which Humboldt’s drawings of volcanic cones have been so often quoted, is conspicuously exhibited in the representations of the Grand Cation, given in Plates VI and IX of Lientenant Ives’ Col- orado report. The inexorable camera has sinee been brought to bear on the scene depicted in Plate VI, and demonstrates that the cliff of granite, there adjacent to the water, and which presents in the en- graving an acclivity of about 80°, has in nature an inclination of no more than 40°. A somewhat similar allowance is needed in the interpretation of the representation of the Black Cation in the same volume. (Plate V.) 69 EROSION. CANONS. VALLEYS. At Diamond Creek, Figure 39, the terrace wall is of Red-wall limestone.* at the base of the Aubrey has expanded to a width of three or four miles, and ale, d by the soft Tonto sh ne turn underm is in the Red-wall limestone LENG NGL VIZ. PZ lEMAX Se ip EG WINE ZEISS LILIA NIN YIM GAG AD) WY Figs. 36-39. Sections of Marble and Grand Cafions. Scale, 1-72000, Base line—sea level. Fig. 36, Marble Cation, near the mouth of Paria Creek; Fig. 37, Marble Cation, ten miles lower; Fig. 38, Grand Canon, at mouth of Kanab Creek; Fig. 39, Grand Cafion, at mouth of Diamond Creek. 1, Trias sandstone; 2, Upper Trias marls; 3, Shinarump conglomerate and lower marls; 4, Aubrey limestone; 5 and 6, Aubrey sandstones; 7, Red-wall limestone; 8, Tonto group; 9, granite and schists. It chances that the sections which I am able to give from my own observations form an.orderly t granite. is poin at th © ce the river flows in Archeean rock *The definition of this and other terms pertaining to the stratigraphy will be found in Chapter VI. 70 GEOLOGY. suite, in which the depth and magnitude of the erosion has an apparent relation to the descent of the river, being least in its upper course, and suc- cessively greater at lower points. The relation, however, is not constant, but is modified by the system of faults. If the reader will refer to Figure 26, which gives a section parallel in the main to this portion of the river, he will readily perceive the cause of the modification. The descent of the water is from right to left, and the line of section crosses the river at MV, W, and J. The cafion sections may be referred to this one as follows: Figure 36, above 7; Figure 37, at I; Figure 38, at C; and Figure 39, below H. Between Mand C the plateau attains its greatest height, and the canon its profoundest depth, cutting farther into the Archean rocks than at Dia- mond Creek, and giving a maximum of erosion in the middle, instead of the lower end of the gorge. In the vicinity of the eastern fault of the Kaibab Plateau (() Professor Powell found the gorge so broadly opened at bottom, as to lead him to distinguish the narrows above and below by the separate titles of Marble Caton and Grand Canon. At Kanab Creek, the highest point at which I entered the Grand Canon, the river runs in the upper part of the Tonto shale, here of firm texture. In Plate VII, which pictures it there, the walls at right and left are of limestone, including the Red Wall and Marbled, and they are capped by the lower Aubrey sandstone, which appears in the middle distance, while the most distant mesa shows the escarpment of the Aubrey limestone. From the mouth of Diamond Creek to the end of the Grand Cafion, a distance of forty miles, the river washes only Archzean granites and schists, and the overlying Tonto sandstone; and to this portion of the canon my own observations of its ziver-action were chiefly confined. With the boat party, headed by Lieutenant Wheeler, I ascended this portion of the gorge, and had my attention especially drawn to the rapids and other phenomena of erosion and transportation.* The river in this part of its course has two functions—of transportation * Besides the opportunities afforded by this boat-excursion, I entered the Grand Cafion at Kanab Creek, and examined Marble Cafion from above, near the Paria. Mr. Gilbert Thompson, of our topo- grapbical corps, kindly made some observations for me in the vicinity of the Uinkaret Mountains and Kaibab Plateau; and Mr. Bell’s photographs from the former locality have afforded geological information. VALLEYS. CANONS. EROSION. 71 and erosion—which it will be convenient to distinguish, though they are intimately interdependent. The transported material is derived from several sources, That abraded from the bottom of the cafon is too insignificant in amount to demand more than mention. What reaches the bottom from the immediate sides is of greater volume, but is chiefly noteworthy because it includes large masses which locally obstruct the channel and produce some of the most violent rapids. Far more important and, in the work it entails on the stream, of the greatest importance is the detritus introduced through tributary cafions. Many of these are of very rapid fall, and are occasionally traversed by powerful torrents, which sweep down bowlders of great size—in some instances 10 or 15 feet in diameter—and heap them in the main canon in dams, that must often be of great depth. Over each of these the water finds passage at the edge opposite the tributary, and descends the lower slope with swift current and broken surface; and thus arise the great majority of the rapids. To roll, jostle, break, and finally grind up and remove these bowlders is the task—perhaps the chief task—of the river, and until it removes them it can perform no work on the solid rock which underlies. In the V-form of the cafion, and in the fact, shortly to be con- sidered, that the river does in places cross a bottom of bed-rock, there is evidence that downward erosion has not ceased; and we must suppose that, in the current cycle of events within the gorge, there are times when each of these dams in turn is removed. The torrents that bring and the torrents that destroy them depend on the rains of regions widely separated, and the former at least are notoriously variable; so that, while the dams will recur at the same localities and with the same characters, they cannot be regarded as strictly permanent.* _ Yet another agent brings into Marble and Grand Canons an amount of detritus even greater than do those that have been enumerated ; namely, the *No observations have been made on their fluctuations in the Grand Cation; but in Black Caiion, where rapids bear the same relation to side washes, we have evidence of a change. Lieutenant Ives, ascending in 1858, encountered a rapid of such violence that he dignified it with a name, and mentioned it in bis hydrographic report as the most serious obstruction to navigation in the caiion; but in 1871, with the same stage of water, I was unable, even-with the aid of his map, to distinguish the “ Roaring Rapid,” so nearly equal in importance were several rifts in that vicinity. q2 GEOLOGY. river itself. From its thousand sources to the ocean the Colorado has no still reservoir to accumulate its sediment, and all that its upper waters detach must find its way, soon or late, through these cafons. The greater part of this material is reduced to the form of fine sand and mud before it enters, but some pebbles of tough crystalline rocks from remote volcanic regions are included. At no season is the water free from the red mud whence the stream derives its name, and the amount of detritus conveyed in time of freshet must be enormous. This brings us to the consideration of the erosion performed by the river ; for the tool by which it is accomplished is this very sand and mud, together with that produced by the trituration of rocks within the canon. Hurried on by the swift water, it gnaws away whatever it touches. Nothing can resist the incessant impact of the fine siliceous particles, and the whole river-bottom, including both solid rock and bowlders, bears indisputable testimony to the mightiness of their work. Every exposed surface is pol- ished at least, and the most salient faces are deeply and beautifully carved. Plate X gives an example of this sculpture, in which the material wrought is a homogeneous, fine-grained limestone—the Marbled limestone of the strati- graphic series—and the carved face lay nearly horizontal, the current cross- ing it from left to right, as indicated by the arrow. The specimen represented was broken from a slab three or four feet in diameter, that lay on top of one of the bowlder dams, and is a fair type of the carving in homogeneous material. The concave facets, of which the surface is composed, appear to be of the nature of paraboloids of revolution, the apices of which are turned up stream. In rocks of less even texture the surfaces are correspondingly irregular, and the greatest variety of pattern is developed on rocks of irreg- ular form, which present faces at all angles to the current. The rapid erosion to which these gouged surfaces testify I am disposed to regard as exclusively—or almost exclusively—the work of the fine detri- tus, propelled by the water just as the sand of the sand-blast is propelled by air, and accomplishing its result on precisely the same principle. The most rapid cutting is doubtless executed by the coarser sand carried by freshets ; and the fine mud borne by quieter water, working in the same manner, but more delicately, produces the perfect polish that everywhere VALLEYS. CANONS. EROSION. 73 prevails. It is to be doubted whether pure water, or water with no mineral matter in mechanical suspension, has any appreciable erosive power. In the beds of streams of clear water, disintegration, if not due entirely to solu- tion, at least depends so largely upon it that the surfaces of calcareous pebbles are covered by spongy films marking the depth to which the removal of the most soluble matter has extended. Under the muddy Colorado, however, erosion is so much more rapid than solution, that no traces of the latter are to be seen upon the rock surfaces. We may assign to the direct action of the water the transportation of detritus, and the solution of calcite and other minerals, after trituration, but the actual rock excavation is accom- plished by means of the transported material. Besides the evidences of erosion already described, there are numerous pot-holes drilled in the bed-rock of the river. They occur in a variety of materials, but are best developed in granite and cognate massive rocks. They are not of great size, averaging only 12 or 15 inches in diameter, but in some places are so thickly disposed that they fairly adjoin over consider- able areas, to cross which one must step from crest to crest of the rocky partitions that divide them. In them are to be found the characteristic worn pebbles that have helped to bore them. On the steep river-walls were seen numerous natural sections of pot-holes, in places where the same vertical seam in the granite that at first determined their position, had finally cleaved away their outer walls, and left the inner fully exposed to view. In these sections are exhibted two type forms. The simplest is that of the chemists’ test-tube, a cylinder slightly flaring at top, and terminated at base by a hemi- spherical cup. In the other form a round Fic. 40.—Typical forms of pot-holes in boss or knob rises in the center of the basal the granite of the Grand Canon. cup, and gives an emarginate outline to the vertical section, as shown in the diagram. The explanation of this peculiarity is not difficult. The peb- bles-and sand that bore the pot-hole are controlled by two forces; the gyraiory motion of the water revolves them, and gives roundness to the 74 GEOLOGY. hole, and gravity keeps them at the bottom, and determines the vertical descent of the excavation. When the motion of the water is simply rotatory, centrifugal force will keep the grinding particles at the periphery of the base, and produce the emarginate form. Where, from the surging of the current above, much vertical movement of the water is combined with the rotation, the simpler form of bottom results.* In addition to the rapids caused by bowlder heaps at the mouths of side gorges, and those produced by rock masses fallen from the immediate walls of the cation, are others due to prominences of the solid bed, and upon them are displayed the finest river sculpture. At these points, cer- tainly, the deepening of the cafion is still in progress, and, though they make up but a small proportion of the entire canon bottom, they suffice to show that the torrent phase of the river is here not yet completed. There have been distinguished in rivers the torrent portion, in which the descent is comparatively rapid, and the bed is sinking by erosion into the subja- cent rock; the river proper, in which the bed holds a constant mean level, and erosion is diverted to the increase of the width of the valley; and the delta, in which the bed is rising by deposition. The river phase is distin- guished from the torrent by the presence of a flood plain, which commonly merges below with the delta plain. In the ordinary sequence of events, the delta slowly encroaches upon the river portion, and that upon the torrent. In the Lower Colorado there is an alternation of river and torrent condi-_ tions. The canals the river is cutting through the Virgin and Black ranges are far from complete, but they progress so slowly that the stream in the intermediate valleys, where it encounters nothing more obdurate than gravel, assumes the true river phase. Below the Black Canon there is the same alternation, but less pronounced, and an equilibrium has nearly been reached. *Tt is worthy of mention, in this connection, that the great ancient pot-holes near Cohoes Falls, New York, are all, so far as examined, spheroidal at bottom. They are grouped on a moulonnée surface, and are referred by Prof. L. Agassiz (quoted by Prof. J. Hall in the twenty-first report of the New York Regents, p. 105) to cascades falling through crevasses in a glacier. The views here advanced as to the origins of the different forms tend to confirm Professor Agassiz’s hypothesis. Moreover, the excavations produced by the Colorado, with its high-water depth of 50 to 100 feet, and descent of 5 to 20 feet to the mile, are, after making all allowance for the difference of rock, of the most insignificant size, as compared with the mighty cisterns of the Cohoes Plain. VALLEYS. CANONS. EROSION. 75 As the work of denudation in the Grand and Marble Canons progresses, and the river sinks deeper below the plateau, there will accompany a grad- ual diminution of the inclination of its bed, of the velocity of its current, ‘and, in consequence, of its erosive power, until finally it can no longer clear its bottom of introduced detritus, and, its downward progress being arrested, the widening of its channel will begin. Of the time that will elapse before this consummation we can form little conception, but it can hardly be less than that consumed in the excavation already accomplished, so slowly will the work proceed as it approaches completion. Of the time already consumed we may some time have an approximate estimate in years, for so rapidly does the sand carve away the rock, that I believe it perfectly feasible to ascertain its rate by observation, and, by considering what part of the rock-bed is exposed and what protected, to assign, within reasonable limits, the present rate of degradation of the canon. To pass from this to the average past rate would require the consideration of somewhat involved conditions, and the result would not be so satisfactory as that obtained from the secession of Niagara Falls, but it would be of great interest to obtain even a crude estimate in centuries of a period of time commencing, as I believe, before the close of the Tertiary age. Throughout the caftons there are no cataracts; that is to say, at no place does the river fall from a ledge of rock into a pool below. Professor Hall has shown that in the future of Niagara there will come a time when the fall can no longer be maintained by the undermining of the limestone from which it leaps and will be replaced by a rapid. In the Grand and Marble Cations this stage has been reached, and the whole descent of 1,600 feet accomplished entirely by rapids. The stratigraphic conditions to the formation of a cataract are indeed not wanting. The Cherty limestone near the mouth of Paria Creek is as massive as the Niagara limestone at Niagara; the underlying Aubrey beds are as soft as the Niagara shales, and their dip is up stream. So, too, with the great Red Wall limestone and the Tonto shales below. But the river passes the hard beds and the soft with almost equal pace. Of the tributaries of the Colorado, Paria Creek, Kanab Creek, and the principal forks of the Rio Virgen rise in the Tertiary and Cretaceous escarp- 76 GEOLOGY. ments, and descend southward through Jurassic and Triassic and (except Paria Creek) through Carboniferous strata. Kanab Creek alone has its geological descent uninterrupted; the others are intersected by folds, which cause them in portions of their courses to rise in the strata. The data are not at hand for a full description of either stream, but a few points will be noted especially pertaining to the phenomena of denudation. Paria Creek.—It has already been remarked, in speaking, in the last chapter, of the great flexed faults, that Paria Creek, near its mouth, follows the anticlinal portion of one of these double flexures. While my observa- tions were not sufficiently extended to place the matter beyond doubt, they tend to show that the flexure determined the course of the creek, and must itself have been of earlier origin. At its mouth the creek runs in the varie- gated shales at the base of the Trias, and has so far washed them away as to give space for a few acres of arable alluvium. By the undermining of the shale the cliffs of the superior sandstone are carried back so as to open between them a valley half a milein width. Ascending the stream-bed, how- ever, Lieutenant Marshall rose above the shale, and found himself walled in by vertical precipices of sandstone, of great height, between which the entire interval was frequently occupied by the stream. Thirty miles above, where the west fork of the creek crosses the same sandstone, (lifted by the East Kaibab fault,) a broader opening has been produced, and the canon walls are separated by a bottom several hundred feet in width. Kanab Creek traverses box cations in two portions of its course, the first where it intersects the Gray and Vermilion Cliffs, (Trias ;) the second, where it descends through the Carboniferous series to the Colorado. In the interval it crosses a broad plain, floored by the variegated marls. At ordi- nary stages the stream is in part subterranean, sinking in the sand of its bed, to re-appear when a ledge of rock rises to bar its way. Its general direction is remarkably straight, and is,in one part at least, determined by a fault, the throw of which is to the west, and does not exceed 200 feet. Traversing the same rocks, and intersecting the fault at a wide angle, are a system of parallel vertical joints, and the combined influence of these on the erosion of the Creek Canon has produced a curious and very interesting result. The fault is of the flexed order, and runs close to the east wall of VALLEYS. CANONS. EROSION. 77 the cation, the erosion appearing to have begun along its western or syn- clinal edge. In descending from the table, the stream encountered first a massive limestone, nearly 300 feet in thickness, then 150 feet of softer cal- careous and gypsiferous beds, and then a second heavy bed of limestone. Through the upper limestone the cation is about 500 yards broad, and of remarkably rectilinear course, the result apparently of its direct dependence on the straight fault; but, in wearing through the lower limestone, the stream has been greatly influenced by the joints, and follows them from side to side of the main valley, producing a narrow, serpentine cafion within a broad, straight one. The photograph, reproduced in Plate VI, was made for the purpose of exhibiting these features. The camera was placed near the base of the upper limestone, on the western side of the cation, and directed southward, or down stream. The fault, which would otherwise appear at the extreme left of the view, is concealed by the haze. Further south, the creek cuts down into the Aubrey shales, the limestone walls diverge, and the cation acquires the form represented in the view, Plate II, of Marble Canon. Still further, it descends through the Lower Aubrey sandstone and Red-Wall limestone to the Colorado, meandering in the latter bed through a defile so deep’ and narrow, that our photographer hardly found light enough to picture it. Its majestic gray walls, rising almost vertically toa height of more than 2,000 feet, impressed us more with their grandeur than their beauty, and we gladly exchanged them for a more open country, with a broader arch of sky. In its upper course, the east fork of the Virgin River follows the line of the great Sevier fault, and, though overhung at the east by a wall of Upper Trias sandstone, has opened its channel in the coal-measures of the Creta- ceous system. Restrained by the resistance of the sandstones through which _ it has cut its progress southward, it has found time to excavate, in the soft Cretaceous shales, a narrow, fertile valley, in which repose the secluded Mormon towns of Mount Carmel and Glendale, (see Fig. 25 &.) The north fork has, in a similar manner, opened a valley in the Creta- ceous, but too narrow for cultivation. From the foot of this valley to the hamlet of Little Zion, the stream traverses, in the most wonderful defile it has been my fortune to behold, the massive sandstones of the Gray and 78 GEOLOGY. Vermilion Cliffs, here combined in a single undistinguishable body, cer- tainly not less than 2,000 feet in depth. At the head of “The Narrows” the top of this bed is at the water’s edge; and, as the strata rise, and the stream descends southward, the height of the cafon-walls gradually ’ increases, until it includes the entire mass of sandstone. At the water’s edge the walls are perpendicular, but in the deeper parts they open out toward the top. As we entered and found our outlook of sky contracted—as we had never before seen it between caiion cliffs—I measured the aperture above, and found it 35°. We. had thought thisa == = minimum, but soon discovered our error. Nearer == /——— and nearer the walls approached, and our strip = —— of blue narrowed down to 20°, then 10°, and — at last was even intercepted by the overhanging . = SS == rocks. There was, perhaps, no point from which, SS ee neither forward nor backward, could we discover ——————_ a patch of sky, but many times our upward view was completely cut off by the interlocking of = the walls, which, remaining nearly parallel to LEE a each other, warped in and out-as they ascended. Sa |=. For a number of miles the bottom of the cleft EE EEE 30 feet in width ting fr 1 EEE Z Ze 22 averages eet in width, contracting frequently to 20, and in many places is entirely occupied SSS by the stream, even at its low stage. Near the head of the cafion it is covered by sand and bowlders of sandstone, worn and fallen from the walls, and these continue throughout; but ata the North Fork of the Virgin certain point a tributary gorge from the west Higen Beale, 27200: brings in basaltic bowlders from some extinct vol- cano on the mesa above, and they abound to the end of the gorge. The superior toughness of the basalt enables it to withstand the shocks that rap- idlv crush the sandstone, and, though its supply must be far less, its rounded bowlders almost exclusively pave the river-bed for many miles. The course of the gorge is exceedingly tortuous, and, though our general direction in traversing it was southward, we yet journeyed toward all points VALLEYS. CANONS. EROSION. 719 of the compass in turn, our view in advance being usually limited at a few rods’ distance by an angle. The side canons all partake of the character of the main, but, being worn by smaller streams, are narrower, and their bot- toms are of steeper grade. Many of them at their mouths are not cut so deep as the one we followed, and discharge at various heights above the river. These illustrate the perfect continuity and integrity, beneath the cation beds, of the sandstone that forms their walls—a continuity that can- not be seen in the main cation, since its bed is everywhere covered by detritus. As a monument of denudation this chasm is an example—and a peculiarly differentiated example—of downward erosion by sand-bearing water. The principle on which the cutting depends is almost identical with that of the marble-saw, but the sand grains, instead of being imbedded in rigid iron, are carried by a flexible stream of water. By gravity they have been held against the bottom of the cut, so that they should make it vertical, but the current has carried them, in places, against one side or the other, and so far modified the influence of gravity, that the cut undulates some- what in its vertical section, as well as in its horizontal. The diagram rep- resents an extreme but not exaggerated case of this departure from verti- cality, and, at the same time, shows the relation of the depth to the width of the cation, where it is narrowest. The form at top is necessarily hypo- thetical; from our subterranean position we could form little idea of it. Upon this line of section, the transition from the massive sandstone to the variegated marls below is gradual, leading to a slow opening out of the canon at its mouth; and the river in Little Zion Valley still flows between its beetling walls before passing finally beyond the limits of the sandstones. Diamond Creek.—At the mouth of Diamond Creek center four valleys of denudation, whose relation to the structure of the Plateau is very interesting. Two of these valleys are occupied by the Colorado and are portions of the Grand Cafion ; that is to say, the river turns here abruptly at a right angle, and its two courses appear to have been determined by distinct causes. The third valley is the cation cut by Diamond Creek, and is a prolonga- tion eastward of the lower course of the Colorado. The fourth is that of Peach Spring wash, and prolongs southward the upper course of the Col- orade. No perennial stream follows it to the river, and it is but twenty 80 GEOLOGY. miles in length; yet it affords an easy descent to the bottom of the Grand Cafion, and is entirely exempt from the precipices that render Diamond Creek and other cations impassable. It is, indeed, the only valley tributary to the Grand Canon, through which a wagon road can readily be made. This character, and its remarkable straightness—I refer to its general course, and not to its details—are due to the fact that it was primarily determined by a fault. On a preceding page may be found diagrams (Fig. 31) of this fault; its throw is to the west, and the amount of dislocation near the river is about six hundred feet. Its strike is north 25° east. For a few miles at least it is included in the upper course of the Grand Cajon, and, as I looked down Peach Spring wash, and commanded with my eye a long vista of the caton beyond, I was strongly impressed with the idea that the dis- . location which determined the one, had also marked out the other for a great distance. Later geographical determinations show that from the neighborhood of the Uinkaret Mountains to the mouth of Diamond Creek, a distance of thirty miles, the general direction of the canon is straight and coincident with the observed trend of the fault. If what now appears prob- able shall hereafter be demonstrated—that the cation for a long distance follows closely the line of faulting—the necessary deduction that the fault antedates the beginning of the cation will be an interesting addition to the chronology of the river. The identity in direction of Diamond Creek with the lower course of the Grand Camion is not a mere coincidence, but depends on their common relation to the Plateau structure. The Aubrey, Cliff, which crosses Arizona in a northwest direction, here intersects the Colorado. Since the general dip of the strata is to the north, and the escarpment is due merely to their unequal denudation, there lie, at the foot of the escarpment, a series of monoclinal valleys, of which the Tonto Basin, the Upper Verde Valley, and Aubrey Valley are examples. Diamond Creek runs, in like manner, parallel to the cliff, and differs from the others only in having excavated a deep gorge, which the low level of its discharge enabled it todo. The same Aubrey Cliff that follows its northern or northeastern margin re-appears be- yond the Colorado, and, for forty miles, bears the same relation to the lower course of the Grand Canon, leading to the belief that the stream was here RP MEU. da a H + RADO RIVE R 4 ee 4 My : me Lar, > ao be -* a : ‘a ‘ x ” : } e ‘ay g e oe) “ sf =f * Ate * + F + a ‘ . na, «3 Se viz S78. S 2 sé t « tint mS ° t 7 > aa .< 4 »~ . - me ‘. * tm E re = = “f @Fy= ae t Po — - “UNIVERSITY OF Pe “ The es ‘ % Sitae! + = Wi at ae Y U wh iN “ ¥ * a ’ wi. ? 2 es ta A ® “s Ndey ays Ck ine AgY ; UNOS af Se 2 iy 4 < es OTR a » mao, ' be : ws | a ood eae y MAS a pare by 2 row ve 2 hie adh Mee ok * ie! a ae ee he ey SE gmieal : =e as a am VALLEYS. CANONS. EROSION. guided, at the first, by the monoclinal valley, and that the Aubrey Cliff, as a topographical feature, is more ancient than the Grand Cajon. now rises from three to five miles back from the brink of the canon, and may be supposed to have retired to that position by slow waste during the excavation of the cafion. Of the immensity of the denudation that has sauna the Plateaus to their present condition, we have unmistaka- ble, and at the same time unexpected evidence, in the exist- ence of insular masses of strata, remote from the mesas of which they once formed part. The most important of these are found between the Shinarump and Aubrey Cliffs, and consist of limited tables of Triassic rocks, resting on the broad Carboniferous floor, and surviving the general destruc- tion in virtue of protective mantles of lava. Mr. Marvine observed a number of outliers of the varie- gated marls southwest of the Colorado Chiquito, near Sun- set Tanks, and there is reason to believe that San Francisco Mountain, distant forty miles from the Triassic mesa, contains an outlier of its sandstone. The evidence in this latter case is not very full, but, taken in connection with the other facts enumerated, can hardly be mistaken. On the northern and eastern flanks of the peak I observed outcrops of cross- bedded orange sandstone, resembling, lithologically, por- tions both of the Upper Aubrey sandstone, and of the Triassic sandstone series, but occurring 1,000 to 1,200 feet higher than the nearest compared exposures gave reason to anticipate the discovery of the Aubrey sandstone; the out- crops are completely circumscribed by volcanic materials, on one side the peak itself, and on the other the chain of later lava and cinder cones that surround its base. The nearest exposure of determined strata is ten miles distant, at Antelope spring, close to the southern base of the mountain, and con- sists of the upper portion of the Aubrey limestone, undisturbed, and dip- ping gently to the north. Dating from this point and making due allowance 6Wws ‘auoyspuvs Aoiqny ‘¢ feuojsoun, Aorquy ‘% fp ye posodxo sey, ‘t fayeseg ‘q foqyAqovary, 2 ‘OOOPFI-T ‘ele9g ‘UIVJUNOPY Oostouvsy uvg Jo uotyIgG—Zp “ONT 82 GEOLOGY. for dip, the thickness of Triassic strata included in the mountain appears to be 700 feet, with the top undetermined. If a line be drawn to connect these several islands, and be compared with the line of the present Triassic outcrop, the included area will be found to approximate 10,000 square miles; and from all this the Lower Trias has been denuded since the eruption of the older lavas of the Uinkaret and San Francisco groups. The geological date of these eruptions we have no means of knowing, further than may be surmised from the fact that in the Upper Sevier country great floods of very similar lava have risen through and overrun lower Tertiary deposits. How much further the Triassic strata extended, we cannot conjecture. The Cretaceous and Tertiary series, which were deposited conformably above an even floor of Jurassic strata, cannot be supposed to have thinned rapidly southward, yet they have been so far excavated, that their escarp- ments aggregate no less than 5,000 feet. Natural sand-blast.—In the discussion, above, of the erosion of the Grand Cain, the idea has been advocated that the transported detritus is the efficient tool, wielded by running water, in excavating its bed. To the same general purport are a variety of phenomena, illustrative of the efficiency of dry sand as an erosive agent, when borne by the wind. The subject is by no means a novel one, and has been touched by numerous writers, especially since the invention of the sand-blast. Some of the phenomena at the West have been described by Newberry, Blake, and Antisell, in the Pacific Railway Reports. My own observations have included so many additional data of the same character, that I am disposed to attach considerable importance to this agent of terrestrial denudation. In humid regions the traces of its action are seldom seen; partly because dry, volatile sands are of infrequent occurrence, and partly because their traces upon rock surfaces are obliterated by the more rapid wasting accom- plished by decomposition and solution. But in arid climates, where ‘the power of frost:is greatly lessened, and vegetation does not suffice to protect the soil from the wind, sand and dust are in almost continual motion, and the cumulative effect of their incessant impact is not merely appreciable, but even important. In passes and contracting valleys, where the wind is VALLEYS. CANONS. EROSION. 83 focused, and its velocity augmented, the most conspicuous results are to be seen; but no inconsiderable work is accomplished on broad plains, where its normal force only is felt. Blake and Newberry observed that in the Colorado desert the pebbles were etched by drifting sand, and our examina- tions have detected the same phenomena in the Gila and Amargosa deserts, and other broad valleys. The most perfect work of this character that has fallen under my observation, is on a broad gravel mesa sloping gently toward the Colorado River, just below the mouth of the Virgin. The sur- face of compacted sand and gravel is hard, smooth, and even, and upon it are thickly strewn loose pebbles, shaped by the drifting sand. Hard, homogeneous stones, as quartzite and chalcedony, are rounded and highly polished, as though by collision in running water; crystalline rocks, as basalt and trachyte, are unevenly worn, the harder crystals maintaining prominences; and limestones are carved, with a net-work of vermicular grooves, into the most beautiful arabesque designs, (Plate IX.) The dust that results from this attrition flies off with the wind, and ultimately finds its way to the playa of some desert, or to some water-course, that carries it to the ocean. Slow as is this process, there can be no question that it is wearing away the mesa; the pebbles that now strew its surface, will, in time, be completely dissipated, and others will be dug from the valley below to take their places. Such wearing cuts no cafions, and leaves no grand monuments of the magnitude of its results, but it is nevertheless a true denudation, applied to broad areas, and, where water is deficient, is no inconsiderable factor in the sculpture of the land. The broad belts of cross- bedded sandstone that are exposed where the Lower Aubrey bed caps the second terrace of the Grand Cafion, and the still greater areas on the Vermilion mesa, are traversed by drifting sand, and probably owe much of their sculpturing to this agency; though it is not easy to distinguish, there, its work from that of frost. As a rule, their denudation has progressed with the most conspicuous irregularity, and their numerous prominences are . carved in fanciful and grotesque forms. At the head of Black and Bowlder Cafons, and at the foot of Monu- ment Cajon, the configuration of the surface so modifies the winds as to give them especial violence, and their achievements are correspondently 84 GEOLOGY. conspicuous. In the first locality, on an exposed spur of the hill to which Lieutenant Ives gave the name “ Fortification Rock,” are examples of sand sculpture, little, if any, inferior to those displayed on the bed of the Colorado. Bowlders of basalt and trachyte, gradually weathering from the gravel of which the hill consists, are here subjected to a natural sand-blast of great power. The wind, confined by the hills, has locally but two directions—directions exactly opposed to each other—and these are con- spicuously portrayed by the carving. In the larger of the basalt bowlders represented in the illustration, (Plate VIII,) a point near the left margin faces the prevalent wind, and from it eroded grooves radiate over the convex surface ; and the course of the blast, as it whirls around its edge, is finely shown on the stone at the right. Just below the mouth of Paria Creek, and thence along the bases of the Shinarump and Vermilion cliffs, nearly to House Rock spring, similar carving may occasionally be seen, but it is poorly preserved by the friable sandstone, upon which it is executed. From Paria Creek to Rocker Creek, a large share of the excavation of the lower cliff is performed by wind and sand. Wherever a fragment of the Shinarump conglomerate, which caps the cliff, falls to the base, it is at once attacked. ‘The wind, deflected by it, has exceptional force at its margin, and scoops away the underlying shale about its base. Moreover a greater amount of sand is drifted close to the ground than higher up, and the base of the block is eroded more rapidly than the top. It results, in time, that the block, now smaller below than above, becomes perched on a pillar of shale, and, as this gradually grows more slender, is finally completely undermined, and tumbles over, only to renew the process at a lower level, (Plate XI.) Where the wind is least restricted, the base of the cliff is swept almost entirely clean of bowlders, and the shale moulded in smooth graceful curves: as, for example, on the south side of Chocolate Butte, (Frontispiece,) an outlier of the Shinarump mesa. Rain-sculpture—In Plate I is represented a very peculiar style of sculpture, executed by rain in half-consolidated sands and conglomerates, and in the softest water-rhyolites. The material, in this instance, is a local sand and gravel deposit, at the eastern base of Mount Nebo, Utah. Similar VALLEYS. CANONS. EROSION. 85 fluted escarpments are to be seen at numerous localities in Nevada and Arizona, as well as in Utah; but in more humid regions I am acquainted with none of purely natural origin. Steep earth-slopes, laid bare in railroad cuttings, are sometimes carved, by the rain, in similar fashion; but the frost soon destroys its work. In the dry air of our desert States and Territories, however, a steep escarpment rarely remains saturated with water long enough to be disintegrated by freezing. It is in the presentation of such subjects as this that the camera affords the greatest aid to the geologist. Only with infinite pains could the draughtsman give expression to the systematic heterogeneity of the material, and at the same time embody in his sketch the wonderfully convoluted sur- face—so suggestive of the folds of heavy drapery. But to photography the complicated is as easy as the simple; the novel, as the familiar. The negative once secured, the observer may at any time, and at his leisure, restudy the view, of which a hurried visit has given him but a first im- pression; and, more than this, he is enabled to publish its lesson, or its story, with the vividness that pertains to all graphic illustration, and with a guaranty of accuracy afforded only by the work of the sun. ° CHAPTER III.. THE GLACIAL EPOCH. We have seen in the last chapter that the valleys of the Basin Range system are filled to a great depth by detritus from the adjacent mountains. Our knowledge of these deposits is eminently superficial, no thorough sec- tion having been discovered. Some of the coarser gravels, resting against mountain-flanks, have been excavated and exposed to the depth of a few hundred feet, where the streams that spread them have so far deepened their mountain channels as to discharge at lower levels, and begin the destruc- tion of their own deltas; and the Colorado River, between Bowlder and Iceberg Cafions—near Callville, Nevada—has cut the valley: beds to a depth of five or six hundred feet; but none of these partial sections reveal any- thing else than half-sorted gravels and saline clays and sands, such as are now gathering along the margins and in the playas of other arid valleys. The beds have afforded no fossils, and we can say of their antiquity only that their deposition commenced before the Colorado had carved its camions. The unruffled repose of all such unconsolidated beds in Nevada and adjacent Utah, is proof positive that no general glaciation has prevailed. It is impossible that ice-floods should have invaded their domain, without molding them into the most impressive and conspicuous glacial monuments; but all their forms and conditions point to their quiet distribution by running water, aided locally and occasionally, as we shall see, by the agency of lakes. Adding to this the merely negative fact that no glacial striae, nor other trace of glaciers in the Basin Range troughs, have been found, though experienced eyes have looked for them, we may conclude, without reserva- tion, that the great ice-field of Eastern North America had no counterpart in the same latitude at the West. The climate of the West was not, however, unaffected in the Glacial 86 THE GLACIAL EPOCH. 87 epoch, and there is abundant evidence of a change similar in kind to that . which occurred at the East. ‘To this evidence our explorations have made some contributions, and to present these, and point out their general rela- tions, is the purpose of the present chapter. Local Glaciers—Although the valleys which separate the mountains of Nevada and contiguous territory were not flooded with ice, yet glaciers formed about the crests of the highest ranges, and their traces have been discovered even farther south than they are known on the eastern coast. The ancient glaciers of the Sierra Nevada, described by Prof. J. D. Whitney, in the Geology of California, extended nearly to Walker's Pass, in north latitude 36°. They occupied large areas on the loftier portions of that range, and stretched long arms toward its base, but were strictly local in character. Northward, on the Cascade Mountains, Dr. J. 8. Newberry noted glacial striz at so low an altitude as 4,450 feet,* and at Puget Sound begins the system of fiords, which, along the coast of British Columbia and Alaska, mark the extension of the ice to the ocean—or at least to regions that are now washed by it. On the Rocky Mountains the southern limit has not been ascertained, but moraines of considerable magnitude were observed in the South Park, by a party led by Prof. J. D. Whitney, in 1869.t Upon the Wahsatch range, near Salt Lake City, glacial phenomena have been noted by Mr. E. P. Austin and others, but I am not aware that any descrip- tion of them has been published. We may look to the forthcoming vol- _ umes-of the report of the Fortieth parallel survey for a full account, not only of these but of similar phenomena on the Humboldt and Uintah ranges. In the third volume of that report Mr. Emmons announces the discovery of glacial striz on the Toyabe range, Nevada, (latitude 39°,) but mentions no associated phenomena. South of these mountains our ex- plorations in 1872 led to the discovery of a number of localities which there is reason to believe are the most southerly in the longitudes in which they occur. * Pacific Railroad Reports, vol. vi, p. 42. t Prof. J. J. Stevenson, geologist of the Colorado division of this exploration in 1873, found moraines as far south as north latitude 38°, on the eastern flank of the Sangre del Cristo Mountains. 88 GEOLOGY. The Schell Creek range, Nevada, has an altitude at White’s Peak, (latitude 39° 15’,) and for six or eight miles southward, of 10,500 to 11,200 feet. The crest is remarkably acute, and is buttressed by lateral spurs, between which are close, hopper-shaped valleys, that once contained very small glaciers. The ice could have moved at most only two or three miles, and the moraines, which are its only observed record, were pushed no lower than 8,000 feet. A little farther south, (latitude 39°,) and in the next range to the east, Wheeler’s peak rises to a height of 12,000 feet, and bears upon its eastern flank a moraine of the same character and at the same altitude as those of the Schell Creek range, but of greater magnitude, and retaining Alpine lakes. I did not myself visit the lakes, and indeed saw only the lower side of the- moraine, but, by the descriptions of Lieutenant Wheeler and Mr. W. M. Ord, who ascended the peak in 1869 and viewed them from above, I am persuaded that the waters are dammed, either by the moraine I saw or by later formed moraines of the same glacier. No opportunity was afforded to look for glacial phenomena on other sides of the peak, and it is not improbable that they shall be discovered a few miles farther south on the same range. Belknap Peak, near Beaver, Utah, overlooks two moraines, lying in sheltered valleys on opposite flanks, and the western contains the waters of a lakelet at an altitude of 9,000 feet. Its latitude is 38° 25’. Sixty miles farther east, in latitude 38° 30’, Mr. Howell observed upon a high ridge of the Sevier plateau a series of terminal moraines, inclosing a chain of small lakes and swamps, (Chapter IX of this volume.) In all of these instances the glaciers were of insignificant magnitude, and confined to the neighborhood of the loftiest summits. Lake Bonneville—From considerations that will appear in the sequel, I have come to regard as phenomena of the Glacial epoch a series of lakes, of which the beaches and sediments are to be found at many points in the Great Basin. The greatest of these with which I am acquainted, covered a large area in Western Utah, including the valleys now occupied by Sevier, Utah, and Great Salt Lakes, and its limits and history have been so far indicated by our examination, that I venture to propose for it the name of Bonneville, in honor of Capt. B. L. E. Bonneville, who first THE GLACIAL EPCCH. 89 afforded an authentic account of Great Salt Lake.* The lacustrine de- posits which form part of the record of this lake, I shall designate the Bon- neville group. The most conspicuous traces of Lake Bonneville are its shore-lines. At their greatest expanse the waters rose nearly 1,000 feet above the present level of Great Salt Lake, and at this and numerous other stages, marked their lingerings by elaborate beaches and terraces. These are very con- spicuously displayed on the slopes of the Wahsatch range near Great Salt Lake, and on the rocky islands of the lake, and have attracted the attention of every observant traveler from the time of the explorations of Frémont and Beckwith. All the varied products of wave-work, as we know them on modern shores, are represented and beautifully preserved. Rocky prom- ontories are cut in notches of greater or less depth, as the water lingered a longer or shorter time, the upper face of the notch being a bluff escarpment, Fig. 43.—Diagram of beach carved in rock. undermined by the waves, and the lower a shingle, consisting of parts of the excavated rock. The water level, as we know from the study of mod- ern shores, was at or a little below the angle of the notch. On promon- tories of softer materials, such as salient curves of the gravel foot-slopes of the mountains, the phenomena are precisely similar save that the inclines are less steep, (Fig. 44.) Along re-entrant curves, and across the mouths. of gy Fg gg Fig. 44.—Diagram of beach carved in soft earth. deep indentations of the contour, beach ridges, or bars, were thrown, hav- ing for their material a portion of the sand and gravel excavated from the *Captain Bonneville saw Great Salt Lake in 1833. His account of it was published by Washing- ton Irving ten years later, in “The Adventures of Captain Bonneville, U.S. A., in the Rocky Mountains and the far West.” 90 - GEOLOGY. promontories, (Fig. 45.) Where considerable streams entered, tabular del- tas were built of their sediments, and gravel bars of great magnitude were thrown across straits. Of this latter feature conspicuous examples are to be Fic. 45.—Diagram of beach ridge thrown up on a shelving shore. seen at Dry Pass in the House range, at the pass between Tooele and Rush Valleys, at the pass between Juab and Utah Valleys, and at that between Utah and Salt Lake Valleys. The last mentioned is especially interesting, from the fact that the Jordan River has cut across it and revealed the con- stitution of the bar to a depth of 500 or 600 feet. The cuttings of the Utah Southern Railway have likewise afforded fine sections at the same locality, exhibiting clean, well-sorted, beach-rolled gravel. No number can be assigned to the successive shore-lines from the highest to the modern. Upon gentle slopes many more can be detected than on steep, and they are of all grades of distinctness. It is doubtless true that some, which are at certain stations conspicuous, as compared to others, are elsewhere, from local causes, inconspicuous, but there are two lines that can, at nearly every point, be recognized as far more strongly traced than any others. One of these is the highest of all, the Bonneville beach. The other occurs about 300 feet lower, and this we have found it convenient to entitle the Provo beach, drawing the name from the town of Provo, on the shore of Utah Lake, near which it is especially well exhibited. These tell us that, during the progressive subsidence recorded by the entire series, there have been two marked epochs, perhaps many thousands of years in duration, through each of which a constant water level was main- tained. The level of Great Salt Lake, like that of other lakes without over- flow, is notoriously inconstant, for the obvious reason that it depends on the ratio between precipitation and evaporation over a limited area—factors which diverge, and change their conditions of equilibrium, with every fluc- tuation of annual mean temperature or humidity. It is difficult to imagine that so unstable a climatal equilibrium was maintained for the time that was consumed in the production of either the Bonneville or the Provo beach, and, before we accept such explanation of their origin, we are led to inquire THE GLACIAL EPOCH. 91 whether at these levels the stage of water was not regulated by an overtiow. The coincidence of one of the constant levels with the highest water stage of all, renders the presumption of an outflow at that stage especially strong. With these considerations in view, we endeavored, in tracing the outline of the lake, to discover its point of discharge, but without success. Our exam- ination was almost exclusively confined to the southern half of the lake, and points to the conclusion that no outlet existed toward the Colorado River. At one low point cf the southern rim, near Hebron, Utah, the observation was not so complete as was to be desired, and the question may be considered as not definitely settled. Prof. O. C. Marsh informs me that he has discov- ered, on the northern shore of the lake, an outlet leading to the Snake River, but I am not aware at what point, nor at what altitude. The northern por- tion of the lake area falls within the field of study of the corps of Mr. King, and when their observations and those of Professor Marsh shall have been published, the relation of the beaches to the outlet, or outlets, will doubtless be known.* Meantime I anticipate that the Provo beach, as well as the Bonneville, will be found to have been determined by an overflow. In the map of Lake Bonneville,t the southern half, and the eastern shore to Ogden, is based on the surveys of our parties in 1872. Wherever the shore-line was crossed by Mr. Howell or myself, its position was noted, and in this way about forty-five points were fixed. These were connected by lines, in part sketched in the field from views more or less distant, and in part assumed from the general relations of the orography to the deter- mined altitudes of topographical stations. The northern and northwestern contours are merely provisional, and are based on some scattering altitudes furnished by the Pacific Railroad explorations, and Dr. F. V. Hayden’s reports. A bay is assigned to Cache Valley on the authority of Dr. Hay- den, (Annual Report, 1871, p. 19.) The southern and eastern portions of the lake were studded with rocky islands, and fringed with ragged, “iron- bound” promontories. The largest open body lay over the Great Salt Lake Desert, and had a depth of about 900 feet. The average depth of the *Prof. Frank H. Bradley mentions four points of possible outflow from the northeast margin.—(U. S. Geol. Surv. of the Territories, 1872, p. 202.) tAt the time of writing, this map has not been executed, but it is hoped to publish it together with others, constituting a geological atlas, either with or soon after the appearance of this volume. 92 GEOLOGY. whole was not far from 400 feet, and the extreme depth 1,000 feet. Its area was not far from eighteen thousand square miles, being a trifle less than that of Lake Huron, and eight times as great as Great Salt, Utah, and Sevier Lakes combined. Its extreme length, from north to south, was about three hundred and fifty miles, and its width one hundred and twenty-five miles. : The altitude of the Bonneville beach was accurately determined, at a point where it is distinctly marked, near Camp Douglas. A system of levels, carefully run by Mr. Gilbert Thompson, establish the relation of this point to the shore of Great Salt Lake, to several ‘‘ benches ” convenient for reference, and to the track of the Central Pacific Railroad, at Corinne, Utah; and the combination of the railroad and local levels affords the fol- lowing: Feet. Water-surface of Great Salt Lake (May 16, 1873) above the sea.- 4,210.4 Instrument pier, Salt Lake Observatory, above the sea. ~~... .---- 4,330.4 Bonneville beach, near Camp Douglass, above the sea... .---.--- ie Wesel Bonneville beach above Great Salt Lake ....-..-..-.-.------- 967.7* The fluctuations of the present lake have been observed for so short a period, and with so little care, that we do not know its mean stage, (if, indeed, we can assume it to have one,) but such meager data as are avail- . able indicate that, at the date of our comparison, its level was some feet higher than it averaged for the past twenty years.t No other determination of the Bonneville beach was made by spirit- level. Aneroid barometers were carried, by Mr. Howell and myself, to numerous and widely-distributed portions of it, as well as to a number of stations on the Provo beach; but, owing in part to the loss of a note-book containing collateral data, the discussion of these observations does not give satisfactory results. To the most important question that we would ask of * Professor Bradley places the altitude near Ogden, in 1872, at 966 feet, a most remarkable coinci- dence, if, as I suppose, his measurement was made by barometer. t Capt. H. Stansbury, describing Antelope Island, in 1850, (p. 158 of his report,) says: “‘ The south- ern part of the island is connected with the main shore of an extensive sand flat, which, in the summer, is for the most part dry, but is frequently flooded to the depth of 18 inches, the water of the lake being driven over it by every gale from the north.” Mr. Joseph H. Barfoot, of the Salt Lake City Museum, writes me of this same sand-flat, in 1874, that “it is crossed at times by the steamer,” and that “ there are now 11 or 12 feet of water at that place.” THE GLACIAL EPOCH. 93 them, they afford but a qualified answer. They render it probable only that the Bonneville beach, on the western foot of the Pah-van range, south of Fillmore, Utah, has a greater altitude than at Camp Douglas, &c.; and that the portion which outlines the southern arm of the extinct lake in. Esca- lantes Valley is nearly 300 feet higher than that about the Great Salt Lake Desert. These facts—if future investigation shall prove them so: to be— will have especial interest as the record, in the middle of the continent, of undulations of the solid earth, produced at so late a geological date that we may presume them identical with changes now transpiring. In the present state of the science we are able to detect and measure the slow writhing of the earth’s crust, only where a broad water-surface affords a datum-plane ; and, for this reason, our data are almost confined to the margins of continents, where, as Professor Shaler has shown,* there is reason to suppose that the amount of motion is least. There are, however, a few interior lake sys- tems, broad enough to tell us something of the warping of their shores, and our continent contains two, at least, that are of value—that of the Lauren- tian lakes, and the one we are considering. The fact that the basin of Lake Bonneville is now nearly dry is rather advantageous than otherwise, since its slow desiccation has left intact, for our study, a series of contour lines, that record, by their flexures, or by their horizontality, the relative motion, or the stability of the parts of a large area, subsequent to the suc- cessive times of their production. Since the geologist has ceased to look upon the present order of things as an ultimate result, and has come to per- ceive that the epoch in which he lives is a geological epoch, that geological history as well as human history is enacting, and that the earth has a future no less than a past, a peculiar interest attaches to every evidence of recent or actual progress. Inquiry is directed to all that seems most per- manent, in the firm faith that the discovery of its instability can only be postponed, not averted; and, actuated by this spirit, the geologist has even prophesied that the growth of mountain-ridges—‘ the everlasting hills ”— will some time be seen. For evidence of their recent progress no better field could be studied than the region of this ancient lake, which bathed the feet of a dozen ranges of the Basin system. * Proc. Bost. Soc. of Nat. Hist., vol. xii, Oct. 7, 1368. 94 GEOLOGY. Bonneville Beds——Intimately associated with the Bonneville and lower beaches are a series of lacustrine deposits, whose history is very clearly de- fined by their constitution and relations. They are largely composed of fine, friable, white, caleareous marl], and this passes, on the one hand, into a cream-colored, partly oolitic sand, of calcareous and siliceous grains, feebly cemented by calcite, and, on the other, into an impalpable clay, charged with chloride of sodium and other soluble salts. All of these beds, excepting the most saline of the clays, are fossiliferous, affording, in great abundance, a few species of lacustrine gasteropoda. The clay is distributed through the lowest portions of the Sevier and Salt Lake deserts and their arms, and, lying for the most part below the reach of modern denudation, is rarely to be seen in section. The marl is best exposed, and probably best developed, on gentle declivities. Its great- est measured thickness, noted on the southern margin of the Great Salt Lake desert, is 30 feet. Usually it is so friable as to crush readily between the fingers; but near Fillmore, Utah, it is consolidated into a chalk, and has furnished the name—Chalk Creek—of the stream upon which that town is built. The sand beds lie also upon the margins of the basin, but are less widely distributed. In most instances, their association with some one of the beaches can be definitely seen, and in all observed instances of superposition, they overlie the marl. On the western flank of the House range, opposite Fish Spring, they are greatly developed, but admit of no section. Near the River Bed station of the old overland stage road they exhibit a depth of 50feet The area covered by the Bonneville group is completely circumscribed by the Bonneville beach, and comprises, with an exception presently to be noted, whatever of the surface of the basin lies below the level of the beach. The waves which carved and molded the Bonneville beach, exca- vated only indurated rocks and subaerial gravels derived from them. The escarpments excavated at all lower water stages exhibit sections, more or less complete, of the Bonneville beds. ‘In fine, the Bonneville beds are the sediments of the lake whose successive margins are recorded by the series of beaches we have described, and their deposition has been continuous, over a gradually restricted area, from the date of the Bonneville beach to the present time. THE GLACIAL EPOCH. 95 In some places the lacustrine deposits have in turn been covered by fresh, rill-borne gravels. The waste from the mountains that, during the existence of Lake Bonneville, was sorted and distributed by its waters, re- ceived, after they retired, only the partial sorting and limited distribution that the mountain streams accomplished. Upon easy slopes, these subaerial gravels sometimes cover and conceal the Bonneville beach, but oftener the modern streams intersect the higher beaches in channels eroded below the general surface, and spread their detritus over the lacustrine strata and the lower beaches. : The general section about the margins of the Bonneville basin may, then, be stated as follows: | a. Subaerial, unsorted gravels; deposited by running water; distributed in unconnected patches; still accumulating. b. Subaqueous sands, marls, and clays; thoroughly sorted; deposited by still water; limited by the Bonneville beach. The greatest measured section shows 75 feet; the maximum depth may be greater. ce. Subaerial, unsorted gravels; deposited by running water; not limited by the Bonneville beach; found under the Bonneville beds wherever their base is visible. Maximum depth unknown; a partial section shows 200 feet. . The gravels a and ¢ are identical in character, and above the beaches are inseparable. They are, in fact, a continuous formation, interrupted locally by the intercalation of the lake beds. So, too, if we pass from the margin of the basin to its lowest points, where are now salt lakes, we find now depositing a saline clay, identical in point of time with the upper gravel, (a,) but in point of condition identical with the Bonneville clays, (b,) and connected with them by unbroken continuity of deposition. That is to say, on the borders of the basin the accumulation of subaerial gravel has been continuous, and in the lowest parts the deposition of subaqueous, while a broad middle ground has received -the two deposits in alternation.. The circle of beach which has always separated the two areas of deposition, has dilated and contracted, so as to enable each, im turn, to overlap the other. Of the history of the beach, or what is the same thing, of the history of the lake, we know only the last few pages. We know that the present low 96 GEOLOGY. tide has been preceded by a high tide, the duration of which, though ex- tended, was not unlimited, and we know that for a comparatively long ante- cedent period there had been no similar flood; but we do not know that there were or were not earlier floods; nor can we tell how low was the stage from which the water rose to its last maximum. Our chief present interest in these phenomena lies in the fact that they are the secular meteorological record of Utah. The water stage of Great Salt Lake depends on the relation of precipitation to evaporation—and these upon atmospheric humidity and temperature—within the area from which it receives drainage. If the air-currents that cross the basin absorb more water than they yield, the lake surface contracts, until the consequent diminution of evaporation restores the equilibrium; if they absorb less, it expands, and the effect is, and has been, the measure of the cause, up to the limit marked by Lake Bonneville, when, an overflow being reached, the water could rise no higher. We may, then, translate our stratigraphical data into climatic, and say that during a period, represented by the lower gravel, (c,) Utah was arid; that its humidity increased to a maximum, and again began to diminish, during the deposition of the Bonneville beds, (b,) and that its present aridity has been reached and maintained during the time marked by the upper gravel, (a.) Some idea of the relative lengths of these periods may be de- rived from the comparative magnitude of the deposits, though our data upon that point are not so full as is desirable. The general impression, derived from a month’s travel in the region, is that, if the gravel a be taken as unity, the lacustrine deposits might be represented by ten, and the known portion of the gravel ¢ by fifty. In passing from depth to time, it should be borne in mind that the lacustrine deposits accumulated faster than the gravels. They were formed during an epoch of greater humidity, when denudation was more rapid, and they received material from wave erosion, as well as from atmospheric. After making this’ allowance, it still remains probable that the Bonneville Lake occupied more time than has transpired since its subsidence, and that the anterior epoch of aridity was many times longer than what time has elapsed since its close. The humidity marked by the Bonneville beds thus appears to have been an episode, occurring in the THE GLACIAL EPOCH. 97 later part of a long era of aridity, and it was the consideration of this fact that led to the introduction of these data in the chapter devoted to glacial phenomena. . The Bonneville epoch and the Glacial epoch were alike climatal epi- sodes, and they occurred in the same general division of geological time, namely, the division of which modern time is the immediate sequel. If it can be shown that the climatic changes were of the same kind, there need be no hesitation in assuming the identity of the epochs. The glacial cli- mate we commonly regard as merely cold, and a low temperature was doubtless its chief characteristic; but it admits, nevertheless, of another view. The climatic condition essential to the formation of glaciers is, that the summer's heat shall be inadequate to dissipate the winter’s snow, and this may be brought about, either by a lowering of temperature, or by an increase of winter precipitation. The profuse precipitation of our north- western coast would maintain great glaciers, if the climate were cold enough ;~rivers of ice would follow the higher valleys of the Rocky Mount- ains if the snow-fall were heavy. To account for the origin of Bonneville Lake, we need to assume a climatal change, that would increase precipitation, or diminish evaporation ; and both of these effects would follow, in accordance with familiar meteoro- logical laws, if the humidity of the air were increased, or if the temperature were lowered. There can be no doubt, then, that the great climatal revo- lution, which covered our northeastern States with ice, was competent to flood the dry basin of Utah; and that it actually did so is at least highly probable. Before quitting the subject of this ancient lake, a few special features should be recorded. Calcareous Tufa.—Along many of the beaches, and especially at points where they are carved in solid rock, the bench or terrace below the water- line is composed of calcareous tufa, usually full of small gasteropod shells, and often involving so many fragments of the contiguous rock as to consti- tute a breccia. In the localities where I found it best exhibited, the beach was carved in limestone, but the deposit is probably independent of the character of the adjacent formation. Mr. Howell observed it upon Granite 7WS . 98 GEOLOGY. Mountain, coating granite, and remote from limestone exposures; and a similar association was seen by Prof. W. P. Blake on the Colorado Desert. Down some steep slopes it stretches, as an apron, for several rods, and, where it rests on soft materials, the waves of the retiring lake have under- mined it and formed caves. Several of these are to be seen on the north end of the Oquirrh range, and the largest, which is popularly reputed to have been excavated by Spaniards years ago as a mine, is remarkable as a specimen of “ Purgatorial” wave-work. The Carboniferous strata have a local northward dip of eighty degrees, and trend parallel to the face of the acclivity. Two beds of limestone, which constitute the walls of the cavern, are separated 12 feet at the entrance, and evenly converge to the rear end, where they are 4 feet apart. At the end, a shale, in place, fills the interval, but I was unable to determine whether this had once occupied the entire excavated space. The roof is built entirely of recent calcareous breccia, and the floor is evenly spread with earthy débris. The of the Oquirrh range. ranging from 2 to 25 feet, and the length is 275 feet. The breccia of the roof pertains to one beach of the great series, and the floor is near the level of another. The wonderful depth of the excavation, in a direction nearly parallel to the shore, is explained by the convergence of the straight walls, between which the waves gained, in their progress, on the principle of the hydraulic ram, enough velocity to compensate for the loss by friction. Great Salt Lake and Sevier Lake are separated by a divide, which, in its lowest part, is not many feet above the level of the latter. When, in the progress of the great desiccation, this divide was uncovered, and the two basins were separated, evaporation proceeded less rapidly on one side than on the other, and for a time there was an outflow across the barrier. The channel opened by this connecting stream is of such magnitude, and so perfectly preserved, that it has been appropriately designated by fron- tiersmen ‘the Old River Bed.” ‘River Bed station,” of the old overland stage road, is upon its margin. Our lines of survey intersected it at two THE GLACIAL EPOCH. 99 points, seven miles apart, but neither end was examined. In its narrowest part, where it traverses mountain gravels, its floor is from 200 to 300 yards across. It has here absolutely ceased to be a drainage line, and deltas of débris from the adjacent hills stretch completely across it, dividing it into a series of small playas. Observations upon its altitude at different points were, unfortunately, not so connected as to determine the direction of its descent, and we cannot be certain which of the two lakes was tributary to the other. It is to be presumed, however, from the fact that Sevier Lake is now by far the less saline,* that it was the upper of the system, and by its overflow gave what salt it had then accumulated to Great Salt Lake. Fossils of the Bonneville group—The shells found by us in the Bonne- ville beds are all of modern species, either fresh water or terrestrial. The specimens in our collections were submitted to Mr. Geo. W. Tryon, jr., for identification, and the following list is from his notes : Limnea desidiosa, Say. Pomatiopsis lustrica, Say. Amunicola cincinnatiensis, Anth. Succinea lineata, Binn. Cypris ? In all the localities we examined, the specific forms were few—one or two—but individuals were usually abundant. The form most widely dis- tributed is Limnea desidiosa, and it ranges through the entire series of mars, from those which rest directly on the older gravel, to those thrown down at the latest stages of the receding water. The greater portion of the fossil- iferous beds are calcareous, and not appreciably saline ; but at a few of the more recent localities examined. salt was visible as an efflorescence, and perceptible by taste. In these saline muds were found a few specimens of L. desidiosa and Pomatiopsis lustrica. At the time of their collection, the only explanation of their occurrence in such association appeared to be that, by slow acclimation, they had survived the change from fresh to salt * Dr. L. D. Gale found in Great Salt Lake water 22.42 per cent. of mineral matter; Dr. O. Loew, in Sevier Lake water 8.64 per cent. The difference, however, is not so great as these figures would in- dicate, for the reason that the two tests were separated by an interval of twenty-two years, in which time the lakes underwent a change. That there is a difference is proved, independently, by a rude observation on their comparative specific gravity. A bather floats so much higher in Great Salt Lake as to indicate that its brine is nearly twice as strong. 100 GEOLOGY. water; but some observations, soon after, on the shore of Sevier lake, led to a different conclusion. The only tributary to Sevier Lake is the Sevier River, and it has no outlet. Its water contains 82 per cent. of saline matter. No trees stand on its shore, nor is it fringed by aquatic plants: Frequent careful exami- nation of the water along its shore discovered no life, save Artemia, charac- teristic of all briny lakes, a few larve of insects, and small floating Algae. Along the highest line reached by the waves were accumulated, just as upon the shores of Great Salt Lake, the dry erwvie of the larvee, and, min- gled with them, we found Alge, numerous dead and univalve shells, small dead fishes, and beaver-gnawed sticks of willow.’ There is no reason to suppose that any of these remains, except the larvae, and perhaps the Alga, belong to lake. The willows could have come only from the Sevier River. The fishes appeared to be the young of fresh-water species. And some, at least, of the shells are known to live in the fresh waters of Utah. It is fair to assume that the shells, along with the willows and fishes, were floated by the waters of the lake from the mouth of the river to their present position, ten or even twenty miles away. Any of these shells that should become filled with water and sink, in their transit across the lake, would be imbedded in the saline-sediments now accumulating, and offer to some future genera- tion the same anomaly that we have encountered. The drifted shells in- clude, (here, too, we are able to give the names on the eminent authority of Mr. Tryon :) Limnea desidiosa, Say. LTimnea palustris, Mill. Physa heterostropha, Say ; and Carnifex newberryi, Lea. It is noteworthy that Anodonta oregonensis, abundant in the river, and too conspicuous to be readily overlooked, was not found on the beach. In view of these facts, we may safely affirm that the mere presence in lacustrine deposits of such fluviatile shells as will readily float after the death of the animal does not prove that such deposits are from fresh water; and we are led to review carefully our opinion, expressed in the preliminary report for 1872, that the water of Lake Bonneville was fresh. THE GLACIAL EPOCH. 101 The water of Lake Bonneville —Considering first the fossils, we note that one of the species is terrestrial, and must have been introduced from the shore. Of the remaining eight species, seven are light fresh-water or am- phibious gasteropoda, the dead shells of which would readily float to great distances, and may have been introduced by streams. The eighth species is a minute ostracoid crustacean, so extremely light that it might be carried along by even a feeble current. Our data are not: sufficiently full to give great value to merely negative evidence, but we may still note the apparent absence of so conspicuous a family as the Unionide. In the examination of localities scattered widely through the basin of the lake, and including every variety of station, as regards depth of water and slope of bottom, myriads of gasteropoda were found, but not a single conchifer—and this, although Anodons are abundant in the fresh water of the region, and the sediments of other ancient lakes of the great basin are characterized by bivalves. Dr. J. 8. Newberry found in a deposit from the ancient expanse of Klamath Lake numerous specimens of Unio; Dr. Jas. Blake reports Anodonta from ancient lake-deposits in the Queen River Valley, and the same genus was found by the writer to abound upon the old beach-line of Owens Lake. While none of these facts in regard to the fossils demand salinity for their explanation, their bearing is certainly favorable to the idea that the waters of the lake were not entirely fresh. The evidence derived from the character of the deposits is, perhaps, even more vague. The salt which is so prominent a characteristic of the present Sevier and Great Salt Lakes, and abounds in all the later sediments of the shrunken ancient lake, is nearly absent from the beds most clearly associated with the upper beach; and its distribution indicates that Lake Bonneville, if not perfectly fresh, was at least far less saline than either Great Salt or Sevier Lake. The deposits which can be definitely associated with the greatest expanse of water are calcareous, consisting, along the immediate shore-line, of the tufa already described, and in deeper water of matls almost entirely made up of crystalline particles. These particles do not cohere, as we might expect them to do if the crystallization took place at the bottom of the lake, but are loosely aggregated, as if they had been formed in the body of the water, and sank to their present position. We 102 GEOLOGY. cannot avoid the inference that, whatever may have been its percentage of salt, the water was saturated with carbonate of lime. As we have already remarked, the strong delineation of the upper beach can hardly be accounted for, save upon the supposition that at that level there was an outflow which preserved a constant stage of water. The observations of Professor Marsh and Professor. Bradley on the “divide” between Great Salt Lake basin and the valley of the Snake River, confirm this view. But, if it be proved that this was so, if by no means follows that the water of the lake was sufficiently free from saline ingredients to be denominated fresh. So long as the inflow was greatly in excess of the out- flow, the water of the lake would retain a great portion of its dissolved salts. A comparatively slight difference of this sort would suffice to saturate the water with calcite, and, if the overflow were comparatively very small, even a high degree of salinity might be maintained. If we suppose, for example, that the inflowing streams contained .0001 of carbonate of lime, and .001 of common salt, and that their volume was fifty times as great as that of the outlet, the remaining water being removed by evaporation, then the outflowing water, to maintain an equilibrium by carrying off both lime and salt, must contain .005 of the former and .05 of the latter, and the water of the lake would be charged in the same degree. But, while this would be perfectly possible for the salt, the water could not hold so great a portion of protocarbonate of lime, and all in excess of saturation would be precipitated in the lake as evaporation progressed. Upon such an hypothesis the profuse precipitation of calcite would consist with the maintenance of a constant level of overflow. In this connection the inquiry is pertinent whether the basin contains the amount of salt which would have sufficed to render the great lake briny. The ancient volume was no less than three hundred times greater than that of Great Salt Lake, (when surveyed by Captain Stansbury,) and the brine of the latter, so greatly diluted, would give only one-thirteenth of one per cent. of salt. But, if we add to the salt of Great Salt Lake that of Sevier Lake, and the far greater but indeterminate quantity accumulated in the sediments of the lower parts of the two deserts, we shall probably have enough to give Lake Bonneville, if it were undrained, the salinity of the ocean. THE GLACIAL EPOCH. 103 In fine, we are led to believe that, while Lake Bonneville certainly held less salt than do its modern representatives, its recorded phenomena com- prise no fact that places it definitely among either fresh or salt lakes. The lake we have studied was but one of a group. Vestiges of a similar flood have been found, by various observers, in many of the valleys of the Great Basin, and it is probable that all of the minor basins of which it is composed were partially, or wholly, filled with water. In the list of those which overflowed, may probably be included all of the northern tier, bordering on the present drainage system of the Columbia River, and those which, lying at the feet of the Wahsatch range and the Sierra Nevada, received the streams from those mountains. What we know of the Death Valley and other southwesterly basins, tends to show that they were not entirely filled. Of the interesting group of lakes that along the base of the Sierra Nevada survive the general desiccation, our route touched but one, and that the most southerly. Owens Lake lies in a trough between the Sierra Nevada at the west, and the Inyo and Coso ranges at the east, and receives its water from Owens River, which, rising seventy miles at the north, follows the trough, and accumulates the streams from the adjacent mountains. It now contains a strong brine, and is without outlet, but it is surrounded by ancient beaches, and in the sands of the most elevated of these are abundant speci- mens of Anode, testifying to its former freshness. Its ancient area did not exceed its modern by more than one or two times, and the channel through which its surplus discharged is distinctly marked. Following the channel southward for forty miles, past Hawee Meadow and Little Owens Lake, we found it ending in a broad desert valley, that stretches eastward from Walker’s Pass and Indian Wells. From this the water probably had no escape. Our line of march compassed the southern margin of the desert, without the discovery of a channel through which it had found outlet. Résumé.—The following are my principal conclusions : I. The general glaciation of the Eastern United States had no counter- part, in the same latitudes, over the region extending from the» Rocky Mountains to the Sierra Nevada, inclusive. If. There were in that region local glaciers high upon the flanks of 104 GEOLOGY. the mountains, the most southerly of which did not extend lower than an altitude of 8,000 feet above the sea. III. There was a general accession of water to the valleys of the Great Basin. Lakes were formed where now are only deserts, and valleys, now nearly empty, were filled to overflowing. The flooding of the valleys is correlated in time with the formation of glaciers upon the mountain summits, on the same principle on which the different local floods are correlated with each other, the local glaciers with each other, the glaciers of the East with those of the West, and those of America with ‘those of Europe, namely, that the phenomena were of the same class and occurred in the same division of geological time. Each took place during the Post-tertiary, and each marked a climatal change of polar tendency. , IV. The phenomena of the Glacial epoch at the West differed from the synchronous phenomena in the same latitudes at the East, for the reason that then, as now, the former region was comparatively arid, and material was lacking for a great ice-field. The configuration of continents was- not so far different from the present, but that the principal climatal districts were marked out, and the great flexures of the lines limiting zones of climate were arranged very much as we now know them. CHAPTER IV. WATER SUPPLY. SPRINGS—-STREAMS—-LAKES—ARTESIAN WELLS. We have here collocated a few groups of facts, connected by the com- mon element of water, but otherwise so little associated that, but for the meagerness of our data, they would be deemed worthy of separate chap- ters. The dependence of the agriculture of the Great Basin and adjacent regions upon irrigation, gives great interest to the subject of water supply. There has been a great deal of speculation upon possible changes of climate to transpire, or now transpiring, through the influence of irrigation, and upon the possible increase of water supply by means of artesian wells. Of the latter we shall have occasion to speak further on. The rise of water of Great Salt Lake ever since, or nearly ever since, the occupancy of the neighboring country by Mormon settlers, has sug- gested to many people the possibility that the change of level is produced by irrigation and agriculture. The working of large tracts, which had formerly been dry and heated, might, it was surmised, be inducing a per- manent change toward humidity, and the wish has been father to the thought, that this might extend so far as to enable the reclamation to agri- culture of a large portion of our desert territory. There can be no ques- tion that the rise of the lake has occurred, nor can it be questioned that this rise indicates an increase of rain-fall as compared to evaporation ; indeed, the lake tide is a most delicate indicator of the fluctuation of the annual climatal means. But I am disposed to doubt the possibility of con- necting the change with the synchronous cultivation of the soil. While it may be true that large areas of land brought under cultivation are cooler than desert surfaces, and hence better able to induce rain-fall from currents of moist air, it is equally true that the coolness is due entirely to the in- 105 106 GEOLOGY. crease of evaporation, brought about by the wide distribution of water in irrigation, and there seems no reason to believe that the result in precipita- tion shall exceed, if indeed it can equal, the expenditure in evaporation. Recent discussions of our meteorological record at the East, have shown the popular belief in the influence of the cultivation of the soil upon the. annual rain-fall to be unfounded, and in Utah—at least until we shall be able to reason from a broader basis of facts—it will be easier to suppose that the rise of the lake is due to a fluctuation of climate, within limits that our observation does not comprehend, rather than to a permanent change, induced by the comparatively slight modifications that agriculture has made on the face of the country. Taking the broadest view, the humidity of the Great Basin depends on air currents that completely traverse it; and nothing will augment it, that does not either increase the moisture of the incoming air currents, or decrease that of the outgoing. Streams.—The water that comes from the clouds as rain, or flows from melting snow, gives rise to a double circulation. One part descends over the surface of the ground, in the form of rill, brook, and, river, to whatever depression is its bourne, and another part, sinking in the earth, descends, by slow percolation, through soil and porous rock, until it reaches the same goal, or until, by some impenetrable barrier, it is crowded once more to the surface. Every bed of sand and gravel, and every porous stratum, while it is a reservoir in so far as it retards the stream, is a water-course in that it lets it pass. The phenomena of springs and wells have everywhere familiarized us with this underground circulation, but its manifestations are peculiarly impressive in the arid West, where precipitation is so small, and evaporation so great, that the superficial circulation is rarely conspicuous, and often is not perennial. It is a peculiarity of the streams of desert countries, that they do not flow constantly over the surface, but alternately rise and sink, appear and disappear. In a varied valley, which is alternately broad and narrow, deep and shallow, of rapid and of slow descent, the flood of gravelly detritus that is slowly carried forward by the agency of the stream, behaves, in many respects, in the same manner as the stream. It acquires width and depth and a surface of slow descent, where the valley is open, and contracts and WATER SUPPLY. 107 thins where the valley is narrow. The associated stream of water at its flood-stage fills a channel upon the surface of the detritus, and is its moving agent, but at its low, or usual state is in part absorbed, and, where the gravelly deposits are broad and deep, sinks entirely below the surface, and creeping along the rock bed of the valley, re-appears only in narrow and shallow places, where the mass of gravel is not sufficient to contain it. As a rule, the minor water-courses of the Great Basin contain a perennial stream only where their channels pass through narrow cafions, and are dry in broad, open valleys. Streams which rise in mountain gorges are peren- nial so far as they flow upon rock in place, but so soon as they reach the detrital foot-slope of the mountain, sink* out of sight, sometimes to re-appear, where some ledge interrupts their progress at a lower level, but more often to evaporate, without ever returning, as running water, to the surface. As - there are subterranean rivers, so, under the playas of deserts, there are subter- ranean lakes, whose surfaces, though spread beneath the ground, are, never- theless, reached by permeating air, and serve as areas for evaporation, just as do the surfaces of superficial lakes. The evaporating surfaces of such an underground lake must be multiplied, by capillary action, to many times its horizontal area, and the rapidity of its evaporation can depend only on the freedom of the interstitial circulation of air, and the air’s capacity for moist- ure. That such evaporation is sufficiently rapid to constitute an important element in the meteorological history of the country, is sufficiently evinced by the fact that numerous shut valleys are relieved of their entire ordinary supply of moisture in this way. Some cognate features of littoral evaporation are both curious and in- structive. The sandy margins of some rivers and lakes in the arid region— bars and beaches accumulated by the adjacent water—are far more saline than the water. The water of the Colorado River, for example, carries so little salt that it is perfectly palatable. But, while camping in the Black *The word “sink,” as applied to streams, has two colloquial uses on the desert. Its ordinary and legitimate use, as a verb, refers to the disappearance of a stream from the surface by absorption, but its familiar use as a noun, arose from a fallacy, fortunately far less prevalent now than the use of the term. The lake, pond, or marsh, in which a stream ends, and from which its water is evaporated, is viciously entitled the “sink” of the stream. “The Sink of the Humboldt,” “The Sink of the Sevier,” “The Sink of Chalk Creek,” are misnomers of this class. 108 GEOLOGY. Canon, and in the lower part of the Grand Camion, it was our custom, in order to avoid the fine mud with which the running water was charged, to dig shallow wells in the sand, close to the water’s edge, and the water obtained from these wells—and which was merely the. river water filtered through the sand—we found always saline, often in such degree as to pre- vent its use. I conceive that the sand, kept moist below by the percolation from the river, and rapidly dried from above, had stored up the saline con- stituents of the water which evaporated within its body, so as to produce the results we observed. Very similar facts were noted on the shore of Sevier Lake. The brine of that lake, though three times as strong as that of the ocean, is far from saturation, and, in the laboratory, must be reduced to one-third or one- fourth of its volume before precipitation of common salt will begin. Never- theless the sand of its beach is highly saline, a deposition having commenced long before the attainment of a condition of saturation. Iam persuaded that in this case, as in the other, there is, within the porous earth of the shore, a slow circulation shoreward, by reason of which the salt of -the lake is conveyed into the sand, just as the salt of the river is conveyed into the lake. In humid regions, where the rain-fall keeps the soil saturated nearly to the surface, the subterranean circulation would be directed lakeward, in- stead of shoreward, and lakes would gain, rather than lose, water by per- colation. That this is the fact is shown wherever fresh water is obtained by wells sunk near the ocean and below its level. Springs.—The name of spring is often given to the issuing or re-issuing of a stream that has been following its valley through the alluvial deposits, but is more properly applied to the outflow of water that has previously run or percolated ouly through the crevices or pores of rocks in place. In plateau regions, the springs, in common with all the other physical features, depend on-the succession and dip of the strata. Porous beds over- lying imporous are water-bearing, and they discharge from the line of con- tact at its lowest exposure. In the case of a mesa composed of strata with a gentle dip, one side being mural and the other gently inclined, springs appear most commonly in embayments of the mural side, and, as this is the prevailing structure of the plateaus, the majority of springs in such regions WATER SUPPLY. 109 are found under escarpments. Nevertheless they are not entirely wanting on the dip sides of inclined tables, and the streams of these slopes are, during rains, more copious than those of the steeper and narrower sides. The rain which falls on such tables is divided into portions, that flow ‘in opposite directions, and often to far distant goals. What penetrates, de- scends to some retaining stratum, and thus finds egress on the face of the escarpment, while the remainder follows the inclination of the upper strata to the opposite edge of the table. In this way the water which runs off from the plateau edge of the Sevier Basin, finds its way into the Sevier River, and is evaporated in the Great Basin, while that which sinks into the ground near the edge of the plateau, re-appears, along the escarpments facing to the south and east, in springs tributary to the Virgin, Paria, Dirty Devil, and other branches of the Colorado of the West. The surface drain- age of the San Francisco Plateau is northward to the Colorado and Colo- rado Chiquito; but a share of its subterranean drainage goes southward, and gives rise to the Verde and other tributaries of the Gila. In the region of the Basin Ranges, the conditions which control the distribution of springs are complex. The universal shattering of the rocks prevents the distribution of subterranean water according merely to the arrangement of pervious and impervious strata, and springs more commonly issue through crevices, from sources whose direction and distance cannot be determined. The phenomena, in both regions, are complicated by the presence of volcanic rocks, the stratification of which, when it exists, is less regular than that of detrital rocks. In some instances, the whole drainage- system has been turned aside by lava streams, while, in others, the lava floods have covered water-courses without damming them, so that copious streams issue from beneath their edges. Virgin Salt Well—Near the confluence of the Rio Virgen with tho Colorado, is a curious natural well. Lieutenant Wheeler first visited it in 1869, and mentions it in his report of that year’s reconnaissance. ‘Two years later, I was enabled to examine it with him. In a smooth, gravelly plain, sloping gently to the Colorado River, is a round, funnel-shaped, or crater- like opening, nearly 300 feet across at top. None of the shallow arroyos of the plain lead to it or from it. The sides are of unconsolidated detritus, 110 GEOLOGY. horizontally bedded, the upper 35 feet being of half sorted gravel and sand, and the lower 15 of saline sand showing a slight efflorescence. At 50 feet below the plain, is a water surface about 120 feet across, and beneath Fic. 47.—Salt well at the mouth of the Virgin River. this the slope of the bottom could be seen, continuous with that of the bank, for 15 or 20 feet. The water is too saline for drinking, and I detected no motion in it. A few hundred yards away, the plain terminates in a bluff facing the river, and under the bluff, at the contact of the sand and under- lying rock—a lava—is a line of springs, the altitude of which cannot be far different from that of the water in the well. Fic. 48.—Section of salt well at dlismonth of the Virgin iver The Devils Hole is near the eastern base of the House Range, Utah, and about ten miles south of Fish Spring. Like the Virgin well, it inter- rupts a smooth plain, and is circular. Its depth, to the water, is 15 feet, and the width of water is 15 feet. Above the water, the earth rises with a steep slope, and beneath, is vertical for a few feet, and then overhanging, (see Fig. 49.) The bottom was not visible. The water was brackish, and a Fic. 49.—Section Devil’s Hole. ycast-like scum partly covered the surface. There is no evidence that either of these wells ever overflowed. The water-ways that would mark outflow are not to be found. The waters are WATER SUPPLY. 111 not thermal, nor are there any marks of geyser action. The openings ap- pear to be due to the undermining action of subterranean currents, flowing in channels sufficiently open to permit the removal of even coarse detritus, and the salinity of the water suggests that these channels may have been opened by the solution of deposits of salt. In the reports of Drs. Loew and Hoffman will be found notice of hot and mineral springs, and in treating of volcanic phenomena we shall have occasion to mention, besides hot springs, some supposed geysers of Southern Utah. Lakes——The lakes that were examined by our parties gave little occa- sion for doubt as to their origin. The most important of them may be called lakes of corrugation. The disturbances which give rise to mount- ains produce at the same time valleys, which are their antitheses; and as there are peaks higher than all their surroundings, so there are valleys com- pletely inclosed by rocky rims. Where the erosion is sufficiently rapid, it may keep pace with the wrinkling of the surface, and either accomplish a complete drainage of these valleys, or so fill them with detritus from the surrounding ridges that no lakes shall be formed. In the Great Basin, partly by reason of the aridity of the climate that has characterized the region for a long period, there have resulted a great number of cups that have never been completely drained. The majority of these are now desert troughs, with playas in their lowest parts, and hold water only during a brief portion of the year; but others contain permanent lakes. The greatest of these, and one which may serve as a type, is Great Salt Lake. It occupies portions of three parallel troughs of the Range System, and is limited, north and south, by broad waves of the earth’s crust, which intersect the meridi- onal system of upheavals at right angles, (see Chapter on Orology.) Sevier Lake is in precisely the same case, save that it occupies but a single one of the trough-like valleys. Utah Lake lies in a portion of the most easterly of the Great Salt Lake troughs, and its valley is separated from that of the Lower Jordan by spurs from the adjacent ranges, which, while they do not - meet, apporoach so near that their gravel slopes intersect and afford an effectual dam. Owens Lake, in Southern California, lies in the narrow val- ~ ley between the Sierra Nevada and the Inyo range, and occupies a depres- sion exceptional to the general slope, which is southward. It is not improb- 112 GEOLOGY. ~ able that volcanic outflows have assisted in maintaining the southern bar- rier. Little Salt Lake in Southwestern Utah is similarly contained in a north and south trough. Stockton Lake in Rush Valley, and an unnamed pond in Cedar Valley, are to be assigned to the same cause, but cannot be called permanent lakes. In some instances, the retaining dams are merely accumulations of gravel, poured out from the larger cations of the adjacent mountains, and would quickly be cut through if the climate of the country were somewhat more humid. Rush Lake, in Southern Utah, Beaver Lake, a small expansion of Beaver Creek, near the North Star mining-district in Utah, and Pahranagat Lake, from which evaporate the waters of the Hyko Springs, are of this character. Little Owens Lake occupies a portion of the ancient channel by which Owens Lake overflowed to the south, and is held in check by a dam of gravel thrown across the channel by an intermittent stream from the Coso range. Another group of lakes is directly connected with volcanic phenomena. ‘Mountain Lakelet,” near the divide between the Sevier and Virgin Rivers, lies in a valley of erosion, between limestone walls, and is retained by fresh lava streams, which have filled the lower portion of the eroded valley. Panquitch Lake, in the same neighborhood, is believed by Lieutenant Wheeler, who visited it, to be a phenomenon of the same character. The “sink” of Chalk Creek, on the edge of the Sevier Desert, is a brackish pond, that appears to have been partitioned off by a fresh stream of basalt, and with it may probably be classed Spring Lake, which lies near the foot of Pah-van Butte, in the same desert. At the foot of San Francisco Mount- ain, Arizona, a small crater of basaltic scoria, with rim entire, contains a pond a few rods in diameter; and a water-pocket near Fillmore, Utah, is an accumulation of rain in the flue of an extinct crater. A description of the latter will be found in the Chapter on Volcanic Rocks. A third class of lakes is of glacial origin, being retained by terminal moraines. Fish Lake, the most considerable of these, was examined by Mr. Howell, and a description of it will be found in his report. Of this character are the lakelets near Wheeler’s Peak, Nevada, and that which lies at the foot of Belknap and Old Baldy Peaks, in Utah. WATER SUPPLY. 113 I have enumerated only those lakes which were examined by members of our expeditions in 1871 and 1872, and which now exist as such during all or the greater portion of the time. All through the region of the Basin Ranges are the vestiges of lakes, which have disappeared by evaporation, or by the cutting of their barriers. The greater number would fall within the first named group, but many belong to the volcanic and glacial classes. The character of lake water, whether salt or fresh, depends chiefly, though not entirely, upon the question of outlet. Utah, Panquitch, and Beaver Lakes, and all of the glacial lakelets, overflow and are fresh. ‘Mountain Lakelet,” which is nearly fresh, has no visible outlet, and its shores show that its level fluctuates. Its highest beach-line is so strongly marked as to suggest that, at that level, its water finds outlet through the shattered lava stream that con- stitutes its lower barrier. The pond in which Chalk Creek terminates is but slightly brackish, and may have a subterranean outlet. The ponds found in craters are fresh, by reason, perhaps, of the restricted areas from which they can derive soluble minerals. The Cedar Valley and Stockton ponds, although they receive the drainage from considerable areas, are said to contain drinkable water; but their conditions are exceptional. The former is chiefly supplied by a stream that is completely consumed during the summer by irrigation, and it is evaporated to dryness nearly every sea- son. The latter has come into existence since the settlement of the country, and covers a tract that was at one time set apart by the Government as a hay reservation. It apparently owes its origin, or at least its resuscitation, to the same general change of climate which has caused the contempora- neous rise of Great Salt Lake.* The anomalous freshness of these waters is doubtless connected with their peculiar intermittence, but in what manner I am at a loss to conjecture. With these exceptions, the undrained lakes of our list are saline. The waters of Great Salt, Sevier, Rush, and Owens Lakes are heavily charged with mineral matter. We are able to give analyses of but two of these brines. That of Great Salt Lake, obtained by Captain Howard Stansbury, *The information presented in regard to the Cedar Valley pond was gathered by Mr. E. E. How- ell; that in regard to Stockton Lake by Mr. Louis Nell, of the topographical corps. 8ws 114 GEOLOGY. in 1850, was analyzed by Dr. L. D. Gale.* The brine of Sevier Lake was collected by Lieut. R. L. Hoxie, in 1872, at a point on the west shore, re- mote from the inflow, and has been analyzed by Dr. O. Loew. Brine of Sevier | Brine of Great Lake, (O.| Salt Lake, Loew.) (L. D. Gale.) (Chlondiofisodiumss seers ae aie seen weenie ne sieneetwinen=se 2 (2 20. 196 SHUEO OE SeV8b S555 Song ea5s posses cesees sss cso Assess sesese se soSoce I. 34 1. 834 Chlorid offmagnesivms 2-2 ee --2 oo =e eee == ase eee ee cece tee ae wee eee 1.03 0. 252 SHUP ES QUPINS, .onc sang ceos Sseese shoes sso obstesseoSss se se sossesese+ 0.04) Tl) sertesteaeeeeee (Gilbya@loreilen tr sono 5 ssasonsesose soddes Ab cS sasoss sous sere Sota st ceds|[ossscs cscc este Trace. Motalhneroolparts of watenlon==—- eee ee ees aaa ee a ee elem alae 8. 64. 22, 282 The areas draining to these lakes are of very similar charactér, and it is not surprising that the brines should be qualitatively identical. The sul- phate of lime in one case need not be distinguished from the chlorid of cal- cium in the other, as the difference is merely one of interpretation by the analysts. The brine of Great Salt Lake is economically superior to that of Sevier Lake, not merely in its greater strength, but in the less relative per- centage of sulphate of soda and chlorid of magnesium. In comparing the _ two waters, some allowance must be made for the difference of date in the collection of the samples. The levels of the lakes and their volumes undergo fluctuations, which must affect the percentage of mineral matter in their waters. While the tributary streams are flooded by the melting snows, the waters rise, and during the remainder of the year subside; and besides this annual oscillation is the still ‘greater one dependent upon slow moving changes of climate. If Sevier Lake has undergone the same fluctuations as Great Salt Lake, and,since the areas they drain are similar and contiguous, it is extremely probable, its volume must have been less and its brine stronger in 1850 than at the time it was sampled. The best data we have in regard to the rise of Great Salt Lake in the interval place it at 10 or 12 feet. The soundings made by Captain Stansbury in 1850 indicate a mean depth of about 13 feet, and the shores of the lake shelve so gradually that a * Exploration and Survey of the Valley of the Great Salt Lake of Utah, p. 417. WATER SUPPLY. 115 rise of this amount would suffice to more than double its volume. In ignorance of the configuration of the bottom of Sevier Lake, we cannot tell what relation maintained between the increase of its surface and of its vol- ume; but if it expanded in sympathy with Great Salt Lake, its brine must now be more dilute than formerly.* In a general way, we must regard Great Salt Lake as saturated with chlorid of sodium; that is to say, whenever, in the irregular rise and fall of its level, depending upon the varying seasons, its volume reaches a mini- mum, there is a precipitation of salt. This was observed by Captain Fré- mont in 1845, and may take place, even at the present day, upon its west- ern shoals, at times when the water is not sufficiently stirred by the wind to prevent local concentration by evaporation. Artesian Wells——The principle upon which artesian wells depend is a simple one, and the conditions essential to successful search for them are few. The well, and the stream which supplies it, are always equivalent to a bent tube, or inverted siphon, filled with water, in the longer leg, to a height greater than the top of the shorter. The well is the shorter leg; the natural conduit, tapped by the well, the longer. The natural conditions upon which the possibility of artesian supply depends are, firstly, that of a series of inclined strata, one, so porous as to permit the circulation of water, shall be contained between others comparatively or absolutely impervious; secondly, that these strata shall somewhere rise to a height greater than that of the point at which the discharge is sought; and, thirdly, that the free dis- charge of the subterranean water shall be checked in other directions. It is not essential that the reservoir shall be completely closed at all sides lower than the position of the well, but merely that the flow of water shall be so far impeded in such directions that the pressure from the head may suftice to raise it to the desired altitude. In the region of our explorations, these conditions are best fulfilled within the limits of the Plateau system. The strata which compose the plateaus are unbroken over large areas, and they are more or less inclined, so as to expose their edges in elevated regions. All along the west side of *According to Mr. H. 8. Poole, the lake brine is found less productive of salt than formerly, in the ratio of 3to 7. Article on “The Great American Desert,’ in Proc. Nova Scotia Inst. Nat. Sci., vol. iii. 116 GEOLOGY. the Sevier Valley, from Monroe nearly to Gunnison, it is probable that an artesian water-supply might be obtained. Throughout that line, the Ter- tiary strata are gently inclined toward the valley, and present, upon the summit and western face of the Pah-vant range, faces adequate for the accumulation of water from rain and snow. Farther south, in the same val- ley, at Panquitch, and thence twenty or twenty-five miles up the Sevier, the conditions are similar; and, in the next parallel valley at the east, it is prob- able that the same favorable relations can be found. To the south of the great Tertiary escarpment which limits the Sevier basin, the country is intersected by cafions, which drain the strata at so low a level that it is improbable that a free discharge could be obtained from deep wells; and, in the neighborhood of the deep cations of the Colorado, the thorough under- drainage which they effect would be sure to negative any search for arte- sian water. The same under-drainage would affect, also, the entire San Francisco plateau to the south of the Grand Canton of the Colorado. In the region of the Basin ranges, the sedimentary rocks are too little continuous to warrant their exploration for artesian water. It is not impos- sible that it may be obtained in some localities; but too great uncertainty would attend the experiment to give it practical warrant. On the other hand, it is probable that water might be obtained from the valley deposits within the area of the ranges. We know too little of these deposits to be certain that they contain continuous and impervious beds; butif the alterna- tions of climate that characterized the Glacial epoch was a repetition of anterior fluctuations, it would indeed be strange if they did not give rise in many places to alternations of gravels and clays in such way as to con- stitute reservoirs that might be economically tapped. The best localities to search for such reservoirs would be found in the broader valleys. In the narrower, we may expect that the deposits close to the flanks of the mount- ains have always been more or less open, and that clay beds, if they exist, are not sufficiently elevated at their margins to retain water at an adequate height. In shut valleys, such as those of Great Salt Lake Desert and Sevier Desert, a supply of water, if obtained, would be almost certain to contain too much mineral impurity to be fit for use; but in others, such as Ralston Desert and Amargosa Desert, which we may suppose to have sub- WATER SUPPLY. 17 4 terranean drainage, it is by no means improbable that a supply of good water may sometimes be brought to the surface. It is to be regretted that the localities which afford the best prospect of a supply are not those which stand in greatest need of it. The valleys of the Plateau region, for the most part, lie at such an altitude that they receive considerable rain-fall, and are better supplied with streams and springs than are the valleys, or even the mountains, of the Basin region. In the latter country, where agriculture can, at best, never become of great importance, and where the principal demand for water is in connection with the ore deposits along mountain ridges, it will be found difficult, and in ‘most cases impossible, upon the mountains to increase the supply already afforded at the surface. D's Wel cl el pl be VOLCANIC ROCKS AND MOUNTAINS. LOCALITIES OF THERMAL SPRINGS IN THE UNITED STATES. At the time of the preparation of this chapter, there is in progress the most active and wide-spread discussion of the whole subject of vulcanicity. Every month brings new contributions to its literature, and speculation and research are reacting with reciprocal stimulation. A chief center of interest is the problem of the source and cause of igneous eruptions, and with it are involved such other questions as the origin of mountain corrugation, and of the elevation and depression of continental areas; the mode and condi- tions of metamorphism; the relations in time and depth of the plutonic and voleanic rocks; the relations in time and space of the acidic and basic eruptive rocks. It is my purpose to make no theoretical contribution in this place to any of these topics, but merely to present such facts as have come under my observation, with occasionally a brief statement of their relation to the problems of the day. Distribution of lavas.—No province of the mountain region west of the Plains has been exempt from volcanic eruption, and hardly a mountain- ridge is composed entirely without lavas. But while the distribution of voleanic rocks in general is thus well-nigh universal, there are distinctions worthy of note in the manner of arrangement in different districts, as well as in the comparative prevalence of the different species of lava. The physical provinces that we have characterized in a former chapter as the Basin Ranges and the Plateaus, as they are contrasted in all other charac- ters, are measurably distinct also in their volcanic manifestations. In the former province, there is a linear arrangement of vents in trends coincident with, or parallel to, the axes of corrugation, and the acidic lavas predominate. In the latter, vents are grouped without evident linear system, and the basic lavas assume greater prominence. 118 VOLCANIC ROCKS AND MOUNTAINS. 119 The material gathered in the Basin region is most readily presented according to mountain ranges, and these will be taken up in such order that those of Southwestern Utah will be followed successively by those examined in Nevada, California, and Arizona. There are no considerable extruded masses upon the Oquirrh range ; . but there were seen, at the head of Middle Caton and upon Lion Hill, upon the crests, that is, of its two principal anticlinal folds, a number of trachytic dikes walled by Carboniferous limestone. The principal mass and the north end of the Lake range are without lavas; but Mr. Howell found a sheet of basalt covering the southern extremity. Lieutenant Marshall observed rhyolite in great force on the crest and eastern slope of the Tintic range. The Champlin Mountains were seen only along the Cherry Creek Pass, in which part the Paleozoic axis is almost completely buried by sheets of rhyo- lite and rhyolitic tuff; and the same belt of eruption appears to be prolonged to the southwest, interrupting the northern margin of the Sevier Desert with a series of lava hills. Volcanic rocks were seen in the Stansbury range at one place only. From Grantville southward to the head of-Tooele Valley, Mr. Howell found a line of trachytic and doleritic eruptions along the east- ern base of the ridge, under the escarpment of Paleozoic strata that there faces Tooele Valley, (see Fig. 97.) The same observer found basalt and trachyte in force at the south end of the Cedar range, in which vicinity the latter rock constitutes the highest peak; but farther north the lavas appeared in the foot-hills only. No volcanic rocks were seen about Granite Mount- ain; but the Thomas range, of which it is an outlier, is buried (except the eastern base) for several miles south of Dug Way Pass by a flood of tra- chyte. The principal mass of the eruption is of a light vesicular variety, which rapidly disintegrates, and it appears to have been greatly reduced by erosion; but one of its summits, a tabular peak, is still the loftiest pot of the vicinity, and probably of the range. Immediately west of this part of the range, and parallel to it, are two short monoclinal limestone ridges, each of which is flanked at the west by a mass of basic lava. No lava was seen on the House range, although it was scanned from one side or the other for a distance of eighty miles. There has been a small outflow of rhyolite near its eastern base on the shore of Sevier Lake, and a line of basaltic 120 GEOLOGY. hills trends parallel to the range just west of its northern member. In like manner, the Confusion range at the west of the House, and the Beaver Creek at the east, show no conspicuous eruptions. A small rhyolite flow was observed at the western base of the former, and a few basalt hills at the northern extremity of the latter. Small outflows of basalt and trachyte were seen in a valley of the Picacho range, two or three miles west of the town of Shenandoah. A great area in the southwestern portion of the Sevier Desert is floored, partly above and partly below the surface of the desert- sand, by basaltic sheets, and they are accompanied in the vicinity of Fill- more by an interesting group of tuff and cinder cones, of which further mention will be made. At the north, the excavation of the “‘ old river-bed” has laid bare one edge of a similar basalt sheet, and it is not improbable that a large portion of the plain is similarly underlaid. At White Mountain Station of the Fillmore and Pioche stage-road, the basalt of the desert rests against a small island of trachyte, that is probably the crest of a range buried by the desert detritus. A little farther south, in the interval between the Beaver and Beaver Creek ranges, are massive eruptions of similar rock, overlapped to the south and southwest by the broad basalt flow, from the margin of which breaks Black Rock Spring. The Pah-vant rangeis, so far as I am aware, non-voleanic ; but its immediate southward prolongation, the Beaver range, is, at surface, almost completely rhyolitic. A nucleus of sed- imentary and plutonic rocks is exposed at a few points, and a few patches of basalt occur at the eastern and western bases; but the great mass of the range—and its top rises from five to six thousand feet above Beaver Valley— is of rhyolite. Between the Beaver and Mineral ranges, but nearer to the latter, there is, at the north end of the Upper Beaver Valley, a lava cone of considerable magnitude, from which streams of basalt have overrun the head of the valley. The Mineral range elsewhere has very little volcanic material; the only locality noted being at the south end, near Adamsville, where, at the foot of the mountain, are inconspicuous eruptions of trachyte and basalt. Mr. Howell, in passing the south ends of the Hawawah and Needle ranges, saw only voleanie rocks; rhyolite, with minor areas of basalt. The spur which stretches westward from the Beaver range, and separates Beaver and Parowan valleys, is reported trachytie by Mr. Howell, VOLCANIC ROCKS AND MOUNTAINS. 121 and the same character is continued for twenty miles southwestward in the mountains facing Escalante Valley. The Pine Valley mountains were found by him to be capped by trachyte of great depth, and flanked at the east, south, and west by streams and cones of basalt. In the Bull Valley Mount- ains and associated ridges at the northeast, he saw only trachyte and rhyo- lite, except at Iron City, where the underlying sedimentary beds are ex- posed. The Virgin range at the points examined by Messrs. Marvine and Howell is not volcanic; but Mr. Marvine observed basaltic outflows along its eastern base in the vicinity of the Grand Wash. In Nevada, the eruptions have been even more profuse than in Western Utah, and over large areas have buried all other rock masses. Throughout the region traversed by the expedition north of the Central Pacific Railroad, from Carlin to the Bull Run mining-district, and thence to Battle Mountain, the high, rolling uplands are volcanic, and other rocks, although constituting the highest summits, are exceptional and insular. The prevalent lavas are acidic—rhyolite and trachyte—and basalt, where it occurs, has an outlying or fringing position. The region abounds in secluded valleys, partitioned by the irregular outburst and outflow of the lavas, and is so well watered that these have all been opened by erosion. The streams, in consequence, traverse a quick succession of cafons and open valleys. The Shoshone range, where crossed by Reese River, is rhyolitic, and, although cut to its base, shows no sedimentary axis. The Toyabe range has been described by Mr. 8. F. Emmons as flanked by lava at several points. The Toquima range, south of Jefferson Pass, is built of granite and Paleozoic strata, but to the north has been completely overrun by rhyolite. A little basalt was seen on Jefferson Creek. The Monitor range, as seen from Belmont, has the characteristic habit of the acidic lavas; and- in twenty miles of its length, examined farther south, these rocks only were seen, save that a single spur of metamorphic rock, at its western margin, faces Ralston Valley. Where I crossed the Hot Creek range, the only point at which I touched it, it is identical in character with the Monitor, and the nearest point I could recognize as other than volcanic was Tybo Peak, ten miles to the north. The same characters seem to be continued southward, in its prolongation, the Kawich. Between the Hot Creek and Monitor 122 GEOLOGY. | ridges, a parallel line of low rhyolite hills divides the valley. The Pancake range derives its homely but expressive title from the low conoid profile due to its constitution. The profuse eruptions that have escaped along its Via. 50,.—A portion of the Reveille range as seen from Timpahute Peak, Nevada. axis, not sufficiently viscous to build—as in the Monitor and Ka- wich ranges—steep-sided ribs and bosses, have spread in every direc- tion from the line of outburst, pro- ducing low, gently-curved forms, of which the only steep acclivities are produced by erosion. The Reveille range, which continues the same structure line southward, is chiefly built of massive rhyolite, flanked by rhyolite tuff and basalt, but exhibits, at the mining-camp of Reveille, a small island of Pale- ozoic rocks. We did not follow it south from that point; but the portion west from, and overlooked by, Timpahute Peak has all the features of the Pancake range, (see Fig. 50.) Still farther south, at what may be regarded as the end of the range, it is still vol- canic, consisting of rhyolite and rhyolite tuff. The Quinn Cation range consists of two parallel mas- sive eruptions of rhyolite, six or seven miles apart, and inclosing a north and south valley, at the — Mount Worthington is an insular mass of Paleozaic rocks, but has volcanic (rhyolitic ?) foot-hills at the north and south and along part of its eastern base. VOLCANIC ROCKS AND MOUNTAINS. 123 The Snake range is nearly free from volcanic rocks. There was probably a small rhyolitic eruption at the north end near the Clifton mining- district, and, at the pass between Kern Mountain and Go-si-ute Mountain, a spur of trachyte from the Antelope range west of it was seen by Mr. Howell to touch the range. The west side of Deep Creek valley and the low ridge known as the Antelope range showed us only trachyte and associated tufts. The Schell Creek range is in the same vicinity—the vicinity of Schell- bourne—overrun by trachyte and rhyolite, but not so completely as to entirely conceal the axial rocks. Southward, to Ruby Hill, its proportion of eruptive rocks diminishes, and none were seen beyond. The Ely range, which continues the same line of uplift to the south, was examined from - Pioche northward by Mr. Howell, and found to be chiefly sedimentary, but flanked on the east in one place by trachyte. The Pahroc range, where intersected by the road from Hyko to Pioche, is of trachyte, and, so far as could be judged from distant views, is volcanic for a number of miles both to the north and to the south. The Hyko range is a low ridge of limestone, accompanied by a few small bodies of trachyte. The Pahranagat, constituted chiefly of limestone, has one large eruption of rhyolite at its north end, where its strata dip below the general plain, and another at Logan Pass, where, at a cross-fault, the structure of the mount- ain is radically changed. 'Timpahute Peak is the culminating point of a massive eruption, which occurs at a similar change of structure in the paral- _lel Timpahute range, and the intervening valley is interrupted by a line of voleanic hills. The Belted Mountain range shows near White Bluff spring, and for sev- eral miles. southward, an axis of quartzite; but its principal mass is of rhyolite and trachyte. Along the eastern front, these are of inflated and tuffaceous yarieties; and, just north of White Bluff spring, they stretch eastward to the Reveille range. Along the crest of the range, there is a heavy cap of more compact lava, and this, extending westward, with slight descent, for ten or twelve miles, terminates in a bold step, overlooking the broad rocky desert that surrounds Oasis springs, the head of the Amargosa “ River.” From these springs eastward thirty miles, to Belted Mountain, westward twenty-five miles, to the edge of Death Valley, and northward as far as we 124 GEOLOGY. could see—twenty-five or thirty miles—the entire surface of the country is covered by lavas. The principal centers of eruption are marked by broad, low-angled cones, and the prevailing colors are those of the acidic Seale, 1:150,000. a, basalt; b, granite; c, volcanic tuff. 51.—Section of Pilot Mountain, California. Fic. lavas. A few groups of small, steep crater-cones could be seen marking the position of basaltic vents, but they seemed quite subsidiary. To the south, this area is limited by the detrital stretches of the Amargosa desert, flanked at the east by the Paleozoic escarpment of Bare Mountain, and at the west by the Amargosa range. The only locality at which lava was observed on the Spring Mountain range is near Good Spring, where there has been a small outflow of basalt. For thirty miles of its length, it has no considerable body of vol- canic rock. In California, our most westerly point was the east- ern base of the Sierra Nevada; and the only volcanic eruptions seen there are some basaltic cones and coulées, a few miles north of Camp Independence,—utterly insig- nificant features in comparison with the granitoid body that overhangs them, and which constitutes, for so many miles, the eastern face of the great range. A little basalt was noted in crossing the Inyo range, but the mountain is not characterized by lavas. Its southward prolonga- tion, the Coso, is so characterized, and south of Owens Lake appeared to us, as we skirted its western base, to be entirely eruptive. We noted, in its débris, rhyolite in great variety, trachyte, and basalt. The El Paso Mountains, southeast of Walker’s Pass, are flanked at the south by basaltic and trachytic rocks, and connected at the east with a large mountain of acidic lavas, enclos- ing and nearly concealing a core of granite. East of this stands Pilot mountain, the monument of an accumulation and an erosion hard to conceive. Its summit is an inclined table of lava, capping and pro- tecting about 2,000 feet of softer voleanic products, (probably tufts,) and VOLCANIC ROCKS AND MOUNTAINS. 125 the whole stands alone on the highest swell of an uneven granitic surface that passes—except jutting peaks—beneath desert sands at the north and south. It appears to be an eccentric remnant of a great voleano, of which denudation has left no other conspicuous vestige. At its western base is a line of tabular basaltic hills of comparatively recent origin. Burnt Rock range is a monoclinal ridge of partially bedded volcanic products. It con- tains a series of trachytic and rhyolitic lavas, conglomerates, and tuffs, which present an escarpment to the east, and appear to have been uplifted en masse. The mountains which flank Death Valley—the Panamint at the west and the Amargosa and Funeral at the east—are essentially mountains of upheaval; but, wherever we touched them, we found lavas present as sub- sidiary features. The Colorado Mountains in Arizona, where intersected by the Colo- rado River in Black Canon, are of massive trachyte, with a deep-buried axis of syenite, and are flanked by basaltic cones and coulées. In Boulder Canon, there is shown an axis of metamorphic rocks, overlapped at the east by acidic and basic lavas in order. The San Prieto mountains about Prescott show very little lava, but in the vicinity of Postal’s Ranch, and thence to Granite Peak, are eruptive in character. Crossing the Black Hills near their northwestern extremity of the ridge, I found an inconspicuous fringe of basalt along each base. Far- ther south, Mr. Marvine found the axis nearly buried under lavas ; and it is probable that the tabular crest lying between our routes is basaltic. A most important feature of these eruptions is their association with the ridges of corrugation. The great majority of vents are along lines of upheaval, and of the remainder, the principal part are arranged in rows parallel to the structure lines. In the case of many lava fields, the points or lines of issue cannot be made out, and there are numerous eruptions that show no conformity to the general rule; but the law that the distribution of the lavas is in sympathy with the ridge structure, rests on too broad a basis of facts to be vitiated by its exceptions. More than this, there seems rea- son to believe that uplift and extrusion are, in a certain degree, mutually complementary, or equivalent. The highest ranges, as a rule, are (compara- 126 GEOLOGY. tively) non-voleanic, and those ranges, or portions of ranges, which exhibit the greatest eruptions are endowed with but low nuclei of other material. Where, in tracing a range, we find its crest exchanging non-voleanic rocks for volcanic, we do not find the latter heaped upon an undiminished ridge of the former, but rather replacing it, as it gradually or suddenly diminishes in height; and the case is strengthened by the consideration that, while the low, buried portion of the nucleus has been guarded by its mantle against the forces of denudation, the higher part has been exposed to a continuous waste. That lavas in a disturbed region should find vent along existing lines of fracture might be assumed as probable upon any theory of mountain genesis; and it does not necessarily follow from the coincidence, in place, of uplift and eruption, that the subterranean loci of the action which has produced corrugation are identical with the volcanic sources. If, however, it be shown that along lines of disturbance there is an inverse quantitative relation between uplift and outflow, a strong argument is adduced, not merely for the identity in location, but for the absolute identity of the up- heaving and volcanic forces; for, if the two modes of mountain building ~ are complementary actions, they must be regarded as co-ordinate manifesta- tions of the same agency. It is by no means easy to demonstrate this interrelation of upheaval and eruption. My own confidence that it exists is derived from the compre- hensive review of my notes, referring to about fifty of the Basin Ranges, and is a result of inspection rather than analysis. I know not how to pre- sent the material to the reader—without special pleading—so that it shall have the same force. The distribution of eruptions is, in detail, so capri- cious, and all estimates of the magnitude of mountain movements are so involved with considerations of erosion, that it would avail little, even were the material at hand, to attempt a full presentation of individual examples ; while, in a more general statement, it is impossible to dissociate the observed facts from those personal impressions that are liable to be shaped more or less by preconceptions. The universality of the lavas has already been mentioned. I have seen no range of the Basin system entirely free from volcanic rocks, and VOLCANIC ROCKS AND MOUNTAINS. 127 the reports of other explorers confirm the impression that such instances are rare exceptions. The lavas of the Basin ranges are chiefly acidic. The basaltic rocks assume an exaggerated importance upon the map, from the fact that, having a later date, they overlie portions of the trachyte and rhyolite, and their thin- spread sheets have suffered less from erosion; but, when masses are con- sidered, they shrink to insignificance. The more ancient basic lava, to which Mr. Richtofen has given the name of propylite, is perhaps of more importance; but its mode of occurrence is so similar to that of trachyte that no distinction could be made when it was not absolutely crossed. It is cer- tainly far inferior in amount to the acidic. The trachyte and rhyolite are characterized by what have been called massive eruptions; that is, by viscous eruptions of great volume, the lava of which, instead of flowing off in coulées, or building cones by slow accu- mulation of congealed streams, has, by single or few issues, formed bosses, often of great thickness, and divided by few or no surfaces of bedding. It is probable that these bosses lie usually immediately above the fissures from which the material has arisen; and they are often elongated into ridges parallel to the fissure system, as though there had been, in each case, a simultaneous issue along a considerable line of fracture. The material of these masses ranges from very compact lavas to those which are nearly as light as pumice, though lithoid in texture and only minutely vesicular. From the compact lavas, there is an easy gradation to the breccias, and the porous lavas are separated lithologically by no trenchant line from the tuffs; but the last, when well marked, always betray more or less bedding. Nearly all of the varieties found in massive eruptions are seen also in bedded sheets; and this mode of occurrence is as general as the other. Considering together the whole regions of the Basin ranges, the prevalence of rhyolite and trachyte tuffs is marked, though in many districts they are entirely wanting. Notwithstanding the rapid destruction to which their accumu- lations are subjected when they occupy elevated positions, they are yet retained in immense volume. Where best preserved, they are protected by caps of harder material, and exhibit bedding with notable inclination ; but their denudation has usually progressed so far that only a hint is given 128 GEOLOGY. of the magnitude of the volcanoes to which they pertained. ‘Tuffs are less frequently associated with the basalts. In volcanic phenomena, as in other features, the Plateaus are in some degree contrasted with the Ranges. Basalts assume a far greater promi- nence, rivaling the trachytes in abundance. Rhyolites are not in great force, and the chief trachyte masses are of basic varieties. The minor manifestations are almost invariably basaltic. Tuffs are nearly unknown. There is no observed arrangement of vents according to structure lines, and (this last, however, is not a contrasting feature) the distribution is unequal as well as irregular. The two principal fields traversed by our parties lie near the boundary of the Plateau system, and have their longer diameters parallel to that boundary. The more northerly is entirely within Utah, and is nearly included in the Sevier Basin. Northward it touches the parallel of 39°, near the town of Salina, and southward that of 37°30’. Westward it passes the plateau boundary, and coalesces with the eruptions of the Bea- ver and more westerly ranges; and eastward its crosses the rim of the Sevier Basin and encroaches on that of the Dirty Devil. Its boundary is — irregular and includes a number of islands of sedimentary rock, but within it a straight lime more than one hundred miles long (in a north-northeast direction) could be traced entirely on lava. The greatest dimension at right angles to this is about sixty-five miles, and the entire continuous area of lava comprises about five thousand square miles. The predominant rock in this field is a trachyte closely related to dolerite, and this gives place eastward to more acid trachyte and rhyolite, and southward to basalt. Ex- cept in the Beaver range the flow of the lavas has been in broad sheets, and these, accumulating in a deep series before the faulting of the Plateau rocks, have been thrown into cliffs and inclined tables, together with the underly- ing sedimentaries. Along the east side of the Sevier Valley, from Red Cation, near Panquitch, to the neighborhood of Glencove, these cliffs, pro- duced by the great Sevier fault, reveal a depth of bedded trachyte that must average 1,500 feet, and at its maximum exceeds 2,000 feet by an un- known amount, the base of the series being unseen. The principal basaltic tracts in this field lie east of Fish Lake and Otter Creek, about the head- waters of the Dirty Devil River, and southwest of Panquitch. A description VOLCANIC ROCKS AND MOUNTAINS. 129 of the former will be found in Mr. Howell’s report. The latter is thickly studded with lava cones and cinder cones of no great magnitude, and is spread with a long succession of coulées, the latest of which are so recent that vegetation has as yet no hold on their black, blistered surfaces. North of this great field Mr. Howell observed two isolated masses of lava, the first of trachyte, constituting the southward spur of the Wahsatch range, which separates the main forks of Sam Pitch Creek, and the second of rhyolite, lying along the western base of the Sam Pitch Mountains. South of the same field are a series of basaltic cones and streams, that may, perhaps, be regarded as outliers of the Panquitch basalt district. They occur upon and to the east of the head of Kanab Creek, about the head of the Virgin River, overlooking the valley of the Virgin from both sides a little below the union of its main branches, and within the valley in the vicinity of the towns of Toquerville and Washington. The Uinkaret Mountains, beginning fifty miles farther south, are a larger group of the same character, carrying the chain, if chain it may be called, to the Grand Cation of the Colorado. _ A few miles beyond the Colorado commences the second great lava field of the Plateaus, one far exceeding that of the Sevier Basin in magni- tude, but only partially included in our region of exploration. Beginning in the neighborhood of Truxton Spring and the head of Diamond Creek, it stretches, in an uneven but continuous belt, east-southeast to Sierra Blanca, and, beyond, spreads several broad lobes over New Mexico, the most east- erly of which reaches nearly to the Rio Grande. Its extreme limits, in longitudes 113° and 107° 15”, are three hundred and twenty-five miles apart. Northward it touches the parallel of 35° 40’, and southward that of 32° 50’. What share of the Arizonian portion we have here to consider has an area of about ten thousand square miles, and is perhaps one-half of the whole. It includes the San Francisco group, the Mogollon Mountains, and the Sierra Blanca, and these follow from west to east, in the order named, along the southern margin of the Plateau country. The San Francisco group includes a series of large cones of trachyte, the product of massive eruptions, and a great multitude of small basaltic cones, associated with broad and, in part, thick sheets of basaltic lava. The 9Wws ; 130 GEOLOGY. trachyte has, perhaps, the greater mass, but the basalt covers by far the larger area. The larger cones, though they may justly be called a group, are separated by intervals of several miles. The largest, San Francisco and Bill Williams Mountains, were ascended, and the character of Mount Floyd was ascertained in crossing its northward spur. Mount Sitgreaves, in form, color, and size, connects itself with the trachytic class, and Mounts Kendrick and Picacho are doubtfully referred to the same class, although in form they rather resemble the smaller, crater-bearing, basaltic cones. While the number of vents of trachyte was small, at most not exceeding a half dozen, the basaltic vents were very many, probably some hundreds in number. As many as one hundred are marked by cinder cones, of which sixty-five with craters, partially or wholly preserved, were counted from the summit of San Francisco Mountain about its foot. In this vicinity the floor of the Plateau is the Aubrey limestone, (Upper Carboniferous,) and there is a gentle dip northward from the Aubrey cliffs to the Colorado and Colorado Chiquito. The cones stand near the upper(southern)edge of the table, and the flowing lavas have in part overrun the cliff, and poured into the valleys of the Verde and its tributaries. The principal roads connect- ing the upper and lower countries avoid the precipice that marks the out- crop of the upper Aubrey beds, by following the easy grades of these black congealed rivers. The Sierra Blanca likewise presents peaks of massive trachyte flanked by basalt. The interval of one hundred and seventy miles between it and San Francisco Mountain is bridged by a chain of basaltic eruptions, merg- ing with those that surround the trachyte masses. Through the greater part of its extent, this basalt flow is low and broad in cross-section, and it neither merits nor receives the title of mountain, save at one point, where a cluster of unusually large basalt cones, near the Sierra Blanca, has been given the name of Mogollon (hanger on) Mountains. Mr. Marvine’s route intersected this field in two places, and its characteristics will be found described in his report. It is well worthy of note that the majority of these eruptions among the Plateaus rest upon nearly level strata, and that where they are associated with inclined strata, such inclination is seen to pertain to a structure extend- VOLCANIC ROCKS AND MOUNTAINS. 131 ing far beyond the volcanic outburst, and evidently not dependent on it as a cause. Among the Basin Ranges the strata are so greatly dislocated, independently, that it is impossible to determine that the eruptions have or have not disturbed them; but where the normal structure is so simple as it is in the Plateau country, a local structure imposed by the extrusion of lava could not escape detection, and we have direct evidence in its absence that the eruptive rocks, in passing through, have not uplifted the sedimentary. This remark applies not merely to the eruptions of basalt, which we know from the narrowness of its dikes and the easy slope of its currents to have been usually a tolerably thin fluid, but also to the most viscous trachyte, which, in the case of San Francisco Mountain, for example, has been built, not a scoriaceous mass, but a pyramid of compact lava, to a height of nearly 5,000 feet, with slopes of 10° to 20°. It is by no means impossible, it is probable, rather, that in upheaved ranges, uprising lavas sometimes force apart rock masses, already greatly dislocated, so as to open the broad fis- sures, in which their dikes are occasionally found. But the idea that ridges of corrugation are lifted by the eruptive rocks that are associated with them— an idea that finds frequent expression in the phrases ‘‘ upheaved by trap,” “upheaved by granite”—appears deserving to be laid on the shelf along with the cognate idea of “craters of upheaval.” Turning now from the distribution of the lavas, we will consider for a moment their petrography. . The proposal by F. Richtofen of a “Natural System of Volcanic Rocks” (Proc. Cal. Acad. Sci.) is of special interest to geologists, as a most able attempt to classify geologically a group of rocks that had been before con- sidered almost exclusively from a chemical and lithological point of view ; and we have endeavored, so far as we were able, to test his classification by examinations in the field. Our material does not warrant a discussion of his conclusions, failing as it does to comprise the results of any detailed study, but upon one point the very width of the field crossed in our rapid transit, permits us to speak. Richtofen’s theorem is that volcanic rocks have a natural order of sequence, viz, propylite, andesite, trachyte, rhyolite, basalt. The first and second of these divisions we have rarely met, and we have no reason to question their inferior position. Of the succession of 132 GEOLOGY. ? trachyte and rhyolite, we cannot speak definitely, although we have seen them more often than other species. Their constant association, their identity in habit, the parallelism of their multitudinous varieties, and their intergradation have prevented their ready discrimination in the field, and, at the same time, occasioned doubt as to the validity of their separation. The basalt group, on the other hand, was everywhere distinguished, and its rela- tions made out. With a single exception, observed by Mr. Marvine, at Truxton Spring, Arizona, it was seen to overlie, wherever it touched, rhyolite and trachyte. Usually there was evidence by erosion of a great lapse of time between the trachytic and basaltic eruptions, and in this way a relation of sequence was established where there was no contact. Along the Sevier fault, near Glencove and Salina, for example, trachyte sheets, conforming to the Tertiary strata, and dipping with them, are shown to have been spread before the disturbance, while basalt, resting unconformably on the tilted and eroded strata, evinces its later advent. The trachyte of Pine Valley Mountain has resisted the erosion that has opened valleys around it, (see report of Mr. Howell,) and it stands a lofty “mountain of cireumdenuda- tién ;” while in the valleys at its foot have sprung up a chain of basaltic cones. Since the eruption of the trachyte of San Francisco Mountain, no less than 700 feet of strata have been removed from about it; and the basalt of the immediate vicinity rests on the new floor of the plain. At this locality, however, the succession is also shown by actual contact and superposition. Superposition was also seen at Mount Bill Williams and Mount Floyd, at Piute Spring, at the head of the Black Cation, at Postal’s ranch, near Litthe Owens Lake, near Logan, Nev., at Quinn Canon, at Reveille, near Copper Canon, between Battle Mountain and Rock Creek, on Maggie’s Creek, near Black Rock Spring, Utah, and by Mr. Howell, near Adamsville, Utah, and in Rabbit Valley, east of Fish Lake. Other cases, less strongly marked, point in the same way, and serve to establish the rule—truly a rule, notwithstanding its exceptions—that in the great vol- canic region west of the Plains, the trachytic or acidic lavas have preceded the associated basaltic.* * The term basalt, here and elsewhere in this report, is used with Mr. Richtofen to include, besides basalt proper, dolerite and anamesite. VOLCANIC ROCKS AND MOUNTAINS. 133 The variety of the trachyte and rhyolite lavas is endless. Nearly every new locality shows a new phase. From a mass,composed of a rough lithoid paste, with imbedded crystals of orthoclase, oligoclase, hornblende, mica, quartz, &c., there is a perfect gradation, in one direction to varieties with a compact and even vitreous paste, and thence to obsidians and vari- colored glasses, and to pumice; and in another to a phase in which the paste predominates, and, while lusterless as chalk, and nearly as soft, is much lighter in weight. No line can be drawn between this and a volcanic mud, nor between the latter and tuff. All varieties contain occasional imbedded fragments, generally of somewhat similar constitution; and, by the multiplication of these, pass into corresponding lava breccias and con- glomerates. A curious imitative phase makes up the principal massof Baldy and Belknap peaks in the Beaver range. An even, finely granular paste, without crystals, laminated, dull, harsh to the touch, it is to be distinguished, in hand specimens, from the buff sandstones of massive, cross-bedded habit, only by the aid of a miscroscope. Its mode of occurrence leaves no doubt of its eruptive character, but it was hard to realize, even when viewing it in mass, that it was not of sedimentary origin. Associated with it are sub- vitreous, laminated to foliated, rhyolites, strongly suggestive, in small masses, of silicified wood. The latter are also, in part, spherulitic, and at the western foot of the mountain include siliceous concretions several feet in diameter. To this class of lavas belong the glasses that at Argenta, Nevada, and Beaver, Utah, have been mistaken for anthracite. The basaltic group shows less variability, its prevalent forms being compact microcrystalline lava and scoria. Obsidian, pumice, and tuff are seldom seen. The crater-cones are built of alight, thin-partitioned scoria never glassy, which weathers, from an original black, to various shades of brown and red. The upper surfaces of lava streams are distended by coarse vesicles with thick partitions, and these, in the older streams, contain crystallizations of calcite and zeolites. Columnar structure is far more frequent than with the trachytes, but in no instance have we observed it with such regular prisms as are found in Ireland and upon the Columbia River. The prisms stand normal to the cooling surface, and closely resemble in form those with which we are familiar in the starch of commerce. In the 134 GEOLOGY. starch, the structure is produced by progressive shrinkage, beginning on the exterior of a drying mass; in the lava, by progressive shrinkage of a cooling mass. In dikes, independent systems of prisms are formed from the two walls, and at their meeting in the middle the rock is unevenly cracked. In coulées also there are often two systems, the one from above and the other from below; and, in this case, the line of meeting is usually below the middle of the mass. The Geological Age of the Lavas is not clearly determined by such evidence as we have gathered. The trachytic rest upon, and intersect in dikes, all the sedimentary rocks from the Archzan to the Tertiary, and they were seen to underlie none of these. Their relation to Cretaceous and Tertiary strata is shown only in the Plateau country, since the region of the Basin Ranges was continental during those periods, and contains their record, so far as we know, only in subaerial, non-fossiliferous beds, continuous with, and not distinguishable from, the Quaternary. At a number of points, trachytes are seen to be interstratified with these subaerial deposits, and near Sevier Lake a sheet of rhyolite is spread near the top of the series. At every point of contact the trachytes and rhyolites underlie the Bonneville beds. These meager data from deposition are supplemented by some facts of denudation. With-the beginning of the post-Jurassic uplift of the Basin Ranges, there began a wasting of the ridges that has continued ever since, and, wherever the facts can be determined, the lavas are found to rest on greatly eroded surfaces of the upturned strata. With reference, however, to the greatest eruptions the facts are not known, since they constitute ranges by themselves, surrounded by secretive blankets of Quaternary gravel. On the other hand, the denudation of the trachytes themselves has been great—so great that it is measured by the same order of unit that is applied to the denudation of the sedimentary beds. Not merely is the original sur- face removed from even the most recent of the trachytes, but all craters have been destroyed, and cones of mingled tuff and lava, that must have assumed the most imposing proportions, have been reduced to the merest ruins. Great dislocation, as well as denudation, has succeeded, in places, the accumulation of trachytes and rhyolites, and mineral veins have been VOLCANIC ROCKS AND MOUNTAINS. 135 formed within them and along their contact planes. Great erosion certainly, and probably dislocation also, of early eruptions, have been succeeded by later eruptions, and stand in proof of the great duration of the trachytic epoch.* Basaltic eruptions have bridged over the chasm from the trachytic to modern times. Mr. Marvine found them alternating with rhyolite at Trux- ton Spring. They overlie all the sedimentaries up to and including the Bonneville beds. They underlie also the Bonneville beds, and are inter- stratified with the subaerial drift. At the Cathedral Mesa on the Colorado, between Bowlder and Iceberg Canons, a basalt bed rests on 200 feet of this drift, and is covered by 300 more. Its antiquity is expressed by the 300 feet of deposition over it, plus the 500 feet of denudation that has laid bare the escarpment. Unless some unknown change of levels has occurred, this denudation has only kept pace with the erosion of Bowlder Cafion, ten miles long, through tough Archzan rocks. At the mouth of the Grand ' Wash a stream of basalt reached the river bed when it was 200 feet higher than at present, and its antiquity is measured by so much degradation of Iceberg Canon. Ata point in the Grand Canon below Diamond Creek, a coulée has entered from a side gorge, and the river has since descended 75 feet into the granite. Camp Apache is built in a valley several miles broad and 1,200 feet deep, excavated in Carboniferous sandstone and limestone by the White Mountain River since the flow of the basalt which caps the adjacent uplands. A second lava stream, and a third, have flowed down the new valley, and have been in turn cut through by the creek, the chan- nel of which is now but 50 or 75 feet below the last lava surface. (The oldest lava of the Uinkaret or North Side Mountains, identified as basaltic by Professor Powell, preceded the denudation that has retired the lower *The localities upon which these observations are based are, for the most part, mentioned, either in the résumé of distribution in the earlier part of the chapter, or in the special descriptions at the end. Trachyte rests on Tertiary strata east of the Sevier Valley, from Panquitch to Glendale, and has been faulted with them. Trachyte overlies subaerial drift in the El Paso Mountains, at Red Rock Caton, and on the eastern side of Death Valley ; it passes under such drift at the foot of nearly every trachytic mountain. At Belmont, Nev., rhyolite rests on uptilted edges of Silurian slates; near Boundary Canon, on Lower Silurian quartzite, from which, as proved in the immediate vicinity, many thousand feet of superior strata have been worn; in Bowlder Canon, of the Colorado, it is seen to rest on Archwan schists. Of great post-trachytic denudation, Pilot Mountain, San Francisco Mountain, and Pine Valley Mountain afford illustration; and San Francisco Mountain shows a later eruption of acidic lava. Bedded tra- chytes are disturbed at Burnt Rock Mountain, and at Red Rock Canon, Cal. 136 GEOLOGY. Triassic escarpment, (Vermilion Cliff,) here 1,500 feet high, to a distance of thirty miles. In contrast with this, there is perched upon the very slope of this escarpment, near Virgin City, a fresh built cone, and other cones dot the intervening plain, and especially surround the base of the Triassic island preserved by the older eruption. Basalt streams and cones, so recent that their surfaces yet afford no soil for vegetation, were seen in Owens Valley, near San Francisco Mountain, and in Utah, near Glen- dale, near Toquerville, in Diamond Valley, (Howell,) near Skumpah, near Pauquitch, near the Cedar range, (Howell,) and near Fillmore. The last named are the freshest of all, and may fairly be called modern, although there is no tradition of their eruption. The weathering of the frail scoria, that caps the latest crater rim, does not seem to have begun; the frothy, taffy-like pellets that, spattered from the bubbling caldron, fell half cooled upon its wall seem as though congealed but yesterday. Only the consideration of the extreme aridity of the climate can countenance the possibility that cen- turies, instead of years merely, may have elapsed since the termination of this eruption; and no one who studies its monuments can avoid the feeling that it is so far an affair of the present, that no surprise would be occasioned by its recurrence. Indeed, when we compare the stupendous denudation that has transpired during the period of basaltic vulcanicity in this region, with the differential film that has been removed since this last manifestation, and when we consider, in addition, that intermittence is a characteristic of voleanic activity, we are not merely permitted to think of a renewal of that activity as possible, but are logically compelled to regard it as probable. There is really no more reason to believe that the epoch of basalt has closed in this region, than that it has barely begun; and it is certainly probable that the few centuries we can know by history and tradition, belong to one of the intervals of quiet, such as separate the more or less convulsive efforts of volcanoes; an interval to be terminated sooner or later by a renewal of activity. More detailed description will be given of a few localities : The Fillmore Group of cones and lava beds rests on the broad floor of the Sevier Desert, west of the Pah-vant range, and far enough removed from it to be considered entirely independent. The Pah-vant Butte, the largest and VOLCANIC ROCKS AND MOUNTAINS. 137 one of the most northerly of the group, is seventeen miles from Fillmore, in a northwest direction. The Ice Spring cluster lies ten miles west of Fill- more, and four miles seuth of it is the Tabernacle cluster. Southwest from the Tabernacle, and six miles distant, stands a small cone that was not visited, and four miles north northeast from Pah-vant Butte is a low lava cone. All of them are surrounded by more or less recent lava beds, and these unite (except two narrow gaps) to form a continuous field twenty- five miles long and three to five miles broad. A full description of the group would probably in- clude also some cones observed by Dr. H. C. Yarrow further south, in the vicinity of Corn Creek settlement. Pah-vant Butte is the only tuff-cone of the group. It is in crescent form, preserving ‘about two-thirds of the wall of its crater. The south- western portion of the wall has been removed, and the highest remaining point is northeast of the crater. The external diameter of the crescent is about one and a half miles. The culminating point stands 800 feet above the base. The mate- rial is a tuff of very light cinders. It is firmly coherent, but the cement does not fill the pores of *qoveq a[tAouuog ‘q fapisat ‘% { 109010 ‘UOITULMR, O49 Jo JUoMeSavIIY O49 Buraoys ‘ayyng uvA-YyV_ Jo UolyegG—ZeG “OI the cinder fragments. The prevailing color on fresh fractures is an ochre yellow; on weathered “O0GL-T fereog surfaces, a dark gray. Successive surfaces of deposition are marked by a rude lamination, con- spicuous in large masses, but not inducing a decided cleavage. This lamination dips both - ways from the rim; inward, at about 35°; out- Jo opisyno ‘0 ward, at from 20° to 25°; the two slopes being united at top by a curve. The Bonneville beach is carved upon the outer slope 300 feet above the lava floor at its foot, and all of the associated lava beds were covered by 138 GEOLOGY. the Bonneville waters. The lavas are in part concealed by Bonneville sands, but, where bare, have a tolerable freshness, the convolutions of the once flowing paste being yet well preserved. The tuff-cone rests upon them. The Ice Spring cluster includes three perfect craters, and vestiges of one, and perhaps two others. The oldest of all is preserved only in a fragmental ridge, 260 feet in extreme height, so curved as to indicate an original inter- nal diameter of one-half or two-thirds of a mile. (a, Fig. 53.) Within its arc is slight indication of the ANT = existence of a smaller cone of Wig) softer material, and at once later than this and earlier than the others. Of the three perfect cones, marked 8, c, and d on the diagram, the newest is the central and largest, c, and the inter- relation of the others was not ascertained. They are all very — WAKE S.0wwye Nt SSa2ww ~ SSN . NAS = \\\\ NSS INNS Sk SS = \\\S recent. The smallest, b, has a Zi aS ‘ rim of uneven height, ranging KN from 150 to 90 feet above the Fic. 53.—The Ice Spring cluster of lava cones, near surrounding lava bed, and the Fillmore, Utah. descent from the lowest lip to the bottom of the crater is 30 feet. The exterior surface is regularly conic, and as steep as the falling scorize would lie, but shows very little loose ma- terial, a great part of the ejected matter having fallen in a molten or viscous condition, so as to cohere in a firm mass. The inner slopes are made of angular fragments, large and small, fallen from the rim, and meet at the bottom, where is a little cool water and a solitary tuft of grass. The water appears to be much resorted to by birds, and a game trail leads to it over the lowest sag of the rim. The central crater is of precisely similar character. The highest and lowest points of its rim are, respectively, 250 and 100 feet - above the outside base, and the dry bottom of the crater is 100 feet lower than the lowest rim. é VOLCANIC ROCKS AND MOUNTAINS. 139 \ The remaining cone, d, is especially interesting, since the lava of which it is built has not fallen down and choked the interior, but all remains precisely as the retreating fluid left it. It is about as broad as the last mentioned, but comparatively low, its rim rising only from 60 to 100 feet above the outside lava field. It is possible that its flanks are partially buried by later eruptions. Its eruption does not appear to have terminated with the ejection of scoria, but, at the last high tide of its lava, a crust was formed about the east- ern border of the crater. When the subsiding flood withdrew its support, a portion of the crust fell, but the remainder still forms a shelf upon the slope. The retirement of the lava was so rapid that no other floor was produced, and the flue through which it entered and departed is unclogged. The relations of the shelf and flue to the crater walls are shown in the sectional diagram. (Fig. 67.) The flue is eccentric, oblique, and unevenly cylindric, with a diameter of 12 feet. Its walls are flecked with arborescent accretions of white calcite. Descent into it is checked at a few rods by water, which fills it to an unknown depth; the level of the water surface being 50 feet below the outside lava plain. The features of this spot were peculiarly impressive. Not often can the eye so fully aid the WALES A 5 UY, iti 7 \ ; Z ee if i E il H hy imagination to picture the former life of a dead crater. Through the narrow sloping tube in which we stood had poured the molten tide that overwhelmed miles of the plain, and down its throat had been swallowed what remained in the crater mouth when the force that ex- pelled it gave way. Black drops of the pasty flood still hung in witness from every angle of the roof and sides, and the crust without was corded with the ropy Wo foldings of the seething caldron. Below the floor that marked the last high tide there was no sign of lingering. With one movement the hollow had ‘qIMpUOd VAT PUL VAT] po[vesuod Jo Joys Surmoys ‘1oysnjo Suradg oo] ey} Jo p ou0d Jo YoJoys puv uolyoIg—pPS “ONL S 140 GEOLOGY. been emptied, and the lava that had formed a glowing lakelet, acres in extent, sank back to the source from which it came. About these cones there are at least two distinct lava floods. The older may have the same date as the old fragmental cone; the newer must pertain to the same eruption as the perfect craters. In the immediate vicinity of the cones the older flood shows only a few islands, and is con- spicuous in the possession of a soil on which the sage has taken root. The newer is soilless and plantless—not even a lichen clinging to its surface— for all that can be seen, just as the cooling left it. Its surface is a chaos of black, ragged slabs of lava crust, piled as are the ice cakes that, in spring- freshets, dam our northern rivers. In places the congealed crust was deserted by the lava beneath and fell in. Elsewhere it was possibly torn by the force of steam from the moist ground over which part of the lava ran. Everywhere the flood is thrown into ragged waves, 10, 20, and even 40 feet in height. The more compact masses are divided by sharp edged fissures, often several feet in width and 10 or 20 in depth. At many places we saw a peculiar, harsh, papillate surface, produced by the dragging of viscous lava against what was already hard—such a surface as a trowel leaves on very stiff mortar. (See Plate XII*.) In one of the lowest depressions of this recent lava is Ice Spring, from which the cluster of cones is named. Lieutenant Marshall found there in July not only water at 32°, but enough ice to justify the name. He regards it, not as a phenomenon of evaporation—for evaporation in that sheltered and shaded place is very slow—but as a natural ice house, storing the winter’s snow. The Tabernacle cluster is named from the resemblance of the distant profile of the chief butte to the Mormon tabernacle at Salt Lake City. The resemblance vanishes on nearer view, and the seeming oval dome is seen to be the fragment of an old crater wall. Itis 150 feet high and about 2,000 feet long, and other fragments of the same indicate that the crater once inclosed had a diameter of half a mile. It is now quite flooded by more recent lavas, and within it are two smaller craters, one of which overlaps * The upper of the blocks represented in the plate was taken from the crest of crater c of the cluster, the lower from the adjacent lava-stream. VOLCANIC ROCKS AND MOUNTAINS. 141 the other; but none of the eruptions have the freshness of those just described. The surrounding lava field, also, is comparatively old, though still nearly bare. Soil enough has gathered in its lowest places to support a growth of bushes and grass. _ Its most interesting feature is the existence of a number of caves, produced by the escape of lavas from their channels, after the formation of a self-sustaining crust. The caves lie entirely below the general level of the lava field, and we discovered them only where portions of their roofs had fallen. Descending through one of these roof openings, Lieutenant Hoxie and I followed the tubular aperture for one or two hundred feet, and climbed out at another break. The width of the cave averaged 30 feet and the depth 18, and in length it extended indefinitely beyond the section we explored. The original bottom was not visible, being strewn with fallen fragments of rock, and covered to an unknown depth by the ordure of owls and bats. The margin of this lava shows an obscure beach line of the Bonneville series, from which were gathered shells of Limnea desidiosa, but it was not examined with sufti- cient care to determine fully its relation to that series. The cones and streams of the Ice Spring cluster were certainly untouched by the Bonneville waters, although their highest points are 200 feet below the Bonneville mark on the foot slope of the Pah-van range. Beaver Range.—A partial section of the Beaver Range, Utah, was obtained at Belknap Peak, one of its culmi- nating points. The peak was ascended from the west, and the character of the eastern base was afterward ascer- tained by a visit to the Ohio mining district. The range at this point rises 5,500 feet above the adjacent valleys, ‘onpoAga ‘4 fsyoor Areyuoutpas ‘p { aj1004s ‘yvog dvayjeg ye ‘aduvar Jaavag jo uoyoeg—'cs ‘O1,T ‘ONT FUG Wwory Jo OAC, = oul] esUg “QOOPFI-T ‘eTvog "9 —<—__. Js 7y- and is eighteen miles broad. At the western base a foot hill, lying chiefly between North and Indian Creeks but cut across by the latter, consists of syenite. The mass has a north and south trend, and is probably flanked at 142 GEOLOGY. the east -by quartzite. I say “probably,” because portions of the adjacent rhyolite were afterward found to so closely simulate quartzite that doubt was thrown on the determination after all opportunity for re-examination Scale, 1-14400, Fig. 56.—Section of Red Rock Cation beds, Southern California. was past. Under the eastern base of the range, the cafon of Pine Creek reveals 300 feet of nearly level strata, including sandstone of several varieties and shale or slate, but containing no fossils, save obscure fucoid casts. 'The whole have been partially metamorphosed, but show no folding. Except these basal exposures, the entire profile is volcanic, and, either way from the crest, the first 4,000 feet of descent is upon lava. Pine Creek exposes a great mass of tough porphyritic oligoclase- trachyte, in great part brecciated, and containing the metallife- rous veins of the Ohio district. Surrounding and overlying this, and extending to the syenite of the opposite base of the range, is an immense body of rhyolite, presenting some diversity of character, but consisting chiefly of the variety already des- cribed as the close counterpart of certain sandstones. North- ward this lava cover continues for about fifteen miles, but probably diminishes in thickness as the range diminished in height. Southward, for twenty-five miles, to Frémont’s Pass the crest of the range, while it grows broader, loses little in height, and it is probable that the lava mass is even greater in that direction. Opposite Circleville, twenty miles south of Pine Creek, the range presents a bold eastward front 6,000 feet high, the whole of which appears to be volcanic. There is probably no exaggeration in estimating the dimensions of this great lava mass at: length, forty miles; average width, fifteen miles; average depth, 2,500 feet; which gives a total of two hundred and eighty-four cubic miles. Red Rock Caiion—In the vicinity of Walker’s Pass there is a long, low, detrital slope from the Sierra Nevada to the desert at the east, and the same exists thirty miles farther south. In the interval the slope is interrupted by the low, irregular El Paso Mountains, which appear to have risen, in part at least, since the establishment of the VOLCANIC ROCKS AND MOUNTAINS. 143 detrital slope. Red Rock Canon, having a southeast course, intersects a southerly spur of the El Paso Mountains, and rises among detrital beds that lie between this spur and the Sierra Nevada. For two or three miles it cuts obliquely a series of beds dipping westward from the El Paso spur, at angles ranging from 15° to 30°. Fig. 56 gives a section normal to the strike, but based on notes taken along the oblique cutting of the cafon. No. lisa lightly cemented coarse sand or fine gravel, pale umber to ochre in color, and consisting of rounded grains of quartz, mica, feldspar, and divers volcanic rocks. Upward it is inseparable from the granite sand of the Sierra slope. It does not cleave into strata, but the direction of bedding is conspicuous in the exposures, and different layers weather so unequally that the whole is carved into a series of escarpments, the faces of which are beautifully fluted by rain. The thickness exceeds 400 feet. Nos. 2 and 4 are basalts, 30 and 50 feet respectively in thickness. No. 3, 100 feet, No. 5, 200 feet, and No. 7, 100 feet, are like No. 1, but more coherent, the cementing material being insoluble in acids. No. 6, 100 feet thick, is a homogeneous, pale pink, vol- canic tuff, containing all the constituents of the adjacent sands, with the addition of pumice and a definite matrix. No. 8 isasand like No. 1, but well cemented by oxide of iron. No. 9 isan orange, massive, subspherulitic rhyolite, and No. 10, a massive fine-grained compound of hornblende, pyrite, anda feldspar. The two, whose correlation was not made out, constitute the spur of the range and wall the cafon for a half mile. Beyond them the sands are resumed (11) with the same dip, but their relation was not estab- lished. 'The line of section, produced eastward, would reach out on an open desert—that in which is the Desert Wells stage station. The chief interest of the section lies in the close relationship of the sand beds to the intercalated tuff. The latter is a product of eruption, endowed with a light vesicular paste, and separable by no sharp line from typical lavas. The former is so closely affiliated to the tuff, on the one hand, and to the ordinary desert detritus on the other, that we are left in doubt whether it was transported and distributed by volcanic or by meteoric waters. Meadow Creek Chimney.—The cation of Meadow Creek, near Belmont, Nevada, is cut through a flow of compact rhyolite, and at one point lays 144 GEOLOGY. bare a peculiar structure that probably pertains to a point of issue. The rock is divided by a set of curved joints, concentric, and, in vertical as well .as horizontal section, concave toward their common axis. The whole mass Fic. 57.Section of lava flow exhibited in Meadow Creek Cafion, near Belmont, Nev., showing the arrangement le The base-line is the level of the creek bed. of cleavage planes. | ¥ The dotted line indicates the level of the creek bed. Fic. 58.—Ideal section of Meadow Creek lava-flow. is apparently homogeneous, but is unequally eroded in a manner somehow dependent on the arrangement of the joints. The core has disappeared, and in its place is an am- phitheatric cove opening to the cation. The walls of the amphitheater are composed of sectile lava, in concentric leaves, like those of an onion bulb, and have somewhat the form of a crater. Outside them a circular line of weakness is marked by an eroded valley, and beyond this lies the general lava sheet. The crateriform wall has a height of 100 feet, and a diameter from crest to crest of about 300 feet. Its relation to the lava field is shown in the annexed diagram, (Fig. 57,) which presents substantially the section afforded by the creek, and the structure of its wall is shown in Plate V, which reproduces a photograph of the portion represented at @ in the diagram. I conceive that the amphi- theater, ¢, is immediately above the opening through which the lava issued, and that the concentric division surfaces are in some way a function of the movement of the lava. If a viscous fluid issue from an aperture in a level surface and spread equally in all di- rections, the portion emerging at any one instant will assume successively some such positions as are represented in the curved lines of Fig. 58, and a lamination resulting from a motion of this character would correspond in form with the divisions just described. The structure of the rhyolite, however, is spe- VOLCANIC ROCKS AND MOUNTAINS. 145 cifically a cleavage, and there is, strictly speaking, no visible lamination. The cleavage planes frequently divide the inclosed crystals of quartz and feldspar. Thermal Springs are so often associated with volcanoes, that they are regarded by many writers as volcanic phenomena, notwithstanding their frequent occurrence in regions not otherwise marked as volcanic. The problem of their relation to vulcanism has so far interested me that I have been led to look somewhat beyond the limits of our explorations for material bearing thereon. A portion of the material gathered led to no conclusion and need not be rehearsed, but the results indicated by some facts of gen- eral distribution are so little ambiguous, that I may be pardoned for present- ing them in this place, even though they involve a conspectus of the entire country. In the present state of our knowledge and speculation in regard to the structure of the earth’s crust, there are several explanations that may be offered of the existence of thermal springs. It is now beyond question that there is an increase of temperature downward from the surface of the earth, and observations are so far accordant, that the range of recent estimates of the rate of increase is only from one degree Fahrenheit for 50 feet of descent to one degree for 90 feet. So we have reason to expect that water, which, between the region where it enters the earth, and the point at which it emerges, passes far beneath the surface, will have been heated and will issue with a temperature higher than the average local temperature of the ground and air; that is, that it will be thermal. Since all spring water passes underground, we should expect, as is found, that spring water as a rule will be, however slightly, thermal. The deeper the water passes in its subterranean transit, the more heat it will receive. The greater its volume and the more rapid its rise to the surface, the less heat will it lose by con- tact with the upper and cooler portions of its channel walls. So hotsprings may be found where the rock structure is such as to lead subterranean water by quick routes from great depths; and, since water follows either fissures or the partings of strata, these conditions will be met only where the rocks are greatly inclined or are fractured. The tilting and the frac- turing of strata are concomitant features of-mountain corrugation, and to 10Wws 146 GEOLOGY. regions of such corrugation we should look for thermal waters, while in regions of unfractured and horizontal strata they cannot arise from this cause. The theory of mountain building, advocated by Messrs. Hunt, Mallet, and Le Conte, and which is now the most prominent, if not the dominant theory, calls mountain corrugation a result of mechanical “work,” due to horizontal pressure, (a function of the secular cooling of the earth,) and announces as a second result of the same work, the development of heat in the /oci of the work. It is held that, in some places, corrugation does not take place, but, instead, there results a local crushing of the rock, accompanied by sufficient heat to produce local fusion, and furnish the material for volcanoes. If this be the true theory of volcanoes, then the equilibrium of the heat of the crust may be disturbed by the production of local maxima, not only where the rocks are pierced by molten dikes, but also in the places, not necessarily very deep seated, where lava is formed, and also along the axes of corruga- tion ; and these regions would naturally contain hot springs. The inequali- ties of temperature would be greatest during the formation of mountains, whether by corrugation or eruption, and would slowly diminish by conduc- tion after the activity ceased; and hydrothermal phenomena arising from such cause would be most intense where mountains are forming, or have been formed at a late date. In any case, except that of waters heated by fresh dikes, the conditions must be such that the currents rise from consider- able depths; and the only difference between the manifestations in a region now undergoing corrugation, and in one that has rested and cooled for many ages, would be a difference of degree. The most intense action would be produced by recent dikes. Where the discharge is small, and the tem- perature high, the source of heat cannot be remote, else the heat would have been lost in transit; and, as this is the rule with geysers, they are probably regarded with propriety as strictly volcanic phenomena, indicating the recent injection near the surface of hot lava, whether or not it has been extruded. , The thermal springs of the United States are now sufficiently known to afford some criterion of the value of such speculations, and, for the purpose of comparing their distribution with that of mountain structures, I have collected such data as are available. In the accompanying table are included, with insignificant exception, only such springs as exceed in tem- VOLCANIC ROCKS AND MOUNTAINS. 147 perature the local annual mean by not less than 15° Fahrenheit. It is not a list of individual springs, but of localities, and the temperatures given are the highest noted at the several localities, except that, where there is reason to believe that a change has occurred, the latest record is quoted. Where no references are given to publications, the data were gathered by members of our expedition.* The accompanying map represents the same localities, save a few so closely adjacent to others, that the signs by which they are indicated would overlap. Where the temperature is known the figures expressing it are used to mark the locality ; where it is not, a cross. Upon the same map are indicated some of the principal structural divisions of the country. At the east is the Appalachian region of corrugation; at the west a larger and com- plex corrugation system, continuous from the western limit of the Plains to the Pacific. This latter district it will be convenient to call the Western Mountain region. In the interval, a region nearly coincident with the basin of the Mississippi, the strata are nearly horizontal, and corrugation is known only at a few insular points, of which the chief are the Black Hills of Dakota, the Wichita Mountains of Indian Territory, and the Ozark ridges of Missouri and Arkansas. Conversely, the Western Mountain region surrounds an island of strata little disturbed, and constituting the Colorado Plateau region, north of which the Laramie Plateau either forms a separate island, or an insular promontory of that of the Colorado. In the region of the Appalachians the phenomena of eruption have always been subordinate to those of corruga- tion, and they appear to be in no wise connected with thermal springs. In the western region eruption has been nearly as universal as corrugation, and, in places, even rivals it in the magnitude of its monuments. In examining the map, the first thing to note is that the Mississippi region contains no hot springs, nor does the plain of the Atlantic coast. The single locality in Arkansas is referable to the Archean Ozark corrugation. In the Colorado Plateau region but five localities are noted, a number decidedly below the mean of the Western Mountain region, which, for the same area, averages thirteen localities. It is true that it is not yet fully * Except in the case of three localities, observed by Prof. J. W. Powell, in the cations of the Colorado. 148 GEOLOGY. explored, but it is nevertheless probable that the record of its hot springs is nearer complete than that of the mountain region. The distribution of hot springs is thus shown to coincide very exactly with that of corrugation, there being none in undisturbed regions, and few in regions of little disturbance. The second result of an inspection of the map, or of the table, is the observation that the range of temperature is far higher in the western region than in the eastern. Omitting the localities without record of tem- perature, there are 67 in the former region to compare with 15 in the latter; of these the former shows 47 as high as 100° F., and the latter but two. This is probably an exaggeration of the contrast, due to the comparative imperfection of our data from the West; but the contrast cannot be imag- inary. The list probably includes every group at the East that shows a temperature above 65°. Itis yet possible that future travel shall double the list of western localities, and it is probable that the present list includes a far larger proportion of the very hot springs than it does of those of lower temperature, such as are not always noted, even though they are visited. Of the same tendency is the fact that the number of localities is rela- tively greater at the West. The regions, as we have limited them, have areas proportioned as 13 to 3, while the numbers of recorded localities are as 24 to 3; and, if all the localities could be given, the preponderance of the West would necessarily be greater, since it is now the less known region. So too the weight of individual localities is greater at the West. It is safe to say that a score of the western localities surpass, in number and volume of springs as well as in temperature, the greatest group of the Appalachians ; and geysers are known only in the larger area. In a word, the larger _ region is in every way far more strongly characterized by hot springs. The geological relations appear to accord with this hydrothermal con- trast. The corrugation and the eruption of the Appalachian region are things of the past, not known to have continued so late as Cretaceous time ; while in the West these actions have persisted to so late a period that we have good reason to believe they have not ceased. Itis dangerous to argue from single coincidences, but, certainly, so far as these facts go, they tend to confirm the explanations of the phenomena that have grown out of the HOT SPRING LOCALITIES OF THE UNITED STATES, Showing Their Relation To The General STRUCTURAL DIVISIONS. Explanation, Springs of Oninowr Temperature are warked by a Cross, this + Those of Known Temperature, bylig- ures indicating the temperature, The heawy Lines indicate boundar tes of Divistors described ire the text. hl * ph syitiny shape TTT! ‘ oc fh Sir bvcrers 2 : a = 7 i om - te] . Pel * a _ 5 ow | - - Frisct «24th i. anh t . ‘ ~ ‘ee Tis, SA EES Ps . tt a ov lsths sau “peas tape ecg bowl ghee eDreg eee Tevanten eae’ rag nctieeyy alt «ta ‘7 ta) ‘ = aa § ‘ a di f ; oP and iT fu alll Ha ' . r 7 aan, a ae 6 . r vale én] * Le umn. ve meet lat Qe ianne Vote wegen tolinare ind ahaa we Sunndes & at nr tien ny iniahany nds Paty hanks B veniphacl ee, iA) Seiityrty Lindt ce nde dine ideas tered a md arene igh aaieecisy aN sstrlqiadt 4 it i=) Axe MAU MT VEN 3f oa FON Ri if : sti i li wt gig aoc Ty + Wh uf E el? fi he i“ 24 4 ° ae atiiitd ine etry vey Wreath tere n 4 f 4 ni ismetinneD fev GhaLs aL wil Any 1. ciogndlw? Sw RSTO aromsiet Of at 8 ‘ ; treet 6 « OPA ybe 14) org plgeny te i: : he - J (3 : 30 . e y dy peesey an a rh awe re all; ba o OF THE $i 5e Fe ams fol secu prick eens i ; hi ALUNOIS iiFaeiliny od “id Lee it & aor Veen ‘ nivfact nerd elt” 7 = 4 4 a4 est > ee 1 mM Lor iit Tie ee is r aL* pEEP Ay 1 [3] Chad M “an iihy ; % ted (Leni vet Jeowla Hedin tess ; X 4 be ye ~ 7 Th \? | wore vd ‘i ; pee +n : Bf mes yaae eas “Sy ais in Jew Soh Be of Le =*5, © ; madi % : we aaluera i Te elie) es Mi seedy Cie ae “nad | @ ‘op vite pre ‘ower Le ee amet Sih Lik Be mare! ved rT ey ee oi ear : “s ; : ; 10 Oe oily diremsers i= lighten aa 1" ret OP hie ener Sele «ila . a Tie 8) oe nal Pie A ey SS meas) uy la $ Viele abe et Pe et ai gee vita - + Ay ee pepe? hire Agel Be ih 1 Alt os —e=-= Sixteen miles southeast of Camp Bayard, New | T. Antisell, Pac. Ry. Rept., vii, p. 456-------- 130 Mexico. Apache Tahoe, seven miles south of Camp Bayard, | F. Klett ...--...---.-.--------------------- 97 New Mexico. Twelve miles northeast of Jemez, Santa Anna | O. Loew..-.--.----..-----------+-- +----+-- 169 County, New Mexico. Canada Alamosa, Socorro County, New Mexico ..|.----- do 12sec eae ee ee At copper mines of the San Francisco River, New |..---- RSS SE BIRGO So -ec ns ojoc5do sacsiecneds 130 Mexico. VOLCANIC ROCKS AND MOUNTAINS. Localities of Thermal Springs in the United Staies—Continued. 153 Near Walker’s Pass, Kern County, California .--. Bridgeport, Mono County, California ...---.--.- Geyser and Hot Springs, 25 miles south of Mono Lake, Inyo County, California. South of Fort Bidwell, California.......--.----- ‘ Bancroft’s Map Locality. Authority and reference, Fabren- heit. Ojo Caliente, 50 miles north of Santa Fé, New | Colton’s Map of N. Mexico......---. .....----|.------- Mexico. Five miles west of Las Vegas, New Mexico ......| F. V. Hayden, U. S. Geol. Sur. Ter., 1870, | 140 (reprint,) p. 164. Diamond Creek, near its mouth, Socorro County, | E. E. Howell -.---.....-. 2... 2-2. 2-2-2222 151 New Mexico. Ten miles south of Zuni, New Mexico ...-......|---- Sr oto OnE OR Ere photo Pepecbesao cea ten| PRseeade Gila River, near Diamond Creek, Socorro County, | W. N. Maguet ....-...----.---.--.--------- *100 New Mexico. On the Rio Grande, below Fort Quitman, Texas ..} Mex. Boundary Survey Map-...----.-.---.----|.--.---- ‘Deschutes Valley, Oregon ..---. ----------+---- J. S. Newberry, Pac. R. R. Rept. 2, p. 74.---- 145 MalheurRiver, Oresone=--="22-s2-ora-4--s->5| FG. xemont, 706. cit, p: IZ02-2--- «2. cee esse 164 North shore of Goose Lake, Oregon. -...---...-. Foley’s Map of California and Oregon. ---.--..-]....-.-- Near Honey Lake, Califomia-.--2-. (5 --<-- 25: E. G. Beckwith, Pac. Ry. Rept., xi, map -:---..|------.- Near Mohave River, Southern California. .......- WSs Bnomeer Map tie ects36- 52. ebe- ce Pee meen Thirty miles south of Lake Tahoe, California .....] J. C. Frémont, Joc. cit., p. 224..-------+---.2--|-------- Near Fort Crook, Northern California...........| E. G. Beckwith, Pac. Ry. Rept., ii, p. 56-..-..).------. Deep Spring Valley, Inyo County, California.....| D. A. Lyle.2..-.--1--.-2-+-2-2-.-222- 2222-2 74.6 Benton, Inyo County, California ...........-.--- Mr. Partz, (quoted by W. J. Hoffman)....-.-- 170 Ten miles east of Telescope Peak, Inyo County, | W..J. Hoffman ..---..--.-....--.--.----.--- 80. 7 California. Saratoga Springs, south end of Death Valley, Cal- | T. V. Brown ....-....-----------2---------- *70 ifornia. - Near Mission of San Miguel, San Luis Obispo | Pac. Ry. Rept., vol. xi, Parke’s Map San Fran. |-.....-- County, California. Bay to Los Angeles. Guayamas Valley, San Luis Obispo County, Cali- | Pac. R. R. Rept,, vol. xi, Parke’s Map ....-.-.|---.---- fornia. Napa) Valley, Galifornia..42--...--2<-2----- ---+|//. Shepherd, Sill. Jour. Il, 12, p:,153 -~-+--.-- 169 Geysers, Sonoma County, California..........-..|..---- COP sents ce sete Le ele nee ce Guee bed Mud Volcanoes, 60 miles northeast of San Félipe, | J. A. Veach, Proc. Cal. Acad. Sci., 1857-..----.|.------- San Diego County, California. Shastaeaky Caltfornra atiue 2. sitesi J. D. Dana; quoted by J. Bell, Min. and Therm. }..--.-.--- Springs U S., p. 353. Near Warner’s Ranch, San Diego County, Cali- | W. P. Blake, Pac. Ry. Rept., vol. v, part 2, p. | 142 fornia. 116, Border of Colorado Desert, California........-.-- Wi P: Blake, 2oc. ctt.,(p2 94- 2 = <2- e2=2 se s= os 120 San Bernardino Valley, California ...............| W- P. Blake, doc. cit., p. 83 -----.------------ 172 J: D: Whitney?s: Mape- een. oe ne ae anion == sehod 0 Oh ie ee On SEE SOC COIG | SeREISene * About. 154 GEOLOGY. Of the localities noted within the Colorado Plateau region, (see map, Plate III,) one is only presumably the site of a hot spring; for at the time of my visit there was no flow of water. The lake named by Lieutenant Jeera wa 59.—Diagram of supposed geyser on the shore of Mountain Lakelet, Southern Utah. b, high-water line ; 8, Tia. shore at low water. Wheeler, ‘“‘ Mountain Lakelet,” lies close to the brow of a westward facing cliff of denudation. The strata dip gently to the northeast, and the upper beds were carved by streams flowing in the same direction, into a series of northeast and southwest valleys and ridges, with a magnitude of 500 feet, before the cliff had been eaten back to its present position, and a natural cross-section of these valleys is exhibited on the face of the cliff. Two miles back from the face of the cliff one of these troughlike valleys has been stopped by a recent lava stream, behind which stands the lake. Perched almost on the top of a ridge of nearly level strata, it is not in a position to receive water from deep-seated springs, and its water supply is not sufficient to give it a permanent out- flow. Its water level consequently fluctuates, and we saw it about 25 feet below its highest mark. Between high and low water there are on its sloping shore four crater-shaped pits, that I believe to be the seats of intermittent but violent springs. The accompanying diagram represents a cross- section of one of them. The upper line, b, s, shows the slope of the shore from the upper beach to the water. The outlet, 0, is 7 feet higher than the bottom of the pit, and the sides are about as steep as the soft soil will lie. The bottom, 6 feet broad, is flat, and consists of clean, coarse, well-rounded gravel, piled, et one or two points, into little cones. Three of the pits were perfectly dry, and the fourth had an inch of stagnant water. From the depth of the excavation, and from the coarseness of the eravel that remained in the bottom, I inferred that the action was violent. From the absence of a surrounding ridge, and from the shallowness of the dry channel that led from it at 0, I was led to suspect that it was chiefly active when the lake covered it. The close vicinity of very new lava cones suggested that it VOLCANIC ROCKS AND MOUNTAINS. 155 might communicate with a hot dike as the source of its energy. Upon such meager data I have noted the locality in the list under the title of “ geyser(?).” If it is a geyser it is certainly a purely voleanic phenomenon. A second locality, noted within the Plateau area, is that of a copious hot spring, ten miles south of the Zuni pueblo in New Mexico, and affords one link of a chain of evidence showing that the usual continuity of the strata is here broken. It is upon one margin of the broad dry Zuni Valley, here limited, east and west, by low sandy hills, in which the geological structure is not displayed. In journeying along and across this valley, from Zuni to Ojo de Benado, a distance of twenty miles, I parted from upper Trias rocks in such manner as to suppose that hidden beneath me were lower Trias, and I was greatly surprised to find the next outcrop at Benado Cretaceous. Mr. Howell, who afterward crossed the same interval by a different route, ex- perienced the same surprise, and we regard the hot spring as a phenomenon of the fault which we: are compelled to assume in the correlation of the stratigraphical facts. Of the warm springs found by Professor Powell in the gorges of the Colorado, one, the “Lava Spring,” issues from the Toroweap fault, in the immediate neighborhood of the Uinkaret group of basalt cones, some of which are of very recent origin; but the springs in Labyrinth and Narrow Canons have no ascertained relation either to eruptions or to dislocations. The hot springs observed by Mr. Nell near Pah-vant Butte, Utah, by Dr. Yarrow near Cove Creek, Utah, and by Lieutenant Lyle near Silver Peak, Nevada, are in the close vicinity of basalt cones of no great age. CHAPTER VL THE STRATIFIED ROCKS. Our knowledge of the distribution of the sedimentary rocks represent- ing the several divisions of geological history is very unequal in the two provinces of our field. Among the level, cafion-cut rocks of the Plateaus, the sequence of the strata is never lost. Save where covering lavas are crossed there is no break in observation. One bed is followed with the eye until it either dips beneath the surface or is ended by denudation, and an- other bearing a definite and evident relation to it is then taken up. Every newly discovered deposit of fossils falls at once into its appropriate place in the general scheme, and conformity and nonconformity are seen at a glance. Nearly every line of cliffs on the topographical map is a geological boun- dary ready drawn. In the Basin Range System the case is reversed. The mountains divide the space with the valley gravels, and only the imagina- tion can fill the gap between range and range. LEruptive rocks serve still further to. mask the sedimentary, and the outcrops of the latter are reduced to the condition of islands, each of which is a problem in itself, which dislo- cation, metamorphism, and unequal denudation serve to complicate. The best of the stratigraphical sections obtained by the writer are in- cluded in the following series, and accessory data helping to correlate them will be given in the sequel. The notation is invariably from the top saan as one reads a page, and this rule is followed throughout my report. The numbers given to the strata in the several sections are independent, each section standing by itself as a fact of observation. At the time of the preparation of this report the collections of fossils have not been studied. A preliminary examination was made of the inver- tebrates by the distinguished paleontologist, Mr. F. B. Meek, and the species mentioned in the sections and elsewhere in the text have nearly all the authority of his identification. A few, however, of the more familiar forms were determined by myself. 156 THE STRATIFIED ROCKS. 157 Section I.—East face of Sam Pitch Plateau, at Wales, Utah. The thicknesses, except of the coal seam, are estimated— Feet. 1. Caleareous and argillaceous beds, with pale ochreous, and gray tints: a. Massive limestone, with some chert, 75 feet. b. Tender, argillaceous limestone, with some calcareous sandstone, 500 feet. [ 1, 025 c. Fine-grained limestone, nearly white, 50 feet. d. Soft shales, with restricted beds of limestone and calcareous sandstone, [ Viviparus, like V. Conradi,] 400 feet. 2. Gray, sectile limestone, containing coal and numerous ) fossils, [ Viviparus trochiformis, Goniobasis Nebras- censis, and seeds of Chara:] a. Limestone, 30 feet. b. Slaty coal, 9 inches. 46 c. Limestone, 2 feet. | d. Bituminous coal, 40 inches; reduced by calcareous | Le Fic. 60.—Sec. I.— Wales bands to 36 inches, net. Utah. Scale,1-7200.* e. Limestone, 10 feet. 3. Gray and cream,soft shales, with thin bands of limestone, [Viviparus trochiformis, Viviparus ; Goni- obasis tenuicarinata, G. Nebrascensis, Planorbis, Physa, Unio vetustus :] . Shale, 18 feet. . Arenaceous limestone, 1 foot. . Shale, 10 feet. . Caleareous sandstone, 2 feet. . Shale, 175 feet. . Dark gray limestone, 1 foot. Shale, 2 feet. . Sandstone, 2 feet. . Shale, 10 feet. 4, Cream and gray soft shales, with cream calcareous sand- stones : a. Sandstone, 10 feet. b. White, sandy shale, 50 feet. ce. Sandstone, 3 feet. d. Shale, 20 feet. é. J. bo bo = Fe yoasccoes >. 147 . Limestone, 1 foot. . Sandstone, 10 feet. g. Shale, 50 feet. h. Sandstone, 3 feet. or Red shalesbase Not Seem .-2.--..-...-. Seon eaw eee en 40 Po ee SS EE +. 158 GEOLOGY. No. la caps the escarpment of the plateau. Back of the escarpment the sur- face rises in a series of terraces, that were not visited, but which are constituted of superior strata, with a total thickness of Sa | Fig. 61.—See. I—As- not less than 500 feet. Akers ans Section II.—Two miles west of Asay’s Ranch, near the head of the main Sevier River, in South- ern Utah. i Basaltierane pees npr eee ae eee ne eee ee 100 2. A variable, calcareous, and argillaceous series, char- ) acterized by white and pink coloring. The sub- divisions are not traceable over large areas: a. White to cream limestone, in’ part concretionary, | also brecciated and cherty, 150 feet. b. Coarse, friable, yellow sandstone, 40 feet. c. White limestone, with chalcedonic geodes, 20 feet. d. Pink and white marls, 20 feet. 560 ' e. Brecciated white limestone, 70 feet. f. Pink and white marls, 150 feet. g. Gray sandstone, weathering with vertical flutings, 15 feet. h. Red marl, 85 feet. i. Gray sandstone, with vertical flutings, 15 feet. aD OLA erireeaers area te a ee ee 660 Srcrion III—The rocks exposed by the north fork of the Virgin River, from the vicinity of Mountain Lakelet to Rockville, Southern Utah. All thicknesses estimated. ‘ ‘ J Feet. 1. White and pink, calcareous beds, limestones and mars, ) subdivisions extremely variable: a. Pink to cream limestone, 50 feet. b. White marl, 20 feet. ce. Pink marl, 100 feet. d. White marl, 30 feet. e. Pink marl, 50 feet. ¢ 1,200 J. Brecciated limestone; white to pink on fracture, pink on weathered face, 400 feet. = — Fic. 62—See. I1— g- Pink (limestone?) softer than J, 75 feet. North fork Virgin h. Pink and white limestone, 100 feet. River. Scale, 1-14400. i, Pink (limestone ?) softer than f, 375. OVry ies 2Si pS >. ee THE STRATIFIED ROCKS. 159 2. Pale green-yellow, soft sandstone and sandy shale ...... 1, 800 3. Pale green-yellow, massive, calcareous sandstone, divided by a shaly zone into two principal beds, [Corbicula ee (Veloritina) Durheet]........-----.----2) 422+. +s 600) 4 == 4, Shales, with coal. A large portion of this was not exposed. Sey eee A portion toward the top is arenaceous and white. The highest coal-bed seen is near the middle of the _——— series, and the shales below itare chiefly gray [Corbula]. 1, 200 eas 5. Gypsiferous shales: — a. Red clay-shale, 100 feet. . 150 =aSSSS b. White clay-shale, with bands of gypsum, 50 feet. 5 6. Cream-colored, sectile, fossiliferous, calcareous, and ) arenaceous beds: a. Bedded limestone [ Camptonectes, Inoceramus], 30 ft. | Z b. Caleareous shale, with the same fossils, 60 feet. ( 1D. | 3) ce. Caleareous sectile sandstone, shaly toward the base | Pinna], 60 feet. 7. Solt.red shale........-. afb et eh EES ANRC Ma eh 8. Massive cross-bedded sandstone, cream- eae above, pandediwith redubelow:-22..2.2.. 54.262 22052054 9. An alternation of red and slate-colored, saline, sandy shales, with deep red, bedded, in part cross-bedded, sandstones; the latter in three principal masses... . 10. Variegated eypsifecous clays. . eee 11. Yellow conglomerate, with silicified attr SARE ae ee 12. Chocolate sandstone, changing below to sandy shale, and banded near the base with slate-colored strata. .... HNGICLL Be Sao oStriot cimtoaoern sree SiO aie eee a Section IV. West fork of Paria Creek. . Argillaceous shales, with coal: Blue-gray shale soar at us problematicus], 50 feet. Coal, 4 feet. : iia Hare shale, 1 foot. . Soft gray shale, 25 feet. . Yellow shale, 3 feet. - Shell-limestone[Ostrea, Inoceramus,Trigonia], 1 foot. . Soft yellow-gray shale, 2 feet. . Coal, 4 inches. . Soft gray shale, 6 feet. Coal, 1 foot. . Soft gray shale, 50 feet. . Coal, 3 feet. -Shale, 15 feet. - . Coal, 1 foot 6 inches. . Bituminous shale, 1 foot. Wie. 63.—Sec... IV.— . Coal, 2 feet 4 inches. Paria Creek, Utah. . Arenaceous shale, 17 feet. Seale, 1-7200.: . Coal, 2 feet 2 inches. = ~amSs S>se2K2 a8 SA zee Sos 8 Ue 160 GEOLOGY. Feet 2. Cream shale, with occasional fillets of red shale, and of Sandst0ne.a2-t- pees ae eee eat in 300 3. Dark red, brown, and purple, soft eeL e ?) sand- SLONO) (eee sei eae a ee eer 400 4, Soft arenaceous shales : 7? a. Slate-colored to cream shale, 50 feet. t 125 b. Purple shale, 75 feet. \ 5. Cream, cross-bedded, friable, massive sandstone......... 120 6. Alternations of shale and sandstone: ) a. Red sandstone, 5 feet. : b. Gray shale, 30 feet. | c. Red sandstone, 10 feet. 95 d. Gray shale, 30 feet. | e. Gray shaly sandstone, 20 feet. \ 7. Massive cross-bedded sandstone, cream to ocherinecolor. 900 8. Massive cross-bedded sandstone, yellow, banded with vermilion, the latter staining the escarpments. .--. 800 9. Variegated gypsiferous clays, with silicified wood. -.-.- "450 10. White (to yellow) conglomerate, with silicified wood, resting on eroded surface of 11.-.....-...-....... 0 to 75 11. Chocolate gypsiferous clays: ? 450 a. Soft chocolate shale, 225 to 300 feet. ' fet b. The same, harder and sandy, 50 feet. 375 ce. Soft brick-red shale, base not seen, 100 feet. 4} Motale Besse A SE eee 4, 275 Thicknesses estimated except in the coal series, No. 1. Section V. Jacob’s Pool, Northern Arizona. Feet. a 1. Massive cross-bedded sandstone, red, with bands of cs a ee LO Re See See cscs ng Hoe Ce ee Peer 500 ill 9, Bedded red sandstone, with alternations of sandy red %, a shale; a transition from 1 to3 .........-...-..-- 500 3. Gypsiferous cherty clay-shale, red at top, variegated below. Numerous silicified logs near base..-.---- 700 4, Gypsiferous cherty clay-shale: ? l Pires a. Chocolate arenaceous shale, 50 feet. f 450 pete as as b. White soft shale, 100 feet. Seale, 1-7200. F ce. Chocolate soft shale, 300 feet. \ THE STRATIFIED ROCKS. Feet. 5. Cherty limestone series: a. Soft red sandstone, 20 feet. b. Dark gray limestone, [Plewrophorus, Bakevellia, Schizodus,| 20 feet. | c. Red sandstone, 10 feet. + 850 d. Cherty limestone, light gray, heavy bedded ; a few feet at top sectile and shaly, the remainder standingina sheer cliff,[ Mcekella, Pseudomonotis, Aviculopecten oc- \ cidentalis?, Hemipronites, Productus ivesii,|* 800 feet. 6. Gray, cross-bedded, calcareous sandstone..-.-..-.....-- 50 7. Red shaly sandstone-......----.--------- Lvasecknstecer ~%00 Beds 1, 2, and 3 were measured; the remainder estimated. A few miles east, in the same escarpment, a red conglomerate appears under No. 3, with a thickness of 75 to 100 feet, and cuts out No. 4 @ and part of No. 4 b. Nos. 5 b and 5 are also replaced in a neighboring ex- posure by a gray, cherty, calcareous conglomerate, result- ing apparently from the local degradation of 5 d. Section VI. The lower cafion of Kanab Creek. Above No. 1 are chocolate and gray shales, equivalent to No. 4 of Section V. Feet. 1. Massivesandstone,(a, dark red; b,yellow; c,red,caleareous) 150 2. Cherty limestone series: a. Yellow limestone, with much white chert (weather- ing black) and a belt of sandstone, 140 feet. ! b. Gray and white heavy-bedded to massive limestone, | with much chert, [ Meekella striato-costata, Productus | ivesii, P. (non des.)Spirifer lineatus, Orthis, Athyris | subtilita, Hemipronites, Fenestella, Cheetetes, Zaph- “770 rentis,] 300 feet? | ce. Shaly limestone, cream to gray, 60 feet. | d. Gypsiferous shale, with massive gypsum, and bands of white, friable sandstone, 90 feet. e. Heavy-bedded, cream to gray, limestone, crinoidal and somewhat cherty, [Productus ivesii, Spirifer lineatus, Fenestella,? Chectetes,| 150 teet. *The form designated by Dr. Newberry, Productus ivesii, is considered by some paleontologists to be undistinguishable from Productus semircticulatus. Whether it deserves to rank as a separate species or only as avariety of the long-established species, it is important to recognize the existence of the form, since it is diagnostic of the Aubrey limestone, being confined, so far as is now known, to that horizon, while P. semireticulatus ranges ia the same region through the entire Carbcniferous series. 1iws Ss Fig. 65.—See. VI— Kanab Cation, Ariz. Seale, 1-7200. i Se 70\FE eee Le Fic. 66.—Sec. VII.— Grand Canon, Ariz. Scale, 1-7200. GEOLOGY. Feet. 3. Shaly and sandy limestone, or calcareous sandstone. .... - 50 4. Red sandstone: ji a. Deep red, friable, bedded sandstone, 350 feet. | b. Red heavy-bedded sandstone, 130 feet. ! ec. Dark gray limestone, 2 feet. { d. Massive, cross-bedded, red and purple sandstone, a 400 feet. i e. Massive, cross-bedded, buff sandstone, 50 feet. J. Massive, cross-bedded, purple sandstone, 50 feet. —§ 5. Purple and white, heavy-bedded, arenaceous limestone, with pink chert; in one bed, passing into cross- bedded sandstone. 2 = 2n-e. Seana ee 200 6. Massive saccharoid limestone, gray to cream, [Spirifer, Orthisy CRONEGES eo ayer amma oc Se oes eels Sa ee 1, 000 7. Massive gray limestone, with some chert; interrupted by bands of hard calcareous shale, and characterized, toward the base, by coralline mottlings-........... 950 8. Green, arenaceous, and micaceous shale.......-.--..--.-- 100 Pot eee ee wedee Je) 935 oanmemonatco See. sshecseccy 4, 200 ‘\ Section VII. The wall of the Grand Canon of the Colorado at itsmouth. Nos. 1, 2, and 3 were not measured nor crossed at this point; they constitute an upper terrace, retreating several miles from the immediate front of the chasm. The remainder of the section was measured by aneroid barometer. Feet 1. Gray, saccharoid, cherty limestone............-----.-- 200 2, Massive, cross-bedded, yellow sandstone. -....---.-..-. 300 3= Friable red sandston@yas sete a ote 800 4, Alternating limestone and sandstone : a. Cream fine-grained limestone, [A%chcocidaris,] 75 feet, | b. Dark gray fine-grained limestone, 25 feet. . 510 c. Cream fine-grained limestone, 20 feet. d. White calcareous sandstone, 35 feet. | e. Gray fine-grained limestone, 40 feet. | Ff. Red and purple cross-bedded sandstone, 315 feet. —§ 5. Gray limestone, massive to heavy-bedded, and in part cherty ; standing in sheer cliff with red-stained face, PSE eg TS) eee Bas = 2S See 800 6. The same limestone, alternating with calcareous shale... 1,565 7. Massive limestone, with coralloid mottling. ..-...--..-. 7d THE STRATIFIED ROCKS. 163 Feet. 8. Shale series, (Tonto shale :) a. Soft green shale, with intercalated pale red sand- | stone, 100 feet. i b. Arenaceous: limestone, with obscure coralloid mot- tling, 25 feet. 605 ec. Greenish shaly sandstone, 40 feet. d. Limestone, like b, 25 feet. e. Green and purple shales, arenaceous toward the ! base, and in part hardened to a shaly sandstone, | [Cruziana], 415 feet. 9. Vitreous sandstone, white to yellow and red; heavy- bedded, (Tonto sandstone) ...........------------ 80 10 Granite, gneiss, &c., unconformable...... ..--..---.--- 90 REM ee teers sce io cistes cen ksuetes BE afejetara 4, 825 Section VIII. Aubrey Cliff, fifteen miles southeast of Bill Williams Mountain, Arizona. Roughly measured by aneroid-barometer. em sunal terete Rene hae ae sacar ew siice pene gnc 65 2. Cherty limestone: ? : a. Gray, heavy-bedded, cherty limestone, [Orthoceras, | Bellerophon, Productus,| 200 feet. 339 b. Gray calcareous shale, 15 feet. [es e. Gray cherty limestone, 60 feet. 5S 3. Massive, cross-bedded, yellow sandstone.......-...----- 700 4, Friable red sandstone... ... .. Soocbenddess ceseauusnee 200 5. Alternating fine-grained limestones and calcareous red and} yellow Sandstonessy .<. -. scm. oo oe ee ee tenes 40 5. Dark brown, quartzose and argillaceous conglomerate... 140 6. Crystalline limestones 2cikee Na eda eee ee eee 85 7 Green shale.c.. dcoscesim. ot ee SR Ee re 20 8. Massive hornblende rock, black to green... ...------.--- 120 Total. «3s oes. Gstes a Oc es Neen ees Sines sc ateintard . 2,155 THE STRATIFIED ROCKS. 171 The accompanying table exhibits the relation of the above sections to each other, and to the general stratigraphical scheme. It will be observed that all the great divisions of geological history are represented ; and these will now be noticed in order. Table showing the correlation of the sections. g 8 g Be e 2s 2 pea var td ieieats % ags a =] y » [[ a BR s a agg a EI : a & a Oanm oO 3 8 p R be w On i a rs) E a Oo O05 o a Qn 8 4 2 ) = Ea 2 = SS g =| 3 5 3 6A o Se ‘a 5 8 io) 3 < =] rs) =) a 5 (5) a Q . Wales. . Asays. . Virgin River. . Paria Creek, . Jacob’s Pool. : Kanab Creek. . Grand Cafion. . Aubrey. . Caiion Creek. Cadiita Creek, . Camp Apache. CCHS ND [ten att sie(c| viseisis sive « «| sins sma direc) canceennercal etal ete XII. Spring Mountain. an a CUE eeerd Se cteicts eisai |ate v'ss'ors ni s| waists sain awa] Seams = amplel wemeameres XIII. Ophir City. SME eae Wate 2n |p ues-ssce|sssaurenee|eeuscopgns|egeaeeneme XIV. Fish Springs. SUN (Genero Sic, siscite | seis sc icaselkseaveracs|ssseccseea peteeeeeealeeeeeeeees XV. Antelope Springs, ery 5308 Sooo HaShhur CocBe| MOS BeERsOG HRBSOBEE 6 REBSRDE ad Recticsecd| Edncnaccrc XVI. White’s Peak. [3 | Meera tietaictel asiiseicieleininehe| ecisics viefaiec| cic'e cv cesca[aaweenncee|sicvesslsvemlsewnelelcens XVII. Silver Cation. | & Hone bosssosaed Fosddoonnad fdoornoocd Secaenadee seebredee erat Asc sanecesc XVIII. Groom. Qi Beery |S sivaivierhand| as cdelce vues |sea cess os |oes e's oc vpleleah teas ead beeeas eeu lense Gs cece XIX. Boundary. 172 GEOLOGY. Quaternary.—The Bonneville beds, a calcareous series deposited during the Glacial Epoch, have already been described in the chapter devoted to that epoch. They are restricted to the lower parts of the Great Salt Lake and Sevier Lake basins. The unconsolidated gravels and clays that flank the ranges and floor the valleys of the Cordillera region, have likewise received mention. They are of Quaternary age at top, but the antiquity of their lower portions is unknown. It is not improbable that they have, in some valleys, accumulated through all Tertiary time, and they may have been begun even earlier. About Camp Apache there are preserved, under basalt covers, portions of a sand and gravel deposit (Section XI, 2) that rests unconformably on what are now the highest portions, topographically, of the Carboniferous and Mesozoic rocks. The evenness of the basalt sheets that spread over its original surface, indicate that the formation floored a plain, and suggest a relation of altitudes far different from the present. The region is now so elevated that its erosion is very rapid. Streams have sunk their channels to a depth of two thousand feet below the old plain, and carried the eroded material to the modern plain of the Lower Gila, which lies so little above the ocean level, that its slopes are slightly inclined, and its arroyosshallow. To this Apache sand bed may probably be referred the bowlder accumulations that have been found, by Mr. Marvine and myself, to cap the mesas and hills at numerous points in Arizona. When they were first seen a glacial origin was suspected, but a search failed to discover upon the bowlders, which are well rounded, any glaciated surfaces. Tertiary—The difficulty that geologists have found in the separation of the Tertiary and Cretaceous, along the line of the Union Pacific Railway, is equally encountered in Southern and Central Utah. The progressive con- ditions, recorded in the sediments, are marine, estuary, and fresh-water. So long as the fauna is purely marine, there is no question; the facies is unmistakably Cretaceous. But the estuary or brackish fauna that succeeded is made up of forms of doubtful affinities, and after the disappearance of all indications of salt water, the remaining animals and plants are of Tertiary aspect. It is not improbable that the two groups of living forms existed at the same time, and shifted their common border, as the line separating the THE STRATIFIED ROCKS. 173 salt water from the fresh was shifted. When the inland sea became finally separated from the ocean, and was deprived, by dilution, of its salt, the marine Cretaceous fauna may still have flourished beyond the limits of the continent. However this may be, there is no immediate hope that the facts of the case will be demonstrated—we cannot yet even point out the barrier that kept out the ocean. But, while we are not certain that our rock series records the termination of the Cretaceous age, we do find in ita history of the local extinction of the Cretaceous marine fauna, and the substitution of a con- tinental fauna ; and it is convenient, in the present condition of our ignorance, to call this latter Tertiary. With this somewhat arbitrary assumption, it is still impossible to draw a sharp line of demarkation, because the change of conditions was not abrupt. Of the three sections given of Tertiary strata, the second and third are but fifteen miles apart, while the first is one hundred and fifty miles to the north. My own data were not sufficient to connect them, but Mr. Howell was able to follow and study the strata more thoroughly, and considers No. 1 of section I equivalent to No. 2 of section II, and No. 1 of section III. Section I includes the Sam Pitch coal seam, which is closely associated with a fauna that Mr. Meek recognizes as identical with that of the Fort Union group of New Mexico. Among the fossils are Goniobasis Nebrascensis, G. tenuicarinata, Viviparus trochiformis, and Uniovetustus. The area mapped as Tertiary lies entirely within the borders of Utah, and caps the highest portions of the Plateau region west of the Colorado. It forms a belt, forty to sixty miles broad, with a north-northeast trend, and coincides very nearly, in its western limit, with the western limit of the Plateau region. It terminates southward, in latitude 37° 25’, in a line of bold escarpments, the Pink Cliffs, from which to the Grand Caiion of the Colorado, eighty miles away, there is a continuous geological descent. (See Figs. 22 and 23.) Eastward also its edge is usually marked by a cliff, and, in a general way, this is parallel to the course of the Green and Colorado. Northward the belt passes beyond our field, and probably terminates on the flanks of the Uintah Mountains, with a total length of two hundred and fifty miles. From Panquitch northward for seventy miles it is completely covered by volcanic rocks. 174. GEOLOGY. Cretaceous——The Cretaceous rocks are characterized by pale colors, with a preponderance of yellow, and are largely argillaceous. They afford the economic coal series of Southern Utah and of Castle Valley. In a general way their outcrop flanks the Tertiary area on the east, south, and southwest, but its configuration is far more complicated by folds and conse- quent inequality of denudation. Its delineation on the maps is almost entirely the work of Mr. Howell, and the reader is referred to his report for descriptions of the beds which compose it. | Jurassic.—Rocks of this age are known in both Plateau and Range regions. In the latter, the only localities that have furnished fossils are the Wahsatch Mountains, near Salt Lake City ; the Mineral range, near Adams- ville, Utah; and the Spring Mountain range, near Good Spring, Nevada. At none of these places were the limits and relations of the beds determined. The rock in each case is a gray limestone. In the Plateau region of Utah, beds referable to the Jura are always found beneath the Cretaceous, but they are not everywhere fossiliferous. Upon both forks of the Virgin River and upon Kanab Creek I found Jurassic forms, (including Camptonectes bel- listriatus and Pentacrinus asteriscus,) in a cream-colored, arenaceous lime- stone, and they appeared to be restricted to a brief vertical range. Farther east, in the basins of the Paria and Dirty Devil, Mr. Howell found the same species in gray shales overlying the cream-colored beds, which are there sandstones. Above these fossiliferous beds, and beneath strata recognized by their fossils as Cretaceous, there are several hundred feet of highly col- ored gypsiferous beds, ranging from sandstone to clay in texture, and usually including a thick bed of solid gypsum. (See. III, 5, and Sec. IV, 3.) In this series the search for marine fossils is well nigh hopeless, since the physical conditions under which gypsum is accumulated are inimical to life, and unless Cretaceous fossils shall be discovered below them, or Jurassic above, their age will always be conjectural. The outcrop of the formation is in detail exceedingly tortuous. In Southern Utah it strikes from west to east across a region interrupted by faults and deeply carved by erosion in a direction at right angles to its course. Between the Paria and Escalante rivers it is carried in a loop far to the southeast by a broad synclinal fold, and further north it becomes so THE STRATIFIED ROCKS. 175 greatly flexed as to lose all semblance of parallelism to the Tertiary escarp- ment. In about the latitude of the town of Salina it passes eastward be- yond the limits of our survey. To the west of the Tertiary belt, and in part within it, the Jura was found, with characteristic fossils, by Mr. How- ell, the localities being the eastern flank of the Wahsatch range, the west base of the Sam Pitch Plateau, and the east margin of the valley from Sa- lina to Manti. Trias—F rom the fossil horizon of the Jurassic downward to that of the. Permo-carboniferous—a vertical distance, in Southern Utah, of 2,500 to 3,500 feet—the age of the rocks is not fixed by fossils. Prof. J. Marcou, who was the first geologist to examine this series, referred it to the Triassic from lithological resemblance of its beds to rocks of that age in Europe; and the same reference has been provisionally made, though on different grounds, by Dr. Newberry. ‘The question is probably not insoluble. Dr. Newberry has found evidence, as yet unpublished, in the valley of the San Juan, to confirm the assumption, and Mr. Howell and the writer have dis- covered fossil localities that promise, when thoroughly searched, to throw additional light. In Southern Utah and adjacent Arizona the series is constituted by massive, cross-bedded sandstone above, and variegated, saliferous and gypsiferous clays below. ‘The sandstone is usually parted by a soft layer near the middle, and forms two lines of cliffs, terraces of the great south-facing escarpment. The upper division has a light buff or cream color, and its cliffs are usually capped by the cream-colored beds of the Jurassic. The lower division is banded with red, the stain from which dyes the whole face of the escarpment, and toward its base is red through- out. The transition from sandstone to shale or clay is usually not abrupt, and the upper part of the clay has the same deep red hue as the superjacent sandstone. The principal mass of clay is beautifully banded with brick red, pale rose, dark lavender, Naples yellow, maroon, pale sienna, white, and chocolate, the last mentioned color predominating toward the base. In the midst of the clays is a bed of conglomerate. The lower shales were somewhat eroded by the current which spread it, as is shown by the inequality of the surface on which it rests. Its thickness is variable, and it is not universally present; but its persistence over large areas is neverthe- 176 GEOLOGY. less such as to excite wonder. In the conglomerate and in the superjacent clays are silicified tree trunks in great numbers. The fossil horizon discoy- ered by Mr. Howell near Toquerville, and another that was noted south of Kanab, are lower than the Shinarump conglomerate. The first geological belt, in the descending series, which, in our field, crosses the Colorado, is that of the Trias. Beginning west of the town of Saint George, and not far north of the Utah and Arizona boundary, it ‘passes east, and a little south, for one hundred and thirty miles, to the Col- orado, at Monument Canon, expanding in the middle of this course to a width of thirty-five miles, and including the boundary line for most of the distance. Its chief inequalities of form are caused directly by erosion, but primarily by the faults and folds which cross the belt at right angles. The Kaibab fold throws the belt twenty-five miles to the north, by making a sinus of that depth in its southern limit, and a corresponding salient in its northern. From Monument Canon, where the belt crosses the river, it runs south-southeast, in Arizona, to the Colorado Chiquito, when, turning more to the east, it follows that stream nearly to its head, and finally disappears beneath the lavas of the Mogollon region, two hundred miles southeast from Monument Caton. Throughout the whole outcrop, from Saint George to the head of the Colorado Chiquito, the general dip of the strata is to the north, or northeast, at a low angle, and, except in the region of that stream, the mural escarpments of the heavy sandstones overlook, at the southwest, a broad floor of Carboniferous limestone that reaches to the margin of the Range system of Arizona. Upon this floor stand a few lava-guarded islands of Trias, testifying to the former extent of the formation. Above the mouth of Monument Canon, the Colorado is flanked on both sides by the Trias as far as the limit of our field, and this river outcrop, dividing the Cretaceous areas of the two banks, serves to connect the south- ern Trias outcrop, just described, with more northerly outcrops, mapped by Mr. Howell to the east of the great trachyte field of Southern Utah. Carboniferous—Strata of this age have great depth and cover large areas, both in the Plateaus and among the Ridges, and they are characterized by thick masses of limestone, filled with organic remains. They are best exposed for study in the former region, and it was found convenient there, THE STRATIFIED ROCKS. VG by Mr. Marvine and myself, to attach local names to the more important subdivisions. They are the Aubrey limestone, the Aubrey sandstones, and the Red Wall limestone. The Aubrey limestone and sandstones constitute the Aubrey cliff, which faces Aubrey Valley, in Northern Arizona, and stretches southeastward nearly to Camp Apache. The Red Wall limestone is so named from the red appearance of its escarpments on either side of the Grand Canon. The Aubrey limestone has a thickness of 820 feet on Kanab Creek, (Sec. VI, 2 and 3,) and this is about its maximum. Its characteristic fossils are Productus Ivesii, P. semireticulatus, Spirifer lineatus, Athyris subtilita, Mee- kella striato-costata, a Hemipronites, and an Aviculopecten closely allied to A. occidentalis. At a few points were found in the topmost layer, Plewrophorus, Schizodus, and Bakevellia, a group of shells suggesting the Permo-carbon- iferous of the Mississippi Valley, and indicating that the great lithological change at this horizon marks the absolute close of the Carboniferous age. Lithologically the limestone is characterized by the great abundance of chert, which, toward the top, sometimes constitutes half the mass. Near the middle it is, in some places, interrupted by a belt of shale, with gypsum. The soft Trias clay above it has yielded so rapidly to denuding agents, and the limestone has yesisted so stubbornly, that its belt is a very broad one. From the Aubrey Cliffs, northeastward, to the Shinarump Cliff, a distance ranging from sixty to one hundred miles, the country is floored by the Aubrey limestone, save only where the gorge of the Colorado bares the lower rocks. The Aubrey sandstone series (Secs. V, 6 and 7; VI, 3 and 4; VII, 2 and 8; VIII, 3, 4, and 5; IX, 2, 3, and 4,) has a thickness, in the Aubrey Cliffs and along the Grand Cain, of about 1,000 feet. In every exposure a portion of this body is massive and cross-bedded, and another portion soft and gypsiferous, but the order of these parts is not constant. In the Aubrey Cliff, the compact rock is at top, and, together with the Aubrey lime- stone, holds a sheer bluff, at the foot of which the softer portion spreads a broad slope. Along the Grand Cafion, at Kanab Creek, and near the Uin- karet Mountains, the upper sandstone is soft, and produces a slope in the profile, while the lower is hard, and unites its steep escarpment with that of 12Ws 178 GEOLOGY. the Red Wall limestone. The sandstones contain no fossils, but an inter- calated limestone, below the middle of the series at Canon Creek, (Sec. [X,) . bears the familiar Coal Measure shells. The Red Wall limestone (Secs. VI, 5, 6, and 7; and VII, 4, 5, and 6,) has, upon fresh fracture, a gray color, and shows its red rust only on weather-stained cliffs. In its general character it is heavy-bedded to mass- ive. At top, sandstone alternates with the limestone for from 200 to 500 feet. Through its lower half, the firm limestone is interrupted by occasional shaly bands, which serve to break its escarpment into a series of narrow ter- races; but above them stands a sheer, perpendicular face, of from 800 to 1,000 feet. The average total thickness is 2,500 feet. Fossils are abundant near the top, but difficult to find in the lower portions. The lowest horizon from which I obtained fossils of value is a trifle below the middle of the series, and they are doubtfully referred, by Mr. Meek, to the Lower Carboniferous. The fauna of the upper portion is rich in species; and, while differing from that of the Aubrey limestone, is equally referable to the Coal Measures. It includes Platysomus, Phillipsia, Nautilus occidentalis, Euomphalus (like E. nodosus), Murchisonia, Macrocheilus, Bellerophon crassus, Pleurotomaria, Aviculo- pecten interlineatus, A. occidentalis, Myalina, Productus semi-reticulatus, P. Nebrascensis, Spirifer cameratus, Spiriferina (like S. Kentuckensis), Athyris subtilita, Hemipronites crassus, Archeocidaris, Synocladia Shumardi, and Glauconome, of which list,all of the genera and every identified species belong to the Coal Measures. With these fossils in view, the provisional assignment by Dr. Newberry of the whole limestone to the Lower Carbonif- erous or to the Lower Carboniferous and Devonian is seen to be erroneous ; but we are not yet enabled to demonstrate a complete correlation.* Of the 4,000 to 4,500 feet of strata that I have assigned to the Carboniferous, a very few feet at top may be called Permo-Carboniferous, and not less than 3,000 feet are to be referred to the Coal Measures. Below this is a single point recognized as ‘probably Subcarboniferous,” and the remainder is blank. The base of the system is arbitrarily assumed at the first marked lithological change, and it is not impossible that it has been placed so low *Professor Marcon (Geol. of N. A., pp. 23, 24, and 62) calls the Aubrey limestone, Permian; the Aubrey sandstone, Coal Measures, and the Red Wall limestone, “Carboniferous limestone,” or “mountain limestone.” THE STRATIFIED ROCKS. 179 as to include the Devonian, or even the Upper Silurian, if those formations are represented in the series. Considerations bearing upon this point will be adduced in speaking of the Silurian rocks. The classification adopted for the Carboniferous rocks in the Gand Canion and along the southern margin of the Carboniferous plateau, is of local value only. Seventy-five miles to the west, in the Spring Mountain range, I was unable to correlate the series in detail, and eastward, from Canon Creek to Camp Apache, the progress of a rapid transformation can be traced. The lower, shaly portion of the Aubrey sandstone becomes interrupted by numerous bands of limestone, and red shales appear in the Red Wall limestone ; and in this way the two series approximate in charac- ter, until the division can no longer be recognized. Among the Basin Ranges of Western Utah and adjacent Nevada, Carbo- niferous strata are recognized oftener than any other, except the Silurian, but our observations do not suffice for a comprehensive view of the litho- logical series. Limestones predominate, the prevailing color is gray, and, with few exceptions, the fossils gathered are of the age of the Coal Meas- ures. In a section upon the western face of the Wahsatch Mountains, near Provo, Mr. Howell found Carboniferous fossils, stratigraphically more than 5,000 feet apart, and the rock characters included between the two horizons are continued for 3,000 feet below the lower. The entire Lake range, and nearly the entire Oquirrh range, are built of Carboniferous strata. They are seen on both flanks of the Stansbury range (Howell) and along the western base of the Pah-vant. They appear at the south end of the Mineral range, and, in the Picacho Mountains, they include a portion of the argen- tiferous veins of the Star and North Star mining districts. They constitute a large part or the whole of the Confusion Range, and they form the eastern face of the Virgin range. They are in great force in the Spring Mountain Range, in the vicinity of Cottonwood Creek and Crystal Spring, and include the lead deposits of the Yellow Pine district. They were recognized by Prof. J. J. Stevenson in the stratified axis of the Reveille range, and the Reveille silver mines are within and-by the side of them. They were identified by Mr. Howell and Mr. Clayton in the Highland and Schell Creek ranges, and they were found in low ridges near Elko and Carlin on the Humboldt River. 180 GEOLOGY. At Mountain Spring, in the Spring Mountain range, a point on the old wagon-road from Salt Lake City to Los Angeles, a suite of fossils of facies older than the Coal Measures was obtained by Mr. C. A.Ogden. Among the forms are Phillipsia, Spirifer, (two species of Devonian aspect,) Rhynch- onella, Hemipronites, Athyris, (distinct from A. subtilita,) Chonetes, Terebra- tula (2), Productus, (like P. subaculeatus,) and Fenestella. The horizon is referable to the Subcarboniferous, and it is, in our collections, the only one between the Coal Measures and the Cincinnati group that is well character- ized by fossils. At Ophir City, Utah, a limestone with Coal Measure mollusks is sepa- rated from another with Primordial trilobites, by 700 feet of limestone, the whole being conformable. Near the middle of the interval is a fossiliferous horizon, exhibiting Phillipsia, Straporollus planodorsatus (?), Conocardium, Hemipronites, Athyris, Ptylodictya, and Syringopora, and referable to the Sub- carboniferous. There remain less than 400 feet of strata to represent De- vonian and Upper Silurian, and we have no evidence, by fossils, of their presence. In our whole field the Carboniferous rocks are not coal-bearing, and we have found vestige of but a single coal plant, a leaf of Pecopteris, preserved in arenaceous shale of the Coal Measures, fifty miles northwest of Camp Apache. In my preliminary report for 1871, the premature announcement of coal in the true Coal Measures, near Camp Apache, was made on an imperfect description of the locality, which I was unable to visit. Later evidence indicates that the coal in question is probably of Cretaceous age. Stlurian— Among the Basin Ranges we have identified the Lower Silu- rian by fossils at fourteen points; and by other evidence, based primarily on the fossils, we have extended the recognition to include portions of seven- ‘teen mountain ranges. At Belmont, Nev., the slates which wall the argentif- erous veins contain Graptolithus bicornis, G. ramosus, and G. pristis (2). The shales of the range next west—the Toquima—are probably of the same age They also contain the celebrated Murphy and other silver mines, and above them are limestones, in which Mr. Emmons found Carboniferous fos- sils Primordial trilobites were bought by Mr. J. Koehler from Eureka, from the Roberts Creek range, and from a point between San Antonio and Silver THE STRATIFIED ROCKS. 181 Peak, and by Lieutenant Lyle from Silver Peak.* An Orthis resembling O. plicatella, but believed to be new, was discovered by Mr. C. G. Heath at Fossil Butte, near Hyko, Nev., and at about the same horizon, in the adja- cent Pahranagat range, I found a score of species. My collection from this locality was unfortunately destroyed in transit, but the field notes, though based on a very hasty examination, suffice to indicate the horizon very nearly. They include Calymene Blumenbachii, Asaphus gigas, Orthis lynx, Strophomena alternata, and Receptaculites. (See Sec. XVII, 2 and 4.)t Silurian rocks, chiefly limestone, here constitute the chief mass of the mountain, and in them are the silver mines of the Pahranagat district. In the next range to the west, the Timpahute, are metalliferous veins, dividing yet lower strata. They are walled by shales, in which are calcareous bands - filled with the disjointed armor of a spiny Primordial trilobite, Conocoryphe. Above the shale (Section XVIII) are limestones, that may correspond to those of the Pahranagat range, and below are vitreous sandstones, closely resem- bling the Potsdam sandstone of New York. The same sandstone was recog- nized in the Belted Mountain range, where it is almost buried by rhyolite, and in the Amargosa range. (Section XIX, 3, and Fig. 12.) At the last station the overlying shale is altered to schist, but retains obscure vestiges of the trilobite spines. In débris from the same range was found a single specimen of Maclurea (magna?). At the base of the anticlinal arch exposed in the cation at Ophir City, in the Oquirrh range, are limestone and shale, with Conocoryphe, Dikelloceph- alus, and Olenus Gilberti ; but a few acres include the whole outcrop. In _ the next ridge to the west, the Stansbury range, Silurian strata are thought by Mr. Howell to form the crest. Close to the ‘Old River Bed Station,” at the north end of the McDowell mountains, I found Bathyurellus Wheeleri in a black limestone overlying vitreous sandstone, and the identity of rock series renders it probable that the Thomas range also is built chiefly of Silurian strata. The House range, which has a simple structure, appears to be built, for fifty miles of its length, exclusively of Silurian rocks. A lime- * Prof. J. D. Whitney announced to the California Academy of Science their independent discovery at Silver Peak and Eureka. ; tA collection of fossils, including Lower Silurian and Deyonian forms, had, at some time previous, been sent to Dr. Newberry from the vicinity, but I do not know their relation to my section. 182 GEOLOGY. stone mass at top, 2,000 feet thick (Sections XV, 2 to 7, and XVI,.1) yielded, together with other forms, Paradoxides (?), Scalites, Receptaculites, and Phyllograptus, and a shale beneath it is filled, at Antelope Spring, with beautifully preserved specimens of Bathyurellus (Asaphiscus) Wheeleri, Conocoryphe Kingii, and an undescribed Agnostus. Beneath this are another limestone and a vitreous sandstone, making a total section of more than 4,000 feet, of which nearly 3,000 feet are limestone. Fossils of Canadian age were found in the Schell Creek range at Schellbourne, and it is highly probable, though there is no paleontological evidence, that the Snake range, lying between the House and Schell Creek, contains Silurian rocks. At the mining town of Pioche, built on a spur of the Schell Creek or High- land -range, Mr. Howell found Primordial trilobites (Olenellus Howelli and O. Gilbertt*) in ashale overlyingthe quartzite which contains the argentiferous veins, and covered in turn by limestone. The following species had been named, and I quote here Mr. Meek’s descriptions, which will re-appear, with figures, in the paleontological volume. Olenus (Olenellus) Gilberti, Meek. This species is so very closely allied in all of its characters known to 0. Vermontana, Hall, that it may be sufficiently indicated by mentioning the few characters in which it differs. In the first place, the anterior end of its glabella differs from that of O. Vermontana in not reaching the ante- rior margin of the head by one-half to one-third its breadth instead of abut- ting close up against the marginal rim. The anterior ends of its eyes also extend farther forward, so as to come more nearly in contact with the ante- rior to be of the glabella, than represented by the published figure of O. Vermontana. Again, our specimens show a narrow marginal rim along the posterior edge of the head, extending all the way out to the lateral angles, not seen in the figure of the Vermont species. A still more marked differ- ence is lobe seen in the direction taken by the posterior margin of the head, near the posterior lateral angles, where in the Vermont species this margin curves gracefully backward to the lateral spines, while in our specimens it “The paleontological collections had been placed in the hands of Mr. F. B. Meek for study, and the work barely begun when he was prostrated by sudden illness and compelled, to our great regret, to relinquish it. THE STRATIFIED ROCKS. 183 curves rather abruptly forward, so as to form a kind of notch at its connec- tion with the bases of these spines on each side. Only a single detached specimen of one of the pleurz is contained in the collection. This is the large third one, which is prolonged and deeply furrowed as in O. Vermontana, but it is not near so abruptly bent backward as in that species. Some specimens indicate that the species under consid- eration attained nearly twice the linear dimensions of O. Vermontana. : The specific name is given in honor of G. K. Gilbert, geologist of Lieutenant Wheeler’s survey. Olenus (Olenellus) Howelli, Meek. This species seems to be related to O. Thompsoni, Hall, from the Ver- mont slates. Its cephalic shield, however (the only part known), differs in some of its proportions, particularly in being much more convex than it seems possible that the corresponding part of the type-species of the Ver- mont species could ever have been, even after making full allowance for accidental pressure. Its anterior outline is also much more narrowly rounded, and its length proportionally greater than in O. Thompsoni, the cephalic shield of which is about twice as wide as long, while the length of this part in the species under consideration is to its breadth as 5 to 7. Pro- fessor Hall also figures and describes his species as having the neck furrow passing entirely across, while in our type it ends. abruptly at about one- third of the distance across on each side. Its neck segment also projects back beyond the posterior margins of the cheeks, while that of O. Thomp- soni is figured on a line with the same. The specific name is given in honor of Edwin E. Howell, of the geo- logical corps of Lieutenant Wheeler’s survey. The localities that I have,thus rapidly enumerated, are scattered through a region extending four degrees in latitude, and five and a half degrees in longitude, and it is not to be expected that, over so large a space, there shall be found constancy of lithological succession. Still it may be noted” that the series, in a great number of instances, exhibits limestone at top and vitreous sandstone (quartzite) at base, with usually shale between—the typi- cal sequence of deposits upon a continent slowly sunk beneath the ocean. 184 GEOLOGY. The base of the quartzite is usually not seen. The quartzite of the Toyabe range, which may be the base of the Silurian, has, according to Mr. Em- mons, a depth of several thousand feet, and overlies granite. At Wheeler’s Peak an anticlinal of the quartzite appears to have a core of granite, but the fact was not fully established. In the Amargosa range, (Section XIX,) Silurian quartzite, 900 feet thick, rests conformably on 600 feet of schist, and what supports the latter is not known. There is strong presumptive evidence that the White’s Peak section (Fig. 9 and Section XVI), showing the Schell Creek range at a point between Schellbourne and Pioche, ex- hibits Silurian strata, although no fossils were found at that point, and, if it does so, then we have the siliceous rocks at the base of the Paleozoic locally developed to the enormous thickness of 11,500 feet. The Virgin range, exhibiting, in Iceberg Cafion, the entire Grand Cation rock series, is believed, for reasons that will be given below, to in- clude therein Silurian strata. The region of the Plateaus shows Silurian rocks only along its margin and in the Grand Camton of the Colorado. The strata which underlie the Red Wall group in the Grand Caiion are, — bee (1) the Marbled limestone, 75 feet thick, Group. (2) the Tonto shale, 600 feet thick, and (3) the Tonto sandstone, 80 feet thick; and the last rests unconformably on crystalline schists. The Marbled limestone is charac- Red Watt terized by ramifying stem-like markings, “Seater Grow. which suffuse the whole mass and give it a SES mottled appearance. The stems usually indicate their organic character merely by pe EES iS their outward forms, but a ee ee ToNTO SHALE, Tonto . -* woxro. ( Group. few specimens gathered by Se Dr. Newberry exhibit a cor- alline structure and appear to belong to the genus Chetetes. The limestone has a thickness at the mouth of the cation of but 75 feet, but there is a hint of its recwTFence 100 feet lower, (See. VII, 8 b;) and in tracing it forty miles up the canon, it is found to gradually increase in Ewe eT SR ae ARN AES EN BEALS TIN KA Fic. 81.—The Grand Caiion rock system and its subdivisions. THE STRATIFIED ROCKS. 185 importance and encroach on the shale below, until, at Diamond Creek, it has a total depth of 200 feet. The coralline stems are not sufficient to identify the bed which contains them, since similar branching forms are known alike of Carboniferous, De- vonian, and Silurian ages ; but it is a noteworthy fact that a mottled lime- stone similar to that of the Grand Canon has been observed at a number of points in Utah, Nevada, and New Mexico, and the fossils associated with it are invariably Lower Silurian, and usually Primordial. The only other fossils yet discovered in the group are a Trilobite in the Marbled limestone and a supposed sea-plant in the Tonto shale. The Trilobite is represented by a poorly preserved Pygidium too obscure for the determination even of its genus. Still, enough of it can be made out to warrant the assertion that it does not belong to any known Carboniferous genus, and, hence, that the rock is at least as old as Devonian. The fossil from the Tonto shale is represented in our ‘collections by a number of specimens; and, though its biological position is uncertain, its geological relations are beyond question. The genus Cruziana was first described by A. D’Orbigny from the Lower Silurian of South America. It has since been found in Lower Silu- rian strata in France and Sweden; in Primordial strata in England, New- foundland, and Montana; in the Chazy group in Canada; and in the Clinton group (Upper Silurian) in New York. Its known vertical range is thus en- tirely within the Silurian and its broadest distribution in the Lower Silurian. Cherty limestone. Aubrey group. Cross-bedded, and other sandstones. Carboniferous. Limestone and sandstone. oe Red Wall group. Place of Devonian and Silurian, (except | Limestone and calcareous shale; without Primordial. ) fossils. Mottled limestone, &c. Primordial. Arenaceous and argillaceous shales. Tonto group. Vitreous sandstone. 186 GEOLOGY. By these facts I am led to conclude that the Tonto group is certainly Lower Silurian in age, and probably Primordial. In the accompanying table is a correlation of the Grand Cation rock system with the rocks of other countries. Archean.—Metamorphic sedimentary rocks, of undetermined age, were seen at a number of points in the region of the Basin Ranges, and have been regarded provisionally, in mapping, as Archzean, and with them have been grouped the granitoid rocks, the age and origin of which I have rarely been able to determine. I will enumerate only those localities at which the observation determined something more than the mere presence of crystal- line rocks. In the Grand Cation of the Colorado (see Fig. 30 and Fig. 81 a), the Tonto sandstone rests directly on plicated and eroded schists and associated granites, and demonstrates them pre-Silurian. Following down the river, the same relation is seen in the Virgin range; and in the next ridge to the west, through which the river has cut Bowlder Caion, are gneisses so similar to those of the Virgin range, that they may safely be classed with them. In Music Mountain, in the Black Hills near Prescott, and on Canton Creek, or, more generally, all along the southwestern border of the Plateau region in Arizona, the Archzean schists and granites are seen beneath nonconform- ing members of the Grand Caiion rock system; usually the Tonto sandstone. To the south and west of this line stretches a great ocean of metamorphic ridges, in which no one has found fossils. Whether a portion of the rocks are altered Paleozoic, or whether the Paleozoic has been completely removed in the progress of erosion, or whether the Archean rocks have been covered by no later ocean sediments, has not been decided. The purity and great thickness of the Carboniferous limestones, up to the very marginof the region, would appear to negative the idea of a permanent continent from Archzean time; if, indeed, it is not negatived by the survival of acute mountain ridges. Résumé—The Archeean strata had been deposited, plicated, raised above water, and eroded, before the epoch of the Tonto group, the first that, in this region, has contributed paleontological data to the geological record. In that epoch a coast line slowly encroached upon the Archzean continent, THE STRATIFIED ROCKS. 187 paring its ridges, filling its hollows, and spreading over all, first, the coarse siliceous detritus that constituted the advancing beach; secondly, the finer mud, sorted out by the waves,and spread by currents in the shoal water that progressively followed the beach; and, thirdly, the limestone that was slowly formed, when the shore became so distant that the currents brought no more matter in mechanical suspension. Where the shore then was we cannot tell, nor do we know what islands remained. The record of the ocean’s advance has been traced as far west in Nevada as longitude 117°, and as far east as longitude 109°, and I know no reason to doubt its continuity, beneath newer strata, to the region of the Great Lakes. From this time the shore did not return to a large portion of our field until late in the Carboniferous age. From the close of the Carboniferous to the beginning of the Cretaceous age, a great area, including the whole Plateau country, appears to have been covered by an inland sea, entirely separate from the ocean; a sea in which were accumulated, probably from local sources, minerals that the world-wide ocean, constant in its generalities, cannot be supposed to have furnished in such quantity. The deposits are pervaded by gypsum and colored by the peroxide of iron, and contain no indigenous fossils, only logs and leaves drifted from the shore. Once only did the ocean regain temporary sway, bringing with it a Jurassic fauna, and then retreating, until, in Creta- ‘ceous time, the domain of the shut sea was finally abolished. Through the Cretaceous age the Plateau country was the scene of a shallow ocean, the shore of which crossed and recrossed it, and was never remote; while the Range Province had become finally continental. Then, by the upraising of some remote barrier, the Cretaceous sea, or bay, was converted into a fresh lake; and, with the gradual drainage of this, the whole region became terrestrial. Since the expulsion of the sea, the elevation of the continent, which caused it, has continued ; and the Plateau region, which, from early Silurian to late Cretaceous, sank (as referred to the ocean) no less than 8,000 feet, has been bodily uplifted to its former altitude. Erosion, which began in the Ranges and the Plateaus, as they were successively exposed to the atmosphere, has labored, during the elevation, to remove the results of the deposition which accompanied and recorded the subsidence, but has accom- plished only a small fraction of its task. [hy verantatG Cun alas Gre Rk ep Yahi i f fj . Beany.* + % 3. sea 7 > ~oe 8 z a ree hae ; hy oe » ‘* Ruy SE TT SOE Feaapaees ° a f ESA EE TE: REPORT oN THE GEOLOGY OF ROUTE FROM ST. GEORGE, UTAH, TO GILA RIVER, ARIZONA. | EXAMINED IN 18. Wee BY A. R. MARVINE. 189 i% ie fie StuvE pd - liaiteyhaeire ald nee Wty 1, ib Eee vit ba ii ah, Bh, = ent fabatinlikas dade ate iaeSE Aino yr Hermits a : Twit eye seer THe Rie —_ ee & hw ot re rtf i meal 5 Ng is, ‘ona ali” tae ni Winte tibiae uitT Ty MTS toe sieteien ir 44." UUOFOTER: 39° o,'% Te ii ' LAriVeL cto Tien Atfo unger z eitagesA fii 2 bali ae obdighil’ df ro at did ls “atom Sh] vd hontva's Se: dfx i ied hind. wud niet f MW NS alt % ey 1 ee a seared 3 ata By ita) Su aha Wasurineton, D. C., May 10, 1873. Sir: I have the honor to transmit herewith my report on the geology of a portion of the region traversed by ‘“ Party No. 2” during the field season of 1871. In the earlier part of this season, duties incident to my position as astronomical assistant prevented my making any geological observations worthy of record here. Between Saint George, Utah, and Prescott, Arizona, though the route followed was hurriedly passed, the object really in view being the speedy establishment of an astronomical station at Fort Whipple, near Prescott, still such facts as were then observed are given in the first part of the following chapter. Fort Whipple being the last point, this season, whose position was determined by the more elaborate astronomical methods of the field, I was here formally transferred to geological work, and such observations as were made from this point throughout the remainder of the trip, to Tucson, form the rest of the report. Hoping the results may be satisfactory to you, I am, very respectfully, your obedient servant, Arcu. R. Marvine. Gro. M. WHEELER, - First Lieutenant of Engineers, U.S. A. 191 F ee haf Thaes MA ~ . AS Th A PAs «AY Ty TN eta One hare ihe 2g ele Bo ® " sa thee Sn ’ , Vs <4 ra z 4 . \ ~ aks } F tee ie sw ~- - sie mand 7 . - id a od J * ‘ > % - iy tong : ‘ i i) { e 4) — i ee oe . tbe “2 Cte arg at ae k : . iF * "i Fate ie 4 i oh . 4 ~ Lar . ; £ ‘ . > Ps CHAPTER VII. GEOLOGY OF ROUTE FROM SAINT GEORGE, UTAH, TO THE GILA RIVER, ARIZONA. SEcTION I.—FRom SAInT GEORGE, UTAH, TO CAMP VERDE, ARIZONA. SecTIon II.—FrRomM VERDE RIVER To LITTLE COLORADO RIVER. Section IIJ.—From LirrLE CoLorapo RIVER TO CAMP APACHE, ARIZONA. Section IV.—FrRom Camp APACHE, ARIZONA, TO GILA RIVER. SECTION I. SAINT GEORGE, UTAH, TO CAMP VERDE, ARIZONA. A line trending nearly southward from Saint George, in the extreme southwestern corner of Utah, to the Colorado River, and thence southeast- ward to Camp Verde, indicates approximately part of a remarkably sharp and well-marked boundary between two regions which, in their geological and topographical aspects, are strikingly the opposites of one another. To the southwest of this line lies the Basin Range System of numerous and nearly parallel mountain chains, for the greater part devoid of sedimen- tary strata, with large areas of plutonic and highly metamorphic rocks, and large detrital filled valleys, which increase in area toward the lower reaches of the Colorado and Gila Rivers. - To the northeast of the line, and rising abruptly from it in sloping ter- races and precipitous escarpments, are the edges of several thousand feet of sedimentary strata, which, dipping at first gently away from their exposed edges, and acquiring, in a succession of abrupt steps, the various members of the overlying geological series, stretch eastward to the Rocky Mountains and from the great Colorado Plateau. The line separating these two regions is approximately the route traveled. South of the Colorado, though rising for a short distance upon the summit of the lowest step or terrace of the sedimentary series, most of 13 WSs 193 194 GEOLOGY. the way was upon the crystalline rocks on which the latter rest, and which mostly form the Basin Range System, &c., to the southwest. Of these, nothing more can be stated than their names, the nature of the jowmey not developing any geological relations among them. North of the Colorado, and between it and Saint George, the Plateau border differs much from that south of the river. Saint Géorge is situated on rocks belonging near the base of the Trias. This formation here consists of many hundred feet of dark red cross-bedded massive sandstones which rest upon a series of shaly and often highly gyp- siferous sandstones, having among them occasional heavier beds, all being approximately horizontal, or dipping slightly toward the northeast, and sus- taining a most sparse and drear vegetation. It is at the base of the massive sandstones that Saint George stands. They here form red bluffs facing south or west, and trending from the town both eastward and toward the northwest in lines approximately parallel with the Virgin and Santa Clara rivers respectively. These two rivers, in fact, here roughly indicate the southern and western boundary of the formation, though its lower shaly portions often stretch beyond them. About sixteen miles above the mouth of the Santa Clara, the river flows directly at the western base of the massive Trias sandstone, which rises above it in a most striking bluff. The dip is here quite decided, and from beneath the bluff, in leaving it westward, outcrop the lower shaly members of the group. From beneath these, in turn, appears the upper bed of the Carboniferous formation, and, with increasing dip, the upturned edges of its lower members successively outcrop as they gradually rise upon the east- ern slope of the Virgin Mountains. These mountains trend in nearly a north and south line west of Saint George, and lying all along upon their eastern flanks may thus be seen the outcropping edges of the inclining strata. Where crossed by the old Salt Lake road, these strata rise high upon the mountains, in places forming their highest points, and, resting below on the underlying crystalline rocks which here form the opposite side of the range, give it a monoclinal character.* This upturned series here *T understand from Mr. Eb. E. Nowell, who, in 1872, crossed the range farther south, and near where it is eut throngh by the Virgin River, that it there presented an anticlinal structure. Later, he found that at the north a fanlt existed along the east base of the range. Iam also indebted to Mr. SAINT GEORGE, UTAH, TO CAMP VERDE, ARIZONA. 195 apparently presents the same sequence of strata as near the Colorado River,* all the upper part certainly being of Carboniferous age, though proof of the actual age of the lowest beds is yet wanting (1872). Beyond the base of the mountains, and near Saint George, are several streams of black basaltic lava, which have flowed down from the north,t+ and end not far from the city. South of Saint George, the Triassic gyp- siferous shales extend some distance beyond the Virgin River. The dip of the formation, however, being somewhat greater than the slope of the south- ern side of the Virgin Valley, the Carboniferous beds here also gradually outcrop in going southward, first appearing not far from the Arizona border. Passing gradually down through the Upper Carboniferous strata, as the ascent is made, the Red Wall limestone is found exposed upon the divide between the Virgin and Colorado rivers at the head of the Grand Wash. In descending into the latter, the rocks are again found for a while dipping somewhat more steeply than the general incline, thus forming of the divide, where crossed, a gentle anticlinal whose axis apparently rises at the west upon the flanks of the Virgin Mountains, and which probably dies out at the east in the main plateau, or else is separated from the latter by a fault which may be just commencing at this point, but which further south, as will be seen, becomes very large. In descending the “‘ Wash,” there gradually appears upon the east a line of abrupt cliffs, which gradually become higher as the valley is descended, until they form an enormous mesa-wall nearly 2,000 feet high, composed of the banded and ribbon-like edges of the sedimentary strata, which appear perfevtly horizontally bedded. This mesa-wall, rising in alternate slopes and precipitous palisades, with its high colors and strangely eroded outly- ing buttes, forms the abrupt eastern side of a great valley whose western boundary is the slopes of the Virgin Mountains, and which runs from the vicinity of the divide before mentioned, southward to the Colorado. The eastern mesa-wall is exposed down to the base of the sedimentary series only near the river. The following section, made at the mouth of the Howell for corrections and information upon several points in the geology about S. int George, which will be found more fully and accurately present: d in his re, ort. * See ante, p. 184. +From craters in Diamond Valley.—C. A. Ogden. 196 GEOLOGY. Grand Canon, has been furnished me by Mr. Gilbert, and gives an idea of the general series of rocks which have already been passed, as well as of those to follow. (See Fig. 82.) All along the western side of the valley and inclining on the slopes of the Virgin Mountains lie the upturned edgesof the same strata. a. At the north, upon descending from the mountains these g may possibly continue out and join the Plateau strata un- < interrupted. Lower in the valley, however, they dip off = from the mountains beneath the detrital filling of the val- = z |ey, are not continuous with the Plateau rocks, but must a = be separated from them by a fault of many hundreds of g = feet. Still lower in this valley, and near the Colorado, Za ridge rising from below the valley detritus shows still 3 another fault. A more correct section of these faults was s § obtained by Mr. Gilbert in the natural section presented 3 ® along the Colorado River. (See p.54.) In the following 2 figure I try to give an idea of the main features of the s) > valley, as seen from a point at the north. . A maze of the eroded remains of the Carboniferous Wash near 2 mesa lines the eastern side of the valley; the upturned = strata occupying the western. Among and resting upon Ss i . | & the latter are large masses of black basaltic lava, extend- wit DasalticL ava. a ing all along the base of the mountains, and in places a Calcareous conglomerate Mes 2 - long distance across the detrital filling which occupies = the middle of the valley, but apparently not reaching | 2 entirely across to the eastern side. In this wide valley = are several lines of drainage, of which the main one, gand that into which most of the others finally enter, is called the “Grand Wash.” These washes generally have ® the canon form—flat, gravelly bottoms, sloping talus, ® and steep escarpment above ; and as, in all but the west- ern side, the intermediate country is rather flat or rolling, the system, though in a valley, has all the characteristics of a mesa country. In the upper part of the valley ee eeeemeSioes 1" Ne Oe ee ee a : Cross bedded yellow Sandstones, massive; fied andi white Shales and Sandstones. ( aw long slope a) y _ 2a Bench several miles wide) Sag ae ad Alternating Sandstones and compact Limestones. S| § N & N ; |Red-wall Limestone- sheer escarpment. R| § : : : 7 Es deo eer 8 imestones in lesser escarpments, with interme diate r oe Catcaréous Shales. a SY Ee s : TORY EL euh Aol eo ha mee nse PO, EE ZANE EON EON Argillaceous Shales, with thin Sandstones,mostly rea. § (forming slope inmany small steps) 600 ‘9 : oe cheb nes oo pease ae See ——<—<$—<—$= = Vv. _. Be Gre om Sterastone, houvy bedded (forming low and narrow bench) SSeS a ie DNR AS Granites Gnetssesetc, to fiver: Mam ee K Fra. 82.—Section of the Sedementary Series at the mouth of the Grand Cation.—G. K. Gilbert. vr ; & ee 3 : > a ne mS : } ‘ $s . ' 4 bn yay ? r 3 ’ ‘ ' ‘ ‘ ‘ . n . — - AS ‘ \ | RE We ~ vt i “ae ‘ aa a 7 ' uf 1a D . 1s a , ‘ a Bays) CrP fs a Ae bas if a 7 =] ie dni main CU fia ; FP. cal Ve tat ¥ ‘ ote “ft / “ ‘ ~ ee | + Maes Core ci " + meee SPAS a x yw 7 + ' : : % ‘ “ee Helse ieee See ait ree 1) 5 ; fini’ tare? i @ _ AIT 4) . : . “* oc M603 4 eT) ‘ 7 wht os bt Ae f ; mY t Ms Le 4h, 771, , ba i? oa vee 4 5 Lorwyn wer et 2 aissat oil rg ee t e i: SAINT GEORGE, UTAH, TO CAMP VERDE, ARIZONA. 197 these cliffs may be several hundred feet high, as at the spring about twenty miles above Pah-ghun Springs, where they are composed of the same rocks, as the adjacent plateau, with a capping of basalt. Lower down, the Grand Wash and adjacent cations are not deep, are generally in the detrital filling which here hides the older sedimentary rocks below, and have usually a basalt escarpment. This lava may be but a few feet thick, while in places the cation has not yet penetrated it, several hundred feet being exposed. Above this lava there almost always occurs more of the detritus. This is composed of a curious mixture of limestone and sandstone fragments derived from the adjoining formations, mostly white, and often containing nodules of chert and Carboniferous fossils. This sometimes has the char- acter of a breccia, and again of a conglomerate, while often it is so cemented together that its structure is not apparent. This “calcareous conglomerate” is in places covered by a second basaltic lava flow. Thus, at ‘ Moccasin Spring,” there was shown upon the eastern side of the Grand Wash, above the main detrital con- glomerate, a lower lava, about 20 feet thick, covered with 30 feet of the calcareous conglom- erate, which in turn had 15 feet more of lava above it, forming the top of the cafon wall. About twenty miles above Pah-ghun Springs, and upon the high cliff above the spring there found, it was estimated that there was 150 feet of this conglomerate lying be- tween the two lava flows. East of the section mentioned, at Cave Spring, the edge of the upper lava is soon reached, and then, also, that of the lower one, the valleys exposing many feet of the conglomerate, which must com- pose an enormous amount of the valley filling. Where free from lava it forms a rolling or hilly surface, often with deep valleys; it is horizontally bedded, and abuts unconformably against the upturned Carboniferous strata which protrude from beneath it. Lower down in the valley, and in the vicinity of the river, a true con- glomerate of large and well worn pebbles occurs. Where observed this was divided into two portions: an upper, containing many pebbles from the sedimentary series close by, separated by an uneven but well marked line from a lower conglomerate, which was very coarse, composed mostly of - Fig. 84 . 198 GEOLOGY. granite rocks, among which were very conspicuous, large bowlders, often five feet in diameter, of very compact and hard white granulite, having but little quartz and large crystals of white feldspar. The narrow cajion lead- ing directly to the river was in these gravels. Allalong its sides were rows of buttresses, with many columns of the compacted gravel supporting great bowlders upon their summits, and giving quite a gothic air to its architecture. These gravels extend to and along the river, resting on the same granite which above lies beneath the Tonto sandstones. In going southward from the river, and following a wash lying quite near the foot of the mesa cliff, a section is encountered quite different from that passed in the Grand Wash. The same gravels are met near the river, growing finer and accompanied at top by fine calcareous shales which =} often contain much gypsum. One hundred feet is prob- ably a small estimate for the thickness of these beds. Above them comes a series of calcareous tufas. These occur in well defined beds of 2 to 10 feet in thickness, mostly white or reddish-brown in color, and though usually full of rather large lenticular pores, the rock portion is often very compact and heavy, and at times slightly crystalline, though generally rather light. The beds are Fic. 85.—Section at sometimes separated by a stratum, a few inches to a few adnate Colornateet thick, of a very light, fine, soft, ashen-like gray or ae Ce oa ae tufa. Dinoach Spring flows from one of these. ward twelve miles. | This section was taken ina distance of about twelve miles, after which granite and schists were passed to Tinnahkah Springs. The thicknesses are about as in the above cut. From the mouth of the Grand Canon the general course of the Col- orado, up stream, is at first nearly southeast. Upon meeting the river, the great Carboniferous escarpment, which forms the eastern side of the Grand Wash, turns and follows up the stream, forming the northeastern wall of its cafon. Only the lower beds of the escarpment, up to the great bed of the Red Wall limestone, form the first step of the westward facing mesa- edge upon the southern side of the river. These at first continue the line SAINT GEORGE, UTAH, TO CAMP VERDE, ARIZONA. 199 of cliffs at the north, trending south to Tinnahkah Springs, when they swing more and more to the eastward to Music Mountain,* near Truxton Springs. The accompanying sketch givesthe = 4g Wan Limestones lower beds of the escarpment series, as shown at the mouth of the Grand Zinto Marble Limestones Cation, somewhat more in detail than in the preceding section. The two snuff- colored sandstones, though quite subor- Tonto Shales dinate in-thickness, form a prominent Colorado fiver. feature of the section, and seem quite 7 n 1 ines e Tonto persistent, Mr. Gilbert having traced JM ce a them to Diamond Creek. They seemed also to be exposed upon the bluff oppo- site Tinnahkah Springs, about twenty — Fic. 86.—Section of the lower beds of the niles apaimonethoo river. lo going Colorado Plateau at mouth of the Grand Cation. southward, however, the Tonto shales seem to diminish in thickness, the thickness from the granite to the snuff-colored sandstone at Tinnahkah Springs being estimated at less than 400 feet. It will be observed that the base of the series has been gradually elevated in going south. A few miles south of Tinnahkah Springs, and where the escarpment was ascended, the Tonto shales were much Mn init Ze imestone further reduced, their estimated thickness being. a less than 100 feet, so far as could be seen upon the winding path of ascent, and they apparently contained little or no calcareous material. The Snuff Sandstone Tonto sandstone had increased much in thick- = ness, and was composed of two rather distinct = parts, being red below and yellow-white mottled CEE with salmon colored spots above. That the “Sv @uanite, limestones here are the continuation of those clay Puts cette tine further north, and not the expansion of cal- nabkah Springs. Estimated height of careous beds included in the Tonto shales, pra ee paeeeeimes ciante seems indicated by their lithological charac- ‘#dstene, under 400 feet. * This is not the Music Mountain of Lieutenant Ives’s map, which lies several miles to the east.— Report upon the Colorado River of the West, Government Printing-Otfice, Washington, 1861. 200 GEOLOGY. ters, the lower bed being of a very dark drab, mottled with irregular red spots, like the lower “ marble ” limestone, near the Grand Cation; while 10 eM the upper beds, as farther a DR AOE a MFT Co Compe ee tes north, grow gradually lighter- annie : : OOM: colored, becoming more uni- ee MTT IT 111 lamest. oe UM! 2a emeetone formly compact and acquiring Cale. shales. A ee ai 8 Dark drab limestone. a conchoidal fracture. They = Cale. shale : Loe segs 9 Dark drab lenestone. all weather with very rough y roug preety = =— Calo. shales. See || Verydarkdrabmartle ‘Surfaces. hs Gere 2 ABE ee The surface of this lower RE Argillaceous shilesand mega presents a beautiful roll- sandstones, probably mutch FE . F less than 100 feet. ing or hilly country, which Gary descends gradually northeast- Ttnto Satidistone ward to the Colorado, on the opposite side of which rises the great northern wall of the T'rc. 88.—Section of mesa-edge where ascended southof Tin- Grand Cafon. Southwest- nahkah Springs. ward its precipices overlook the Hualapais Valley, with the dry flat of ““Red Lake” and the distant Cerbat Mountains, which appear composed mostly of plutonic rocks. In nt ce Granites approaching Music Mountain, most of the limestones and Tonto shales are more and more eroded away from the surface of the lower mesa, and mostly remain as mesa hills, often bordering the Plateau edge, the intermediate val- leys being sometimes cut to the granite below. Music Mountain is sucha remnant, reaching up to the second limestone above the shales, the Tonto » shales being thicker than at Tinnahkah Springs. The country does not fall away particularly as a result of this erosion, however, as the base of the sed- imentary series, the Tonto sandstone, grows more and more elevated, the mesa edge being here as high or higher than near the river, but formed mostly of underlying granite The drainage is away from the edge northeastward to the river. Upon the surface several patches of lava were met, forming limited areas of ‘mal- pais.” The canon of New River, which heads just north of Music Mount- SAINT GEORGE, UTAH, TO CAMP VERDE, ARIZONA. 201 ain, has served as a channel for a flow of the same lava. A new cafion has been cut in this lava, exposing the following section : No. 5. Surface soil and débris, mostly Cation of New River th. ne of Tonto sandstone. EE EO he a _ Afiert No. 4. Ten feet; compact and often 3)20 banded calcitic tufa or a calcareous con- 2)%5 glomerate so closely cemented as to appear homogeneous. V"1 /120 No. 3. Forty feet; very fine to coarse conglomerate, mostly of limestone, with sandstone, granite, and lava bowlders ; hor- fa izontally bedded, filled in largely with lime. — o. No. 2. Fifteen feet; bowlders of No. 3, pete and the finer material of the same mixed, at the top, with feslgen of No. 1, antte. but below serving only as a filling of cracks and spaces in the very scoria- ceous and amygdaloidal top of No.1. The amygdales of the latter are filled mostly with carbonate of lime with some zeolitic mineral, and the rock filled with soft, reddish-brown, crystal-like specks, as if of dseoeposud olivine. No. 1. About 120 feet exposed in all, not cut through; very compact, grayish black lava, with smooth but uneven to hackly fracture, and occa- sional grains of a transparent green mineral, apparently olivine, which de- compose to a reddish-brown soft material. This, and the lava met farther north are nearly typical basalts, and much like others met upon the Col- orado Plateau. At Music Mountain, the mesa edge suddenly turns eastward, leaving a deep bay or area extending toward Aubrey Valley, and in which Truxton Springs is situated. In descending from the bottom of the Tonto sandstone, which forms the base of Music Mountain, to Truxton, about 1,500 feet of granite and allied rocks are passed through, of which about half is in the first steep descent from the mesa. This granite, with the accompanying rocks—of which the most frequent is a very fine-grained gray syenite, .com- posed of a uniform mixture of small white and jet black particles, as if a loose sandstone—at first forms abrupt hills, and contains frequent highly- 202 GEOLOGY. feldspathic veins or dykes, which, being harder than the adjacent rock, generally protrude several feet above the surface. At two or three points several of these appeared in company, at one point as many as seven, all being parallel, trending nearly east and west, a few rods apart, and 2 to 5 feet thick. Some were of handsome white cleaving orthoclase. Gradually the granite hills become capped and often wholly covered with a dark lava, like that at New River, and as the surface of this gradually becomes lower, itin turn becomes covered with a light pink or white rhyolite, the two being separated by several thin, soft, stratified layers of white tufa, which assist in causing the rhyolite to break in palisades which line the cafons. The granite was subjected to much erosion before the lavas covered it, its surface being very irregular, points of it sometimes projecting through both lavas, while, again, some of the cafions cut through many feet of the lower lava without exposing the granite. These granite hills toward the west, where they form the low eastern edge of Hualapais Valley (in the extension of the line of higher mesa edge at the north), are quite free from. the lavas ; eastward, or back from the valley, as near Truxton, granite and lava both largely occur; while further east, in which direction the lava-cap gently dips, the lava appears to form large unbroken areas. Its relation to the sedimentary mesa which rises at the east Ido not know. Toward the south and along the western valley border it occurs much as toward the north. As the hills grow higher the rhyolite first thins out and disappears, and finally the lower lava, leaving high hills of granitic rocks. It would thus appear that the rhyolite occupies a broad but shallow basin in the lower lava. I do not think that I observed it at any point thicker than 60-or 80 feet. Near its northern limit, and where it was first observed beneath the capping rhyolite, the lower lava was almost precisely like that at New River. It is nearly black, or grayish black, and somewhat dull in color, and very fine-grained or compact, uniform, and close in texture, breaking with an uneven fracture. In this base are sprinkled from a few to numerous small grains of olivine. These usually show a discolored film upon their surfaces, while near the weathered surface of the rock the mineral is often changed SAINT GEORGE, UTAH, TO CAMP VERDE, ARIZONA. 203 throughout, having the color and nearly the consistency of hard brown soap. All stages of this decomposition may be observed. This lava has all the characteristics of true basalt, and is like the Plateau basalts that I have seen, excepting, perhaps, that the olivine is more prone to decomposi- tion. The greater part of the upper lava consists of a white, light, fine- grained, but rough and open textured mass, in which are scattered numerous colorless, cleaving crystals of sanidine, and occasional flakes of a bronze mica and small crystals of hornblende. A few grains of quartz are also present, and as the rock so strongly resembles some of the typical Nevada rhyolites, it probably also contains free silica disseminated through the mass unperceivable by the eye. In places the paste is more compactly textured, being then heavier, with a smoother and more conchoidal fracture, and ringing when struck much like phonolite. It is frequently of a delicate pink color, and weathers dark, dirty brown, while it often contains scoriaceous pebbles of the underlying lava. The following cut is a section observed near Truxton Springs. In this vicinity spt there are more than two strata of the , 9) | i 8 Rhyolite basalt exposed in places; Mr. Ogden “hh | stating that he observed four at one 8 SX § Stratified, sort point, all separated by stratified con- \ glomerates, as in the accompanying sec- - “Amy gdaloidal Basalt. tion. I observed but two myself, in my m1 I amygdaloidal, the amygdales beingquite 49 = hurried passage. These were both quite Dn. = 3 Conglomerate and numerous, mostly small and round, and Sandstone ooh : 2 Basalt containing carbonate of lime; the dark, Wy Lan compact matrix being quite thickly yy Mle Ge BO sprinkled with the yellow-brown, decom- iP ?- 1Granite ~~ posed olivine grains. Atthe scoriaceous Fic. 90.—Section of lavas at Truxton Springs. summit of the lower beds, especially where they are much commingled with the overlying stratified volcanic sands, &c., the soft decomposed min- eral largely abounds. The following is a detail description of the section, (figure 90 :) 204 GEOLOGY. No. 8. Forty feet. Rhyolite; matrix grayish white, fine-grained, very finely porous, light; fracture rough, uneven. Embedded in this matrix are numerous crystals, often rectangular, of a colorless glassy cleaving feldspar, probably sanadine; a few small crystals of black hornblende, flakes of a bronze mica, and grains of quartz. It incloses frequent fragments of scoria- ceous basalt, which contains decomposed olivine crystals. Near the base the matrix is more compact; fracture, conchoidal; embedded crystals fewer ; color, light pink ; rings like phonolite. Between No. 7 and No. 8 is a narrow seam of very soft, fine rhyolitic sand, loosely compacted; color, light pink. No. 7. Two feet very fine sandstone, thinly bedded, but much broken up. It is like the compact rhyolite near base of No. 8, only not so cohe- rent, and containing fewer scattered crystals. No. 6. Six feet rhyolitic sand, much like No. 7. Between 5 and 6 is very soft seam, reddish and white bands. No. 5. One and one-half feet soft, slightly coherent, stratified, grayish- white rhyolitic sand. Junction between Nos. 4 and 5 is not well defined, the exceedingly amygdaloidal surface of 4 bemg much broken and mixed with 5. Former has compact black base, full of yellowish-red decomposed olivine crystals, and has about 50 per cent. of amygdules of carbonate of lime and perhaps a zeolite. No. 4. One hundred feet, basalt; very compact, hard, black base, hay- ing conchoidal fracture, and numerous small, yellowish-brown, crystal-like spots of decomposed and decomposing olivine, with numerous very small and fewer larger white amygdules—former wholly filled and round, latter lined with carbonate of lime and apparently zeolites. Bottom much mixed with bowlders, &c., of— No. 3. Twenty feet, conglomerate and sandstone, mostly white, of vol- canic sand and many granite pebbles. No, 2. Basalt like No. 4, but less amygdaloidal. No. 1. Granite; whitish and pinkish; red and white feldspars, little quartz, and congeries of small flakes of green mica. Near Truxton, however, considerable variations among the lower lavas SAINT GEORGE, UTAH, TO CAMP VERDE, ARIZONA. 205 occur, chiefly in the extent of amygdaloid character or amount of decom- position of the olivine. In fact, in these characters, but in these alone apparently, these lavas show considerable external differences at first from other basalts of the region, but the accompanying stratified beds show that the lavas also have been deposited under water, when the conditions have generally been supposed to be such as to promote peculiarities of texture and especially amygdaloidal character. The variation from the true basalt of the same bed a few miles at the north, however, is really small, and in- volves no change in specific character. It would seem, then, that there is here a case in which rhyolite is younger or more recent than basalt, and one of the few known exceptions to the usual sequence of these volcanic rocks of the West, as first established by Richtho- fen.* I did not observe the source from whence these lavas came. At one point between Music Mountain and Truxton Springs, in an expansion of a small canon in basalt, with rhyolite above, there occurred, crossing the bottom of the cation, the curious appearance of five parallel granite or feldspathic dikes penetrating the basaltic bottom, and all within a distance of about 500 feet. A short distance below there was granite exposed forming the cafton-floor. The lava, in flowing over the uneven sur- face of the granite, must have here covered a system of projecting dikes, such as have been described above, while the subsequent erosion has pro- ceeded just far enough to expose them without removing the surrounding | basalt. In leaving Truxton, the road passed southwestward through granite hills, at first mostly lava-capped, but growing less so, to the eastern edge of an arm of Hualapais Valley, where it turned to the left and followed south- eastward along the western edge of the granite hills. The valley’s edge was rolling and covered with picturesque groves of low pines and junipers, but the center appeared sterile and flat, though probably cut with dry cations. The Peacock Mountains, opposite, exhibit plutonic outlines, with considerable lava near their bases, the larger but more distant Hualapais Mountain, exhibiting similar outlines. | *Natural System of Volcanic Rocks, by F. Baron Richthofen, California Academy of Sciences, 1867. 206 ~ GROLOGY. As the granite hills upon the left grow higher, the lavas upon them gradually disappear, till at Cactus Pass, where the road again turned in among the hills, none appeared. In the continuation of the road before turning, however, and upon the western side of the granite, a few large hills occurred apparently composed of dark lava. The granite hills of the pass reach a considerable height, and form the northern extremity of a low range called the Aquarius Mountains. Feld- spathic veins and metamorphic rocks as usual accompany the granites. Upon ascending through the pass, a region in which volcanic products pre- dominate is again entered, being first encountered in a large flow of basaltic lava similar to that north of Truxton, and which is passed through in a shal- low box cafion, in an expansion of which the deserted camp of Willow Grove is situated. Issuing from this cafon we found ourselves upon a beautifully rolling country, sprinkled with groves and open glades. While granite occasionally appeared, the surface seemed formed mostly of volcanic tuffs and occasional conglomerates, with some rhyolite (?). Upon the south and west are the low granite hills of the Aquarius Mountains, while curv- ing around in partially circular form at the north and east is the Lower Car- boniferous mesa edge with occasional solitary and broken outliers. At Fort Rock are several rhyolite capped hills, while the ranch at the place is partially built of fine white rhyolitic tuff quarried near by. This region of voleanic products is probably a part of that near Truxton, though I did not see the direct connection. Cross Mountain, near Fort Rock, is a prominent mesa outlier, having a granite base, and reaching up through the Tonto sandstone and Tonto shales to the second or third of the more prominent limestone strata. Pass- ing near the foot of Cross Mountain, and approaching Aztec Pass, the road, after passing through a short box cafon in dark basaltic lava, rises slightly upon a low table composed of loose volcanic material, mostly tuff and agelomerate, generally light colored, and having scattered upon the surface much obsidian. Standing on this table, a short distance to the southwest, is aremnant of a voleanic cone, Mount Gemini of Lieutenant Whipple. What the nature of its lava is I do not know. In passing through Aztec Pass, we were once more upon the limits of SAINT GEORGE, UTAH, TO CAMP VERDE, ARIZONA. 207 the sedimentary rocks, the pass itself being in granite, which, upon the left, is capped with the lower strata of a southward projecting point of the lower mesa, called the Juniper Mountains. This series apparently consists of the Tonto sandstone at the base, with not so great a thickness of the Tonto shales, as at the Colorado, but greater than south of Tinnahkah Springs above; capped with three or four of the lower limestone and intermediate caleareous shaly strata. It presents, in fact, the usual lower beds of the stratified series of the region, and is similar to Cross Mountain and the many sections of the edge of the Tonto sandstones, shales, and upper lime- stones previously noted.* Upon emerging from the pass and leaving Camp Hualapais, which is situated at its eastern end, the edge of the Juniper Mountains recedes upon the left to joi the main mesa at the north, the road entering upon the large area of plutonic and metamorphic rocks which surrounds Prescott. This is in part a rolling country, and in part covered with abrupt hills, and even mountains, mostly sprinkled with junipers, or often with fine large pines, with their accompanying characteristic vegetation and frequent open val- leys, all forming a most delightful region which is apparently susceptible of successful cultivation. Granite and: allied rocks largely occur, but highly metamorphic rocks, as schists, slates, &c., also occur, often covering con- siderable areas, and with which many of the silver and gold bearing lodes of the country are associated. Lavas occur, but apparently in subordinate amounts. Between Prescott and Agua Fria Valley basalt is encountered capping granite hills. The detrital filling of the valley is mostly of granite, with subordinate amounts of metamorphic rocks and lavas. Upon approaching *The section as observed at this point, with the correlations founded on the same, by Mr. Jules Marcon, geologist of Lieut. A. W. Whipple’s expedition, near the thirty-fifth parallel, will be found in Report on Pacific Railroad Exploration, (War Department,) Vol. III, Part IV, p. 156 and p. 170, and Geology of North America, p. 24, while Dr. J. S. Newberry’s strictures and criticisms upon the same are in the Report on Colorado River, Lieut. J. C. Ives, Washington, 1861, Part III, p. 69. Hastening to Prescott with but two com: anions, to there establish an astronomical station, and in a hostile Indian country, there was no opportunity for detailed observation, even the notes having to wait a few days before they could be written. My many opportunities, however, for seeing even hurriedly the limiting edge of the sedimentary rocks along a continuous line, made me familiar with its characters, and they could hardly have been misunderstood in this instance. The section thus obtained differs somewhat from that given by Mr. Marcon, and still more from that inferred by Dr. Newberry from Mr. Marcou’s notes. 208 GEOLOGY. the Black Hills, which lie between Prescott and Verde River, bordering the latter, much disturbed metamorphic rock is passed om their southwestern flanks. Where observed they consisted of some semi-schistose rocks and some highly changed shaly limestones. The main mass of the range fol- lowing was of a very handsome syenite-granite, coarse-grained, and com- posed of a pretty uniform mixture of quartz and whitish feldspar, not well crystallized, and large, scattered, well-defined rectangular crystals of black hornblende. In the eastern part of the range the syenite became finer- grained, the feldspar reddish, while the hornblende, losing its crystalline form, became green, and occurred in irregular, small, apparently amorphous. or fibrous spots and particles. _On some of the low hills at the west, and on many of the higher ones along the eastern front of the range, were caps of black basaltic lava, often many feet thick and composed of many flows. The one of these observed was a very compact black basalt, containing very numerous scattered grains of green olivine. ° In descending the eastern slope of the range a magnificent view is had of the Verde River and Valley lying at its base, with the abrupt edge of the Carboniferous mesa, which is here again encountered, rising in highly colored cliffs all along on the valley’s farther side. Patches of its strata occur high up on the flanks of the Black Hills, and though not positive as to the geological relations between them and the syenite of the hills, I think that between the gently inclining strata, which certainly do rest upon their flanks, and the syenite, the strata are not upturned, though a fault may there exist. If not the latter, the Black Hills must have penetrated far up into the sedimentary rocks, and have been an island during the time that the older deposits were being formed. ‘This was the impression received at the time. Upon descending to the river, the valley-bottom was found to be in the ~ Red Wall limestone. VERDE RIVER TO LITTLE COLORADO RIVER. 209 SECTION, TE: VERDE RIVER TO LITTLE COLORADO RIVER. See Plate IV, (end of chapter,) Section 1. The valley of the river Verde, in the vicinity of Camp Verde, occu- pies the line of demarkation between the edge of the Carboniferous mesa bounding it on the northeast and the Black Hills, which form its southeast- ern slopes. The latter, in fact, have here determined the course of the val- ley, the river having eroded its channel along their edge, and in the softer and horizontal sedimentary beds which formerly abutted against and rested upon their harder syenitic flanks, until it has finally worked its way some distance into the Red Wall limestone in which it now flows. The surface of this limestone here, as elsewhere, forms a bench or step, before reaching the overlying Aubrey group of rocks which forms the higher mesa beyond. Toward the northwest, the upper and harder member of the Aubrey group, here a heavy cross stratified sandstone, is present, and protecting the underlying and softer members of the same series, molds the mesa’s edge into a well defined escarpment, which stretches up the valley in long per- spective, fading in the distance a banded ribbon of white, red, and white. South and east of the post, the escarpment soon bends out of sight, leaving the Black Hills inclosing the view, and giving a distant glimpse of the Mazatzal range, both of the latter presenting the characteristic contours of the metamorphic and crystalline rocks which lie below the sedimentary, - modified here and there by capping masses of lava. For several miles directly back (northeast) from the post, the eroding agencies, except in isolated instances, have removed the upper and protecting Aubrey bed, and left the softer and lower strata forming an undulating inclined plain, gently rising from the summit of the Red “Wall limestone. Later, a flow of basaltic lava poured down from the north and east, covered the upper strata, surrounded, island-like, the old mesa remnants, in places ran down into the then existing cafons, and even to the main valley, or ended in a thin sheet upon the gentle slope. } 14ws ide abet ledz- 210 GEOLOGY. Finally, subsequent denudation, having naturally its greatest hold upon these thin and weaker edges, and at those points where the lava had sur- rounded the older mesa islands, has broken the former into scattered patches of lava, which now cap outlying elevations, while at the latter it has com- menced to carve canons which now reach considerable depths and are often impassable. These canons in their downward cutting have occasionally sur- rounded, narrowed the base, but not wholly removed the mesa remnants which originally determined their courses, so that they now stand isolated buttes, springing from the canon bottoms, and reaching far above the sur- rounding plain of lava. Banded horizontally, as they are, in stripes of every width and of all colors, from white through yellows and browns to vivid reds, the sandstones and limestones of the Aubrey group, their precipitous sides buttressed and pinnacled, cathedral-like, from base to summit, they present some of the most weird of nature’s architecture. We scaled the Red Wall limestone escarpment a few miles above the post, and proceeded eastward up the gently undulating slope before men- tioned. This was covered with vegetation, so that we unconsciously rose through the lower members of the Aubrey series, in which we found our- selves upon descending into the cation of Beaver Creek. This creek unites with the Verde near the post, and in its lower reaches, which are cut in the Red Wall limestone, are many interesting and unique remains of the buildings of an ancient race. Some of these are several stories high, and carefully and methodically constructed of stones and adobe, with wooden beams, on which rest the floors. They are generally perched in almost inaccessible niches directly upon the faces of cliffs, or in crevices under overhanging bluffs 30 feet or more from the base. Besides these, there are some ruder habitations in caves in the limestone which are well defended by walls. Many relics of the ancient inhabitants, even pieces of cloth, have been gathered from this interesting locality, but there now remain only the ruined buildings and the scattered pieces of broken pottery. Betore descending into the canon of Beaver Creek several low, lava- capped mesa outliers were passed, forerunners of the main sheet. From the cafon, as before mentioned, several buttes, composed of the Aubrey strata—red predominating near the base and lighter colors above, and prob- VERDE RIVER TO LITTLE COLORADO RIVER. 211 ably capped with the cross stratified sandstones—trise far above the surround- ing lava-covered plain. There seems to be a hardly perceptible dip to the eastward. ‘The eastern side of the cafion is here about 1,000 feet high, the lower half being of red Aubrey sandstones, the upper half of layers of com- pact black basaltic lava, with a stratum of pinkish-white, calcareous, light volcanic mud or marl intercalated near the base. Some quite fresh-looking scoriz was here observed on the surface, which was mostly covered with some- what scoriaceous bowlders, often weathering in concentric spherical masses. The greater resisting nature of the hard lava, as compared with that of the softer beds below, causes it to form the real western limit of the higher mesa. From its edge a commanding view is had of the Verde Valley and the Black Hills beyond. From this point the lava extends a continuous mass forty miles to the eastward, our route revealing no cafons which pene- trated through the mass to the underlying strata, though north and south of the line both the cross stratified sandstone and overlying fossiliferous cherty limestone have been observed as thus exposed, the lava resting directly upon them. The highest point on this mass of lava passed by our route was about midway between its eastern and western limits, or about twenty miles east of Beaver Creek, where it reached an altitude of about 7,000 feet above the sea. Its greatest altitudes seemed to be along a line stretching from this point toward San Francisco Mountain. From this medial line the lava appears to extend, first as abrupt hills, then as more undulating country, until finally it flows out in all directions a nearly even, gradually descend- ing and thinning sheet. It is impossible to give its limits accurately. Its western edge is nominally the mesa’s edge, from which it extends eastward about forty miles, though, as stated, small outlying remnants line the mar- gin and extend more or less far from it, proving both its original greater extent and the great erosion which has taken place since it was erupted. Toward the south it falls in a long slope, and must extend far past our trail ; while at the northwest it descends toward the San Francisco Mountain. When observed, its lithological character varied from a very compact to a rather fine-grained basaltic lava. The former is very compact, very dark-colored to black, and has plent’fully sprinkled through it small grains of a transparent, green, or resinous: colored mineral, with not well-defined 212 GEOLOGY. cleavage and vitreous fracture, olivine. Occasionally, it is somewhat amygdaloidal, with amygdales of carbonates and zeolites, or of quartz sur- rounded with a pellicle of green earth. The coarser-grained varieties, prob- ably dolerites, are grayish in color, sometimes free from any past or matrix, and consist mostly of a granular crystalline aggregate of small white and colorless triclinic feldspar and an augitic (?) element, with frequent larger grains of olivine, as in the compact variety. The olivine in smaller grains seems to compose a considerable per cent. of the rock. The olivine is often affected by decomposition, being generally brownish or more resinous in color, with irridescence, and sometimes slightly resembling mica, and again apparently replaced by a soft iron mineral, producing numerous red spots. This lava has probably been extruded into its present position from below through fissures, which probably extend approximately underneath its line of greatest elevation, and along which faulting may or may not have taken place. The causes which gave it birth are no doubt identical with those which have produced the many other basaltic masses which rest in a similar manner on the Colorado Plateau, while their occurrence probably has a connection with those deep-seated causes which have acted, and are yet probably acting, in modifying the plateau. The soil upon the lava is black and meager, and in places where but little exists the twisted scoriz are often remarkably well preserved, seeming as fresh as if formed but yes- terday. Large pines (Pinus ponderosa) clothe its higher altitudes, juniper (Juniperus occidentalis) and the pifion pine, opening out into grassy glades, the lower portions. The black color of the lava, and of its derived soil, or, more probably, of the dark green vegetation, as seen from a distance, has given to this part of the plateau the name of “Black Mesa,” while from its rough surface is derived the term “Mal-pais,” the Spanish equivalent of the more familiar French “ Mauvaise Terre.” The eastern edge of the Black Mesa presents a very different order of things from the western. Instead of looking down into a deeply eroded valley, the eye wanders over an extensive plain lying a few hundred feet below the edge, and falling with a gentle inclination eastward toward the Little Colorado. The descent to this plain is precipitous. Where we passed it the basalt-cap was perhaps 100 feet thick, the lower limit being hid, how- VERDE RIVER TO LITTLE COLORADO RIVER. 213 | ever, by its own débris. Skirting the edge is a series of island-like remnants of the mesa, on which the cappings of basalt still remain. This lava here rests on a dark red shaly sandstone, which in turn rests at its base conform- ably on a grayish, somewhat cherty, limestone, the few feet of which that are here only exposed, being unfossiliferous, so far as observed. From this point to ‘Sunset Tanks,” a distance of about ten miles, this limestone composes most of the floor of the gradually descending plain be- fore mentioned, a few others being exposed here and there. These are much like the first, of from a few to perhaps 15 feet in thickness, drab or gray in color, and usually cherty. About midway between the mesa edge and Sunset Tanks, a few imperfect fossils were obtained from one of these beds. Such as they are they present a general resemblance (one of them probably being a schizodus) to fossils obtained by Mr. Gilbert from about the same horizon near the Paria, about one hundred miles north, and which Mr. Meek considers as being the equivalent of the Permo-carboniferous fossils of Kansas. _ These limestones, then, the top of the Aubrey cherty limestones prob- ably, may be considered as forming the summit of the Carboniferous ;. the shaly sandstones above-being conveniently considered as of Triassic age.* At Sunset Tanks there occurs another line of several mesa outliers, approximately parallel with the mesa-edge, the higher ones being still capped with many feet of the same basaltic lava, and reaching an altitude of over 1,200 feet above the plain. These are also mostly made up of fine shaly sandstones, mostly red, some cream-colored, of the rocks of presumed Triassic age resting on the preceding limestones at the base, and mostly covered with the débris from the capping lava. Pieces of petrified wood were numerous near the top, this occurrence being in this region character- istic of the Lower Triassic beds. Though several feet of the lower sand- stones are exposed in the cation at the Tanks, no fossils were observed. A comprehensive view is had from the top of these table-hills. San Francisco Mountain towers grandly up at the northwest, and the lava- *See Newberry in Ives’s Report of Colorado River, Part III, pp. 70 to 77, and Marcon, Pacific Rail- road Report, Vol. III, Part III, pp. 153 and 170, and North American Geology, pp. 14, 15, and 23; also the latter, who first called these rocks Permian in ‘Dyas et Trias,” Genéya, 1859, p. 38; and “Le Dyas au Nebraska,” in Bulletin de la Société Géologique de France, Vol. XXIV. 214 GEOLOGY. streams east of it plainly show, reaching a point 30° west of north. The edge of the basaltic mesa, which was just left, here bends to the west and north, leaving a wide bay separating it from the lavas near San Francisco Mountain, while in the opposite direction it extends about 30° east of south as far as one can see, forming a long, even, thickly-wooded stretch of hori- zon. ‘To the southeast, a distant view of the flatly conical Mogollon Mount- ains is dimly revealed. Below, and to the east and north, lies the long slope cut by many shallow box cafions in the limestones and overlying sandstones, descending with the slope eastward to join the river upon. whose farther side a new mesa-edge is presented. This is of irregular and worn contour, though it rises, a step of dark-red color, to a considerable height. Far beyond, and resting on the preceding, is still another but far better marked step. It is the famous great white mesa. First visible at 20° east of north, it stretches, a thread of dazgling white, along the horizon until it disappears to the north behind the spurs of San Francisco Mountain. In the vicinity of Sunset Tanks the eastward inclination of the Upper Carboniferous limestones which had formed the floor of the plain, being greater than that of the surface, they disappeared beneath it, becoming covered with red soil and flat mesa remnants, which give an indefinite roll- ing character to the general incline. These low hills are composed of dark- red shaly Triassic sandstone, often ripple-marked and gypsiferous, with occa- sional thicker beds. Patches of gravel generally occur scattered over the higher points, the pebbles being highly siliceous, well rounded, seldom larger than an egg, and of many colors, often brilliant, white, yellow, red, green, black, and often accompanied by fragments of silicified wood. These characters continued to the Little Colorado, which was forded at ‘“‘Sunset Crossing.” The same formation was found upon the opposite side of the river, but more marked, and rising a few hundred feet in irregular bluffs, while beyond to the northeast, and forming a still better marked series of cliffs, were more massive sandstones, the same line of cliffs that occur at Saint George, two hundred and twenty-five miles to the northwest, and men- tioned at the beginning of this report. At this point, and above, the river is not at all typical of this region, inasmuch as it does not flow in a cafon. On the contrary, its flood plain is in places a mile or more in width, through LITTLE COLORADO RIVER TO CAMP APACHE. 215 which it winds its muddy current in quite a tortuous course. It practically occupies a monoclinal valley between the Carboniferous and the Triassic. Proceeding up along the north bank of the river to where it is joined from the south by the river Puerco, the irregular Triassic bluffs were upon the left, and we gradually rose through the strata composing them. As on the opposite side of -the stream, these are mostly composed of dark-red and chocolate-colored shaly sandstones, with occasional cream- colored and thicker beds, the shaly sandstones being often ripple-marked, and all often highly gypsiferous, numerous small veins of gypsum often ramifying through the mass. At the highest point reached, these beds were capped with a conglomerate of siliceous pebbles, the ‘‘Shin-ar-ump Triassic conglomerate” of Powell. The irregular gravel deposits generally capping the gentle elevations west of the crossing, as mentioned above, have.their origin in this bed; the erosion near the river removing the lower beds, but leaving the less easily removed pebbles which had resulted from the disintegration of the con- glomerate. The dip of the formation here seems to be a few degrees toward the northeast, in which direction the formation, according to Newberry, flattens.* SECTION III. LITTLE COLORADO RIVER TO CAMP APACHE. Plate IV, Section 2. The route from the Little Colorado River southward to Camp Apache formed nearly a right angle with that from the Verde to the Little Colorado. Both approaching the edge of the Carboniferous Plateau at about the same angle, and being of about equal lengths, very nearly the same geological section was found in each. Even the Black Mesa south of San Francisco Mountain has its counterpart here in the Mogollon Mountains. The latter, about the nature of which there has been some speculation, are a mass of basaltic lava resting on the Upper Carboniferous strata in nearly all respects precisely similar to the Black Mesa mass. They are more abrupt in con- *Ives. Report on the Colorado River, Part II, p. 77, Fig. 19. 216 GEOLOGY. tour, reaching a height of about 2,000 or 2,500 feet above Camp Apache, or about 7,000 feet above the sea, and trend more nearly east and west, but have the same lithological and structural characters. The details of the section are as follows. Rising upon the long slope which forms the southern side of the valley of the Little Colorado, but descending through the eroded remains of the Lower Triassic, the friable yellow cross-stratified sandstone of the Upper Aubrey is found outcropping from beneath the latter and forming the rim or summit of the incline. The overlying cherty limestone was not here observed. The dip of the strata is quite strong to the north or northeast, while the predominant dip of the cross-strata of the Aubrey sandstone appeared to be eastward. This sandstone forms a cedar sprinkled ridge a few miles south of the river, and bounds the northern side of a shallow, rolling depression. The latter is devoid of trees and covered with a red soil, derived probably from underlying shales and sandstones of the Aubrey group. Its southern bound- ary, about fourteen miles from the river, is a gentle step, ascending which the cross-stratified sandstone is again encountered. It here forms a low, rolling, cedar covered plateau, extending about eight miles along our route, and is cut through by a narrow box cafion 200 or 300 feet deep, in which flows , Bouché’s Fork. The general dip of the strata is toward the northward, and of the cross-strata mostly eastward. Descending from the southern edge of this sandstone plateau, and to the level of Bouché’s Fork, the route was mostly in undulating Aubrey shales, the hills being often capped, however, with remnants of the sandstone. Lava-capped hills also begin to occur, and finally the continuous lava- sheet from the Mogollon is met, forming a low, irregular edged mesa. This at first gradually rises as an even sheet, with occasional steeper slopes and more level benches, then as low hills, which finally merge into the larger and more abruptly contoured masses of the summit. No volcanic cones were encountered. Wherever observed, the rock was of dark, compact to fine-grained basalt, containing much olivine, and identical with that upon the Black Mesa. From the summit, San Francisco Mountain, one hundred and thirty miles distant in the northwest, is distinctly visible. LITTLE COLORADO RIVER TO CAMP APACHE. Din The southern edge of these mountains is very irregular, erosion having cut valleys and canons through the lava to the Aubrey rocks below, and which extend quite to the mountain mass, leaving the ridges as long, lava- capped promontories. There is, therefore, a belt of territory in which both voleanic and sedimentary rocks largely occur, and no well-defined line can be drawn separating the two, while the edge of the Carboniferous mesa, which elsewhere is generally so distinctly marked, can here hardly be said to exist. To the eastward are the White Mountains, running apparently north and south, which present the same aspect as the Mogollon. The masses of the two seem to unite at the northeast, and the two are probably identical in all their features, structural and otherwise. Generally along the border of the Carboniferous mesa, the dip of the strata is such that the water divide is directly at the mesa edge, so that but little water can accu- mulate upon the escarpment side to erode it away, this action being much greater in the monoclinal valleys lying between the softer and harder strata at the base of the cliff, and which tends to preserve the latter sharply de- fined. Here, however, the Mogollon and White Mountains throw the water- shed several miles back from the bluff, so that there is directed upon it the powerful erosive action of all the waters that accumulate on their southern and western slopes. To this action, combined with the protecting effect exerted by the several lava flows which have descended from these mountains upon the softer beds they cover, is due that indefinite and broken-up mesa country which exists near these two ranges, and which presents such a strong contrast to the abrupt border which generally limits the plateau rocks. In leaving the mountains, the North Fork of the White Mountain Creek was followed. Its valley rapidly sank through the basalt and into the soft Aubrey rocks below,* when it began to assume the true canon form, the capping basalt on either side giving vertical walls. The Aubrey sandstones, &c., appear the same in character as near Camp Verde, and as the canton deepens there is exposed upon its sides a similar series of red and yellow strata of all shades and intensities, banded in a most beautiful and wonderful *The uppermost sediments encountered may have been higher than Carboniferous, the Mogollon Mountains, like the Black Mesa, probably including some of the higher beds beneath them, not repre- sented in the section. The southward dip of the rocks north of Apache in the section is incorrect. They should have a gentle northward dip, except for a short distance south of the post. 218 GEOLOGY. manner, and with which erosion has in places played most fantastic freaks. Another feature lends interest to the valley. Since the main cation was cut down through its lava capped sides to more than its present depth, a later flood of similar lava has poured down its channel and filled up all its bottom. Again, the aqueous agencies had to commence work upon the hardened bed, and now the stream flows in a nar- row box cafion cut in the lower lava. Nor is the latter action the work of a day, for even this has in places already penetrated to the sediment- ary rocks below, exposing several hundred feet of perpendicular lava cliffs. Upon nearing Camp Apache, the deepening valley cuts fossil bearing limestones, which belong to the Red Wall limestone, in the upper horizons of which the camp is situated, while the lava capped mesas, having also gradually fallen in height, here reach an altitude of from 800 to 1,200 feet. Throughout the valley the strata are all very nearly horizontal. SECTION IV. FROM CAMP APACHE TO THE GILA VALLEY. Plate IV, Section 3. Camp Apache is at the mouth and near the junction of the canon valley of the North and East Forks of the White Mountain Creek. East of the post, lava seems to predominate, and in rising upon it toward the White Mount- ains, whence it seems to have come, a country similar to that described toward the Mogollon would probably be encountered. When there in November, much snow lay on both ranges. West of the post is a more open country, the floor of which tends to be of the Red Wall limestone, though the preservative effect of the hard basalt has been to keep it covered with mesa-like buttes and ridges of the banded red and yellow Lower Aubrey beds. Where the protecting lava-caps of these is gone, arolling and hilly country of the same beds takes the place of the more broken mesa country, while in places even these have disappeared, FROM CAMP APACHE TO THE GILA VALLEY. 219 and level, open stretches, floored with the Red Wall limestone, occur. It was through this region that we passed before reaching Salt River, which was crossed at a point about eighteen miles west of the post. About midway in this distance, and near the river, a dip of the strata of several degrees to the southwest was observed, the general dip of the region being slightly to the northeast. Where crossed, the Salt River flowed in a cafion in the Red Wall limestone, the northern side of which, being descended after nightfall, was not examined. It was much lower than the southern side, however, which reached a height of nearly 1,800 feet above the stream. Of this about ten or twelve hundred feet were of Red Wall, capped with some sandstone, the remainder being basaltic lava. At many points the limestone was highly fossiliferous, and affected by strong local dips. It reaches several hundred feet above the top of the limestone bench on the north side of the canon, indicating a fault in the latter ; while it must all be affected by a strong, con- stant northeast dip, for, passing over the high basalt top southward two or three miles, the Lower Tonto (vitreous) sandstone is encountered at a height equal to that of the top of the limestone near the river, the whole thickness of the latter, together with that of the Tonto (Silurian ?) shales, being cov- ered with the lava. This lava capped hill was near the western end of a series of similar ones, which appeared to line the southern side of the cation to the east; this side being generally higher than the northern side. South of these hills the floor of the country is mostly of the vitreous sandstone, but covered with hills of the overlying shales, of which many are lava capped. Eastward this hilly character increases, but diminishes to the west, where the vitreous sandstone predominates, its surface being eroded into a beautiful rolling country, and having a strong, constant dip to the north and east. Down this slope the streams flow in characteristic box- cafions to join the Salt River. This vitreous sandstone rises gradually toward the south for ten or twelve miles from the river, when it breaks off precipitously and forms a high wall or bluff, bounding the northeastern side of the San Carlos Valley. This abrupt mesa edge, standing probably 5,000 feet above the sea, and 220 GEOLOGY. equalling in height the neighboring mountain masses, forms the southwestern boundary of those sedimentary rocks which compose the great Plateau System stretching northeastward to the Rocky Mountains. a0 To the northwest of the point on which we stood this edge was deeply cut by the lower cation of Salt River, but rising again on the opposite side, it forms the Sierra Ancha, a massive, squarish, steep-sided mesa- mountain of the Tonto sandstone. To the southeast it swings to the eastward, widening the valley, but soon appears lost among masses of apparently plutonic and eruptive rocks. Below, it rests on granite, occasional abrupt detached outliers of sandstone-capped granite lining the edge, while similar isolated remnants appear on the flanks and top of the Apache Mountains on the opposite side of the valley. These also occur still farther south, and search would probably discover them even to the verge of the Gila Valley. They afford evidence of the former greater extent of the sedimentary rocks, and of the enormous erosion which must have taken place to have so effectually removed them. The southern masses of sandstone have been faulted down with respect to those lying north. Mesa Fuge. Detrital —>. NE Basattio [79.75 Fia. 92.—Section across San Carlos Valley, Arizona. San Carlos Valley With the mesa is left a pleasant vegetation of pine groves and grassy glades. In descending into the San Carlos Valley, (see section,) the edge of the Tonto sand- stone shows a thickness of several hundred feet. It rests directly upon a granite or granulitic rock, which consists nearly wholly of red orthoclase and some quartz, and which forms the base of several rugged hills capped with the sandstones. Lower down, darker colored rocks, resembling diorites, prevail, weathering characteristically in many small, sharp, irregular ridges. The detrital filling of the valley is soon encountered, descending in what, at a distance, appears a long even slope, but which is much cut up by ravines, many of which cut through it SOW —Archacan. Apache Mts. FROM CAMP APACHE TO THE GILA VALLEY. 221 to the rock beneath. Naturally, it is mainly composed of débris from the Tonto sandstone with the other rocks of the valley. The lower part is well stratified, the surface generally less so, often not at all. Near the center of the valley, but most apparent in its southern side, a mass of basaltic lava lies under this alluvium, occasionally projecting above it, but mainly exposed by ravines. In ascending the Apache Mountains, we passed directly from detritus, composed of Tonto sandstone, without seeing granite, on to the portion of the bed itself, which here forms the summits of the range, its whole f thickness, with some of the overlying shales in places = \ Bee still remaining. A spur to the southeast of the line of © eS section, but lying much below the summit, also appeared i capped with the sandstone. The general dip was north- & east, and the mass generally lay below the edge of the mesa, of which it was once a continuation, the displace- 3 ment probably being due to a fault in the valley, the = downthrow being on the southern side. 2 The southeastern end of the range appears to have e less of the sandstone upon it, probably being composed z of the underlying rocks. = vty Crossing the divide, there are found upon the south- 5 8 western slope of the Apache Mountains two or three lines 3 § of hills composed of the Tonto sandstone, each preserving # [ a gentle northeastern dipand resting on granite, but faulted downward with respect to the summit mass. This system of faults seems to continue to the southwestern side of the Sierra Ancha, where several hills with precipitous a southern sides, like others near the ‘“‘ Wheat-fields” of & Pinal Creek, are visible. The valley of Pinal Creek (see section) lies be- tween the Apache Mountains on the northeast and the Pinal Mountains on the southwest. Where crossed, the main mass of the latter was of granite, but upon their northeast flanks is a long area of highly metamorphic rocks, 222 GEOLOGY. consisting mostly of crystalline schists, micaceous, chloritic, and talcose, their erosion forming an intricate maze of small valleys, separated by sharp ridges, which present a strong contrast with the more massive features of the mount- ains. An adjacent spur of the Pinal Mountains seems still capped with Tonto sandstone, which dipped into the range at an angle of about 10°, the last recognized southwestern remnant of the Plateau beds. The north- eastern flanks of the valley, where exposed, consisted of red granite and allied rocks. Upon this side the detrital filling of the valley naturally consisted mostly of the débris of the Tonto sandstone, while upon the opposite (southwest) side granitic and metamorphic rocks prevailed. This detrital filling, as in the San Carlos Valley, is composed of two distinct parts, the lower, b, of strati- fied sands and gravels, having a gentle inclination toward the valley, and d,e. Present surface slope, 4° to 7°. e. Unstratified mass of more or less angular bowlders. b. Stratified gravels and sands having gentle inclination toward the valley. a,a. Crystalline schists. resting upon the bed rock below, and an upper portion, c, mostly of angular bowlders, wholly unstratified and resting upon the irregular summit of the lower portion, its general surface inclining toward the valley at an angle of 4° to 7°, increasing toward the bounding ranges. These valleys present an interesting transition between the valleys of Nevada, which have long been free from water that their subaérial detritus largely predominates over, or wholly covers, any subaqueous filling which they may have contained, and the valleys of and near the Gila River, which are almost wholly occu- pied by nearly level subaqueous deposits, and in which subaérial action has as yet hardly had time to commence. ; The main Pinal Creek, (so called, though perfectly dry,) where crossed, had not yet cut through the stratified material to the bed-rock below. The Pinal Mountains were approached by ascending the west branch FROM CAMP APACHE TO THE GILA VALLEY. 223 of Pinal Creek, which carried us across the zone of erystalline schists, and into the granite, which at this point forms the mass of the range. Gold quartz and copper ore were frequent in the stream bed. The granite is a handsome coarse-granular aggregate of quartz grains and orthoclase, large projecting crystals of the latter, which is mostly white, mottling the weather- ing rock, while the mica is subordinate, occurring in small black flakes. It is characteristically cut in deep and rugged ravines, and is at first strongly affected with joints having a southern trend, and inclined 60° to 80° east- ward, with a subordinate system of east and west joints, dipping north, the two together tending to stud the surface with large tombstone-like slabs of rock. The first set of joints swings westward as the range is crossed. In crossing the range this granite axis was found to extend continuously to Camp Pinal, and seemed to form nearly all of its northern and lower parts. To the southeast, however, the topography changes, the range rising in long, even slopes to three flatly conical, massive mountains, which form its highest points, and have the contour of rhyolite, of which they are probably composed. At Camp Pinal a light pink rhyolitic lava is encountered bordering the range, and apparently derived from the higher points to the left, though now separated from them, I understand, by the canton of Mineral Creek. The camp is situated in a narrow valley, which forms the line of demarka- tion between the granite and the bordering rhyolite; the junction north- ward along the range being more strongly marked by the cation of Pinto Creek. This bordering rhyolite stands nearly as high as the main granite ridge where crossed, and, though having a rather undulating surface, its sides break down in most rugged palisades, whose precipitous faces overhang the cations and rim the borders of the range with almost impassable cliffs. These form an abrupt termination to that mountainous country bordering the Plateau region through which we had passed, and, extending a long distance either way, look off at once upon the mountain-studded deserts of the great Gila Valley. Immediately beneath these skirting rhyolitic cliffs, the sloping front of the range, at many points, and apparently for many miles, is composed of the upturned edges of a series of sedimentary rocks, which dip into the range at a high angle. At Surprise Valley, where this series was first 224 GEOLOGY. encountered, a thickness of about 2,000 feet is thus exposed between the covering rhyolite and the dark plutonic, highly metamorphic rocks forming the base of the slope, and on which they rest, with an inclination toward the east-northeast of about 35°. The rocks first appearing beneath the rhyolite are here but little changed, soft, red, with some shaly, sandstones ; these are followed by partially metamorphosed and highly crystalline lime- stones or marbles, while nearly all the lower half of the series—not seen near by—appeared red, as if sandstones. At first there was much débris of lime- stone, lithologically the same as much of the carboniferous limestone of the Plateau series. Had opportunity offered, search would probably have been rewarded by fossils, but none were observed, and the rocks remain un- recognized. I am inclined to believe that they will prove to be a remnant of the Plateau series, and have so colored them on the map. Near where the range was left, and below its more abrupt slopes and skirting foot-hills, are several groups of low scattered hills and occasional high table-topped buttes, which often rise precipitously from the rather flat border land of the valley, and which are apparently composed of rhyolite. A high butte called Tortilla is the most conspicuous of these. Looking back, the mountain edge presented a formidable barrier, and, for many miles, above the foot-hills of plutonic rocks, presented its slopes of sedimentary strata capped with the lava palisades. In the far distance to the northwest, and near the border mountain region, stands the curious looking Superstition Mountain, showing nearly horizontal strata, apparently of lavas or perhaps sedimentary rocks. ; At the few points observed the bed of the valley was of the ancient plutonic and metamorphic rocks similar to those of the foot-hills, but these soon passed under the continuous alluvium of the approaching plains, which descended with a gentle slope to the Gila River. From here on our route remained constantly on the alluvial filling of the valleys of, and tributary to, the Gila, so that even hurried opportunities for observation here ceased, and the nature of the formations and ranges passed became a mere matter of speculation. The main physical features of this great region, however, though so often described by others, are of sufficient interest to warrant remention. FROM CAMP APACHE TO THE GILA VALLEY. 225 It is a great depressed mountainous region, deeply buried beneath the sediments which have been eroded from its own mountains by a surround- ing sea. This action has filled the valleys, gradually covered the foot-hills, and, removing the débris from the mountain bases as fast as formed, has left their clean and sharp cut tops projecting above the surrounding plain with- out the usual accompaniment of foot-hills and border region which surround nearly all ranges, the changes on the contrary from mountain slope to the gentle incline of the plain being generally very abrupt. The mountains seem to be of ancient plutonic or metamorphic rocks, or else of lavas; the _ former more often forming ranges of which the majority trend about north- west and southeast ; the latter more frequently occurring as striking isolated peaks. The detrital filling varies from gravels traceable to the rocks of adjacent hills to the finest of alluvium, the dust of which the winds often carry for miles into Northern Arizona. It is sparsely sprinkled with a dreary vegetation, composed principally of scattered individuals of many species of mimose and of cacti, the most striking of the latter being the tall and isolated Cereus giganteus. To stand on the edge of the Pinal Mountains upon a quiet day, and look off upon these wonderfully silent and arid plains, with their innumer- able ‘lost mountains” rising like precipitous islands from the sea, all bathed in most delicate tints, and lying death-like in the peculiar, intangible after- noon haze of this region, which seems to magnify distant details rather than to subdue them, impresses one most deeply. The wonderful monotony seems uninclosable by an horizon; and one imagines the scene to continue on the same and have no end. Though the gulf and ocean are three hundred miles away, yet here is the continent’s real southwestern border. Were the waters of the Gulf of California suddenly changed to gravel and sand, with its precipitous and rugged mountain islands left pro- jecting from the surface as now, there would be so produced an excellent representation of these deserts, and, geologically speaking, it is but as yester- day that precisely the same action was going on over all this enormous area as is now in progress in the more confined region of the Gulf. The slow elevation which has in part probably caused the gradual receding of the waters may still be extending the area of our continent. 15 Ws GEOLOGICAL SECTIONS | FROM THE Y VERDE RIVER TO THE GILA RIVE R, ARIZG|NA TER. Along The Route Travelled By Party N22 Of The Exploratior | of 1871. To Accompany theReport of AHCHLR.MARVINE. ! SEC. 1. | From Verde River to the LittleColorado. __ | The Black: Mesu Pinal Oreck Sunset Tanke. Lille Qlorndo Re (Sunset Oras: = Rubrey Group, Red Pill Limestone. SEC. 2. FromLittle Colorado To Camp Apache. Mogollen Mountatrs. Tittle Colorado River SEC. 3. } EromCampApacheTo TheGilaRiver. | ey Salt ver Tordilion. Meer, Wea ighaots aviv. Se Hetamorphasel. Rect Hele — & Stratified \Sgnadetone. Tice writally Or) 2 Jechasare Parti i ee ts =< Sandstone. Tntinestone. aan [estaler Cranttes, ets; i Diorites, Schests ' Rhy olite_ Basaltic- 4 Have. Lava. f 2 Horizontal Stale Smiles -Lin- | Pew er, EEE. so REPORT ON THE GEOLOGY OF PORTIONS OF UTAH, NEVADA, ARIZONA, AND NEW MEXICO. EXAMINED 1N THE YEARS 1872 AND 1873. BY d EDWIN E. HOWELL. COMPRISING CuapPTEeR VIIIL—THE BASIN RANGE SYSTEM OF SOUTHWESTERN UTAH; IX.—PLATEAU SYSTEM OF PORTIONS OF EASTERN UTAH, NORTHERN ARIZONA, AND WESTERN CENTRAL NEW MEXICO. 227-228 i . a 4 . lien f 4 ~f : rt s3 es ‘ 7 c - vs ie ae jikea malo y ke a = 7 . ag i 4 = a r . Te Bier itceu is ci! fea As Mane (£0 (TkDoM te ubowe! _ iv ( Svie Saed Vat; me OeK - ; ~ » Tage Bite ueG Seat ee ‘ - (ie at eT ey > * ae ? Eee: — a at + se is 4 ; Dei oy son ees | ‘i «4 iY. : i ‘ > y ' we oun (gehe > ay reat rreie arta te Bare ‘ . ; ; - % ae < ire. Gi Le AAD ES firey z Shoes Ft a bier ads is crag perira| 4 Py , ; eats arte va linos ono “> Fives Ne rt - eal fy Tia a pes) " aya ff) = tT. eee ae ee aiiph i re ‘eile THES, va 00R# Pa a VG Testes Sait I Our xl & patty ay) Fi Nin re bevairhiaes ead, ant er : a LA pear ye Slide ate Giger as > riiy ‘ to Masiltis none Bint me eee Iie ree td ‘ ae at 2 tpt ahr Abe 1 RHR oH icant aaa i} sage ey Eee eS RRL RS MY eset hen leet ¥ i 4. ANS, Bees: ie rey rsotwlt, 5 if to atl , 2 | Sire Shred Shins Ga vie 3 ‘ wie <<) ar Md PRs oD Si ‘cttonties “i C=. eae it a is of raha st 201 | os : sdeeke HI CTIA, SPEER on gee “lies * : “ 4.5380 WM os 421333 stout AF Sere Ngee eS Unirep States ENGINEER OFFICE, GEOGRAPHICAL EXPLORATIONS AND SURVEYS WEstT OF THE ONE HUNDREDTH Menip14y, Wasuineton, D. C., July 1, 1874. Sir: I have the honor to submit herewith a report upon the geological material gathered during my two years’ connection with the survey under your charge. In 1872, the route of the party to which I was attached traversed por- tions of the Sierra region of Western Utah and adjoining Nevada, and of the Plateau region of Central Utah. ; In 1873, I once more entered the Plateau country in Utah, and con- tinued upon it to Arizona and New Mexico, making in the latter Territory a detour southward among the Sierras. The entire data in regard to the plateaus I have found it convenient to combine in a single chapter. The description of the mountain ranges examined in Utah and Nevada consti- tutes another chapter; and my notes upon the Sierras of Southern New Mexico I have turned over to Mr. Gilbert, to be combined by him with the data he has gathered in an adjoining and nearly surrounding belt. The report gives the result of no detailed work, and I do not dare to hope that it will prove free from error, either of observation or of deduction. Probably the least unworthy contributions to the report relate to the distribution of the several geological formations, and to the description of the folds and faults of the Plateau System. My especial thanks are due to Mr. Gilbert Thompson for assistance in the collection of geological facts and specimens. Despite his onerous duties as topographer, he gave untiring and intelligent attention to the subjects that occupied me, and his contributions were both numerous and valuable. Very respectfully, your obedient servant, Epwin E. Howe t, Geological Assistant. First Lieut. Gro. M. WHEELER, Corps of Engineers, nm Charge. 229-230 a Fae 2. a > oa. 7 hae 7 ba - re a . = sé . - oa “eT » D4 i PG a 2 , ° pe ee 1) on A Pie “oe - : ot = : - a Md 7 ; ' ~, ; = < a 5 r ‘ : me F 2 ‘ ae eX : a ly - 4 + . - - . ‘ . © > ‘ ars ‘ _ " i, “. Pa 2 ae ae sb PAE © nies - + at ' 1% li ; ‘ TA j 2 : eee Sah < ’ ‘ Cis Aa ft ici lf —. ee a a P ° ; cL “kL 9} 4p oe - S25 gn) aoa [ +™ ly . i : t vite cA y 2 i ‘ TaeAt aah Gee Wee Mah ‘ . 5 . . “-e , fT] x s al asl ‘4 x j . ; o ' = pA LTE Ace Ag i : + Oy “+ 7% aS 70, 5 i OMY SE “3 ree lg a! onT e A . 3 jks eo te lye Fr Pont he ait al rail i : ae ain Hy, eyes tha ail Foe tae bike Mb arg f A 4 : ‘ -, ) A uy ai a ait st : sinseaie 4 : a > ; | je i Lildie hi uit Roa Bis & ‘ , ae ae iy ee ; ‘ , : j aes 4 i ral bee Tose: xe. ; fin Se | a Pa tlh, SE saz bd ‘v Bsr a Fite ° As 7+ ; ay cit b He Mir = j = { { 1%. "5 q ‘ Cit. gia AB tf ati . . ms eo OU". Bel eal Waa raising ater ity tat a | = - é 'y rd 4 Me ry ee Ra Set Wht, yo CHAPTER VIII. THE BASIN RANGE SYSTEM OF SOUTHWESTERN UTAH AND SOUTHEASTERN NEVADA. SEcTION I.—MOUNTAIN RANGES: THEIR GEOLOGICAL STRUCTURE, AGE, THICK- NESS, AND CHARACTER OF STRATA. Section II.—VALLEYS: THEIR RELATION TO GEOLOGICAL STRUCTURES; LAKES, ANCIENT AND MODERN; RIVERS; WATER SUPPLY. Section III.—VoLcAnic PHENOMENA; LItHOLOGICAL CHARACTER AND DISTRIBU- TION OF VOLCANIC ROCKS AND MODE OF OCCURRENCE; THERMAL SPRINGS. : SEcTION IV.—Economic GEOLOGY. SECTION IL MOUNTAIN RANGES: THEIR GEOLOGICAL STRUCTURE, AGE, THICK- NESS, AND CHARACTER OF STRATA. There is such a gradation of the range into the Plateau System, along their line of intersection in Southern Utah, that it is impossible to draw a line which shall have all range structure on one side, and all plateau on the other. From the Uintah Mountains south to Mount Nebo, the eastern base of the Wahsatch, is a line of perfect separation; but south of this mountain the Wahsatch line of wplift drops down, and is soon lost beneath the Ter- tiary and Cretaceous beds of the Plateau System; and the division line is crowded westward to the next parallel line of uplift—the Pah-vant range— the western base of which Mr. Gilbert found to be an anticlinal, formed of Paleozoic rocks, overlaid on the east with Secondary and Tertiary beds This line may be followed south to Baldy Peak, where everything is buried beneath immense beds of lava. A few miles farther south, this ridge flattens out and joins the Plateau System, and we are obliged once more to strike west or southwest from the 231 Da GEOLOGY. neighborhood of Frémont’s Pass to the Iron Mountains, which may be fol- lowed to Iron City and Pinto. At this point it becomes doubtful where the line should be drawn, but I believe fewer difficulties are encountered by continuing it in a southwest direction to the head of the Virgin range, which, from this point southward to the Colorado River, gives once more a well- - marked line of separation. This line separates two regions, that cannot be better contrasted than by the terms Sierra and Plateau. The first of these, which now claims attention, is characterized throughout Southwestern Utah and Eastern Nevada, as elsewhere, by nearly level arid plains, separated from each other by parallel mountain ranges, which occur at irregular intervals of fifteen to thirty miles, giving, on the average, a range of mountains every twenty miles, with a trend varying but little from north and south. In structure these ranges are both anticlinal and monoclinal, the latter being the prevailing form, while pure anticlinals are seldom met with. Very few ranges, however, have the same structure throughout their whole extent. Frequently, in tracing a monoclinal, we find it changing to an anticlinal, or more frequently to a faulted anticlinal—the axis of the anti- clinal being at the same time the line of a fault, showing the beds on one side of the axis ata much lower level than the same beds on the opposite side. Further followed, the anticlinal would probably be found (after a cross-fault or disturbance) with the downthrow on the opposite side, which, still further followed, would give amonoclinal again, with the dip in the opposite diree- tion from that first started with. Thus, not unfrequently, a great variety of mountain structures may be found represented in a single range. These plains, or valleys, have an average height above sea-level of about 4,500 feet, while the height of the ranges above the plains varies from 3,000 to 6,000 feet. If admitted that this section has been covered with the heavy beds of Triassic and Jurassic rocks, which are seen lying, conformable to the Car- boniferous, on the borders of the system, and which Mr. Clarence King assures us in his Mining Industry, page 451, have capped the ranges of this same system a little farther to the north; and if we admitted, also, that the main folding was completed in late Jurassic times; then, before the erosion, MOUNTAIN RANGES. 233 which has gone on since the early Cretaceous, the height of the ranges above the then much lower valleys must have been truly wonderful. But in the region of our examination no evidence was found to warrant the assertion of such former extension of these beds. At only two localities, and both of these near the border of the system, have any beds been seen that could with propriety be referred to these horizons. The first of these localities is on the south end of the Mineral range, near Minersville, where some red beds, several hundred feet in thickness, were seen overlying a yellowish- gray limestone, which furnished fossils of Permian or Upper Carboniferous types. Overlying these red beds, and a little farther to the north, Jurassic fossils were found by Mr. Gilbert. The second locality is a little west of Cedar Mountains, where there is an exposure of 2,000 feet or more of yellowish-brown siliceous limestone, which, although no fossils were seen, is probably of Triassic Age. No- where else inside the system have we seen any evidence of beds, other than the subaérial gravels and modern lake deposits, lying above the Carbonifer- ous; the hard limestones of which now cap most of the ranges. Omitting any further description of this region, the leading features of which have so often been described by others, let us now examine a little more in detail the different mountain ranges visited, and then call attention to some features which are common to all. WAHSATCH RANGE. The Wahsatch, as already stated the most easterly range of the sys- tem, is in the main monoclinal in structure, with an average dip to the east of 25° or 30°; but our observations extended only to the southern portion of the range—that which faces Utah and Juab Valleys. To the descrip- tion as above given, Mount Nebo is an exception. It is set off to the west, so that its eastern base is in line with the western base of the range farther north, and appears to belong to the same line of fracture; the uplift in this case being to the west of the line, giving a western dip to the strata. If we imagine a continuous anticlinal, with Nebo as the only remain- ing portion of the western half, opposite which the eastern side has been removed, it will give a correct idea of the relation which this mountain bears to the rest of the range. That the missing portions of the anticlinal never ex- © 234 GEOLOGY. isted, there can be no question ; the deposition of the later beds on the eastern base of Nebo being sufficient proof as regards that portion, and we are unable to conceive of a force which should remove the western portion, referred to, so completely, leaving the eastern side and Mount Nebo undisturbed. To the west of Nebo, and running north for some distance, is another ridge, with a parallel strike, which dips to the east, making a synelinal fold with Nebo; but the structure is quite complicated at this point, and time did not permit to trace it out. A section of the range made at Rock Canon, near Provo (Fig. 95) Provo Beach —y Ink Fic. 95.—Section of Wahsatch range near Provo. 1, sandstone and limestone; 2a, shaly limestone; 2b, massive limestone; 3, quartzite ; 4, chloritic schist. represents an exposure of about 10,000 feet. Carboniferous fossils, Athyris subtilita and Hemipronites, were found almost at the top of the series. The conformable Triassic and Jurassic beds lie farther to the east, denudation having completely removed them from the summit of the range. Our sec- tion is— 1st. Seventeen hundred feet of sandstone, a large portion of it vitreous, and 600 feet of massive and shaly limestone, arranged in alternate layers with the sandstone, tothe number of fifty, and containing Athyris subtilita, Productus semireticulatus, Spiriferina, Hemipronites, Chaetetes, Discina, &c., 2,300 feet. 2d. a. Two thousand feet of limestone, all more or less shaly, with some beds of calcareous shale. A mile or two north of where this section was measured, a thin stratum of clay slate was seen containing cubical crystals of iron pyrites. There is also a single layer of vitreous sandstone 10 feet thick. b. Four thousand feet of massive limestone, in the main highly metamorphic. The changes in this division from shaly to massive, and from slightly meta- - morphic to highly metamorphic are so gradual that any separation of them ‘ MOUNTAIN RANGES. 239 must be arbitrary. The fossils found in No. 1 were seen continuing down through this division until the rock became so much changed that organic remains could not be recognized, 6,000 feet. 3d. Hard, typical quartzite, pale flesh-color to nearly white, with a little pale-green, 1,500 feet. 4th. Nonconformable pebbly chloritic schist, 250 feet. Prof. Frank H. Bradley found similar rock associated with the granite farther north, and could we have fol- lowed our section a little deeper, we should doubtless also have found granite. Although no fossils were seen here or elsewhere on this range below the Carboniferous, when this section is compared with those made of other ranges farther to the west, as well as those made farther north on this same range by other geologists, I have no hesitancy in referring the heavy quartzite bed (No. 3) to the Lower Silurian, and a portion of the metamorphic limestone above it should probably be referred to the same Age, but how much, I am unable to say, as at no point was a marked change in the character of the rock noted. Iwas unable to make a satisfactory section of the Triassic and Juras- sic formations, but Fig. 96, as seen in passing up Spanish Fork Canon, may be considered as a fair continuation of Fig. 95, (1,) the lower beds in this section corresponding very closely to the upper beds in the first section. From Rock Cation to Spanish Fork the strata dip very much to the south as well as to the east. In passing up the cation, above limestone containing Carboniferous fossils, I found a lighter colored, very hard siliceous limestone, some of which might, with more pro- priety, be called sandstone, or even quartzite, in which no fossils were seen, but from its position I am disposed to consider it as belonging to the Trias. This formation is of great thickness, probably 4,000 or 5,000 feet. ‘auOJSeIMI, SNOeFIUOgIRD *z { OMOJSaUTIT SNodorTIS Sula, ‘9 {seuOySspuLS pue seTeYs oissBANe ‘G ‘F's ‘BL + ys -amo[su0o ‘p $syisodep Arviqsay, snooavoyeo ‘0 ‘q ‘v { yIOT 8 AMIP[OY Je YoyvsyeA JO osvq U19}seM JO WOT}XIS—'9G “OY BSD <— 2 or, SSR, SSNs & ss FOO fo PPS JOO OS 509 Tt (9) C00 008 70 606 50.0009 AXTeKS 006 nea 06 OX ar ie or. Nore SY a ‘SET YWOpOSUIN, 236 GEOLOGY. 1. Yellow and cream-colored sandstone, with occasional bands of gray conglomerate and sandstone, about4,000 feet. 2. Calcareous shale, light drab to slate-colored, 200 feet. 3. Red, cream, yellow, and buff cross-bedded sandstone with Penta- crinites asteriscus, 575 feet. 4. Red shaly sandstone, 500 to 1,000 feet. 5. Lying conformably above and dipping to the east-southeast at the same angle (25° to 30°) are sandstones more highly colored, (red, yellow, and buff,) very vitreous at the bottom, but becoming less so above, and con- taining fragments of characteristic Jurassic Pentacrinus, 1,000 to 3,000 feet. While the upper portion of this division is undoubtedly Jurassic, the lower portion is probably Triassic, but the section was not well enough exposed to determine a line of separation. This completes the exposure of from 6,000 to 8,000 feet of strata that must be classed as Jurassic. Lying nonconformably above, and jutting up against the Jurassic, as shown in section 2, is, first— d. A thin bed of red conglomerate, which to the eastward increases rapidly in thickness to 2,000 feet, in a distance of three or four miles, and then dipping eastward is lost below more recent beds. This conglomerate is composed largely of quartzite, but limestone pebbles, in which Carbonif- erous fossils are not infrequent, are very abundant in the upper portion. I was unable to determine the age of this conglomerate, and have not been able to discover its equivalent in other localities. Itis overlaid with— a, b, and c. Limestone marls and calcareous shales of Tertiary Age, which further up the mountain are in immediate contact with Jurassic and Triassic (?) beds. 'To the south of Mount Nebo, and along the western base of the ridge which separates Juab and Sam Pitch Valleys, the same being a continuation of the Wahsatch uplift, there are overlaid with red conglom- erate—probably the same as the above—quite extensive beds of Jurassic Age, composed mainly of greenish gypsiferous shales with occasional layers of sandstone, which furnish Pentacrinites asteriscus, Comptonectes, Trigonia, and other fossils. These same beds appear again near Manti, and skirt along the western side of the valley nearly to Glencove. In Salina Camion, to the east, (above) the much distorted gypsiterous MOUNTAIN RANGES. 2Sit shales are 4,000 or 5,000 feet of strata, which doubtless correspond to Nos. 1 and 2 of Fig. 96, given above. Where these beds first make their appear- ance from below the overlying, nearly horizontal strata, they dip 25° to the east. Following westward down the cafon, we find them gradually increasing in dip, coming even to the vertical before the gypsiferous beds are reached. I was unable to trace a complete connection between the two formations, although such a connection doubtless exists. About 1,000 feet of the lower portion is gray and red freestone, with occasional beds of con- glomerate toward the top, agreeing in this respect with No. 1, at Soldier’s Fork, Fig. 96. The main mass above this is a yellowish, friable sandstone. LAKE RANGE. This range, just west of Utah Lake, is a low monoclinal ridge, the strata dipping to the east about 8°, and is composed entirely of the charac- teristic bluish-gray Carboniferous limestone. A few specimens of Productus and Spirifer were the only fossils obtained, owing partly to the highly met- amorphic character of the rock. Mr. H. Engelmann, geologist of Captain Simpson’s party, found in the limestone of this range the spiral axis of an Archimedes, together with some badly preserved Brachiopods. Messrs. Meek and Engelmann, in speaking of this,* say : ‘“‘As the genus or subgenus Archimedes has not yet, so far as we know, been found as high in the Car- boniferous System as the Coal Measures, and there are apparently no decided Coal Measure forms in the collection from this rock, we are inclined to regard it as belonging to the Lower Carboniferous series.” OQUIRRH RANGE. The beds of this range are so much and so irregularly disturbed that I am unable to speak with any confidence in regard to its structure. Data collected from several points indicate the axis of an anticlinal, with a strike north about 35° west, passing near Ophir and Lewistown; and another, nearly parallel, passing through Middle Caiion, and coming out not far from Cedar Fort; and that in a general way the northern end of the range is a continuation of the eastern side of this latter anticlinal. The Carboniferous limestone is largely developed, and furnished fossils *Proc. of the Acad. of Nat. Sci. of Phila., April, 1860, page, 127. 238 GEOLOGY. at the north end, near Great Salt Lake, Tooele, Ophir, Lewistown, and along the road leading from Fairfield to Rush Valley. In the lower part of the limestone at Ophir, not more than 300 or 400 feet below beds containing Euomphalus, Conocardium, Hemipronites, Phillipsia, Athyris subtilita, and other fossils, recognized by Mr. Meek as a Carboniferous fauna, were found some Primordial types, including Dikellocephalus. Mr. J. E. Clayton found below this limestone an exposure of partly calcareous and partly siliceous and micaceous shale, containing several species of trilobites and Discina, specimens of which he very kindly furnished. The Carboniferous and Lower Silurian fossils are found so near together, that I am led to believe that the two formations are in contact at this locality. All our evidence from other localities indicates that this relation is common to the whole region, and renders it improbable that the Devonian or Upper Silurian will be found in Southwestern Utah. To the west of this are some localities, discovered by Mr. H. Engelmann, and the survey of the Fortieth Parallel under Mr. Clarence King, which are pronounced Devonian by Mr. Meek,* and Professor Sanborne Turney has discovered two species of Zaphrentis, and one of Syringopora in the Wahsatch range, between Little and Big Cottonwood, which Mr. R. P. Whitfield refers to the horizon of the Upper Helderberg. That the limestone of this range corresponds in general to that of the Lake range, I think there can be no doubt, and not only are the Devonian and Upper Silurian formations wanting, but the Lower Carbon- iferous, as indicated by the Archimedes before mentioned, must be restricted to very narrow limits, unless we include in that division the beds (or at least the lower portion of them) which contain Euomphalus, Phillipsia, &c., a point that may be left to the paleontologist to decide. ONAQUI AND STANSBURY RANGES. Passing westward, the Onaqui range is found to be a monoclinal ridge, with the usual north and south trend, the-strata dip to the west at an angle varying from 25° to 70°. Perhaps in this case the term “faulted anticlinal” might be used with more exactness, as there are a few hundred feet of very much disturbed limestone, but with a general dip to the east * American Journal, 1873, page 139. ‘MOUNTAIN RANGES. 239 along its eastern base, which doubtless corresponds to the limestone that is seen on the western slope of the range, overlying the heavy bed of quartz- ite, which makes up the main mass of the mountain. The eastern base of the range marks the line of a fault, and the force which lifted the range to its present po- sition tilted the beds east of the line of fracture to some extent, giving usa section like the following, (Fig. 97). This lava can be seen stretching along the base of the range for a long distance. There appears also to have been a slight flow along the line of fracture be- “gyeseq 91391] & AT[eaOIs -vooo pure ‘azAqovr} ‘pf fod snosasimogivy Fo S[Issoy Jo s}ueMHeIy Moy v paystainy ynq ‘pasoydiomejom yYonut ‘T “oN tween the quartzite and limestone, and it is not improb- able that the mass along the base of the limestone came from this source. This range was crossed over a pass four or five miles south of Grantville, where there is a small cross-fault, with the downthrow to the south. These cross-faults are of common occurrence in the ranges of the Basin Range System, and frequently de- termine the position of mountain passes and cations. CEDAR MOUNTAINS. From Beckwith’s Spring north, as far as seen, Cedar range is a monoclinal ridge, with a dip to the west. At Beckwith’s Spring, and southward for a short distance, it is an anticlinal, the western half being a continuation of the monoclinal, which changes its trend at this point from north and south to northeast by southwest. The completion here of the anticlinal ex- pands the range to the east, and there appears to be an- other anticlinal to the southeast en échelon, but the whole soon flattens down into low hills. On the western side of the range were seen yellow sandstone and dark lime- stone, slightly bituminous, and somewhat shaly, containing Carboniferous fossils, Fusulina cylindrica, Productus, and Rhynchonella. The same forms were found on the eastern side, where the limestone is highly metamorphic. The relations of the sedimentary beds are very much masked here by tra- 0} Sarpuodsaatod ‘ouoysauny ‘g ‘4097 O00'F 03 000‘ ‘a1Z}1UND ‘% £49a7 000'S 01 OOG'T ‘euoysount ‘T—‘oSuva1 Ainqsuryg— 76 “D1,7 240 GEOLOGY. chyte. There are also one or two slight outbursts of basalt. A mile or two west of this range is a ridge, exposing 2,000 feet or more of yellowish-brown siliceous limestone, dipping to the northeast 25° or 30°. This limestone so closely resembles the beds referred to the Trias in the Wahsatch, that, in the absence of fossils, I am inclined to regard it as belonging to that formation. GRANITE ROCK. Granite Rock rises abruptly from the plain, and stands as an island in ~ the desert, as it once stood an island in Lake Bonneville,* the old beach- lines of which are plainly seen surrounding it. The whole island is granite, save a little dark-colored rock along its western base, which appeared, although seen only from a distance, to be limestone. It is difficult to make out any bedding to the granite, yet all the evidence points to a north and south trend, with a high angle of dip (60° or 70°) to the west. The western side of the mountain is of a darker granite, and weathers more slowly than the eastern. Veins are abundant everywhere, but those crossing the darker granite are more numerous and larger, they intersect the rock in all directions, and are of all sizes, yet the most of them are confined to two systems. ‘The first, which comprises a majority of all the veins, trends northeast by southwest, and dips northwest, conforming very nearly to the apparent bedding. The veins of the second system cross these at right angles, and, in general, appear to have been later formed. So far as I observed them, they consisted almost entirely of feldspar; some veins were five or six inches wide, with from one to two inches on either side coarsely crystalline, the center being formed of apparently the same material in a much finer state. The granite contains orthoclase in considerable excess, and much of it occurs in large crystals. SNAKE RANGE. Gosi-ute and Kern Mountains are included under this head, as they belong to the same line of uplift, and are in fact all parts of the same range. Structurally the range is in part anticlinal and in part monoclinal. At * The old lake, which once covered so large a portion of Utah, and of which Great Salt Lake is the modern representative, bas been described by Mr. Gilbert, in a previous chapter, under the name of Lake Bonneville. MOUNTAIN RANGES. 241 Uiyabi Pass and northward, for some distance, the range is anticlinal, but from there southward to Pleasant Valley it is a monoclinal, dipping to the west. At Pleasant Valley the structure again changes, and Kern Mount- ains are anticlinal or quaquaversal. Thence southward to Sacramento Pass the range is monoclinal again, with the dip as before to the west. From the pass southward the rocks form an anticlinal fold, the axis of which rises to Wheeler’s Peak, and then falls again, producing an elongated quaquaversal. A short distance south of the peak the western half of the anticlinal disappears, leaving the ridge a monoclinal, with its bluff face to the west. Thus it will be seen we have a series of anticlinals and monoclinals, following each other in quick succession. There is also in some { places a local mingling of these and other systems, which it is not deemed advisable to note in a general descrip- tion like the present. Patches of rock, sometimes of con- siderable extent, with a reverse dip, were seen along the bluff bases of the monoclinals, but they are small in amount and exceptional in character. The nucleus of the range is granite, which is exposed at many places, overlaid with quartzite, shale, and limestone. South of Wheeler’s Peak there is an exposure of 4,000 or 5,000 feet of limestone of the usual bluish-gray color. Immedi- ately under this comes quartzite, with thickness unknown, but probably not less than 1,000 feet. This forms the summit and slopes of the peak, but the deep cafons from = IPSS ts eee oe "8807 07UIUUN.LD ouogsauny = SS Ss piss Bis = EB eee es —s EE = oe Csi Op 2MIID A the same penetrate the granite, as is shown by the bowl- 5 ders brought down in the wash. S Four to six miles north of the peak is a high pass— Z |i BY a depression in the profile of the mountain due to a cross- fault, with the downthrow to the south. Fig. 98 shows the structure at this point, the line of section being length- wise of the range, and east of the axis of the anticlinal, so that the beds represented have an easterly as well as a westerly dip. his fault brings the granite well into view, and exhibits its relation to the overlying quartzite and limestone. 16ws OnUM LYE ‘vag 819/00] AA 0} SSUJ OJLOTMNIOVY Woz oduvsI oYLUG JO 1019098 [vuIpugisaoy—gg “91,1 242 GEOLOGY. From Sacramento Pass northward to the Kern Mountains the bluff east- ern side of the range presents limestone with fissile micaceous quartzite at the base. The whole central portion of Kern Mountains is granite, and is flanked on all sides with quartzite, shale, and limestone, which dip outward at a high angle. From Pleasant Valley to Uiyabi Pass the base of the range is granite, overlaid and flanked on the west with quartzite and limestone, except at the head of Deep Creek, and northward for a few miles, where the limestone and quartzite have been worn away, leaving the bare granite. At Uiyabi Pass there are from 200 to 400 feet only of quartzite between the granite and limestone, which shows it much thinner than at Wheeler’s Peak, and the little evidence collected indicates a gradual thinning of the quartzite on this range, from south to north. All of the limestone exposed doubtless belongs tothe same bed. The order of superposition is always the same—limestone, frequently a little shale, quartzite, and granite. At Uiyabi Pass I estimated the thickness of limestone at 3,000 to 5,000 feet. At Pleasant Valley the same, while south of Wheeler’s Peak, the exposure is apparently still greater. The prevailing color is bluish-gray. It is everywhere more or less changed, and much of it is very highly metamorphic. Only a few fossils were found, but all indicate Carboniferous Age, and at Uiyabi Pass Fusulina cylindrica was among the number. SCHELL CREEK RANGE. From Patterson, which is at the southern terminus of the range, north- ward for twenty-five or thirty miles, the rocks, as I saw them, appeared to dip toward the east at a high angle, while farther to the north they pre- sented a bluff face, showing a westerly dip. At Patterson a heavy bed of quartzite is exposed, dipping east-southeast about 45°. A few miles farther north, this is covered with conformable bluish-gray limestone; limestone was also seen to the west of the quartzite at Patterson, apparently forming with it a faulted anticlinal. Ten or fifteen miles north there is a low lime- stone spur sent out from the range, which extends across to Fortification range, and separates Spring and Duck Valleys. In crossing this ridge, which I have considered as a spur of the Schell Creek range, I found a few MOUNTAIN RANGES. 243 crinoid stems in the hard limestone. The rocks of the range were touched at no other point, and the fossils found are not sufficient to determine their age, but as this limestone agrees lithologically with that of the Snake range to the east, and Highland range to the south, and is underlaid with a similar bed of quartzite, I think it should be classed with them as Carboniferous. HIGHLAND RANGE. Directly south of Schell Creek range, and apparently along the same line of uplift, comes Highland range, which continues south past Pioche, the mines of Ely district being in a spur which runs out southeast from this range. At the north end the dip is south at an angle of 8°, and 1,500 or 2,000 feet of limestone are exposed Following southward three or four miles we come to a pass, caused apparently by a cross-fault, beyond which the dip is 10° or 12° to the southwest. The total exposure here is 2,000 feet, consisting almost entirely of limestone containing well marked Car- boniferous fossils—Athyris subtilita, Spirifer cameratus, Spirifer, Spiriferina, Productus semireticulatus, P. punctatus, Hemipronites, Retzia, and others. Below the limestone at this point, and apparently interbedded with it at the base, are some thin beds of quartzite. A few miles farther south is another depression in the range, and trachyte comes on the scene, masking all strat- igraphical characters. Still farther south, at Bristol district, the general dip is 10° to 12° north-northeast, just the opposite of that observed twenty miles farther north, and quartzite was seen along the western base, the whole upper portion being highly metamorphic limestone. At Pioche the spur of the range has a southeast by northwest trend, 4nd in structure is a faulted anticlinal, to the peculiarities of which attention will be called in the fourth section of this chapter. There is here 4U0 feet of highly metamorphic limestone of the bluish-gray color, in which no fos- sils were found; but in the absence of proof to the contrary, I am disposed to consider it as of Carboniferous Age, and as belonging to the same bed which yielded fossils farther north. Immediately below the limestone comes about 400 feet of reddish cream-colored calcareous and siliceous shale, the lower portion being siliceous and also micaceous. This shale in places yields Lower Silurian fossils in abundance. Below this is quartzite 244 GEOLOGY. to an unknown depth. This quartzite, as well as that seen farther north and on Snake range, corresponds, I believe, with that of the Onaqui and Wahsatch ranges. And I consider in like manner all the exposures of lime- stone as parts of one bed, once continuous from the Wahsatch to Nevada. Glancing once more over the field to see how the facts will bear out this conclusion, there is everywhere the same sequence of limestone, shale, quartzite, and granite, with the lithological characters similar through- out. I find, first, a heavy bed of bluish-gray limestone of Carboniferous Age universal. On the Wahsatch this is overlaid with Triassic and Jurassic beds, but in the other ranges where it occurs it is the topmost rock. This bed has been identified by its fossils on the Wahsatch, Lake, and Oquirrh ranges, at numerous localities—Cedar Mountains, Snake range, at Uiyabi Pass and Pleasant Valley, and at Zion Mountain on the Highland range No fossils were found at Bristol district or Pioche, and only a few crinoid stems where the spur of the Schell Creek range was crossed, but the absence of fossils at these localities, or rather failure to find them in the very limited search made, is due no doubt in the main to the highly metamorphic charac- ter of the rock. Underlying this limestone is an equally universal bed of quartzite. At Uiyabi Pass this bed is only from 200 to 400 feet thick, but at no other locality have I seen it so thin. Usually it is not less than 1,000 or 1,200 feet, and frequently much more. Between this bed and the over- lying limestone there is generally to be seen a thin layer or bed of arena- ceous or calcareous shale, varying in thickness from a few feet to 400 feet at Pioche. Where this shale has been examined it is separated from the limestone by a more definite line than from the quartzite ; still, occasional thin layers of limestone are seen interbedded with it near the top, but there is a much greater interbedding with the quartzite at the bottom of the shale. Mr. Watson, superintendent of the Newark shaft at Pioche, told me that in sinking through the lower shale he met five or six layers of quartzite, one of them being 11 feet in thickness with 137 feet of shale below it, and I learned from Mr. W. H. Clark, assistant superintendent of the Raymond and Ely mine, that in sinking the Lightner shaft he passed through 100 feet of shale before coming to the solid quartzite, but that in this one hundred there were fifteen or twenty layers of quartzite from 2 to 8 inches in thick- MOUNTAIN RANGES. 245 ness. I was also told that a stratum of shale 12 feet thick was met with in the Washington and Creole mine below 500 feet of quartzite. Besides this alternation, of which more examples might be given, there is also a gradation of one into the other, showing that the shale is not an essential feature, and may be represented by quartzite, or even in part by limestone, in some localities. Some of the more calcareous portions of this shale at Pioche furnished Primoridial fossils in great abundance. Similar fossils, several species of which are identical, were found by Mr. Clayton in the shale below the limestone at Ophir, Oquirrh range. Mr. Gilbert also found Lower Silurian fossils in a dark shale on the House range, but in this case with a very considerable thickness (much greater than seen elsewhere) of limestone and calcareous shales below them. Wherever erosion or upheaval reveals the base of the quartzite, itis seen to rest upon granite. . I would also call attention to a few facts outside of this field, which confirm the position here taken, and show that the same generalization may be carried over a still larger area. Mr. S. F. Emmons gives a section of the Toyabe range and another of the Toquima range near Belmont, in each of which we find the same order of sequence—limestone, shale, quartzite, and granite. Mr. Emmons discovered Fusulina cylindrica in the limestone of the Toyabe range, and in 1871 Mr. Gilbert found graptolites of Lower Silurian type in the shale at Belmont. Thus we have not only the same lithological sequence which we find at Pioche and eastward, but the same geological horizons also. Prof. Frank H. Bradley gives some sections of the Wah- satch at Ogden and Little Cottonwood, which are also interesting to com- pare with our sections farther south and southwest.* On page 194 I find a section near Ogden with, 1st, 3,000 feet of limestone, “plainly of Carbo- niferous Age ;” 2d, below this, from 2,000 feet to 2,500 feet of quartzite ; 3d, nearly 2,000 feet of limestone; 4th, ‘something over 1,000 feet of gray caleareous shales ;” 5th, 1,500 feet of quartzite which rests non-conformably on metamorphic rocks, which are ‘‘mostly hornblendic gneiss with some gran- *See report of Frank H. Bradley, geologist of the Snake River division, in Sixth Annual Report of U.S. Geol. Surv. Territories, Washington, 1873. 246 GEOLOGY. ites, and occasionally chloritic and tale-mica schists. Professor Bradley found fossils in the upper limestone, which are, he says, “plainly of Carboniferous Age,” and that in the lower quartzite bed are “indistinct fucoidal markings, resembling in general appearance the Arthrophycus Harlani of the Medina sandstone, but plainly not identical with it.” (Fucoidal markings answer- ing to this description were seen in the siliceous shales at Pioche.) Professor Bradley refers this quartzite, the shale, and the lower bed of limestone to the Silurian Age, leaving the upper quartzite bed only undisposed of. On page 197 he tells us that at Little Cottonwood, about fifty miles far- ther south, he found, as at Ogden, a heavy mass of quartzite resting uncon- formably upon the granite; above this “lies a series of limestones, the lower part rather thin bedded, the upper part in heavier layers.” This upper limestone he refers to the Carboniferous Age, and the lower to the Silurian, and considers it analogous to the lower limestone at Ogden. Thus the quartzite which separates the Silurian and Carboniferous limestones at Ogden is found disappearing southward, and the Silurian limestone, shale, and quartzite represented by a thin-bedded limestone and quartzite, which shows a rapid approximation to the sections farther south and west. Some data have been collected from a number of ranges in Southern Utah which indicate that they have in general the same geological and litho- logical sequence and character, but the nature of the data is too fragmentary to be of much value in any attempt at generalization. I have already mentioned the occurrence of Jurassic and Triassic beds near the south end of Mineral range, overlying cherty-gray limestone of Upper Carboniferous or Permian Age. This range, as seen to the north, has a granite nucleus, but the voleanic rock which forms the eastern and highest ridge at this point overlies everything to the south, and is followed to the southwest by low hills of the same material, which form the eastern boundary of Escalante Valley. The southern continuation of the Picacho Mountains, west of Hot Springs, gives an exposure of 4,000 to 6,000 feet of quartzite and sandstone, the upper 600 or 800 feet being quite fri- able. This is overlaid with about 2,500 feet of bluish-gray limestone, the whole dipping to the south at an angle of fifteen or twenty degrees. Over- lying the limestone again is volcanic rock, and in passing along the south- MOUNTAIN RANGES. 247 ern ends of Hawahwah and Needle ranges to Desert Spring, and from Des- ert Spring northwest to Pioche, the same immense beds of lava are the only rock seen until the latter place is reached. Southward from Desert Spring to the Bull Valley Mountains the same thing occurs on every hand, and no sedimentary beds are seen until the Virgin range is reached. This range has nearly a north and south trend. Mr. A. R. Mar- | vine crossed it near the northern end in 1871, and found it a moniclinal at that point, dipping to the east. The western base is formed of crystalline rocks, flanked on the east by heavy beds of quartzite and vitreous sandstone, and these in turn are overlaid with limestone of Carboniferous Age. In crossing the range near where the Virgin River cuts through it, I found it anticlinal, and the same structure could be seen continuing southward for many miles. I did not get below the Carboniferous limestone at this point, but a few miles to the north gneiss and sand- stone were seen outcropping along the western base. Fig. 99 represents a section from this range to the Pine Mountains, about twenty miles distant, which gives an exposure of from 12,000 to 15,000 feet, reach- ing from the Archaean up to the Tertiary. Capping Pine Mountain appears— us orssvang ‘9-p {o[eys paw euoyspurs snodsdvjaap ‘g + 9N09SeT!T Suoo dmmaenigg ‘T] {oeucyspuvs Ajeys pue seyeys seer, ‘OI-G + edojspavs f {sanoo sept ‘qv ssureyunoy AaT[LA Ul oq} OF eFaLt WISALA OJ WMOIy UOIDIg—'"GG “OM No. 1. Trachyte, 1,700 feet. No. 2. Red, mixed with some white and yellow, con- cretionary limestone—Tertiary—300 feet. No. 3. Yellow, red, and white, mostly friable sandstone— Cretaceous—3,000 to 4,000 feet. This part of the section was not examined, and it is probable that a portion of No. 3 is Tertiary. : No. 4. Yellow massive sandstone—Jurassic (?)—500 feet. No. 5. Buff and yellow oolitic limestone, alternating with red, calcareous, and gypsiferous sandstones—Jurassic— 500 feet. No. 6. Red and yellow shaly sandstone—Jurassic—200 feet. ‘ssiauy ‘G7 fauoyspurs put ajizjaeud ‘aT feuojspuvs pay ouoysamity snosagzimoqiey ‘L1-PL {gfrvor pov soyeys sviiy, ‘gI-ST oyvaeuI oy SLILT, peppeq-ssorio ‘p-2 fauojsamMI[ paw stoyspit Areyaay, °% §oykqovry, No. 7 Buff cross-bedded massive sandstone—Trias—1,200 feet. 248 2 GEOLOGY. No. 8. Red cross-bedded massive sandstone—Trias—2,000 feet. No. 9. Red shaly sandstone—Trias—400 feet. No. 10. Purple and red gypsiferous shales—Trias—150 feet. No. 11. Yellow conglomerate, with silicified wood, very abundant, (Shinarump conglomerate,)—Trias—1U0 feet. No. 12. Chocolate-colored shales—Trias—300 feet. No. 13. Slate-colored shales—Trias—500 feet. No. 14. Mostly red, with some buff shales—Carboniferous ?—800 feet. ‘ No. 15. Same as 14, with occasional thin beds of limestone—Carboniferous—550 feet. No. 16. Yellow, cross-bedded sandstone—Carboniferous—200 feet. No. 17. Limestone, dirty-yellow above and pale-red below—Carboniferous—2,000 feet. No. 18. Quartzite and sandstone. No. 19. Gneiss. a and b. Basalt. The Iron Mountains are a very irregular low range, formed almost entirely of volcanic material. From Iron City a ridge runs north to Ante- lope Spring, which shows sedimentary beds below its capping of trachyte. At the Silver Bell mining-district quartzite and sandstone were seen, but no evidence was collected which throws any light upon their age. SECTION II. VALLEYS: THEIR RELATION TO GEOLOGICAL STRUCTURES.—LAKES : ANCIENT AND MODERN.—RIVERS: WATER SUPPLY. The Basin Range System as seen in. Southwestern Utah and Eastern Nevada has already been described as divided by mountain ranges into broad, arid plains or valleys, which conform to the lines of uplift, and have a north and south trend. Many of these valleys are inclosed basins, or are divided into a series of small basins separated from each other, sometimes by lava floods or other rocky ledges, but frequently by simple bars of detritus, through which a stream could easily cut a channel, if such a stream existed to perform the work; but the annual rain-fall is so light that these basins are, with few exceptions, left dry the greater part of the year. In some of these the water collects to a considerable depth during the rainy season, and in some cases the supply is sufficient to form permanent lakes or marshes, which are, as a matter of course, salt. The only exceptions that VALLEYS. 249 T am aware of are Stockton Lake, and a lake or marsh near Fairfield, Cedar Valley. The first of these, it is known, did not exist ten or fifteen years ago, and the second is nearly dry now a part of the season, and its exist- ence as a permanent marsh is doubtless of-recent origin. These valleys are filled to a great and unknown depth with the débris from the surrounding mountains in the form of gravels, sands, and marls, and their history shows, first, a long period of subaérial denudation, suc- ceeded by a lake period, when these valleys were covered with water to a depth of several hundred feet, distributing and sorting to a considerable extent the accumulated material, leaving beds of sand and marl inclosing the records of fluvial and lacustrial life. This period was followed by the present, in which the lakes have mostly disappeared, leaving the arid plains before mentioned. The largest of these, called the Great Salt Lake Desert, has an altitude varying but little from that of Great Salt Lake, and stretches from Granite Rock, which has previously been described as an island in the desert, far northward beyond the region of this survey, and sending out its arms to the south, one of which, Snake Valley, reaches below the Thirty- ninth Parallel. Between Granite Rock and the Gosi-ute Mountains the desert for eighteen miles is almost a perfect level, with not a spear of vege- tation of any kind to be seen, but, instead, a thin &lm or white incrustation of common salt, giving an appearance similar to that of a light fall of snow on a frozen pond. The smaller valleys of this region are not quite so bar- ren, but over the greater portion of their surfaces little is seen excepting the inevitable sage-brush. The whole western portion of this section is of very little value for agricultural purposes. Stock-raising can be and is carried on to some ex- tent, the springs and small mountain streams, which sink as soon as they reach the loose gravelly deposits of the plains, furnishing water enough for that purpose, and the mountains themselves are usually well stocked with nutritive grasses. A strip along the eastern border of the system, thirty to fifty miles in width, includes a series of valleys such as the Jordan, Utah, Juab, Cedar, Tooele, Rush, and others farther to the south, which are much better sup- plied with water than those to the west of them. Considerable portions of 250 GEOLOGY. these are already under successful cultivation, and still larger portions are capable of being worked with profit. As examples, might be mentioned the old benches or deltas at the mouth of the Provo and Spanish Fork Camons, containing in the aggregate not less than thirty thousand acres, all of which it is believed may be successfully irrigated by these streams. During the lake period referred to, the major part of this whole area was covered by one immense sheet of fresh water, which rose to a height nearly 1,000 feet above the present level of Great Salt Lake, leaving many of its old beach-lines so plainly marked that they attract the attention of even the most common observer. This lake has been so fully described by Mr. Gilbert in another chapter under the name of Lake Bonneville, its ex- tent marked out, and prominent beach-lines noted, and the evidence in regard to its history so thoroughly treated, that it hardly seems desirable to say anything further; yet a few additional notes in regard to some of the localities not visited by him may not be amiss. Among the many beach lines that can be traced in favorable localities, two are so much more prominent than all others that they are scarce ever lost sight of, and have been deemed by him worthy of individual names. To the first, which is the highest of the whole series, he has given the name of Bonneville Beach, the same name as that attached to the lake which formed it, and to the other, 300 feet lower, Provo Beach, from its unusual development at the mouth of Provo Caton. When the old lake stood at this level, the detritus brought down by Provo River formed a delta, cover- ing at least twenty thousand acres. Another delta was formed at this time at the mouth of Spanish Fork Cafion, in the same valley, which covered an area of eight or ten thousand acres. The streams which formed these deltas have a rapid fall, and reach far back in the soft rocks of the Platetu System, which accounts for the large amount of detritus carried by them. They lowered their beds with the lowering of the lake, and have cut chan- nels through these deltas, leaving them as elevated benches. In Escalante Valley, which was the most southerly arm of this lake, the upper or Bonneville beach was traced to latitude 37° 45’, being only fifteen or twenty miles from the southern boundary of Utah. This bay was shallow, and left very indistinct beach-lines, which can only be traced VALLEYS. 251 in the most favorable localities. A broad arroyo at the southern extremity, near Desert Spring, suggested the possibility of an outlet in that direction to the Colorado. As this is the only point at which a southern outlet was possible, it is to be regretted that it could not have been relieved of all doubt; but it was impossible to make the desired examination. Informa- tion, however, which was obtained from different sources, and deemed trust- worthy, confirmed my own suspicion that the head of this arroyo was in the Bull Valley Mountains, and was formed by water flowing into the val- ley, rather than out, and that there is a well marked divide between this and the drainage to the Colorado. Accepting this, it becomes necessary to look to the north for the outlet to the ancient lake, and one has been dis- covered, by Professor Marsh and Professor Ward, draining into the Snake River. Professor Bradley also reports three or four possible points of out- let in the same direction. In the southern end of Snake Valley, where the water was shallow, the ancient beach-lines are also indistinctly seen, but farther to the north, where the bay was deeper and broader, they are preserved with wonderful clearness, and not only the more prominent beaches, but, in favorable local- ities, fifteen or twenty others can be distinctly traced. At Granite Rock, and on the north end of the Oquirrh range, the prominent beach-lines are marked by extensive deposits of calcareous tufa, which, like the marls in other localities, contain several modern species of fresh-water shells. The line of tufa marking the Provo beach at Granite Rock is 2 to 3 feet in thickness, and 20 or 30 feet in breadth, lying on the slope of the rock. The curious phenomenon of this granite island, surrounded by Pands of cal- _ careous tufa, is one not easily explained. . It has already been mentioned that Spanish Fork and Provo rivers drain portions of the Colorado Plateau System, and flow westward through the Wahsatch range, emptying their waters into the Great Basin. The inter- esting question may be asked, why did not these streams flow southeast into the Colorado, rather than force their way through a lofty barrier like the Wahsatch? That their courses through the range are along lines of weakness, is undoubtedly true; Provo River makes the axis of a synclinal, and at Spanish Fork there is probably a fault, and in a much disturbed 252 GEOLOGY. region like that of the basin ranges it will be generally found that the larger canons are formed along the axis of anticlinals or synclinals, or lines of fracture. But this only illustrates the tendency of eroding water to attack the weakest points, and while it serves to explain the selection of these par- ticular lines for crossing, it leaves untouched the question why the streams crossed the range at all, instead of escaping to the eastward over the lower barriers, which in that direction limit their basins. The most plausible- answer to this question is, that the cations through the range existed pre- vious to the establishment of the present drainage, and this assumption shifts the inquiry to the manner of their formation. When the Cretaceous and Tertiary seas covered the present Plateau region, the Great Basin, as it is now called, was the continent which furnished the material for the heavy beds of rock which were then deposited, and we believe the formation of Provo and Spanish Fork cations was begun by streams which carried the débris from this ancient continent down to these ancient seas. When the sea-bottom was lifted slowly to form the present plateau, overlooking the area from which it had derived its sediments, the channels of those former streams served as convenient gate-ways for drainage in the opposite direc- tion.* The Tertiary and Cretaceous conglomerates, made up of quartzite and limestone, point with sufficient clearness to the Great Basin as their source. I have already spoken of limestone bowlders in the-conglomerate on Sol- dier’s Fork, containing Carboniferous fossils identical with those found on the Wahsatch and elsewhere. And the fact that this bed of conglomerate, which has a thickness here of 2,000 feet, is not recognized, and apparently has no representative, farther to the east and southeast, would argue that it was formed at the mouth of a rapid stream, and was similar in character to the old deltas before referred to in the Utah Valley. Whether the conglom- erate of Echo Canon is likewise a local phenomenon, and had a similar origin, I cannot say. When the first cations were carved through this range it was not the lofty ridge that it is now, for the uplift of the plateau has been accompanied, at least to a great extent, by the elevation of the range—the line between the ~All these remarks apply with equal force to Weber River, and probably to Bear River also. VOLCANIC PHENOMENA. DS comparatively stationary Basin Range System and the upraised plateau being along its western base. This will help to explain its great elevation above the neighboring ranges of the same system. Had it been lifted above its companions at the main folding of the Range System, greater denudation would have been the necessary result; whereas the contrary seems to have been the case, more recent beds being found upon its summit than in the .ranges to the west. The position of the Tertiary and Cretaceous beds on the eastern flank, as represented in Fig. 96, shows that the two have moved together. South of Nebo, the Tertiary and Cretaceous beds, which covered the old line of uplift, have been severed by the more recent movement and carried up, exposing a bluff face to the west. A few miles to the east of the Wahsatch is another line of uplift, and along these two lines have been the main movements which have reversed the positions of the two systems ; placing the plateau above the plains of the Basin Range System. SEC PION BRE VOLCANIC PHENOMENA.—LITHOLOGICAL CHARACTER AND DISTRIBU- TION OF VOLCANIC ROCKS AND MODE OF OCCURRENCE.—THERMAL SPRINGS. It is not deemed practicable to attempt the separation of trachyte and rhyolite, owing to the impossibility of limiting the area occupied by each, and the difficulty, frequently encountered, of distinguishing one from the other, and in giving the distribution of volcanic rocks only two divisions will be made. First, basalt; second, trachyte and rhyolite. No volcanic rock older than trachyte was met with, except in a few doubtful cases. 1st. Basalt—This rock is not very abundant, and occurs mostly in the form of massive eruptions; craters being seldom seen until we enter the borders of the Plateau System, when they become quite frequent. It gen- erally occurs in connection with trachyte and rhyolite, but is seldom, as remarked by Baron Richtofen, seen overlying them, yet that it is more receni in age there can be no question. Great erosion has occurred in many places after the trachytic and rhyolitic flows and before those of basalt. This, as 254 GEOLOGY. I shall have occasion to note in another chapter, is notably the case in the Plateau region, where also are found numerous instances of faulting and folding having occurred between the deposition of the two rocks. At the south end of the lake range a thin sheet of basalt covers some of the low foot-hills. It is very limited in extent, and appears to be entirely independent of any older lavas. It alée occurs in connection with trachyte along the eastern base of the Onaqui range, and to the west of Cedar Mount- ains a small jet was seen in the center of a mass only a few rods in extent, and evidently of very recent age. No basalt is seen farther west until near the southem boundary of Utah. On the west side of Escalante’s Valley, four or five miles north of Desert Spring, a small area is covered with this rock, while the higher hills and range beyond are composed of, or covered with, rhyolite and trachyte. Another similar area is seen a few miles north of Sulphur Spring. Near Adamsville, along the east base of Mineral range, it forms a ridge of considerable height for a short distance, rising above, and overlapping, rhyolite, which is exposed to the west of it. It is, however, developed on a much larger scale to the north of the range, where a large area, visited by Mr. Gilbert, is covered with a sheet of basaltic lava, and numerous craters have been formed. It is also seen at a few places farther south, but not until the neighborhood of Pine Mountains is reached are any developments worthy of note met with. These mountains, which owe their existence to a heavy bed of trachyte that protected them while the surrounding country was denuded away, are flanked on the west, south, and east, by a belt of basaltic craters, the latest of which are perfect in form, although made up of loose scoriaceous materials, and are as yet uncovered with vegetation. One of the most recent is in Diamond Valley, just south of the mountains. It is a perfect cinder cone, 300 or 400 feet in height, and about 400 feet in diameter at the top, with a regularly formed crater, 75 feet to 100 feet deep. A few small streams of lava have issued from the same vent, but none have extended more than a quarter of a mile. The valley of the Santa Clara has been flooded with basaltic lava for eight or ten miles below Pine Valley settlement, filling up the channel of the river, which has carved for itself a new course, partly by the side of the lava stream, and partly pep ae Aya Tele ay CA val ila ot id BE chm een tol Fs ais ott igi liege “pga horses «oe oth anaemia tia shes er hones ‘wan wie . ke er wis ea at? Hit tie i= 3 « 77 s Biw Ad age Sond od kr et 1 .: 4; ech 7 ha tay : : ~ - : - - + e = Ss Mr. Gilbert visited Pioche in 1871, and AAT i Wath \\\ i i Mt AN “COL “OM ih | Fy SSS I am pleased to find that our observations agree on this point. The lime- stone and quartzite, notwithstanding the débris, are seen to approach each other near enough in places to demonstrate the existence of a fault, and Mr. 260 GEOLOGY. Gilbert was fortunate enough at the time of his visit to see a shaft sunk on the contact vein of this fault, which clearly revealed the relation of the two formations. To explain the existence of the shale, pierced by the shafts of the Ray- mond & Ely, Newark, and other companies in that immediate vicinity, it is necessary to suppose another fault, running through the town nearly ona line with Main street. (See Fig. 105 and ¢ ¢, Fig. 101.) The Newark shaft was sunk through 365 feet of shale, which lay conformable to the quartzite below and dipped about 10° to the northeast. The Lightner shaft of the Raymond & Ely Company was sunk through 100 feet of shale, which dipped with the quartzite 15° to 20° to the northeast. As shown in Fig. 103, the main fault is a little to the west of this point, and beyond the fault the dip is to the northwest. The different levels run west from this shaft, cross this line of fracture. The third level was run west of this line, 35 feet through quartzite, to the conformable shale above, which dips to the northwest, as before stated, 10° to 15°. The position of this level is shown in Fig. 103. Unless the shale on the northeast of this fault is considered as interbedded with the quartzite, and passing under the hill northwest of the town, a highly improbable assumption, it seems to me, the existence of the cross-fault ¢c, must be admitted. The difference of throw along the main fault, as illustrated in Figs. 102 and 103, (assuming the shale on both sides as parts of the same bed,) is in harmony with this supposition. The throw illustrated in Fig. 102 is not less than 600 feet, whilc in Fig. 103 it is only 100. If there are no other faults the difference of throw at these two points should be equal to the throw of the cross-fault, and this is nearly as I make it. And farther, it seems to me that erosion is not sufficient to account for the topography at this point. Following the main fault southeast to the divide, I find the throw (see Fig. 104) as great perhaps as at the point represented in Fig. 102. This would seem to militate against previous conclusions, but I think we need not be troubled on that score when the disturbed condition of the rocks in the neighborhood of the Raymond and Ely and Newark mines is considered. And in following along the line of this section a little farther to the west, another fault (D D, Fig. 101) with a north and south trend is discovered, and with a throw of 100 feet to the east. This may be ECONOMIC GEOLOGY. 261 a continuation of the fault running near Main street, with a smaller throw at this point, or it may be an entirely independent fault. The throw of the main fault being to the southwest, and the dip of the Pioche vein where worked by the Raymond & Ely Company 70° south, it might be expected that the vein west of this fault would be thrown to the north, but on the contrary it is found to the south, which fact can only be explained by a: horizontal throw. Five hundred and seventy feet east of this is another parallel fault dipping 70° southwest, and the same vein worked by the Meadow Valley Company to the east of this fault, is found over 100 feet to the north. To account for this, another lateral throw must be supposed, as the downthrow has been as before, to the west; or as usual, on the side of the hanging wall. It is obvious that the effect of the vertical faults— the vein dipping south and the throw being to the west—would be to carry the outcrop of the vein west of the fault to the north, but as it is found carried to the south in both cases, the evidence of lateral faulting must be admitted. Owing to the greater resistance to erosion exerted by the quartzite, the valley separating it from the shale along the line of the main fault is being continually crowded over farther into the latter. The Vandemark tunnel afforded an opportunity of measuring the amount at that point. This .tun- nel (see Fig. 104) was run 75 feet through loose material, mostly quartzite, which served for a protection to the shale below it, and then 185 feet through shale before the line of fracture and the quartzite were reached. As the mouth of the tunnel was about 40 feet from the lowest point, 300 feet appears as the total amount of crowding. The shale at this point appears to dip nearly north 15° to 20°, and the quartzite on the other side of the fault dips about 20° north-northeast. The dip of the fault here is 60° to the west. Next the quartzite, which has a tolerably clean face, there are 6 inches or 8 inches of finely pulverized material, then 10 or 12 feet of broken and ground shale, after which comes the solid shale which is unusually hard and vitreous for a few feet. IRON. An excellent quality of magnetite is found near Iron City in South- western Utah—very easy of access, and in quantity practically inexhaust- 262 GEOLOGY. ible. There is one butte of solid ore 500 or 600 feet in length by about 200 in breadth and 150 feet in height. But this is not all; Mr. Thompson noted dike-like masses occurring a mile or so to the northeast of this, and also near Iron Spring about twenty miles to the northeast. Lieutenant Dinwid- die visited some mines at this latter place, and collected specimens of both ‘magnetite and hematite. About three-fourths of a mile west of the ‘Iron Butte,” and considerably lower, geologically as well as topographically, is a bed of hematite which covers the southeast slope of a ridge, and from a hasty examination seemed to be a bed 5 or 10 feet in thickness, inclosed in limestone and siliceous limestone, having a dip of 10° or_12° to the south- east. ‘The surrounding country is so completely covered with Trachyte that the sedimentary rocks are but little seen, and their age was not determined. The following analyses, made by Capt. C. E. Dutton, of the Ordnance Corps, U. 8. A., show the extreme richness of the ore, but since it is very refractory the difficulty in its reduction will be to obtain sufficient heat. This region is so sparsely wooded that a permanent supply of charcoal cannot be expected, but some experiments made with an open fire to pro- duce coke from coal, which is said to be abundant in the Cretaceous rocks, ten or twelve miles to the southeast, give fair promise that the element needed may be derived from that source. Analyses by Capt. C. E. Dutton, United States Army. Red hematite ore: By decimal parts : Insoluble residue, (silica and silicates) ....--..--.-...- ..-.-------.----- 3.34 Macnetic oxide of tron; (Hes O))jo4s6 ee ae serie eee eee 5.64 Peroxid6.of:iron,-(HesOs)\i..5..ct2 «steele oes) hoes. eee icon: ee ee eee 82.97 Water ..ts2: Sbaven 2. tp aaeerin cere ce ro ee eels leis trae epi otete aie tere reeset 6.06 PU lit: oer Seen eee Rane A Sa RS BASRA cena aoe comcast - 1.35 Sulphur sese eS Mes MAOH COSS fe SOO Ge Sus aa SOUS ¢ SSS Aces. 06 Phosphoric:acid . st<0<' eae, : - & . ; : : - » ont ra A ea? = isi ; vi = ae : -" we 7 = 7 : J - - + “we = oa) ony ad é‘ ‘<8 =. iw ‘ m7 7 , ¥s . ie ni eee ee ore ty p ‘ rave ae Aelia 5 i 5 c 1 ae a, at in | f ) = ) Mas ; %. y + a st Te al "5 a = ~ 7 a ye aes Mithist art = aa OA) Fey tlk Me 2 r5 a ay ; eo salaeahe ay air a Tid hn. tie # Shales ts iv . EM) a Mg a ae ; . *%; a te. §) i: S$ SS Seay 4? ines = , ~ a - +. Ak athe = = y eS Tere +o ‘ * At A ENON i ee Fi i a. 4s .f er r| q ee a 7 . is . x Fy ¥ . es U4 j ~~ i he ng . 7 st.e ee t 3 . . . ’ . te cae * _ #)if , . - 2 » le ot? ad . J r ye STRATIGRAPHY. . DD southern limits of the Cretaceous in Arizona may be very closely defined by a line run westward from the Fort Defiance anticlinal in latitude 35° 40’ as far as the Moqui towns, and from there due northwest to the Colorado River. These beds are composed mainly of soft, more or less calcareous, cream-colored sandstones and dark, argillaceous and carbonaceous shales, containing extensive beds of coal, with almost an entire absence of lime- stone. The most satisfactory examination of the whole series was made near the Last Bluff, in Utah. A section at this point (see Fig. 109) gives about 2,600 feet as the total thickness of the beds which we have called Creta- ceous; but neither the upper nor lower limits of this formation have been determined as definitely as could be desired. The reasons for placing No. 5 with the Cretaceous are based upon lithological considerations entirely, as I was not fortunate enough to secure any fossils from this bed. It differs materially from No. 4, but agrees very closely with No. 6 (which is unques- tionably Cretaceous) in color and texture. These beds are naturally sepa- rated from each other at this point, for the reason that the lower part of each is softer than the upper portion, which results in the formation of two distinct lines of cliffs; but to the northward no such division was seen, and I was not able to separate the two. No.5, and the greater portion of No. 6, also, are wanting in the portion of Arizona visited; but in New Mexico, between Fort Defiance and the Rio Grande, both beds are apparently present, though no separation of the two could be made that would hold good for any great distance. Although many minor divisions could be made. at any one place, they would not correspond to, and could not be correlated with, those made at another; yet, taken as a whole, the series everywhere presents the same appearance. As there is no evidence to the contrary, I think the intimate relation which exists between the two beds justifies placing them in the same formation. Fossils are not very abundant in No. 6, but enough were collected to determine its geological horizon. Professor Meek recognized, in a hasty examination, Inoceramus, Car- dium, Corbicula, and Neritina Dostia(?) like those found by him at Coalville, 276 GEOLOGY. on the Union Pacific Railroad, and assigns to it a position in his Coalville series so far below the summit of the Cretaceous that there is ample room for No. 5 in the same formation, and a lithological comparison of sections from the two localities favors that idea. And, as before intimated, it may even be questioned whether No. 4 also should not be placed in the Cretaceous series. The same difficulty is met with in attempting to separate the Cretaceous from the Jurassic, as no fossils were found in No. 9, and only a few in the upper part of No. 8, and the division between the two is not a marked and constant one. A slight non-conformity by erosion was noted in one instance near the Paria; but a similar non-conformity was seen between 9 and 10, fifty miles to the northeast, in Water Pocket Canon. While No. 10 is Juras- sic, there can be very little doubt that No. 8 is Cretaceous, (at least the upper portion,) and the difficulty arises in disposing of No. 9. My reasons for placing it in the Jurassic with No. 10 are, first, the fact that at Soldiers’ Fork and Salina Canon there is a heavy bed of Jurassic sandstone not very unlike this in texture, lying immediately above the green gypsiferous shales, which shales are apparently the equivalent of the No. 10, and I think the inference is fair that the overlying sandstones are also equivalents. Second, I find, in going to the eastward, that while No. 8 is constant, the whole © Jurassic series, including No. 9, thins out rapidly, and finally disappears in Eastern Arizona and New Mexico, leaving No. 8 resting immediately upon 13. As this is a variable bed and disappears with the known Jurassic, while the Cretaceous above and Trias below are constant, there seems to be a propriety in placing it with that formation. Still, it must be admitted that, so far as observed by us, it was more fully separated from No. 10 than from No. 8, and more careful study may show that it should be placed with the Cretaceous. The main divisions of the Cretaceous retain their distinctive characters throughout, although subject to considerable variation in color, texture, and thickness. Attention has already been called to the intimate relation which exists between 5 and 6. They have the same general appearance in New Mexico as in Utah, although containing apparently a little more dark shale, and STRATIGRAPHY. 277 perhaps, also, more coal; but it would require more careful examination to decide this latter point. Several exposures of coal were noted between Fort Defiance and the Rio Grande, and also in Southern Utah, and as far north in Castle Valley as Muddy Creek. The coal of the Placer Mount- ains near Santa Fé, judging from the accounts given of it, probably belongs to this horizon. No attempt was made to trace these coal exposures, but enough was seen to indicate that some of the beds will prove to be of considerable economic value. As before stated, only the lower part of No. 6 is present in Northeastern Arizona, and this was not seen along the line of march more than twenty or twenty-five miles west of Orayhe, but it was seen in greater thickness far away to the north, northwest, and northeast, and it is probable that not only the whole of No. 6, but No. 5, also, is there represented. The whole region in the neighborhood of the Moqui towns consists of broken mesas, capped with from 100 to 300 feet of cream sandstone and dark shale, the lower part of No. 6. Below this are the dark argillaceous and carbonaceous shales of No. 7, from 300 to 500 feet in thickness, while at the base of the mesas, and forming the floors of the valleys, may be seen the soft, yellowish-white sandstone of No. 9. The Moqui towns are all built on the salient angles or peninsulas of these mesas. At the town of Oraybe, No. 6 has a thickness of 150 to 200 feet. Five miles to the northeast it is considerably thicker. A section, be- ginning at the top, is as follows: Feet a. Almost white, coarse sandstone, estimated ...-...-.... --....--+-.--.--- 70 # Cream sandstones and shales: ...-... 00... 2. 222. 220i. so ee ae dee 60 c. Dark carbonaceous shale .... ...-. LE ET rte Mon Dba te oe abo wee 35 (CRORE UMISLORWAILGISANGSUODG..ccc. 0c wee ses (ose wesc. cee Se en eee 30 é. Dank and) cream’Shale .......2....... Lady Oem late Soe Gio aie 35D J. Hard eream sandstone ..-.....--- Shy Bie kh estSrd. xe tesatehe, a ie See eae ete eee 30 260 No. 7 shows throughout a great degree of constancy in its general char- acter. Although cream shales and sandstones are always present in variable quantities, the general appearance is everywhere that of a dark-gray shale. The thickness of this bed, in New Mexico, Arizona, and Southern Utah, is usually from 400 to 700 feet, but in the northern part of Castle 278 GEOLOGY. Valley it attains a thickness of 1,000 or 1,200 feet. Professor Meek recog- nizes the fossils collected from this bed in Utah, Arizona, and New Mexico as the same that are characteristic of No. 2, or Nos. 2 and 3, of Meek’s Ne- braska Cretaceous. The determination of this horizon is especiaily inter- esting from the fact that it is pre-eminently the coal formation of the area embraced in this chapter, and probably of the whole Colorado Plateau System, I have already mentioned the occurrence of coal in the Tertiary beds in the vicinity of Sam Pitch Valley, of excellent quality, but of limited extent, and also a second horizon in the Upper Cretaceous (Nos. 5 and 6) of Utah and New Mexico, but the lowest and most important of all is now reached. The data collected indicate that the coal bed or beds of this hori- zon have extended, with but little, if any, interruption, from the western border of the plateau, near Cedar City and Kanara in Utah, to the Rio Grande in New Mexico, a distance of over five hundred miles. Mr. F. Klett, of our party, brought in some very fine-looking speci- mens of coal, collected from the summit of the bluff just east of Kanara. His section at this point is: Ist. Black soil capping the bluff. 2d. “ Shell-bed,” (the only fossils recognized by Mr. Meek are, Corbicula and Corbula of Cretaceous types.) A 3d. Coal and carbonaceous shale, 15 feet. 4th. Red sandstone, 2,000 feet. The fossils collected were merely enough to show it to be of Cretace- ous Age, but the fact that all below the coal is called ‘‘ red sandstone” indi- cates that it is near the base of the Cretaceous; and evidence from other sources goes to prove that only the lower part of the Cretaceous is present at this point. The shell-bed above, and the dark soil, (shale?) indicate, moreover, that the horizon is the equivalent of our No. 7, b. And, still fur- ther, Turritella and oyster-shells were brought in by other members of the party from the same plateau, a little farther to the east, and probably from the same shell-bed. It will be seen from Mr. Gilbert’s section on the North Fork of the Virgin, that he met with coal there at the same horizon. I would also eall attention to his section on the West Fork of the Paria for the details of the STRATIGRAPHY. 279 coal series at that locality. Another section, which I saw near the town of Paria, is as follows: Feet a. Oyster-bed, of light-cream color ........--6....- 2-220 --es ee cece ee eens 4 BMPLAINKASAUM SCONE sco c.o cite wiccicte a iste Slane a0 52 soe cha s ote iaseere era upete are Male etna area 3 ec. Argillaceous, carbonaceous, and cream shales, with some coal........ --.- 40 nm ORGANS Neal Geert tera tec ne oe Pe! s/c fe sin) cis cies ei wae «sm abiere swe olathe a enemyeeee 10 e. Argillaceous and carbonaceous shales, with coal; one vein of good quality, UE MONGOLE 5 od Cab CAS EON OE ete ener ene In Moree nA emis FOIA fi 10 RA VGlLOW ANG GLE AMPS AMO SHOU Oho a -ystors wiore. 14 ele os) sine. hin aes eigeease ce aitaee 4 g. Argillaceous and carbonaceous shales, ae coal; one vein 18 inches thick. . 20 h. Cream sandstone.. ..-...... arate! dist erc! ocSlans Seal eee ete 10 i. Cream shale and green ar miilaeculs ime BMAGL Sh. Sei Beek ee Be eee se 10 j. Argillaceous and carbonaceous shales, with some coal ....-.,-.. .-.-..--- 20 mATANAGEOUS Shales WibieSClOMIbG! 2... --. <2 - 32-002 soe esse oe te ete eet eee 10 l. Brownish-gray conglomerate and sandstone, upper part of No. 8. In some parts of Arizona the coal is confined to fewer beds, and seems to be present in much greater quantity. Near the head of a little canon, twenty- five miles northwest of Oraybe, one bed of very pure coal, 84 feet thick, was seen and measured. A little farther down the canon a lower bed was seen, 4 or 5 feet in thickness, while two or three miles to the north only one bed was seen, which had a thickness not far from 25 feet. This is probably the same bed which Dr. Newberry mentions as 30 to 50 feet thick, farther to the north, on the San Juan.*. To the eastward coal was not seen in such thickness, and it probably does not exist, although the loose, shaly rock weathers in a way well cal- culated to conceal the coal at this horizon, but exposures were seen at vari- ous localities near the Moqui towns, and east of Mount Taylor, enough to indicate that the bed continues with greater or less thickness to the val- ley of the Rio Grande. And the coal mentioned by Dr. John L. Leconte,t near San Antonio, is probably from the same horizon. This coal horizon in Utah extends far northward in Castle Valley, and just outside the limits of our survey, on the Muddy and San Rafael, are coal-beds, reported by the Mormon explorers to be of great thickness. If the thick beds of Lower Cretaceous coal reported by Dr. Newberry, as occurring in the San Juan region, do indeed belong to this same horizon, * Am. Journal of Science, April, 1873. i Notes cn geology, from Smoky Hili River, Kansas, to the Rio Grande. 280 GEOLOGY. then this Lower Cretaceous coal horizon of the Colorado Plateau System is one of the most extensive known. The bed of sandstone, No. 8, immediately below the coal series, shows considerable variability in texture and color, as well as thickness. In making a section near Paria, I found it 500 feet thick, but the greatest thickness was seen fifty miles to the east of this, near the Colorado, where it is about 800 feet, and much of the upper portion is made by a fine con- glomerate of gray or cream color. No. 9 also attains its greatest thickness at this point, and is but little thinner than No. 8. There is a gradual thin- ning of both beds toward the north, and on the Dirty Devil River No. 8 is about 300 feet thick, with much the same lithological appearance, oxtail that the conglomerate of the upper part is a little coarser. To the eastward, in Arizona, it has a thickness in places of at least 500 feet, and its usual color is a greenish or yellowish white, sometimes becom- ing nearly a pure white, with streaks of red or pink toward the base, which frequently extend well up. It is granular in texture, very soft and friable, but farther to the east becomes thinner and harder again, more nearly resembling its appearance in Utah. I had an excellent opportunity for ob- serving and measuring this bed at the Zuni Buttes, four miles northwest of Zuni, where I found it 130 feet in thickness, cross-bedded, of a reddish-buff color, and resting immediately upon No. 13, which it resembles perfectly in color and texture, and from which it is separated only by a small fissure or crack, which could be plainly traced in the adjoining buttes also. A simi- lar separation is seen at Inscription Rock, where No. 8 is not more than 75 feet thick. When the rocks are soft there is no fissure or crack showing, and it is frequently impossible to separate the two beds, but usually No. 8 is redder than No, 13. JURASSIC, Considering the thinness of the Jurassic formation, its outcrop occupies considerable space in the western part of our area, and this space is covered mainly by the lower two members of the series, and is due to the fact that No. 11 is a much harder bed, and weathers far slower than the upper beds and the Cretaceous series, and so forms a thin capping for a part of the STRATIGRAPHY. 281 Trias over considerable areas. The formation, throughout, is characterized by large quantities of gypsum, and in some parts of Utah-by extensive salt deposits. It is somewhat interesting to note that the limestone of the forma- tion frequently corresponds in its oolitic character to rocks of the same age in Kurope. The most northern point in the plateau country, where the series was examined, is on the Dirty Devil River, where the estimated thickness is about 800 feet, divided as follows: No. 9. Soft, pale-red, gypsiferous sandstone . ...-..........-.--.----------- 500 No. 10. Green, gypsiferous shale, hardening toward the base into soft limestone, containing Camptonectes, Trigonia, Aviculopecten, and Gryphea?..... 250 No. 11. Pale yellow, cross-bedded, calcareous sandstone.....-..-..------- oe 20 Nor lZreited manl-and shaleicco. ..-.- 52-20-2500 ~ Sept eisics 5 SerccerS.c 10 Tate oo he da ca 6 So Se Oe UCAS Dee Cen peor ae ae RO a tere oye fens COC 780 On the southwest side of Escalante River, sixty miles farther south, the series is from 200 to 400 feet thicker, and contains much more gypsum in the lower part, where workable beds 8 or 10 feet in thickness were seen. In the section on the Paria (Fig. 109) I found the Jurassic only 500 feet thick, but seventy miles to the westward, near St. George, it has a thickness more than double this, (see Fig. 99,) and this thickness is small compared to the 6,000 or 8,000 feet noted along the east base of the Wah- satch. To the eastward it thins out rapidly, until, in Eastern Arizona and in New Mexico it probably disappears entirely. Beds evidently belonging to this series were seen near the Moencopie, but no definite idea of their thick- ness could be obtained. Between White Rock Spring and the Pueblo Col- orado, 20 or 30 feet of red marl were seen lying just above No. 13, which are believed to represent the Jurassic series. South and east of Mount Taylor a series of beds having a thickness of about 125 feet were seen, holding the proper position, and closely resembling the Jurassic as seen in Utah, but no fossils could be found. Mr. Gilbert found a Camptonectes, fifty miles north of Camp Apache, closely resembling, if not identical with, the species found in the Jurassic of Utah; but the associated fossils indicate Cretaceous Age, and the question of its age is an open one, as is the whole question whether there is any Jurassic in Eastern Arizona and Western New Mexico. That 282 GE -LOGY. the Jurassic is absent in some localities there can be nod doubt, unless a por- tion of the so-called Trias is of that age. This is proved by what has already been said in relation to the Zuni Buttes and Inscription Rock. Where Nos. 8 and 13 are in contact and resemble each other so closely as these two beds frequently do, it is not an easy matter to separate the Creta- ceous from the Triassic ; and IJ find that Dr. Newberry has classed all below the lower coal at the Moqui towns in one series.* As the Lower Creta- ceous and Triassic are both unusually soft and marly in this region, it would probably be impossible to draw the line between them, even for one whose previous observations had convinced him that two distinct formations were there represented. That two such formations are there represented I can hardly doubt, as in no single instance where a section could be made out satisfactorily did I fail to find a bed of sandstone (No. 8) interposed between the coal series and the Trias; this is separated from the Trias in Utah by beds 500 to 1,000 feet in thickness, which thin out to the eastward, and finally disappear entirely in parts of Arizona and New Mexico, leaving only a fissure or crack to represent them, or mark their place, where the rocks are hard; and where soft, nothing whatever. TRIAS. Nos. 13 to 17, (inelusive,) of Fig. 109, give a typical section of the most characteristic group of rocks found in this plateau country. This group, by the common consent of geologists, has been called Trias, although as yet it has furnished no fossils to, satisfactorily establish this conclusion. This formation, like those above, terminates to the southward in abrupt cliffs. These cliffs, usually two in number, and sometimes three, as seen in Fig. 109, run from Southwestern Utah, near St. George, in a very irregular line to the Colorado River near the mouth of the Paria, and then southeast to the head-waters of the Little Colorado. East of the Colorado, they con- form very closely to the axis of a monoclinal fold, and form a tolerably straight line, but to the westward they are crossed at right angles by folds and faults, and as the beds thrown down by these movements weather more slowly than those retained at a higher elevation, they are left behind in the *Ives Report. STRATIGRAPHY. 283 northward retreat, and a very irregular line of cliffs is the result. The plateau south of this extended line of cliffs is capped with rocks of Upper Carboniferous Age, while to the northward the lowest exposures are usually Triassic. The most important exception to this in the area embraced in this report is the Zuni Mountains, which are composed of Carboniferous rocks with a crystalline nucleus, exposed near their southeastern extremity, while the range is wholly surrounded by Trias cliffs, similar to those described above, (see Figs. 115 and 116.) The thickness of this Triassic series in New Mexico and Eastern Arizona is from 1,200 to 1,800 feet. This gradually increases to the westward, until in the section near Paria (Fig. 109) it is estimated at 2,250 feet. Ninety miles to the northeast, on the Dirty Devil River, 1,700 to 1,900 feet is found, while at the extreme western point examined, near St. George, the same series is estimated at between 5,000 and 6,000 feet, (see Fig. 99.) This is perhaps an overesti- mate, but the thickness of the series is undoubtedly much greater here than anywhere to the eastward. The two upper members of this series (Nos. 13 and 14) are usually soft, massive, cross-bedded sandstone. The color of the upper member is generally pale-yellow or buff, while that of the next is some shade of red; but this division is not a constant one, and to the eastward any attempt to separate the two becomes impracticable. Moreover, the division, which is usually very well marked in Utah, between these beds and the variegated marls below, is also very indefinite, as the base of 14 becomes soft and shaly, making an easy gradation from the marls below to the sandstone above. The whole upper part of the series is much softer in Eastern Arizona than it is either to the west or east, much the same character being seen in New Mexico as in Utah. Considerable limestone was seen in the variegated marls series (No. 15) in Arizona and New Mexico, and east of the Colorado, for a distance of fifty or sixty miles, the series has a thickness of 500 or 600 feet. The conglomerate bed, No. 16, to which Mr. Powell has given the Indian name, Shinarump, is a very singular formation. Having a maxi- mum thickness at St. George of 100 feet, it seldom exceeds 40 or 50 to the east, but is co-extensive, so far as I know, with the Trias of the Colorado 284 GEOLOGY. Plateau. Occasionally it is little more than a coarse sandstone, and some- times thins out to 8 or 10 feet, but never have I passed that horizon with- out seeing it. One of its constant features, almost as constant as its exist- ence, is the great amount of silicified wood which it contains. ) = SSeS TH SS | SN | Sait | eS AS | | | Fia, 111. Belleview Clift Figs. 111-114 are sections near Toquerville, Utah, showing a non-conformity between the Trias and Carbonif-rous; 13-14, cross-bedded sandstone, (Trias); 15, variegated marl series, (Trias); 16, Shi- narump conglomerate, (Trias); 17, shales, (Trias); 16, limestone and sandstone, (Carbouiferous.) STRATIGRAPHY. 285 Being harder than the beds above and below it, this caps a line of cliffs, which are the second or lower line of Trias cliff, previously referred to. Just below this line of cliffs, near Toquerville, in Southwestern Utah, a few fragments of lamelle branch shells were seen. Although too indefi- nite for determination, they indicate that more careful search will yet pro- cure the evidence needed for determining the age of these beds with cer- ° tainty. A very interesting instance of non-conformity between the Trias and Carboniferous was seen a little north of this town. Fig. 111 shows this non-conformity as it appeared at a distance of two or three miles. Later experience and more careful examination of the weathered exposures along monoclinal folds have had a tendency to throw doubt on this as a true case of non-conformity, but I am still disposed to think that the relation of the beds was correctly seen. The Carboniferous limestone, forming the Belleview Cliffs, a little south of the line of this section, makes a twist, and the western edge dips rapidly to the south, and soon assumes a nearly horizontal position, as seen in Fig. 112, one and a half miles farther south. It is soon after buried beneath the Triassic rocks. . Fig. 113 is a section half a mile south of the point represented in Fig. 112,.and in Fig. 114, one mile farther, we find the Shinarump conglomer- ates capping the cliff just east of Toquerville. If this be, as I believe it is, a true case of non-conformity between the Trias and Carboniferous, it is the only one of which I am aware, and deserves more careful study. CARBONIFEROUS. I have before stated that the plateau country south of the great line of Trias cliffs is capped with rocks of Upper Carboniferous Age, but my work southward ended at the base of the Trias, and only at a few places did I enter the Carboniferous at all; so that no facts were gathered except in regard to its geographical distribution. About 2,000 feet of yellowish-gray limestone and sandstone, belonging to these series, are revealed by the Hurricane fault, near Belleview, in Southwestern Utah, as shown in Fig. 110. Fria. 115. 286 GEOLOGY. A gray calcareous sandstone, probably Il Wu g R = of Carboniferous Age, was seen at the base | seil[ = of the Trias, between the Dirty Devil and S a Escalante rivers, and a few other cases were -.\| = met with where the rocks were doubtfully ss 2 of Upper Carboniferous or Lower Triassic 2 5} 2 Age. The whole crest of the Fort Defiance = “| ¢ anticlinal is so near the base of the Trias, :. : = that a cation anywhere, a few hundred feet 2 deep, would expose the Carboniferous. er The Zuni Mountains have a trend north- = west by southeast, and are an elongated Gre quaquaversal, from which all the rocks above Ie ae the Carboniferous have been denuded, but is Be the Trias and Cretaceous are seen in bold ore aS cliffs facing the mountains on all sides, as = WwW 5 2% shown in Figs. 115 and 116. Here and in E E E = the Fort Defiance anticlinal are two fine = illustrations of the more rapid denudation = 2 which results from an increase in elevation. Fig. 115 is a section across the range at the north and near Fort Wingate.* Fig. 116 shows a section twenty or twenty-five miles farther southeast, while Fig. 117 is a section at the southeastern extremity, where the ero- sion has revealed the crystalline nucleus. This nucleus, however, is probably only a highly metamorphic condition of the Car- boniferous rocks, and a very easy gradation can be traced from red siliceous sandstone, eo through sectile quartzite, still retaining some of its red color, and showing small rounded rintion Rock. * A section of the western Zuni fold, twenty or twenty-five miles to the north of this, is shown in Fig. 123. = = S =) — RD é — — 1 ie) A nl = D S = Cc — inser bee STRATIGRAPHY. 287 crystals or crystalline grains of quartz, into rocks showing a less perfect bedding, but more highly crystalline structure, which, with an increased development of feldspar and mica, merges into a rock, that in selected hand specimens no one could hesitate to call granite. Immediately above these rocks are: Feet. Wee inisand red SANGSvONGs ss. cette a=) a ale = eee we His rate = al =1= =| tats =l= = 500 or 600 embink to, onayeliMestOne emer « «cise - «<1 mew ott laieie 1 eel eet 75 to 100 GORA SANGSTON CRAG AIM eran nos mises See ois so West of the Fort Defiance anticlinal the country for a long distance is remarkably free from disturbances of any kind, as may be seen from the section across the Colorado, (Figs. 119 and 120,) but just before reaching the river it crosses a monoclinal fold, (the Paria fold,) with an easterly downthrow. This fold crosses the Colorado at the mouth of the Paria, and runs in a north-northwest direction to the Last Bluff, keeping a little to the west of that point, and extending, apparently, but little farther in that direc- tion. When last seen, the throw was only a few hundred feet, and was diminishing rapidly. A section south of the Last Bluff is shown in Fig. 109. The same fold keeps a- south-southeast direction from the Colorado River to the Little Colorado, and follows that stream for a long distance. A partial section of it near Big Dry Fork is given by Dr. Newberry in Ives’s Report, page 77. This point is over two hundred miles from the Last Bluff, but how much. farther the fold may continue, I know not. Mr. Mar- vine crossed it fifteen or twenty miles farther to the southeast in 1871, and gives a section as seen by him in Plate IV of this volume. This section, like the one given by Dr. Newberry, would show the true character of the fold better if continued a little farther. This is a more recent fold than the Eastern Kaibab, as is shown by its crossing and displacing the latter on the East Fork of the Paria. The Eastern Kaibab fault follows the eastern side of the Kaibab Plateau, and northward from Paria bears a little to the east. It was last seen a few miles to the east of the Last Bluff, and evidently does not extend much farther in that direction. Its drop at Paria is not far from 3,500 feet. About twenty miles to the west of Paria there is a small fault with the drop to the west. This is probably the continuation of the western Kaibab fault. = Between the Last Bluff and the Henry Mountains the rocks are folded and thrown into waves on a greater scale than elsewhere seen. This exces- sive corrugation is especially shown in Figs. 129 and 130. East of Thou- ‘sand Lake Mountain, which is a lava capped mesa butte, is a monoclinal fold, which shows as a fault in some parts of its course, with the drop to the west. And two are so near each other, that they might, taken together, be called an anticlinal with a flattened top. A section of this mountain is Coyvunrxordde) Goo QO0‘OPG = HULL :0TBOg Sele BEA TLLLLLLLLLLLLLLLLLLLLLL LL ALLL Bee “LOL “SUL (oyumrxordde) ‘40a¥ 000'GGs = MOU! T + TBS TLL LL EEL z ea LL, SS So ye ‘96T “OTA Coyvurxordde) ‘oo 090'GtG—= YOUL T : 9[v0g GEOLOGY. oa Pee ceorcee eee try hd ed ed end Ed ed ed ad ay ng pe ee 2 ee — LLL SS Lye Vv x 2 nurs sco “GOL “OM ices TALULA og Wl MT PUNSNOYT 292 ‘POL “ONL ‘soreys Arvryqoy, ‘f ior) = £ onoqseuny Arviqaoy, ‘e-T seviay, ‘p foisseane ‘o £ snosoeyoI1D ‘q foykyoury,‘n ‘sprog : a ‘a ‘0 ‘a SV “Woy 4yoos10}UL sMOT0eS JuotaBIp Of} Tor qv squiod oy9 pur ‘gq pur Yy Sploy oq} JO sosanod oT9 SUIMOYS WeISVIP SITET “SLT ‘WINos oF YILOU Wory Jopsio ur pesuvsre o1v pue ‘neoqyel[d snienby pur yuyig ysv'T oy} Jo ysvo ‘AaTjeA opysup Jo puoe ULoyINOs oy} Ut APoryo vYLIAYS OJ JO UOTZBOOTSIP OY} GUIFZIGIXO SMOT}OS OIG OFI-FST ‘SOL : “TSE “OM TR a . ra . B (‘oyeurxordde) 44903 000‘00F = WUE T :9T80g fy aN C—O arr A La ) amteyT ms Tate! oi earl: | Ae2 - YO WU Pe L2 : ou Rose rt SORE a FTL = tae SPOTS AEE OV REPORT ON THE GEOLOGY OF A PORTION OF COLORADO. EXAMINED IN LSC 3. BY Pror. JOHN J. STEVENSON. COMPRISING CuaprErR X.—GENERAL PHYSICAL FEATURES ; XI—METAMORPHIC ROCKS; XII.—PALEOZOIC ROCKS; XIIL—MESOZOIC ROCKS; XIV.—ERUPTIVE ROCKS ; XV.—SURFACE GEOLOGY ; XVI.—MINERAL SPRINGS; XVII.—STRUCTURE AND AGE OF THE ROCKY MOUNTAIN SYSTEM. 303-304 University, New York, June 8, 1874. Str: I have the honor to submit herewith a report upon observations made in Colorado during the season of 1873. As the main object of the exploration was to obtain material for a topo- graphical atlas, and the area was large, it was found necessary to move with such rapidity that detailed work in geology could not be performed. Under the circumstances the duties of the geologist were the more arduous, as, unlike the mountains of Utah and Nevada, the region examined during 1873 is for the most part densely wooded on the slopes to an altitude of from 10,000 to 12,000 feet. At the same time I trust that the accompanying report will be found, as far as it goes, an acceptable contribution toward the elucidation of the general structure of the region. I am under obligation to Mr. J. J. Young, the excellent topographer of the party, for many favors. The illustrations are from sketches made by him in the field, and afterward drawn on the wood by him. To Lieutenant Marshall, who commanded the party, I am indebted because of his constant endeavor to aid me. Very respectfully, your obedient servant, Jno. J. STEVENSON. Lieut. G. M. WuHeEertEr, Corps of Engineers, in Charge. 20 Ws 305-306 a See ae =¢ } . ee etre iy Tata, < 2M a ja) i Ne, Taspateegess 3 aa te PEED TASER ae ; ee ; | ase ae y i ; | | Wii == De het) eR is ¥ ny a =— = ‘ ae i ‘ na : Pier. oie + e ; aed fats , ¥: T(E! Meee ty [* bj vwiketas: ; ert ig , Pi Hin “ : . ™ — +E -SS ; m F nate oe a . et aE ie oa . + 7: ‘A ‘ va | iW at Dae og ; » . #9 we A ree tikes : yO WIie oF SSE Pi | 5 : 5 24i¢s 3 eae? otsini jan aici ao - c id M4 : » . : i ~ ; 7) tinal Ai tapi: 7 ia j : ‘ MLR IT yt ately oe q at ; ‘oe : ‘ ® : ped a , ee 88 tg” Uw BE eA epee E y father Far Ody “eager, Ei: otal , ; 44 iif = a bit ‘ i K : 3 ho ond iN Vil ry sal Lf its ee | i F ’ Oj ike Siti, | + ye t.4 »! * + % t 7 RUS lena thag sy 6 ‘it ; ie id ae ides? i Tae barrest arti - : ; , "SVG DAT Bis © he: car 1.1 . 4 Giants 40 ~ re Ie S ' 5 eal s tri. , i * ~~ a 7 w a ~i gals *¢ 5 é c aus Le Bey! ay 4 im i : ; oad CUNT? 3 sd eek t . CHAP TE Rak: GENERAL PHYSICAL FEATURES. Section I.—ToPpoGRAPHy. SEOTION II.—CLIMATE AND AGRICULTURAL RESOTRCES. SECTION I. TOPOGRAPHY. The area examined during the season of 1873 is embraced between the meridians of 105° and 107° west from Greenwich, and between north lati- tude 39° 45’ and the southern boundary of Colorado, giving a length of one hundred and ninety miles, and a breadth of about one hundred and six. Besides this rectangle there was explored a smaller one at the west, reach- ing almost to west longitude 108°, and extending from the southern bound- ary of Colorado, northward to the Rio Grande. The number of square miles included in the whole area is not far from twenty-two thousand, of which barely three thousand were not visited or examined to some extent by the main division of the party. Excepting only a narrow strip, reaching ten to fifteen miles west from the one hundred and fifth meridian, and the plains known as South Park and San Luis Valley, the whole region covered by our observations is mountainous, exhibiting, perhaps, the grandest development of the Rocky Mountains to be found within the United States. The ranges are more massive, more sharply defined, and the average elevation is much greater than in any other portion of the chain. The district thus brought under our notice includes portions of five Norr.—The altitudes given were obtained by the field parties under the charge of Lieutenant Mar- shall, Corps of Engineers, from barometric observations computed at the office of the survey in Wash- ington, D. C. 307 308 GEOLOGY. great drainage areas, whose chief rivers, with one exception, -find their source within it. These are the South Platte area, the Arkansas area, the Rio Grande area, the San Juan area, and the area of the Grand and Gunni- son. ‘The first three are east from the great water-shed, and are drained into the Gulf of Mexico, while the other two are merely portions of the widely extended area of the Colorado River, which empties finally into the Gulf of California. The area of the South Platte occupies the northeastern part of our dis- trict, embracing South Park, Clear Creek County, and the plains east from the mountains as far as, say, fifty miles south from Denver. The Arkansas area is irregular in outline. Its upper portion, which is exceedingly nar- row, lies directly west from South Park; the next division lies directly south from the Park, and extends for more than fifty miles in a north and south line; the third division lies east from the mountains, and reaches south- ward to beyond the southern boundary of Colorado. Of the Great Rio Grande area but little lies within our borders. From the head of the river, a narrow cation, opening here and there into insignificant parks, extends for about eighty miles, in a rudely east and west direction, like an enormous tongue separating the San Juan from the Grand and Gunnison. At the -mouth of the cation we have the extensive park of San Luis Valley, em- bracing the counties of Costilla and Saguache, with a portion of Conejos, and reaching far beyond the Colorado border into New Mexico. This area lies west and south from that of the Arkansas. Still less of the San Juan area comes under our notice, as the greater portion of it is in New Mexico, or in Colorado, beyond our extreme western limit. It occupies the south- west corner of our district, embracing the most of Conejos County. The Grand and Gunnison area is of enormous extent, embracing all the north- western portion of Colorado, but not more than nine thousand square miles fall within our limits. To the geologist this region will prove most inter- esting, owing to the strangely complicated stratification. A thorough study of this area will afford the solution of many perplexing problems in dynami- cal geology. Tue Divives.—The Main Divide——Of the numerous divides, the great water-shed between the Atlantic and Pacific first claims our attention. TOPOGRAPHY. 309 Beginning at our northern line, about forty-four miles west from Den- ver, its trend is south and west of southwest to the head of Tennessee Creek, the West Fork of the Arkansas describing a curve, whose convexity is toward the southeast. From the head of Tennessee Creek, the course is east of south to the head of the South Arkansas River, a distance of sixty-nine miles. Thence the direction is rudely south of southwest to the canon of the Rio Grande, about thirty miles above its mouth. There it bends abruptly westward to the head of that river, about fifty miles, to 107° 30’ west. longi- tude, where it turns sharply upon itself and follows an easterly course for fifty miles. These two divisions form the walls of the great cation of the Rio Grande. At the head of the South Fork of the Rio Grande it takes a southerly direction, which it maintains until it crosses the line into New Mexico, after which the course is changed to south of southwest. The divide then is made up of six divisions, well marked by variation in the trend. Asa whole, this main divide, though not coinciding with the geo- logical arrangement of the axes, is the most imposing portion of our mount- ain series. Its greatest development is seen in the first two divisions and in the fourth and fifth, the third and sixth being of comparative insignifi- cance, owing, however, only to the gigantic dimensions of the others. Near the northern extremity of the first division, as included in our district, are seen the Twin Peaks of Gray and Torrey, both reaching to a height of more than 14,000 feet, and distinguishable for many miles. South- ward from these are numerous peaks without fixed names, whose synonymy would fill a page. Near the extreme eastern projection of this curved divis- ion is a massive group, in the vicinity of Evans and Rosalia Peaks, which are among the highest yet measured. These rise nearly 3,000 feet above the timber-line, and retain throughout the year immense masses of snow. Following the ridge westward, we reach Gilpin’s Pillars. These twin mountains, whose altitude is about 13,500 feet, are enormous knife-edges, with smoothly planed abrupt slopes on the west, but jagged and torn by huge chasms on the east. Viewed from the south, their resemblance to each other is not striking, but their northern presentation is such that, seen separately, it would be hard to determine which one is under observation. Farther westward is Mount Morton, locally known as “ Silverheels,” similar 310 GEOLOGY. in outline to those just mentioned, and having an elongate crest running rudely northeast and southwest. Its eastern slope is scarred by an immense excavation, which always contains more or less snow. This peak has an altitude of 14,044 feet. A few miles farther west is Mount Lincoln, with its mate, Mount Bross, together an enormous, almost characterless mass, reaching to 14,300 feet above the sea. It is almost wholly separated from the main divide by immense gorges, in which rise the South Platte, Arkan- sas, and Blue Rivers. The main divide here is a narrow precipitous wall, so narrow, indeed, that, standing on its crest, one might with equal ease throw a stone into the waters of the Pacific or into those of the Atlantic slope. The passes of this division are by no means devoid of interest. At the extreme north is Berthoud’s Pass, leading from Clear Creek into Middle Park; a pass of comparatively easy grade, and the main line of travel over the range to the park. It has been supposed by many that a narrow-gauge railway might be constructed by this route, but the grade is too sharp to admit of it without extraordinary outlay. The ‘‘Argentine,” or “Grizzly Bear,” Pass leads from Georgetown to the Peru Fork of Snake River, and crosses the range in a saddle between Gray’s Peak and the McClellan Mountain. The approaches are very difficult on each side, and the summit, which is at an altitude of 13,283 feet, is exceedingly narrow. ‘This pass is choked with snow for from five to seven months each year, and is little used, except for passage of pack animals. A wagon-road has been con- structed, but, notwithstanding its numerous windings, is so steep as to be almost unavailable. A similar pass exists near Montezuma, at the head of the other fork of Snake River. ; The old Georgia, or Jefferson Pass, from Buffalo Flats, on Swan River, a tributary of the Blue, to the town of Jefferson, and thence to South Park, leads across the divide east from the easterly one of Gilpin’s Pillars. Until within half a mile of the summit, the approach from the Blue River side is very gradual, but beyond that it is abrupt. On the other side, the grade is equally abrupt near the summit, but diminishes rapidly below, and near the opening into the park is comparatively slight. The altitude of the sum- mit is 11,776 feet. TOPOGRAPHY. 311 It is a narrow trough between high peaks, and is apt to choke with snow, so that it may remain closed for seven or eight months in the year. Though formerly used as a wagon-road, it has been little traveled since the town of Jefferson was deserted. Adjoining it is the Frenchman’s or French Gulch Pass, reaching over 12,000 feet. Like the last, it remains closed until late in the summer, and is no longer used. The Hamilton Pass, between Gilpin’s Pillars and Mount Morton, leads from Hamilton, in South Park, to Breckenridge, on the Blue, and is the regular road for stage-coaches. Though nearly as high as the Georgia Pass, it is much more available, as the grade throughout is quite easy, and the broad, open summit permits early melting of the snow. Indeed, there is no reason why this pass should not be kept open during the whole year without serious difficulty. As matters now stand, it is the best in the region. The Hoosier Pass, crossing from Breckenridge to Montgomery, on the headwaters of the South Platte, is, however, the one most likely to prove available for all purposes, though the present direction of the wagon-road is contradictory to any such conclusion. From Breckenridge, the road follows the Blue to near its source, when, turning off somewhat sharply, it ascends the mountain with an unnecessarily abrupt grade. The summit, which has an altitude of 11,600 feet, lies between Mounts Lincoln and Quandary on the one side and Mount Morton on the other, three of the grandest peaks in the whole Rocky Mountain chain. On the Platte side the road descends with painful grade to the now almost deserted village of Montgomery. This direction was chosen from necessity, as, when the road was constructed, ‘Montgomery was an important center of mining operations. A much better, though somewhat longer, route would be to carry the road along the east- erly side of the cation from the summit to Fairplay, about eleven miles away. The grade then would be little more than 100 feet per mile. An equally favorable grade can be obtained on the Blue River side, at com- paratively small expense. Under such conditions, the pass would be avail- able for railroad purposes. The Arkansas Pass leads from the head of the Arkansas to the head of Ten-Mile Creek, a tributary of the Blue. On the southerly side the ap- 312 GEOLOGY. proach is very gradual, and a wagon-road could be constructed without dif- ficulty and at little expense. The summit has an elevation of only 11,500 feet, and, if necessary, could be kept open during the winter. It is doubtful whether the descent on the opposite side can be utilized, as the drainage is exceedingly bad, inducing a marsh which stretches entirely across the sum- mit and extends for miles down the stream, involving the hill-sides, and ren- dering passage hard even for pack-animals. The second section of the divide, beginning at the head of Tennessee Creek, separates the waters of the Grand and Gunnison Rivers from those of the Arkansas. It is by far the finest portion of the divide. Standing on the west side of the Arkansas River for sixty miles, an unbroken wall of magnificent mountains, deeply cut, with harsh, rugged outlines, and reach- ing far above timber-line, its naked peaks fully equal one’s ideal of the Rocky Mountains. It shows no airy pinnacles, no slender needles orna- menting its crest; everywhere it is massive; imposing because of bulk, and not because of eccentric outline. The average height of the whole division falls little below 13,000 feet, and few of the peaks are less than 13,500, while many reach even to 14,000. At the head of Tennessee Creek is the Homestake group, 13,000 feet high, with a remarkable series of glacial cavities on the eastern slope, and a similar series scarcely less wonderful on the western side. South from this in close succession are Massive Mount- ain, Mounts Elbert, Harvard, Yale, Piseah, and Usher, and Hunt’s Peak, with many other peaks of almost equal importance, but still unnamed. The only depression falling below 12,000 feet, and extending for any consider- able distance, is at Colorado Gulch, about ten miles south from the head of Tennessee Creek. No similar break occurs elsewhere in the whole division. ~ The passes are few, and, with the exception of that near the head of Tennessee Creek, are wholly unworthy of the name. The Tennessee Pass belongs, indeed, properly to the first division, but for the sake of conven- ience is described in connection with the second. It crosses the divide at the head of a small tributary of Tennessee, and leads to the Eagle River, a tributary of the Grand. It is low, barely 10,681 feet at the summit, where it is covered by a dense forest of pine and spruce. The approach from the Arkansas is exceedingly gradual, and the summit is broad and easily TOPOGRAPHY. 313 drained. On the Eagle the grade is somewhat sharper for a short distance, but can be overcome with little difficulty. The natural drainage on this side is more imperfect than on the other, and can be remedied only by care- ful working. The low elevation of this pass and the ease of its approaches have made it a favorite with railroad engineers. Its main drawback is, that the region of the Upper Arkansas, for fifteen miles below the pass, is com- pletely closed by snow early in the winter, and so remains until late in spring. Trails cross the divide at the heads of Lake, Cottonwood, and Chalk, as well as of several other creeks. These can hardly be called passes. They owe their origin to mountain sheep, and have been used to some ex- tent by the Indians. At the three localities given above, one can cross without much risk to life and limbs, and, this being possible at few points in this division, they are regarded by prospectors and explorers as quite feas- ible passes. The crossing at Lake Creek is reached with some difficulty through a bad morass on the Arkansas side, and is so abrupt near the sum- mit that a pack-mule with a light load can climb it only by painful effort. On the opposite side it leads, with a grade almost impracticable for horse and rider, to a tributary of Taylor River, the chief fork of the Gunnison. The trail is so difficult and abrupt that to construct a wagon-road seems almost impossible. At the summit, which has an elevation of 12,237 feet, the divide is exceedingly narrow. The source of Lake Creek is a little pond, with, in August, an area of about fifty square yards, which is sepa- rated by a wall of rock, about 5 feet high and 20 feet wide, from a similar pond which is drained into Taylor River. It is quite probable that these ponds, greatly enlarged by the melting of the snows, communicate with each other during June by means of numerous fissures in the rocky wall which separates them. The so-called passes of Chalk and Cottonwood creeks are wholly undeserving of notice, being almost impracticable for foot-passen- gers. The summit of the Cottonwood trail is nearly 13,000 feet above the sea, and that at the head of Chalk Creek but little superior to it. The third division consists of irregular, comparatively low mountains, seldom attaining an altitude of more than 12,000 feet. It separates the waters of the Gunnison from those of San Luis Lake or Swamp, which in 314 GEOLOGY. a previous epoch was undoubtedly connected with the Rio Grande. This portion of the divide, as seen from the west, shows an evenness of crest, quite remarkable in the Rocky Mountains, and reminds one of the Appala- chian ridges in the Alleghany division. The mountains may be crossed without much difficulty at many points, but the only pass employed is the Cochetopa, leading from a tributary of Saguache Creek to Pass Creek, which empties into the Gunnison River, through Cochetopa and Tomidgee Creeks. It is very low, having an altitude at the summit of little more than 10,000 feet, and is open throughout the year. The approaches are exceed- ingly gradual, there being abrupt grades in no part, and in this respect it is superior to any pass yet referred to. Except the Hoosier and Hamilton, it is the only pass with easy grade really available for a wagon-road, as it reaches into an extensive district of open country, practicable for wagons. Through this pass the Gunnison wagon-road was run in the year 1853. The fourth division extends westward as the north wall of the Rio Grande Cafion, and as a divide is very narrow. Until near the head of the river the crest is quite regular, much torn by erosion, but easily accessible at very many localities from the north side. Its altitude is very great, there being at the head of Cochetopa and Lime Creeks a group of high peaks, among which a rounded knob with an elongate summit reaches to 13,700 feet, and others more peaked, farther west, reach 14,000 feet, while at the head of the Rio Grande, Middle Fork, there are several jagged peaks rising to an altitude of not less than 13,500 feet, and to the north and south some miles, groups reaching 14,000 feet. As by far the greater portion of this division lies within the Indian reservation, no passes other than trails exist. There is, however, a well-marked Indian trail leading from the agency across the divide to Antelope Park, on the Rio Grande, fifty miles above the city of Del Norte, situated at the mouth of the cation. This is not diffi- cult for pack-animals, and was formerly an important trail leading from the Gunnison River to the Rio los Pinos and the Pagosa Hot Spring in the San Juan area. At the head of the Rio Grande, Middle Fork, and at the end of this division, is the wagon-road pass now followed to the San Juan mining district. The summit has an altitude of 12,400 feet, rendering this one of the highest passes in the Rocky Mountains. Indeed, nothing but dire TOPOGRAPHY. o15 necessity leads to its use, for it is closed by snow from the beginning of November until late in June. From the Rio Grande it is reached by very difficult approaches, continuing for several miles; so difficult that, if one may judge from the numerous wrecks by the way, they are almost impracti- cable for wagons. On the western slope, leading to the Rio de las Animas, a tributary of the Rio San Juan, the condition is still worse, for the road descends more than 2,000 feet within one mile from the summit. Wagons are let down by ropes wound around the trees. Notwithstanding these serious drawbacks this pass will probably be used as long as the mines can be made attractive, as itis many miles more direct than any other route from Del Norte, the immediate point of supply. The fifth division forms the southern wall of the Rio Grande Canon, and in all respects resembles the last. It is exceedingly abrupt on the face toward the river, but has more gradual slopes southward. The only trails across it are a continuation of the one already mentioned as leading from the Indian agency to the Rio los Pinos and the Pagosa Springs, which being over a comparatively low pass, has been found available for pack-animals, and has been employed by trains going to Animas Park on the river of the same name, and another almost in disuse, leading from the Upper San Juan to the South Fork of the Rio Grande. The fifth division merges into the sixth, which, beginning near the head of the so-called South Fork of the Rio Grande, follows an irregular south or west of south course to the line of New Mexico, where it turns to south of southwest. For a considerable distance, indeed to near the New Mexico line, it coincides with the mountains called the San Juan, and separates the waters of the San Juan River from those of the Rio Grande. Beyond that line it is lower, and separates the Rio Chama, a tributary of the Rio Grande, flowing on the west side of the San Juan Mountains, from the Rito Navajo, an important tributary of the Rio San Juan. At the north, it reaches to a great altitude, and is very rugged in its western slopes, but followed south- ward it diminishes in importance, breaking down into table-land as it crosses the line into New Mexico Within the limits of Colorado there are no true passes over this por- tion of the divide. The mountains have been crossed from San Luis Valley 316 GEOLOGY. to the headwaters of the Rio San Juan, but only once, the difficulty being so great as to prevent repetition of the attempt. In New Mexico, not far beyond the line, an excellent pass leads from the Rio Chama to the Laguna de los Caballos, and is known as Horse Lake Pass. Itis very low, and the grade is almost imperceptible. It is crossed by the old wagon-road leading from Animas Park to Abiquiu, N. Mex., which coincides mainly with the homeward trail of Capt. J. N. Macomb, Corps of Topographical Engineers, in his expedition of 1859. Divide between the Arkansas and the South Plaite—This divide is very narrow and in many portions quite intricate. Beginning near Mount Lin- coln it follows a southerly course to the summit of Trout Creek Pass, a dis- tance of twenty-eight miles, beyond which it is deflected eastward, and has a south of east, then east, trend until it passes beyond our eastern limit upon the plains. The first division forms the western boundary of South Park. The general slope toward the park is quite regular, but the numerous streams tlowing into the South Platte have their sources in huge cul-de-saes near the central line of the divide. On the Arkansas side the slope is abrupt. At the north, the crest is quite irregular, with several sharp peaks rising far above timber-line. Mounts Mary and Sheridan are rude cones, with an alti-_ tude of 13,900 and 138,850 feet, respectively, while in the immediate vicinity are Goat Peak, 14,100 feet, and Fourth-of-July Mountain, 13,600 feet. Southward from these the crest is quite even until it reaches Buffalo Peak, its altitude being about 13,000 feet. Buffalo Peak consists of two great humps, 13,329 feet high, dome-shaped as seen from South Park, but having on the northern side an enormous gash, with walls almost vertical and rising 2,500 feet from the bottom. Though quite regular in outline, its ascent is much more difficult than that of many of the more rugged peaks on the other side of the Arkansas. The passes over this division are quite numerous. Mosquito Pass ascends the ridge from a deserted village of that name and reaches the Arkansas water, near Oro City, at the head of California Gulch. It is of little value, and is seldom used, as its grades are difficult even for pack- animals lightly loaded. Its altitude at the summit is 13,308 feet. The TOPOGRAPHY. 317 ordinary route of communication between South Park and the Upper Arkansas is via the Stony Point or South Fork Pass, over which a good wagon-road has been constructed. From the east, it is reached by a com- paratively easy grade along the South Fork of the Platte, through a romantic cation, but the descent on the Arkansas side is very rapid. The summit, with an altitude of 12,108 feet, is closed ordinarily for several months, but that it can be kept open throughout the year was proved in the early days, when ten thousand men were engaged in gold-washing at California and Colorado gulches, on the Arkansas. The best pass is the Trout Creek Pass, which leads from the Arkansas up Trout Creek to its head, and descends thence into South Park, entering it not far from the Salt Works. The grade throughout is very easy, and the altitude at the summit is only 9,612 feet. It is an excellent wagon-road pass, and may yet be utilized for rail- road purposes. The second division begins a few miles south from Trout Creek Pass and extends to the main easterly range of the Rocky Mountains. It is the southern boundary of South Park, and so irregular in direction as to be defined only with much difficulty. It consists of low, rounded or rudely conical hills, seldom reaching to timber-line, yet ordinarily bare of trees, with numerous little areas of undulating surface called parks. Through these, the tributaries of the Platte and Arkansas wind about in the most perplexing manner. No peak in this portion of the divide attains consider- able height, though two of them are very conspicuous, owing to the low altitude of their surroundings. Basalt Peak, between Thirty-one-Mile Creek, Buffalo Slough, and Badger Creek, is a curiously eroded hill, a frag- ment of the great sheet of eruptive rock formerly covering the entire region. In shape, it is an inclined plane, sloping westward, but with precipitous sides toward other points. It is over 11,000 feet high, and is a topographi- cal station of much value. Thirty-nine-Mile Mountain, at the head of Cur- rant Creek, a tributary of the Arkansas, is a cumbrous mass of trachytes and volcanic breccias, whose altitude was not determined. Across this divide is a wagon-road leading from the South Platte by way of Buffalo Slough to the head of Currant Creek and thence to the Arkansas River. The pass is very low and is open during the greater por- 318 GEOLOGY. tion of the year. It is, however, by no means a satisfactory one, as the structure of the country renders swamps a common feature, while the abso- lute sameness of the scenery for miles would make it difficult to follow the road, were there merely a few inches of snow. From Thirty-nine-Mile Mountain eastward the divide is exceedingly complicated, taking in the line across the front range of the Rocky Mount- ains, and reaching as a high ridge covered with timber far out into the plains. In this portion of the divide there are no high peaks, though both north and south of it there are several of great altitude. The passes are the Ute, Hayden’s, and Cherry Creek. The crossing at the head of Cherry Creek is quite easy, being approached by very moderate grades. The summit is broad and exposed, so that it readily catches the snow, and is said to be one of the coldest localities east of the mountains. Divide between the Arkansas and Rio Grande.—This divide, the Sangre de Cristo Mountains and Spanish range, extends southeast from Poncho Pass beyond the southern boundary of Colorado. In its northern portion, from Poncho to Sangre de Cristo Pass, seventy-five miles, this range, m average altitude, sharpness of outline, and general impressiveness, is scarcely inferior to that on the west side of the Arkansas above. In some respects it is better defined, rising abruptly from the Wet Mountain Valley on one side, and from San Luis Valley on the other. The crest is irregular, deeply serrate or cleft into many fine peaks, which retain their individuality to below timber-line. Coalescing, they thrust into the plain long, narrow, bench-like tongues, separated by trough-like ravines, heading far up in the mountains, and usually closed in front by heaps of talus. Through these heaps narrow cafions have been torn by streams flowing in the ravines. The range is narrow, not more than twelve miles wide, but some of its peaks are of magnificent proportions. On the Rio Grande side, and over- looking Sangre de Cristo Pass, is the group called Sierra Blanca, of which the most conspicuous is Old Baldy Mountain. This is a naked mass of eruptive rock, reaching beyond 14,000 feet, a grand landmark, visible for many miles north and south. Beyond Sangre de Cristo Pass the range is much lower, though some of its peaks, as the Trinchara and Culebra Peaks, attain to nearly 14,000 feet altitude. TOPOGRAPHY. 319 The passes across this divide are quite numerous, but with two excep- tions they are seldom employed. Poncho Pass, leading from the Arkansas to the head of the Rio San Luis, is a broad low pass, and is one of the best in this whole country. It has an elevation of only 8,900 feet at the sum- mit, and is crossed by an excellent wagon-road. The Sangre de Cristo Pass leads from a branch of the Huerfano River, a tributary of the Arkan- sas, to a branch of the Trinchara, a tributary of the Rio Grande. Its alti- tude at the summit is 9,600 feet, and itis said to remain open during the winter, there being seldom more than two feet of snow. It is crossed by a wagon-road which follows the natural grade. At some points this is difficult for a short distance, but could be improved easily and at slight expense. The Mosca and Sand Hill Passes are lower than either of these, but are impracticable on account of the heavy sand-hills which: obstruct them on the western slope. Subordinate divides—As several of these will be referred to frequently in the following pages, it is best to give some details respecting them here, in order to avoid repetition. The Kenosha range, forming the eastern boundary of South Park, divides the North Fork of the Platte from the river. It is a bold, rugged range, and joins the main divide a few miles east from the Jefferson Pass. Near its northern extremity it is cut by Tarryall Creek, a tributary of the North Fork, and at the southeastern corner of South Park it is broken by * the South Platte, which there has worn a magnificent cation. For the greater portion of its length the range is badly broken into ridges, and is impassable for even unloaded animals; but near its northern extremity it is crossed by the Kenosha Pass, leading from South Park to the village of Grant. This, though attaining an elevation of 10,200 feet, has compara- tively easy approaches on each side, and is on the direct road from Denver to South Park. Four or five miles north from the Platte Canon the range is crossed by the road to Colorado Springs, which has easy grades through- out. The altitude of this range is not great, and few of the peaks rise beyond 12,000 feet. Followed southward, this range becomes the Hard- scrabble or Greenhorn Mountains, and terminates almost northeast from the Sangre del Cristo Pass. This portion separates Wet Mountain and Huer- 320 GEOLOGY. fano Parks from the plains, and is cut by the Arkansas River and Grape Creek, these streams uniting at the mouth of the cation above Camion City. The Blue River range, as it is locally termed, is merely the extension northward of the western boundary of South Park, and derives its local name from the fact that the Blue River flows along its eastern base. It begins at the head of Blue River in the Quandary Mountain, which is but 150 feet lower than its neighbor, Mount Lincoln, with which it was formerly one. The general trend of the range is nearly north 12° west. In its southern portion, where it forms the divide between Blue River and Ten- Mile Creek, it is a rugged, unbroken mass, showing a comparatively easy slope on the east, but jagged and abrupt on the west. Beyond the junc- tion of Ten-Mile Creek and Blue River it gradually breaks into individual peaks of great height and abruptness, the whole apparently increasing in these characteristics northward within our limits. The most prominent peak of this range is a massive, dome-shaped mountain, not far below the junc- tion of Ten-Mile Creek and the Blue, which has been called Colorado’s Skull in honor of a Ute chief, who, with a small band of followers, infests North and Middle Parks. Unfortunately, the only available path to its summit was choked with snow at the time of our visit, and any attempt to climb it would have been not only hazardous but fool-hardy. Its height, therefore, is still undetermined. Over this range no satisfactory pass has been found within our area. A trail leads from Breckenridge on the Blue to McNulty’s Gulch on Ten-Mile Creek. It is very difficult even for lightly- laden pack-animals, and_is now little used. Tue Strreams.—The South Platte River—This stream has its source in two small lakes in a magnificent glacial amphitheater directly under Mount Lincoln. It follows a southerly course for eight or ten miles through a broad, deep gorge, between Mounts Lincoln and Bross on the west and Mount Morton on the east, and enters South Park near the village of Fair- play. From that village the course is southeasterly until the river reaches the Kenosha range, where it enters a close caton. There it turns toward the northeast and holds that direction somewhat rudely to the plains, after which its course is more toward the north until it passes beyond our north- ern line. Above Fairplay it receives several strong tributaries, and at or TOPOGRAPHY. 321 near that village it is joined by a number of small streams, so that it is at once a river of much importance. Twelve miles below Fairplay it is still further increased by the addition of the South Fork, which has its origin in several small streams far up in the divide at the west. Below this, within the park, a few other tributaries are seen, but they are very insignificant. e The North Fork of the South Platte lies wholly without the park, sepa- rated from it by the Kenosha range. Rising under Evans and McClellan peaks, this stream follows an east of south course for several miles, when, turning more sharply to the east, it enters a cation and soon after empties into the main stream. Its principal tributary is Tarryall Creek, which rises in the Hamilton Pass and breaks through the Kenosha range. The North ‘Fork carries little less water than the main stream itself. East from the foot- hills, along the east face of the range, the tributaries of the South Platte are numerous, but for the most part comparatively insignificant, until we reach Clear Creek, which enters the river near Denver. Of this the South Fork has its source in several large streams, rising under Gray’s Peak and McClellan Mountain, and uniting near Georgetown. Thence the stream flows through a most magnificent canon to the plains. The North Fork lies without our area. The Arkansas River rises in an enormous gorge, directly adjoining that of the South Platte, to which it bears great resemblance. The river flows southwestwardly for about ten miles to its junction with Tennessee Creek, after which the course is about south of southeast through a succession of broad, alluvial plains, separated by canons, until it reaches the mouth of the South Arkansas. Then it turns to south of east, and retains this general direction until it passes beyond our line on the plains. This portion of its course is simply a succession of cations, first through the range forming the western boundary of South Park, and afterward through the Greenhorn Mountains and their spurs. In its upper portion the Arkansas receives many tributaries. Those from the east are for the most part insignificant, as the divide is narrow, but from the west flow down Tennessee, Willow, Half-Moon, Lake, Cottonwood, and Chalk Creeks, and the South Arkansas River, all of them large streams, and carrying much water throughout the year. In the second portion of 21Ws a22 GEOLOGY. its course it receives few accessions until it reaches the great cation extend- ing to somewhat more than twenty miles above Canon City. Near the western extremity of this canon it is joined by Badger and Currant Creeks from the north, and by Texas and other smaller creeks from the south, while at the mouth of the cafon, Grape Creek enters it, having come from Wet Mountain Park at the south, and broken through the Greenhorn Mount ains. A number of petty tributaries, of which Oak and Hardscrabble Creeks-are least insignificant, are added to it below Canon City, while at a considerable distance beyond our eastern limit it is joined by the Huerfano River, which rises in the Sangre de Cristo Mountains, and flows out to the plains at the southern extremity of the Greenhorn Mountains, and by other | tributaries, such as the Apishpa, Purgatoire, and Fontaine qui Bouille, head- ing in our area. The Rio Grande del Norte rises about eighty-five miles west from the town of Del Norte in the San Luis Valley. In relation to this matter the knowledge of settlers seems to be somewhat indefinite. In 1849, Captain Frémont ascended the river to Antelope Park, about fifty-six miles from Del Norte, and there met with the disaster which put an end to his explorations in that direction. Up to that park the river is generally known as the Rio Grande. Above it, about twenty-two miles, the stream is seen to be formed by the union of three forks. The Middle Fork is known as Deep Creek, and, being regarded as the main fork, this name has been retained for the river to its entrance into Antelope Park. The Rio Grande, however, really be- gins at the junction of the forks about sixty-eight miles above Del Norte. The Middle Fork is not the main fork, for the greater body of water evidently comes down by the North Fork, or Pole Creek, which rises near the Un- compahgre Mountains, and not far from the head of the Rio de las Animas. Deep Creek rises near the wagon-road pass, already described as leading to the San Juan mining district. The South or Hines Fork carries much water, but is not very long, as the divide on that side is quite narrow. These streams all flow in deep, dismal cafons, cut out of eruptive rock, which unite to form a stupendous canon, extending quite to Antelope Park. Below the park the river flows through an excavation, bounded on both sides by high mountains, and varying in width from three hundred yards to TOPOGRAPHY. one almost a mile, until a few miles above Del Norte, where the valley widens out as it enters the Great San Luis Valley. In this portion its tributa- ries, with the exception of the South Fork, which drains a considerable area, are unimportant. After reaching San Luis Valley the river turns sharply toward the south, and retains that course until it passes beyond our southern limit. Here its branches are very numerous, coming from the Sangre del Cristo and Spanish ranges on the east, and from the Sierra San Juan on the west. From the former the Rio Trenchara flows out near Fort Garland, being formed by a number of small streams rising in or near Sangre del Cristo Pass. A few miles farther south the Rio Culebra, formed by the union of “many insignificant rivulets, breaks through a mesa-like wall, separating its park from the valley, and enters the Rio Grande not far from the mouth of the Rio Trinchara ; while on the boundary of New Mexico the Rio Costilla, a petty stream, is the last tributary from the east. From the west we have the Rio Alamosa and the Rio Conejos, both large streams, rising far up in the high and rugged Sierra San Juan, and following exceedingly tor- tuous courses from their headwaters to the Rio Grande. On the west side of the Sierra San Juan, at a short distance south from the Colorado line, the Rio Chama drains the whole country east from the Horse Lake, and follows a rudely southeast course until it enters the Rio Grande in New Mexico. _ In the northern portion of San Luis Valley there is a small area con- taining numerous streams which have no true outlet. The main streams are the Rio San Luis and Saguache Creek, both large and carrying much water, which empty into the swamp or “sink” termed San Luis Lake. Numerous petty creeks issue from the mountains on each side, but of these, few reach the streams mentioned, as, at a short distance from the mountains, they sink in the sand. This interesting district, formerly joined to the Rio Grande, will be fully discussed in another connection. Leaving now the streams which flow on the Atlantic slope, we come to those on the opposite side, and first review the complicated net-work in the great area of the Grand and Gunnison. The Grand River lies wholly with- out our boundaries, and of the Gunnison we have not more than fifteen, or, at most, twenty miles. We have to deal, theretore, with their tributaries. 324 GEOLOGY. The streams emptying into the Grand have a northward course, while those tributary to the Gunnison flow in a southerly or westerly direction. The Blue River rises under Quandary Mountain, almost within stone’s throw of the headwaters of the Arkansas and Platte, and flows in a north of northwest direction, at the base of the Blue River range, until passing beyond our northern line it enters the Grand River near Gore’s Pass. It is a rapid stream, and receiving many accessions, is barely fordable at Breck- enridge, eleven miles from its source. Below that village it is further in- creased by Swan River, rising in Georgia Pass, and by Snake River coming from Peru, under Gray’s Peak, and from Saint John’s, under Glacier Mount- ain. On the west side it has many larger tributaries, of which Ten-Mile Creek is, perhaps, the most important. The East Fork of Ten-Mile Creek begins in a small crateriform cavity overlooking the Arkansas at the Arkansas Pass. It flows in a northerly direction, and breaks through the Blue River range, cutting a magnificent cation from which it issues to join Blue River. The West Fork comes in about ten miles from the Arkansas Pass. It is a stream of small importance, flowing almost east. It heads near the North Fork of Eagle River in a mo- rass, which crosses the almost imperceptible divide between the two streams. Though this morass crosses the divide there can be no doubt that the june- tion is merely superficial, and that the water of the summit does not pass indifferently into either stream, except, perhaps, by capillary attraction through the matted layers of vegetable matter forming the crest. The fall of the North Fork of the Eagle for the first six miles is nearly 250 feet per mile, and for the next sixteen miles about 70 feet per mile. This rapid descent has induced the formation of a very close cation, which, with occasional openings, continues to the junction with the South Fork, a distance of about twenty.-three miles. The latter stream rises in a group of glacial excavations nearly west from Tennessee Pass, and flows north and northwest to the junction with the North Fork, after which the stream flows west of north. Like the North Fork, this is a large stream, with rapid de- scent, and its course is marked by several cations of great depth. The Roaring Fork of the Grand River heads against the main divide near Red Mountain, and in the Elk Mountain group near Mount Whitfield, TOPOGRAPHY. 325 in a number of magnificent gorges, or rather culs-de-sacs, from each of which flows a litile stream, cutting for itself a deep catton. These unite to form one broad, deep canon, through which the main stream flows in a north, and afterward in a northwestward, direction. Almost due west from the head of Roaring Fork, at a distance of not more than ten miles, we find the headwaters of Rock Creek, another tributary of the Grand River. This stream for the first eight miles has a fall of 300 feet per mile, and at one mile from its source enters one of the most remark- able canons in this area, which continues for six miles, and afterward opens into a narrow plain beyond the extreme western limit of our district. ; The remaining streams in our portion of this area are tributary to the Gunnison River, which is formed by the union of Taylor and East Rivers about fifteen miles above the Indian stock ranch. Taylor River is formed by several small streams, each about five miles long, which unite directly under the main divide about south of west from Twin Lakes. It flows through an open park for about nine miles, and there enters a narrow and with difficulty passable cation, which continues for nearly sixteen miles to the junction with East River. The tributaries of Taylor River are very numerous, and before reaching its cafon it is a stream of much importance. East River, the other fork of the Gunnison, rises near Rock Creek, and has an east of south course to its junction with Taylor. For the most part it flows through a broad, open plain, has a fall of about 25 feet per mile below the union of its forks, and carries a by no means inconsiderable body of water. West from East River, and entering the Gunnison about eleven miles below the junction, is Ohio Creek, an important stream, flowing through a very broad and rich plain. It comes from the northwest, and has its source beyond our western limit. The principal tributary of the Gunnison from the east is Tumichi Creek, which enters the river about one mile below the stock ranch. It is an important stream and drains a large section of country. Its northerly fork is almost parallel with Taylor River, and flows through a similar canon for twelve miles. The southern fork rises not far from the headwaters of the South Arkansas and joins the other near Tumichi Dome, a round mount- 326 GEOLOGY. ain about thirteen miles from the Gunnison. Nearly three miles below the junction, Cochetopa Creek comes in from the south, draining an immense extent of country, almost the whole of Division No. 3 of the main divide. It is, however, a stream of small importance, owing to the absorbent nature of the soil through which it flows. It is formed by the confluence of a vast number of petty streams near the Indian agency, and is little more than twelve miles long. The San Juan River rises in Division No. 5 of the main divide, and flows in a southerly direction until it crosses the New Mexico boundary, beyond which it soon turns to the southwest and then to the west. In Col- orado the San Juan is a stream of rapid flow and carrying a by no means inconsiderable quantity of water. It receives no noteworthy accession from the east until near the line of New Mexico, where it is joimed by the Rio del Navajo, a stream of moderate size, rising in the Sierra San Juan, and flowing in a south of west direction. Westward, however, we find several streams of importance, all flowing from the north and rudely parallel to that portion of the Rio San Juan which is in Colorado. The first of these is the Rio Piedra, a large, rapid stream, and scarcely inferior to the San Juan. Besides its two main forks, its only tributary is the Rio Nutria, which comes in from the east, the course of which is very irregular, but for the most part southwest to its junction with the Piedra near the territorial line. The width of its bed and the numerous ravines seen along its course are evidence that at some seasons of the year it is a comparatively rapid stream, but in autumn and most probably during the latter part of summer it is quite dry. This is due to the rapidity of its fall, as well as to the fact that its drainage area is small. The Rio de los Pivos, about fifteen miles west from the Rio Piedra, is somewhat larger than the latter, and flows through a broad, rich valley. The next stream is the Rio Florida, a branch of the Rio de las Animas, and of not great importance. The Rio de las Animas is much larger than any of those yet mentioned. It is a bold, rapid stream, rising near or in the Uncompahgre Mountains, not far from the North Fork of the Rio Grande. It follows an almost due south course through a succession of wonderful but small parks and impas- CLIMATE AND AGRICULTURAL RESOURCES. 327 sable canons to the Rio San Juan, which it enters in New Mexico. The scenery along this river is unequaled by any observed elsewhere within our district, and will be discussed in another connection. SECTION II. CLIMATE AND AGRICULTURAL RESOURCES. The mountain region of the Arkansas and South Platte areas affords little opportunity for agricultural operations, and the same is equally true of so much of the Grand and Gunnison area as is embraced within the lim- its of our survey. The land is sufficiently fertile and the supply of water for irrigation is ample, but the climate is so harsh that the cultivation of even the hardiest garden vegetables is exceedingly uncertain everywhere. In South Park the air is pure, but during the agricultural season the climate is by no means mild or dry. During the day the thermometer frequently shows a range of 40°, diminishing rapidly after sunset, ren- dering heavy clothes and a good fire essential to comfort at all seasons of the year. Observations made in the southern and lower portion of the park on the last three days of July, 1873, showed a temperature of 26°, 28°, 28°, respectively, at sunrise, while at 2 o’clock on the same days, the mercury varied little from 70° in the shade. Heavy rain fell on six of the twelve days during which we were engaged in the park or its outlying valleys, while on two days large hail accompanied the rain, and on two other days snow fell to the depth of one inch. Notwithstanding the great fall of rain, the air is by no means saturated with moisture, there being sometimes a difference of 20° between the readings of the dry and wet bulb thermometers. Heavy dew was deposited during eight of the twelve nights, but disappeared quickly after sunrise. The winters are long, but not con- tinuously severe; the thermometer seldom falls below zero, and over the greater portion of the park snow rarely falls to a depth of more than two feet. The change from summer to winter and from winter to summer is -very abrupt. The average altitude of the park is between 8,500 and 9,000 feet. 398 GEOLOGY. Owing to the great and sudden variations in temperature, due, doubt- lessin part.to the comparative dryness of the atmosphere, South Park is much disturbed by high winds, which descend from the cold mountains to the heated plain. The sky is usually more or less cloudy during July and August, and the mountains are rarely altogether free from clouds. As might be expected, this park, having an area of not far from nine hundred square miles, and hemmed in by high mountains, afforded excellent oppor- tunities for determining the effect of mountains upon the course of storms. These usually began at the southwest corner and followed the rim entirely around, the sky over the park being only partially overcast. With but one exception no rain fell within the park until the storm had passed around the border, following the mountains, and had reached the low divide at the south. The northeastern portion of the park is well watered by Tarryall Creek and its tributaries, but is so poorly drained that much of it is a treacherous marsh covered by a dense growth of coarse grasses. South from Tarryall Creek to the southern border, the eastern portion is almost without water, and consequently destitute of vegetation. Some white sage is seen, but so -dwarfed as to resemble a moss; a small flowering plant occasionally occurs, but the only plant which seems to flourish is the melon cactus, which, how- ever, does not attain large size. On the western side of the park, where streams are very numerous, native grasses grow abundantly upon the “ bot- toms,” and in moderate quantity upon the higher ground. In the southern portion, and on the divide, the grass is most luxuriant, growing in bunches 18 to 20 inches in diameter, and occasionally matting over the surface so as to render traveling difficult. The many ravines in the mountains show little parks or meadows, covered with grass, which prove very valuable for winter pasture. The only trees in South Park are cottonwoods, pines, and spruces, whick cover the little hills, and stretch far up the mountain sides. The timbe: line varies only from 11,200 to 11,500 feet, being higher on the northen. side of the mountains. Above that line, no trees exist, but a scraggy pine, usaally prostrate, reaches in small clusters sometimes to 200 feet beyond. The cottonwoods are almost as hardy as the spruces, and thrive well up to CLIMATE AND AGRICULTURAL RESOURCES. 329 within 1,000 feet of the timber line. Wherever the pines and spruces have been burned off, the cottonwoods have replaced them, having overcome the slowly-developing conifers by their rapid and vigorous growth. It is by no means probable, as some have supposed, that the cottonwoods were the original possessors of the soil. Their seeds being provided with a pappus, are carried by the wind and deposited in the open space, where they rapidly develop. Along the streams of South Park there are willows, birches, and alders, small swamp species. For the most part the soil is very porous. In the southern portion of the park it is undoubtedly alkaline, for there are frequent white patches, containing much saline matter, which bear no vegetation, and when well wet are, to all intents and purposes, bottomless. In most portions it is very good, though light and absorbent. This property, combined with the rapid evap- oration which goes on in the sunlight, renders necessary a very abundant supply of water to render it productive. An interesting illustration of this is found on the low divide at the south, The low, broad, rounded hills of the divide in no case reach to timber line, yet in nearly every case they are entirely bare of timber. The exceptions are those hills whose slopes are steep so that the northern side is protected from the sun’s rays. On that side small trees are found reaching quite to the summit, the porous soil, unaffected by the intense heat of the day, retaining the moisture, and yield- ing it to the trees. For purposes of irrigation the supply of water in South Park is practically unlimited everywhere, except along the eastern border, where the streams are few and very small. Still the advantage of irrigation is questionable. For ordinary farming purposes South Park is worthless. Not even the hardy garden vegetables ean be raised, potatoes being cut down by the July frost. Along the North Fork of South Platte, and on Tarryall Creek in the Kenosha range, potatoes have been cultivated successfully at several localities, and oats have been known to ripen. These crops, however, were obtained, not in the park, but beyond its eastern limit, and at an altitude of 1,200 to 1,500 feet below the lowest point in the park. The only use to which South Park can be put is the pasturage of stock. During the summer, cattle feed on the grasses which grow on the bottoms, in the autumn on the bunch grass of the 330 GEOLOGY. bluffs, while in winter they’ disappear in the mountains, where they find abundance of food in the little meadows or parks already referred to. The area of summer pasture can be greatly increased by irrigating the bluffs, but if the number of cattle were larger than now, winter feeding would be necessary, as the winter range in the mountains is limited. At present stock raising is very profitable. Whether or not it would bear the addi- tional expense involved by irrigation and winter feeding is questionable. In this connection it is well to note that the native grasses found throughout this Rocky Mountain region are by no means as valuable as the domestic erasses of the East. They are not less nutritious, but do not bear continued cropping. Growing, too, in bunches, and ordinarily forming no mat upon the loose soil, they are easily tramped out. The result is that great “ranges,” formerly supposed to be capable of supporting an indefinite number of cattle, have become exhausted. This, I understand, is now the condition of one of the finest portions of South Park. Under such circumstances the cattle are removed to some distant locality, and in about five years the grass is in a measure restored. ; Along the line of South Clear Creek and its branches, agriculture may be regarded as impossible. The cafons of these streams are tod narrow to afford room for farming, while, aside from these, the whole country is irreg- ularly mountainous, with an average elevation of little less than 11,000 feet. At Idaho Springs potatoes have been raised successfully, but every other article of consumption, even hay, must be brought in from the plains east of the mountains. In the Arkansas area, within the mountain region, there is much varia- tion in climatic conditions, owing to the extent of the area, and the difference of altitude. Even in the upper portion, extending from the junction of the river and Tennessee Creek to the mouth of the South Arkansas, the rapid fall of the river induces well-marked differences in agricultural condi- tions. This portion consists of two subbasins, the upper reaching from the ; mouth of Tennessee Creek to the Granite Cation, a distance of about seven- teen miles, and the other extending from the mouth of that canon to the cation below the South Arkansas River. In the larger part of the upper basin, which is broad, and coyered with a fairly-rich soil, agricultural pur- CLIMATE AND AGRICULTURAL RESOURCES. 331 suits are impracticable, as the surface is usually deeply buried under snow for about six months each year, and occasionally for a longer time. The snow ordinarily disappears about the beginning of June, and keen frosts occur early in September, giving a brief season of less than three months, during which frosts are almost unknown. The change from winter to sum- mer is very abrupt, so that the more rapidly-growing vegetables can be raised with good success. Mr. Dumary, living at the mouth of Colorado gulch, near the upper end of the basin, states that for a number of years he has succeeded in raising turnips, lettuce, radishes, and onions in considerable quantity. He has several times endeavored to raise oats, but has found the season about two weeks too short. The grass in this region is good, though not abundant, and little has been done in stock raising. Mr. Dumary, how- ever, had, at the time of our visit, one hundred head of cattle, which were evidently thriving. He thinks that this would be a good summer range for ten times that number. During the winter, cattle must be sent to the lower basin, or driven out upon the plains. Toward the lower portion of this basin the climate is milder, there is less snow, and the season is somewhat longer. The difference in elevation is not sufficient to account for the diminished rigor, and evidently is not the only cause, for at Twin Lakes, on Lake Creek, emptying into Granite Cation near its head, we find at an altitude of 9,300 feet a much milder climate than at Colorado gulch. The difference in altitude is very little, while the difference in latitude is barely one-fourth of a degree. Yet at Twin Lakes it is possible to cultivate the more tender garden vegetables, and the fall of snow is not sufficient to incommode seriously the family living on the lake shore. In the lower basin, the country is open throughout the year. Some snow falls, and the thermometer occasionally indicates a very low tempera- ture, but upon the whole the winter is mild, and cattle run during the season without shelter. The rain-fall in the basin is small, the clouds dis- charging chiefly upon the mountains on each side. The atmosphere is quite dry, but the daily variations are not so great or so abrupt as those in South Park. The high and numerous terraces on the west side of this basin interfere See GEOLOGY. much with its agricultural value. Fortunately, however, erosion has greatly removed these in several portions, so as to leave a broad, level plain as the main terrace, varying in width from two to four miles. The river flows near the eastern side and considerably below the plain, while the creeks from the mountains on the west, Chalk, Brown, Squaw, and Gas, have exca- vated deep, broad troughs in the basin on their way to the river. These troughs are several hundred feet wide, with a deep, rich soil, which yields excellent crops of wheat, and of nearly all the common garden vegetables. They are already cut up into small farms, which belong chiefly to persons engaged in stock raising. The plain itself presents a most forbidding aspect. For miles one sees not a single blade of grass, and the soil, is apparently too poor to sustain even cactus. But all it needs for reclamation is a plentiful supply of water. Some.adventurous ranchmen have tried the experiment and have been rewarded by crops of the most satisfactory character. The irrigation of the greater portion of this plain on the west side is a problem of no slight difficulty, owing to the fact that it is so much broken by deep troughs as to render transfer of water from the Arkansas by canal exceedingly expensive. The mountain streams themselves issue from their canons usually at a level below that of the plain, so that they are not imme- diately available. The southern portion can be irrigated without much difficulty from the South Arkansas, and two or three small creeks above can easily be utilized for the same purpose. The trouble is to water that portion between Cottonwood and Gas Creeks, and the only way to effect this seems to be by building flumes in the canons of Cottonwood, Chalk, and Brown Creeks, by which a sufficient supply could be brought into ditches on the plain. The cost of this work, however, will prevent any from attempting it until our population becomes very much denser than at present. On the east side the difficulty is not great; few streams come in from that side, and the plain can be irrigated readily with water drawn from the river itself. Through the canon beginning below the mouth of the South Arkansas, and continuing for nearly twenty miles, the river falls with great rapidity, so that at Pleasant Valley, between this and the great canon, the altitude is greatly diminished. In this little basin there are several good farms on the CLIMATE AND AGRICULTURAL RESOURCES. 333 lower terrace, which are irrigated by water obtained from the river or from Little Cottonwood Creek. Passing southward into the basin of Texas Creek, the character of the country is much changed. Hitherto we have had a dreary plain, destitute of vegetation and relieved only by the occa- sional troughs of mountain streams. Here, however, we have a broad basin, seven to nine miles wide, well watered by numerous streams flowing from the Sangre de Cristo Mountains, and supporting a good growth of grass. Texas Creek flows in a camion along its eastern side to the Arkansas, entering the great cafion a few miles below its head. Few ranches are found in the basin itself, though there are several in the broader portions of the cation, the selections having been made doubtless because of the greater ease of irrigation, as the fall of the stream is very rapid. Good farms, however, can be obtained in many places in the basin itself. : The divide between this basin and that of Grape Creek, or Wet Mount- ain Valley, is very slight, and so badly drained as to be a marsh of the most treacherous character. It is covered by rich grasses and can be used as pasture for cattle, but is dangerous ground for horses or mules. Wet Mountain Valley has many features in common with the basin of Texas Creek. The name was given because, during June, July, and August, each day a severe storm of rain, frequently accompanied by hail, breaks over the valley and extends into Huerfano Park at the south, as well as into the basin of Texas Creek at the north. These rains begin at about three in the afternoon and continue well on into the night. The lowest point in the val- ley has an altitude of 7,200 feet. The agricultural season is long, begin- ning early in May and ending in the latter portion of September. In sum- mer, the heat is intense during the day, but at night the temperature is moderate. The winter is mild, there being but little snow and seldom any extremely cold weather. Notwithstanding the great rain-fall, the atmos- phere is not heavily saturated with moisture, and traces of the storms disap- pear rapidly in the sunshine. The principal stream in this basin is Grape Creek, which receives a number of small tributaries from the Sangre de Cristo Mountains on the west, but no permanent ones from the Greenhorn Mountains on the east. From the south its only branch is Antelope Creek, a small stream carrying 334 GEOLOGY. no large amount of water, but having a somewhat rapid fall. The surface of this valley descends from all sides to the center, there being a succession of broken terraces, distinct on the southern and eastern sides, less so at the north and almost obliterated at the west. At the bottom there is a con- siderable area of land, probably sixty square miles, requiring no irrigation, having in some parts a surplus of water. The whole is a natural meadow of the finest character. Barley, wheat, and potatoes grow well and mature when not injured by storms or insects. No difficulty is caused by the fre- quent rains of summer, as the surplus moisture in most places is quickly removed by evaporation, but the hail is often fatal to the crops. From all accounts this valley is a favorite resort of grasshoppers, which do a vast amount of injury. At the same time, farming on the bottom has- proved reasonably successful. On the bluffs or terraces, and on the gently-sloping land surrounding the bottom, irrigation is essential, as the soil is so porous that the frequent rain-falls are of little positive advantage. These bluffs are far more exten- sive than the bottom; but, though covered by good soil, are so dry that they are almost destitute of grass, and support only the common species of cac- tus. This is especially true of the western and southern portions, where the soil is sandy with but little clay. On the eastern and northern sides the soil is richer and more retentive of moisture, being made up chiefly of detritus from the eruptive rocks of the Greenhorn Mountains. Unfortunately, the amount of water available for irrigation of these higher portions is very small. The streams from the Sangre de Cristo Mountains are of insignificant size and barely sufficient for the small farms adjoining them. Many of them are simply wretched sloughs 6 or 8 feet wide. South from Grape Creek the supply is derived from Antelope Creek, which, though not large, has sufficient fall and water to render it of much service in irrigation. On the east side there are no streams, which is the more to be regretted since there the soil is exceedingly rich and so retentive that only a small amount of water would be needed. Stock raising is an important occupation in Wet Mountain Valley, and one which has proved eminently successful. The rich grass of the bottom is supplemented later in the year by the bunch grass, which grows in CLIMATE AND AGRICULTURAL RESOURCES. 335 remarkable luxuriance in all the ravines of the Greenhorn Mountains open- ing toward the valley. In 1873, the number of cattle was estimated at twenty thousand, and many more were in the basin of Texas Creek. The opinion prevails that sheep driving is permanently injurious to any cattle range, and heavy penalties are imposed upon any who bring sheep into the valley. It is certain that sheep nibble the grass even with the ground, so that it revives with difficulty, and that where they do not crop it so closely they impregnate it with an odor which seems to be especially offensive to horses and cattle. This was our own experience, for our mules frequently refused to feed on excellent pasture, over which sheep had passed. Whether or not the injury to the range is permanent, is difficult to ascertain from the conflicting accounts of those interested. Crossing the divide at the south we descend rapidly into the basin of the Huerfano River, or Huerfano Park. Unlike Wet Mountain Valley, this is not a broad, open park. It undoubtedly was such at one time, as is amply evident from the almost uniform height and level surface of the bluffs. This old basin has been cut and eroded into broad, deep swales by the numerous streams, so that the area of arable land is considerable. The climatic con- ditions are similar to those of Wet Mountain Valley, except in this, that owing to the lower altitude and the sheltering influence of the bluffs, the seasons are more regular and the mean temperature somewhat higher. The soil is exceedingly rich, the supply of water for irrigation ample, and wheat and Indian corn mature well, yielding good crops. The inhabitants are mostly Mexicans, and are exceedingly negligent in their method of farm- ing. They raice much wool, but the quality is inferior, as the wed are mostly Mexican, unmixed with any other breed. In the Rio Grande area, the arable land is found principally in the aan Luis Valley. The numerous parks in the Rio Grande cafion are at too great an altitude for farming, and are useful only for grazing purposes. In San Luis Valley rain is almost unknown, and in winter only a thin coating of snow is ever seen. The houses are built of adobe, plastered outside with clay, and have no projecting eaves upon the roofs. During the long spring and summer the temperature is high. Winter sets in about the end of - October and practically closes in February. During this season the ther- 336 GEOLOGY. mometer occasionally marks excessively low temperature, but this condition seldom continues for more than two or three days. For the most part the weather is very mild, resembling the close of September or the beginning of October on the Middle Atlantic coast. The soil is rich throughout the valley, being simply volcanic sand and dust. Near the mountains it is somewhat too coarse for farming, but where it has been subjected to the sorting action of streams, it forms a soil which cannot be excelled. In the northern portion, in and around Saguache, is an old Mexican settlement, long celebrated for the fertility of its soil, which has recently attracted the attention of Americans, many of whom have entered it. This region is low, and, ‘to the eye, a perfect plain, almost level with the surface of Saguache Creek. Nothing can be simpler than irrigation here, for one need only plow a furrow from the stream through his land. This creek rarely overflows, and maintains a steady supply throughout the year. The excellence of the soil is shown by the fact that the Mexicans have frequently obtained thirty bushels of wheat per acre with their rude and careless modes of cultivation. Vegetables of all kinds thrive well, and Indian corn matures notwithstanding that the altitude is somewhat more than 7,500 feet. Hay ranches are numerous along the little streams issuing from the mountains, and occasionally a grain field is seen. The grain crops are not very satisfactory in most cases, as the Mexi- can proprietors are usually too lazy to do the preparatory work properly. In the southern portion of the valley there are numerous Mexican vil- lages situated along the tributaries of the Rio Grande, around each of which is a greater or less area of cultivated land. The soil yields readily, and the principal crops are corn, potatoes, and red pepper, these, with a little wheat, seeming to supply all the necessities of the inhabitants. Away from the streams the whole valley presents a very dreary aspect. There is no grass, and the vegetation consists only of the various plants grouped under the vulgar name of “greasewood,” with here and there a little sage brush. The many ravines along the water courses, especially those on the west side of the valley, are exceedingly important as cattle ranges. In some ot these the grass is remarkably fine. The little parks on the Upper Rio Grande, as already mentioned, support many cattle. Statistics can be pro- CLIMATE AND AGRICULTURAL RESOURCES. sor cured only with great difficulty, but the best information leads me to believe that more than twenty thousand head were in the valley during the autumn of 1873. The Mexican residents in the southern portion pay attention especially to sheep and goats. The result is that there the grass has been so closely clipped that the country resembles a desert. The sheep are still poor, but the rancheros are endeavoring to improve the stock by crossing with merinos. Labor being exceedingly cheap, wool raising proves quite as profitable and quite as easy as stock raising. On the westside of the. Sierra San Juan, along the Rio Chama, it is the chief dependence of the population, there being, according to the statement of the assistant agent at _ Tierra Amarilla, not less than two hundred thousand sheep within a radius of twelve miles from the agency. The wool is inferior, but the proprietors are making vigorous efforts to improve their stock. In the San Juan area no agricultural operations have been carried on for many years. Until recently the greater portion of this area, as embraced in our district, was within the reservation of the Ute Indians and inaccessi- ble to the whites. That which lay outside of the reservation has always — been regarded by the Jicarilla Apaches as their hunting-ground, and con- sequently was nota desirable locality for settlers. It is impossible, therefore, to give any satisfactory statement respecting its meteorology, the more so as we were prevented by snow from spending much time in this area. This region is well watered by large streams, flowing through broad, level valleys, covered with rich soil bearing a magnificent crop of native grasses. Where the influence of the streams is not felt, there is evidence that the country is agriculturally dry. On the elevated plain between the Rio Piedra and the Rito Nutria, there is little grass, but the excellence of the soil is amply attested by a wonderful forest of sage brush, averaging’ more than five feet in height. This growth is unequaled in our whole district, and is approached only by that on the terrace of the Rio Chama, near Tierra Amarilla, where the soil is so fertile that it has in one instance yielded eighty bushels of wheat per acre under Mexican cultivation. The climate in these broad valleys cannot be severe, for at Animas City, on the Rio de las Animas, no frost occurred until October 15. In Animas Park, a few miles below the “city,” the newly arrived settlers were making extensive 22Wws 338 GEOLOGY. preparations for farming, and it was expected that in 1874 nearly the whole park would be put under cultivation. Throughout this region the timber is magnificent. Along all the streams there were seen groves of white pine, in which the trees were one and one-half to two feet in diameter, and in similar groves were yellow pence two to four feet thick. No such timber was seen elsewhere. Fine grass, with wild rye and oats, is plentiful in nearly all portions of the area, so that the region will probably prove, as a stock country, worth fully all that the Government has agreed to pay the Indians for it. The sheep drivers, however, are already invading the eastern portion, and are likely to injure it as arange for larger stock. They claim, it is true, that sheep driving does not destroy the grass, which is said to come up as strongly as ever in the following spring. This seems hardly possible, for along the Rio Navajo the sheep have eaten the grass down to the very roots, and in addition have torn out the roots with their hoofs. If this be the ordinary result of sheep pasturing, one can hardly conceive the possibility of recovery. Of the Grand and Gunnison area little of interest from an agricultural point of view is embraced by our district. We have, for the most part, only high, rugged mountains, broken by deep, narrow canons, which here and there widen into little parks. In the northern portion the altitude is so great as to cause long, dreary winters, followed by brief summers, whose nights nearly always bring frost. Southward, beyond the junction of Kast and Taylor Rivers, the conditions are somewhat changed, as the country is more open. Yet here, owing to the altitude, the winters are harsh and frosts are not unknown during summer. Respecting the meteorological conditions little is known. Until very recently, the whole area west of the main divide was supposed to be within the Ute reservation, and was shunned by all the whites, except a few adventurous prospectors. The mean annual temperature varies greatly in different portions, for at the north, on Rock Creek, the timber line is barely 10,000 feet, while on the Rio Grande divide, at the south, it reaches to nearly 12,000. To explain this great difference is not easy, for the distance between the two localities is hardly one degree of latitude. No attempt has been made to test the availability of the country for CLIMATE AND AGRICULTURAL RESOURCES. 339 farming purposes. At the Indian agency, on Los Pinos Creek, a tributary of Cochetopa Creek, very near the southern limit, and almost directly under the Rio Grande divide, a small garden is cultivated, in which the ordinary vegetables are raised so successfully as to give reason for supposing that in this little basin some of the grains might mature. The soil is rich enough throughout the whole area, and along the river bottoms is usually covered with bunch grass and wild oats. This mixture of grasses is remarkably abundant in the valleys of East River and Ohio Creek. The many ravines in the Rio Grande divide will eventually prove very serviceable to stock raisers. Like the San Juan area, this whole region is almost untouched, nothing having been done beyond the herding of a few cattle at the Indian stock ranch, on the Gunnison. The supply of water is ample everywhere, and the streams maintain a steady flow throughout the year, being sustained by the heavy snows of winter and the equally heavy rains of July and August. Of the Great Plains, lyimg east from the great mountain region, only a narrow strip, from five to fifteen miles wide, reaching from Denver to the New Mexico line, and embracing portions of the Platte and Arkansas areas, falls within the limits of our survey. Though this strip is so small, it includes no inconsiderable part of the land already under cultivation in this region, and is of much interest, as in or near it there have been performed successfully some gigantic experiments in artificial irrigation. Rain or light snow is of frequent occurrence during the winter and early spring, while later, until about the beginning of June, heavy rains are common. From June until well on in the autumn the climate is agriculturally rainless, and artificial irrigation is necessary to successful farming. ‘As a whole the climate has some interesting features. By those inter- ested it is said to be mild and uniform; but such a statement needs to be much restricted before final acceptance. The long summer and autumn are pleasant, the days being warm and cheery, while the nights are invariably cool. Toward the close of November the weather changes somewhat ab- ruptly, and the thermometer is apt to fall to zero, or to several degrees below it. From this time until the middle of March the variations in tem- peratnre are very great and equally abrupt. Ordinarily, January is quite 340 GEOLOGY. mild, but during February the thermometer may vary in twenty-four hours from 20° to 70°. These abrupt changes cannot fail to prove injurious to invalids, notwithstanding the many violent assertions to the contrary. At the same time, owing to the dryness of the atmosphere, the evil influence is very much less than it would be on the Atlantic coast, where the air is so fre- quently saturated with moisture. The climate of the year, as a whole, how- ever, is exceedingly favorable for thoge afflicted with diseases of the digest- ive and respiratory organs. There can be no doubt that many lives have been prolonged here by the climate alone. The advantages of this portion of Colorado in this respect are so evident that the very exaggerated statements made by many are inexcusable, not only because they are false, but because they are unnecessary, the simple truth being sufficient for all purposes. As the dry season begins in June, and continues until autumn, all farming operations are entirely dependent upon artificial irrigation. The supply for this purpose is drawn from the Platte and Arkansas, with their numerous tributaries. These streams derive their water, in the early part of the season, from the melting snows of the mountains, and later on from the heavy rains falling on the interior ranges, so that they always carry abundance to meet all necessities. The soil along the rivers, both on the bottoms and the higher terraces, is very good, though somewhat coarse on the latter. It is from 18 inches to 4, or even 6 feet deep, resting in many localities on a white tufaceous limestone, or fresh-water marl, which decom- posing readily may eventually come into use as an amendment. This soil is easily prepared, and yields very good crops. The average number of bush- els of wheat per acre has been put at twenty-eight, but this is too high, and the best information within our reach leads us to place it at not more than twenty, nor less than eighteen. Exceptional cases near Denver show in one instance thirty-seven, and in another sixty-five bushels per acre. These, however, are useful only to prove what can be done by skillful farmers, of whom there are too few in the Territory. The wheat, like that of Califor- nia, is of very superior quality, and seems to contain much more gluten than wheat raised east of the Mississippi. The dry atmosphere renders the crop more certain, as many of the diseases so injurious at the East cannot exist here. Oats do fairly, averaging thirty to thirty-five bushels, while barley CLIMATE AND AGRICULTURAL RESOURCES. 341 yields thirty-five bushels per acre. Vegetables of all kinds do well, and in the southern portion Indian corn gives a fair crop. Along this strip there is little timber, except upon the mountains facing it, but on the higher portions pifon and red cedar grow in large quantity. Along the streams cottonwoods grow to large size, but the wood is worth- less as timber. On the upper terraces southeast from Canon City cacti grow to a great size. Stock raising has proved more profitable than farming. Bunch grass is found everywhere, in greater or less abundance, and in quantity sufficient to support a vast number of cattle, owing to the great extent of range. . The climate is such that ordinarily no winter shelter is required, and the snow fall is so slight as hardly to interfere with pasturage. The only ex- pense is the outlay for herders. Sheep do well, being free thus far from diseases common east of the Mississippi, and the wool is clean as there are no plants to injure it. The extent to which irrigation of the plains can be carried is now a question of much importance, and, having been formally presented in a mes- sage by the President, deserves at least passing reference here. These plains are not, as is commonly supposed by those who have not seen them, a vast level, broken only by occasional waves. On the contrary, the sur- face is exceedingly irregular, and, though in the distance resembling a plain, it is in fact anything else, being much torn by erosive agencies. Only a small portion of this great area can ever be cultivated by irrigation. That which is available lies along the larger streams and their tributaries, some of which are now permanently dry, and consists of the flood-plains, and the older terraces rising above them. These present the level surface which is essential to successful irrigation. Of such land, immediately available, it is estimated that Colorado, east of the mountains, has in all barely four mill- ions of acres, or about six thousand two hundred square miles, an area scarcely larger than a strip extending from Denver to the New Mexico line, with a width of thirty miles. It might be possible, by means of extensive and very costly works, to double this area, but not more. Under such con- ditions, one can hardly fail to doubt the feasibility of an enterprise to recover any considerable portion of Colorado by irrigation. 342 GEOLOGY. Even were Colorado, east of the mountains, one unbroken plain, the duiiculties would be quite as serious. To irrigate, one must have an abun- dant supply of water. As the rain falling upon the plains is uncertain in amount, it can afford no assistance, and the whole supply must be drawn from the mountain region. The problem, then, would be to irrigate, in Col- orado alone, nearly sixty thousand square miles, with the water which falls on less than eleven thousand. Could this water be husbanded in such a manner as to lose none, this would not be impracticable, for irrigation is needed only from the beginning of June until at farthest the early part of August. But such a husbanding is impossible. A large part of the water precipitated upon the mountains never reaches the plains by the streams, and were irrigation fully carried on along the Upper Arkansas and the Upper South Platte, only a small portion would pass east of the mountains. As it is, the Arkansas, where it issues from the mountains at Canon City, is very much smaller than at Pleasant Valley, only thirty miles above. More than this: The atmosphere on the plains is so dry, that the temperature fre- quently falls 40° without inducing deposition of dew. It is clear that the loss by evaporation would be enormous. The porous soil would absorb an equal amount, and from these two causes not less than half the water entering the canals would be lost within sixty miles. The amount of water issuing from the mountains is not sufficient to bear this loss and still supply what is needed for irrigation. Careful calculation has shown that the water of all the streams would hardly suffice to irrigate the whole country to a distance of thirty-five miles from the base of the mountains. The Platte itself, though constantly receiving tributaries, diminishes in im- portance as it descends, until at Julesburg, during the agricultural season, it is comparatively insignificant. CHAPTER XI. METAMORPHIC ROCKS. The metamorphic rocks are well exposed in the complex east range, fronting upon the plains, as well as in the range west of South Park. On the former range they prevail, none of the unaltered rocks occurring, except at the foot on the east, in the narrow series of hog-back ridges. In the second range they are seen only on the west side, facing the Arkansas River, being concealed on the east by rocks of Carboniferous and Silurian Age, except near the heads of the numerous streams, which run through deep gorges cut out of the eastern slope. In the Sangre de Cristo Mountains they are seen only on the western slope, where the exposed mass is quite extensive. The numerous spurs, passing from the eastern range, are usually made up of metamorphic schists. In the range west from the Arkansas, rocks of undoubted metamorphic character are not seen until we approach the head of Tennessee Creek, from which point northward they prevail near the center of the axis. West from this range, in the area of the Grand and Gunnison, they are exposed in only a few localities, and in those principally because of the extensive series of faults. This area is covered, for the most part, either by rocks of volcanic or eruptive origin, or by unaltered sedi- mentary rocks. Along the various axes seen in the San Juan area, the metamorphic schists were observed. The prevailing rock is a micaceous schist passing into gneiss, and con- taining much granite, which in some localities entirely replaces the others. Not unfrequently the mica-schist is displaced gradually by hornblende- schist, which becomes a hornblende-gneiss, containing masses or strings of syenite, as the other form contains ordinary granite. Slates are almost wanting, and thick strata of quartzite belonging to this series were observed at only two or three localities. Serpentine and limestone seem to be absent altogether. It is impossible in the present state of our knowledge to come 343 aw 344 GEOLOGY. -to any definite conclusion respecting the relations of these rocks. Dr. Hay- den, in one of his reports, has referred them, with doubt, to the Laurentian. To determine this matter, careful investigation at the north is still needed. At several localities in the Grand and Gunnison area there is found underlying the lowest stratified rock a peculiar gneiss. This is regularly laminated, and from dark-brown to almost black in color. In structure and appearance it frequently resembles a micaceous sandstone, and, hastily exam- ined, might. be mistaken for a rock of that kind. At most exposures it is little distorted by pressure, the lamine being straight for many feet, and preserving distinctly the original planes of bedding. Struck by the ham- mer, it breaks along well-defined lines of cleavage into fragments 6 inches or more in length, but along the plane of deposition it splits like straight- grained wood. Indeed, so regular is this splitting, that large fragments are not unlike silicified wood. Occasionally it shows small flexures, as if from lateral compression, and at some exposures it contains thin seams of quartz, or of quartz and feldspar, occupying the cleavage planes. At the junc- tion of Taylor and East Rivers, this rock is seen in the cation almost black and somewhat contorted. Followed up East River, it becomes lighter in color, more micaceous, and the wrinkling of the laminz disappears. About a mile above the junction it contains a good deal of segregated granite, by which, apparently, it is eventually displaced. In the canon of Taylor River it continues for two or three miles above the junction and then disappears, the walls of the gorge thenceforward consisting of coarse granite. At the head of this caton the stratified rocks are again seen, and under them appears this gneiss, showing the same characters as before. In Beattie Park, about a mile south from the canon, it is somewhat talcose, and por- tions of it bear much resemblance to serpentine. In the long canon of the Arkansas, just below the junction with the South Arkansas, it is quite vari- able in its character, sometimes resembling a red micaceous sandstone, and at others so much like a diorite in physical character.as to be somewhat perplexing. This rock is of extensive distribution west of the Arkansas, but was not seen in or east from South Park. It always occurs directly under the sedimentary rocks, and no similar formation occurs lower down. It is clearly unconformable to the great mass of the schist and gneiss, though pre- METAMORPHIC ROCKS. 345 cisely like them in its changes. In consideration of all the circumstances, one cannot resist the temptation to regard it as belonging to a later period. On the North Fork of the South Platte the schists are exceedingly con- torted. Thin layers of quartz or feldspar are separated by laminze of mica, which readily give way, so that one not unfrequently sees a very pretty little arch lined with mica, the lower layers of the rock having been removed. Near Bailey’s ranch, on this stream, mica occurs in very large sheets. A very interesting feature was here observed for the first time. The schist contains nodules of quartz or feldspathic granite, with but little mica, which ‘are usually quite small when abundant, and vary from one- fourth to one-half inch in length. Their longer axis bears no necessary parallelism to the lines of bedding in the rock. In some of the especially- micaceous layers these nodules are very numerous, and are regularly arranged, as if in accordance with some law. At several localities they were observed in layers. Though ordinarily small and rudely oval wher- ever they are numerous, they occasionally attain a length of 3 or 4 inches as independent nodules. The especial interest attaching to them lies in the fact that they are often combined, giving a mass 2 or 3 feet long, true gran- ite imbedded in the gneiss. In many instances the large masses of gneissoid granite string out like veins on all sides from the center, and these vein-like projections break up into these nodules, and thus finally disappear. It is sufficiently evident, then, that these are not metamorphosed pebbles, but concretions, the result of segregation, which mark the formation of the separate layers of quartz, feldspar, and mica in gneiss, and of the great masses of coarse granite which occur so frequently in the gneiss and schists. Gneissoid granite is exceedingly common. It often occurs in the gneiss as great included masses, of irregular shape or in elongate-vein form, spreading from a center, and throwing out seams which become exceedingly thin before they disappear. In each instance the deposit seems to bear no relation to the bedding of the including rock. For the most part, however, it is found entirely displacing the gneiss, and forming the prevailing rock for miles. In every such instance, however, it occasionally changes into gneiss for short distances. Not unfrequently seams of granite are found along the planes of cleavage. This granite, which may be termed segregated 346 GEOLOGY. granite, to distinguish it from the granite which many regard as eruptive, is coarsely crystalline, with the feldspar in great quantity, while the propor- - tion of mica is very small. The feldspar varies in color from white to red, and the rock as a whole yields readily under the influence of the weather. A syenite of similar character is occasionally seen. It occurs in masses in hornblendic gneiss, and often as veins along the cleavage planes. It bears a very close relation to the other rocks, for in several cations it is easy to follow mica-schist into gneiss, and this into either hornblende-schist or hornblende-gneiss, and the latter into syenite, which may pass into schist within a few feet, and this again into the ordinary granite. So indiscrimi- nately are these several rocks, the micaceous and hornblendic, thrown to- gether, that there is no room to doubt their common origin. In the cation of Taylor River the prevailing rock is this gneissoid granite, soft and coarse, here and there changing somewhat abruptly into gneiss. The granite frequently contains only rare scales of mica, which preserve a rude parallelism to each other. Toward the middle of the canon this rock passes into a very fine, compact, feldspathic granite, showing many crystals of feldspar 2 inches long. This bears close resemblance to the granite ordinarily regarded as eruptive; but since cliffs along this canon, 1,000 feet high, exhibit both varieties distinctly, passing the one into the other, with no line of separation, there is no room to doubt that they are of common origin, and that the whole is a metamorphic rock. At the junction of the two forks of Ten-Mile Creek the gneiss is exceed- ingly compact, and upon hasty examination some portions might be mis- taken for quartzite. Some of the layers are made up of geodes lined with drusy quartz, but they are not extensive. Half a mile below the junction, and where the stream enters a very fine canon, the wall of gneiss on the east side rises almost vertically for nearly 2,000 feet, and, being entirely naked of vegetation, offers a good exhibition of the rock. Here we see an immense segregation of granite, thoroughly vein-like, interlacing in every conceivable way, running in all directions, with and across the bedding, but not persistent, as each of the veins, if we may so term them, tapers off until it disappears. Above the forks a porphyritic gneiss was seen in fragments, but not in place. METAMORPHIC ROCKS. 347 At the head of Tennessee Creek the gneiss is somewhat variable in character; sometimes so compact and free from mica as to resemble quartz- ite; at others itis schistose, with the layers thin and straight for many feet, - causing it to cleave like dry wood. The quartzose layers are sometimes granitic, and in such cases originate as lamine, one-eighth of an inch to one inch thick, but in all cases these unite to form a thick layer. Their thickness varies from one-eighth of an inch to 20 feet. In every instance they resemble in structure the little nodules of granite already referred to, which are very numerous here, and can be traced in connection with the larger masses. Similar segregations form along the planes of cleavage, and are often seen intersecting each other along the main planes. Upon the east face of this range the gneiss and schists are well exposed northward, but very sparingly southward from the head of Tennessee Creek. In the cation of the Arkansas, above the junction of the river with Tennessee Creek, there is a gneiss which bears close affinity to the gran- ites usually called eruptive. It contains very beautiful crystals of translu- cent feldspar, one inch long and one-third of an inch wide, closely packed together. This gneiss gradually passes into a micaceous schist, in which the crystals are seen, but they are neither so numerous nor so exact in form as in the gneiss. In the vicinity we find immense fragments of a granite, reddish, and coarsely crystalline, very compact, and containing similar crys- tals of feldspar in vast numbers; indeed, some fragments seem to consist almost wholly of these crystals. The granite could not be traced into thé gneiss, as the rocks were not seen in contact; but so marked is the similarity in constitution, that we must regard them both as metamorphic, unless, indeed, we are willing to concede that gneiss is eruptive. On the east side of the Arkansas River the metamorphic rocks can be traced all the way to the great canon below the South Arkansas. On Trout Creek syenite occurs in small quantity, but is displaced by a soft, coarse granite, which gradually assumes a gneissoid structure. It contains fragments of gneiss from 6 to 20 inches in diameter, which are fragmental in shape. Their presence is diffi- cult to account for. If the granite be eruptive, these might be included fragments, but there is no reason to assign any such origin to it, for its grad- ual passage into the gneiss is easily traced. This rock exhibits thick seams 348 GEOLOGY. of grayish-red quartzite, which invariably occur along the cleavage planes. In the lower canon of the Arkansas, above the bridge, the gneiss is dark and very micaceous, and contains much coarse granite. The latter rock weathers here as well as on Trout Creek most readily along the cleavage planes, and at length separates into rounded blocks, which resemble enormous bowlders. Neer the mouth of Texas Creek a high knob is covered by such fragments, and looks as though it were part of a great mass of drift. On Currant Creek, a tributary of the Arkansas, the changes are very prettily shown. There the mica-schist becomes a schistose gneiss, contain- ing numerous segregations of the granite of large size, together with immense _numbers of the little nodules already mentioned. The gneiss gradually be- comes more compact, and at last is lost in the granite. In the long Dry Cation, leading from the Arkansas River to Wet Mountain Valley, the exhi- bition is equally satisfactory. The transition from mica schist to granite, and from hornblende schist to syenite, is shown quite frequently, and the rocks of one series readily give place to those of the other. On the west side of South Park the exposures of the metamorphic rocks are not extensive, as they occur only in the gorges of the streams, but in the vicinity of Mount Lincoln the clifis are from 2,000 to 3,000 feet high, and show most satisfactorily that the coarsely-crystalline feldspathic granite is not of eruptive origin. The prevailing rock of the mountain is gneiss, but near Montgomery a magnificent bluff, overlooking a glacial amphithea- ter, exposes immense masses of granite having a vein-like form. These are very irregular in shape, and vary in dip from 25° to 90°, while the includ- ing gneiss varies only from 15° to 26°. These masses can be traced many hundreds of feet on the mountain-side, and are seen to cross each other at varying angles without any faulting. Viewed from a distance the granite and gneiss are distinctly separate, but when one examines closely he finds that for many feet on each side of the granitic mass the gneiss shows an ap- proximate structure, with more and more of the granitic concretions as it approaches the mass, so that at last the change is absolutely imperceptible. A similar condition exists in the canon of Fairchild’s Creek under Mount Bross. Entering the eastern range at Mount Vernon Gulch, a few miles south METAMORPHIC ROCKS. 7 Oe 349 from Golden, we find the sedimentary rocks resting on a schistose gneiss con- taining many thin layers of pegmatite. From this locality to Clear Creek the character is the same, but beyond the crossing of the creek the gneiss is more compact with here and there narrow dikes of eruptive rocks. There is not much of the coarse granite until we have passed Idaho, but from that village to Georgetown this increases in quantity. At Idaho there is much syenite which changes, often abruptly, into hornblende schist. Along the road from Idaho to Chicago Lake the coarse granite is in large quantity, and shows more of the dike-like form than at any other locality examined. About one mile above the saw-mill, on Chicago Creek, a great mass of coarsely crystalline granite feldspathic and yellowish-white stands boldly out from the wall. It contains very little mica, and occasionally a little hornblende. It is about 70 feet wide and dips 8° more than the surround- ing gneiss. The most interesting feature here is the abruptness of the transition from the gneiss to the granite and the absence of strings from the latter. The line of separation between the two is almost as distinct as that between a trap-dike and the adjoining gneiss. No similar instance was observed elsewhere. At Georgetown, Leavenworth Mountain consists prin- cipally of gneissoid granite and gneiss cut by several dikes of trachyte, which is quite porphyritic. In the Marshall tunnel, at 980 feet from the mouth, there is a seam of metamorphic slate, 30 feet thick, gray, finely laminated, and disintegrating readily upon exposure to the atmosphere. This was not seen on the surface. No similar slates were observed elsewhere within our area, except in the vicinity of Mount Lincoln. On Brown and Republican Mountains, near Georgetown, the rock is chiefly the coarse eneissoid granite, with but little gneiss. This rock seems to pass into syen- ite. In all these mountains,as well as along the upper portion of Clear Creek Canon, there is much porphyritic granite which will be referred to in another connection. -2. 2-22 -0s-- 4 ----resne eee 70 11. Conglomerate, quite (COaTSGn2- =} = - ie ee ie ee 14, 15. 16. 17. 18. 19. 20. CARBONIFEROUS ROCKS. . Sandstone, reddish-gray, micaceous, fine-grained, except at base, where it is conglomerate with fragments 1 inch in diameter.... ....--.-. .---..--- . Limestone, on top, gray, shaly, micaceous; lower, blue, siliceous, and very hard ; then, blue, shaly, ferruginous, and weathering yellow ; at base, blu- ish-gray, shaly, micaceous, and passes imperceptibly into No. 14.... ..-.. Sandstone, light reddish-gray, laminated, micaceous, calcareous ...-.. .-.--- Imperfectly exposed. At Red Mountain, four miles above the junction of the forks, where this section was obtained, this interval is mostly concealed ; but in a bluff three miles farther up the stream, it is occupied by lime- stones and sandstones. The former predominate and are bluish-gray and fossiliferous. The latter are fine-grained and reddish-gray. From the limestones I obtained Athyris subtilita, a Bellerophon, near B. montfortianus and Lophophyllum proliferum ....-.-... (Gosk Rae Sas Bete wig! sa yates @ ee Sandstone, red to gray, laminated, sott, micaceous. Das ST Limestone, blue to nearly black, eoniemnat siliceous ar a brittle; pon above, shaly below; shaly portions almost black, with thin films ‘of quartz and cherty nodules ; fossils numerous and minute, chiefly crinoidal stems, with occasional mollusks, but all so badly weathered as to be indeterminate Made 6) SURTING (ES Sead Soe oaatan s Dol SHO HAC CROC GE On abe E Cone ae eSre Sandstone, above, gray to white, and coarse; below, red and very coarse... . Sandstone and Limestone. Not well exposed; some shale; sandstone fine- grained and gray. Near the middle of this interval is a limestone, 7 feet, bluish-gray, brittle, and with much calespar. It is rich in individuals of a few species of fossils, among which are Productus prattenianus, Productus muricatus, Spirifer Rocky-Montani, Retzia Mormonii, and Athyris sp. These ANLOCGHTANEOOCUCONdIHOM ss 5 tebe.4 ee see = eee, s Ahecetsojoets eee ane Sandstone, light-gray, friable, shows niaek cross-bedding..........-..----- . Sandstones and Shales, including the Gypsum beds. This enormous mass is first seen on the North Fork, about three miles above the junction of the two forks, and continues in view along the South Fork to above the caton. The gypsum-beds are best seen below the junction, where they are visible for seven or eight miles, the stream running in the direction of the strike. In the upper portion, for 700 or 800 feet, there is nothing but very coarse sandstones, some of which are very coarsely conglomerate, containing frag- ments of gneiss, in many, 10 inches long and 4 to 8 inches wide and thick. These fragments are but little water-worn. In this portion the color is red- dish-gray. As we ascend the South Fork, we find the character changing. The sandstones become finer in grain and Jess massive, many of them be- ing laminated. The color becomes lighter, and light-yellow is the prevail- ing tint. Interstratified with the sandstones are reddish arenaceous shales, which, as we descend in the series, increase in importance, until at length they equal in amount. the sandstones with which they are interstratified. The yellow sandstones are more or less ripple-marked, and one enormous stratum of conglomerate, nearly 150 feet thick, shows as handsome ripple- marking on its finer layers as I have ever seen. This group is fully exposed 24Wws 369 Feet, 40 100 50 370 GEOLOGY, Feet. along the South Fork. It was examined as closely as was possible under the circumstances, but no limestones were seen; estimated thickness... - - 2, 000 22. Conglomerate. This is somewhat altered, but in all other respects resembles the conglomerate seen at the head of Taylor River; exposed..-...-.-.-.- = 40 With this stratum, which is not more than 2U0 feet above the bottom limestone, the measured section closes. The river here issues from a deep, narrow canon, in which the lower rocks of the Carboniferous can be seen, which is utterly impassable, and the trail mounts rapidly up the cliff, and continues along the edge of the canon for several miles. Here the whole country is covered with débris, and no exposures were seen. Along the trail, however, fragments of the Carboniferous limestone were seen mingled with others of Silurian Age. It is somewhat difficult to connect this section with that obtained on Rock Creek. The portion from No. 2 to No. 19, inclusive, bears some resemblance to the group overlying No. 20 of the Rock Creek section, in case we regard the latter as inverted. Still, this comparison would require a very considerable thickening of the sandstones westward, the number and general character of the limestones being much the same in each case. I am free to confess that the material at my command does not justify me in any attempt to connect these sections to any degree of detail. Our line of survey did not extend far enough northwestward to enable me to pass round the short mountain spur on the west side of the Eagle, so as to make ‘direct junction with the rocks of Roaring Fork, and thence with those of Rock Creek. The exact relations can be determined in no way other than by making detailed sections along this somewhat crooked line. In addition to this, the country between Roaring Fork and Rock Creek is faulted in so eccentric a manner, that to make any conjecture whatever respecting its geology would be hazardous in the extreme. Crossing Tennessee Pass, we reach the Arkansas region. On the west side of this river no rocks belonging to the Carboniferous are seen until we reach the vicinity of Hunt’s Peak. Specimens brought to me by members of our party show that there these rocks occur. To what extent I am unable to say, as [was unable to visit the locality. That the Silurian rocks at one time reached to the west side of the river has already been asserted, CARBONIFEROUS RORKS. 371 and I feel no doubt that the Carboniferous rocks, before the great upheaval causing the mountains, formed an unbroken sheet, stretching from South Park westward to beyond our western line. On the east side of the river, upon the ridge separating it from South Park, the exposures are by no means infrequent, but they show only the base of the series. At Iowa Gulch, immediately south from Oro City, there is a very satisfactory exhibition. The crest of the ridge is covered by trachyte, below which is a mass of sandstones resting on the dark limestone, which here does not weather to a light eolor. Immediately underlying this limestone is a thin stratum, much resembling one in similar position at the head of Taylor River. - A section of this gives, descending— 1. Limestone, with much gaunt, some malachite, and gray copper...- 3 feet. 2. TEGIDNDS SASF oe) SSR OSS OF Se COTO ate OSORIO n Sea area 1 foot 6 inches. 3. Limestone, with azurite, hematite, heavy spar, and some galena...- 1 foot 6 inches. Nos. 2 and 3 are quite rich in silver. The stratum rests upon a light-col- ored siliceous limestone. Following down the river to its cation, through this ridge, we find, about two miles below the head of the canon, the limestone well exposed, while not far above, and separated by shales and sandstone, the gypsum beds are seen on both sides of the river. The ready decomposition of these beds has covered the walls with variegated débris, a feature by no means uncommon. Upon the gypsum rests an enormous mass of reddish and gray sandstones and shales, not less than 2,500 feet thick, which form the cafion’s walls to its mouth at Pleasant Valley. Here, as on Kagle River, no limestones were observed. The sandstones are coarse, and, where mas- sive, show cross-bedding. The shales are all arenaceous, and in greater quantity toward the base. The whole mass is micaceous. Following this range southward, we find these sandstones in the Sangre de Cristo. Mount- ains, until we pass the divide between Wet Mountain Valley and Huerfano Park. Beyond this to Sangre de Cristo Pass they have been cut off by dikes and removed by erosion. The lower portion of the group is very coarsely conglomerate, with rolled fragments of granite and gneiss, varying in size from 2 to 8 inches in diameter. In Sangre de Cristo Pass the sand- stones are finely exposed, and at one locality the limestone is seen, with many imperfect fossils, of which Productus semi-reticulatus is most abundant. 372 GEOLOGY. Going northward and following the eastern slope of this range, we trace the Carboniferous rocks into South Park. At Trout Creek Pass the limestone is seen, with the overlying sandstones and shales. A curious con- dition exists in the pass, for the sandstones are seen abutting against the Silurian rocks, while the Carboniferous limestone is far above them on the cliffs. It would seem as though there had been a double fault here cross- ing the line of strike. In the canon of the South Fork of the Platte the limestone is occasion- ally seen. Where the cation opens out there are numerous exposures of the gypsum beds, resting on a reddish-gray sandstone. The gypsum is of a dull gray color, and is by no means so pure as that seen on Rock Creek. Though containing much foreign matter, it is burned and employed in fin- ishing the interior of houses. It is known as “mountain gypsum.” The demand must be somewhat extensive, for along the road numerous heaps were seen, and at one spot rude machinery had been erected for grinding it on a large scale. At no place in this vicinity is the rock exposed for a thickness of more than 40 feet. Followed southward, we find the same gypsum beds between the forks of Salt Creek, underlying the overflow of: eruptive rock. Here the surface is broken down to a fine powder, and in wet weather the whole vicinity is covered with a gypsum mud. On the North Fork of Salt Creek there is a mass of fine-grained, rather shaly sand- stones, red and gray, and more thickly bedded on top, having a total thick- ness at the exposure of about 150 feet. The precise relation of this to the gypsum was not accurately determined, but the latter seems to underlie it. The underlying sandstone is well exposed on Buffalo Peak, where it is capped by the eruptive rocks. Following down Salt Creek, we find the surface deeply covered by gypsum, which has been mistaken by some for an alkaline efflorescence. At the Colorado Salt-Works is a butte capped by trachyte, but composed mainly of gypsiferous shales, overlaid by gray, thin bedded sandstone, more or less micaceous. The salt-works are quite extensive, but at the time of our visit were not in operation, owing to litigation among the own- ers. The brine is obtained from two springs, which must yield very abun- dantly, if the statements of those in charge can be relied upon. There is CARBONIFEROUS ROCKS. 373 sufficient to produce from one hundred and fifty to two hundred barrels of salt daily, and the strength of the brine is 5.75° Beaumé, or about one-half pound of salt to the gallon. Two wells were drilled to reach the reservoir of brine, but were unsuccessful. No record of the borings was preserved, but in the first well the succession descending was shaly sandstone, con- glomerate sandstone, and imperfect quartzite, the last at a depth of 150 feet. In the second, the tools were caught in gypsum at the depth of 225 feet, and the work was stopped. The salt is said to be of good quality. From the cation of South Fork of Platte, the Carboniferous rocks are more or less fully exposed in most of the deep ravines running far back into the mountains. On Four-Mile Creek, the limestone at the base is seen near the top of Bald Peak, very dark, almost black, and showing only rare fossils. Here, too, we find the curiously-banded limestone observed on Taylor River. In the canon of Fairchild’s Creek, the same rock is well seen, while above it the sandstone is exposed to a thickness of 270 feet. This contains many layers of lead-colored, somewhat argillaceous shale, with much iron-ore, and is clearly equivalent to the sandstone and shale directly overlying the limestone at the head of Taylor River. On Mount Lincoln the limestone is well exposed, and, like the same rock on Taylor River, is very sparry, especially in its lower portion. It is of much interest, as containing the singular deposit of silver-ore, which is now assuming some economical importance. On the crest: of the mountain we find a thinly- bedded micaceous sandstone, of which but little is exposed. The metamor- phic influence of a dike is well seen on this mountain, where for 3,000 feet no trees or vegetation of any sort conceal the rocks. A dike of moderate dimensions and almost vertical passes from the summit downward along the face. The sandstones in contact with it have been converted into a struc- tureless quartzite for nearly 20 feet on each side, while the limestone was affected to a much less distance and to only a slight extent. Its color was changed from black to brownish-yellow and the rock was rendered fissile. Along the eastern border of the park no Carboniferous rocks were seen, and, to my mind, it is doubtful whether they ever existed there. But at various localities, for eight miles east from the base of the mountains at the west, occasional exposures occur of coarse sandstones, with a few thin siliceous By ae GEOLOGY. limestones of dark-blue color, and containing many small univalve mollusks. Following these exposures northward, we see on enormous mass of red and gray sandstones, more or less finely conglomerate, capping the mountains on the main divide, and including several of these thin limestones, two of which are seen in Hamilton Pass. This sandstone forms the crest of Mount Morton, and is the rock which prevails on the northwest side of Georgia Pass. On the Quandary Mountain, at the head of Blue River, the dark limestone was observed, and it was traced some distance northward. On Snake River the gypsum shales occur, and the rocks in the vicinity are evi- dently saliferous, as the springs have a distinctly brackish taste. In the San Juan area* the Silurian rocks are nowhere exposed, or, af they are, it was impossible to identify them, and the Carboniferous series rests directly upon the metamorphic rocks. Along the upper portion of Rio de las Animas, the disturbance produced by dikes is so extensive, that the relations of the quartzites in the San Juan mining district could not be determined accurately during a preliminary reconnaissance. They belong to the Carboniferous series, but beyond this nothing was ascertained. The metamorphosis is complete, every trace of lamination having disappeared. These quartzites contain much iron pyrites, and numerous veins of argentif- erous galena, more or less well defined, and for the most part quite nar- row. Aside from these are some enormous deposits of galena, whose true character cannot be determined without extensive development. The quantity of argentiferous galena here is very great. In crossing the first summit from the San Juan mines to Las Animas Park we find a mass of sandstone, more or less conglomerate, with some shale, and near the top a thin siliceous limestone, the whole having a thick- ness of about 500 feet. Leaving the summit the trail falls rapidly into a deep canon between the first and second summits. In the sides of this canon exposures are unsatisfactory at the best, and when we passed through the whole was covered with snow. Occasionally one sees a conglomerate sandstone of gray color, and here and there he catches a glimpse of a thin siliceous limestone containing few but characteristic fossils of Carboniferous *The examination of this area was almost wholly for topographical purposes, and the geological notes are simply those of a hasty reconnaissance, with a view to more systematic work during the coming season of 1874. CARBONIFEROUS ROCKS. » 38d5 Age. Near where the trail strikes the bottom of the cafon the limestone at the base is seen, at a depth of nearly 2,500 feet below the conglomerate on the summit, which I regard as belonging to the upper sandstone group of the Eagle River section. On approaching the second summit we cross an axis on which are exposed some bluish quartzites, whose age is uncertain. At the summit the dark shales of the Taylor River section are well exposed. From this down the river to Animas Park the Carboniferous rocks continue in view on each side of the valley forming great bluffs. On Cascade Creek there is a dark- blue limestone, which contains in large masses a Chaetetes, which is hardly distinguishable from C. milleporaceus of the Coal-Measures in the Mississippi Valley. Together with this are numerous sections of crinoidal stems and of - characteristic brachiopoda. About seven miles below Animas City another limestone was seen in the bluffs, which contains Productus semi-reticulatus, Productus Prattenianus, Productus Nebrascensis, and Athyris subtilita. 'The Carboniferous rocks are exposed no farther south than half way down Ani- mas Park, where they underrun rocks, identified as Triassic, by Dr. New- berry, which rest unconformably against the older series. The Carboniferous rocks exposed along the Animas River from the second summit, referred to above, to the disappearance under the Trias, evidently belong altogether to the lower series of sandstones in the Eagle River section, and have a total thickness of little more than 1,200 feet. South from Lieutenant Macomb’s trail from the Rio San Juan to the Rio de las Animas, no Carboniferous rocks are exposed in Colorado. Between those rivers, and north from the trail, they form the numerous hog-back ridges of the several anticlinal axes, but they disappear at some distance west from the San Juan, where the axes are so gentle that they involve also the overlying rocks. They are not seen again until we reach the Sierra San Juan, where they are entirely meta- morphosed, and in an almost vertical position. On the trail from Tierra Amarilla, New Mexico, across this range to Conejos, Colorado, these rocks -occasionally contain small amounts of galena and iron pyrites. On the east side of the San Juan axis the Carboniferous series is entirely concealed by the overflow of eruptive rocks. Along the east face of the Rocky Mountains, the Pike’s Peak, and Green- 37 6 GEOLOGY. horn ranges no Carboniferous rocks were seen. It is highly probable that, like the Silurian, the Carboniferous has its western outcrop far to the east of the base of the mountains, and that it is deeply buried under the more recent formations. This appears the more probable since we find the Triassie rocks tilted at an angle varying from twenty to eighty degrees, and in some cases even pushed over five or eight degrees, yet not exposing the under- lying Carboniferous. Careful investigations by Mr. Gilbert have proved the existence of a great limestone group at the base of the Carboniferous in Arizona, and full of remains, which show it to be of Lower Carboniferous age. A similar limestone, less thick, is at the base of our series, but the fossils obtained are insufficient to decide the question of age, as they are species of the widest range, reaching from near the bottom of the Lower Carboniferous to the Upper Coal-Measures. Enough has been found, however, to determine that the section at Rock Creek, as well as the limestones on North Fork of Eagle River, belong to the Coal-Measure epoch, the species of mollusks being those which are familiar to every one who has worked in either the Illinois or Appalachian coal-fields. Economical geology of the Carboniferous—As already intimated, the stratigraphical relations of the quartzites along the Upper Animas have not been accurately determined, though they, beyond doubt, belong to the Car- boniferous. They hold mineral deposits which have attracted much atten- tion in Colorado, and for several reasons deserve especial notice here. As one descends Cunningham’s Gulch toward the Animas River he sees on the opposite side of the river an abrupt wall rising nearly 3,000 feet from the plain. On the face of this, quartz veins stand out in relief and interlace so as to form a rude net-work. The first impression is that a great number of logs have fallen down the cliff and been caught on projecting points of rock. From the head of the Animas to Baker’s Park the veins are as distinct as these and show the same mode of interlacing. I know of no other district in our whole western region where the veins are so numerous, so distinct, or so easily followed as in this one. Up to the time of our visit to this, the San Juan mining district, only one lode had been developed to any extent. This, the Little Giant, is evidently CARBONIFEROUS ROCKS. ote a true vein varying from 2 to 20 inches in width, but probably averaging about 4. In the quartz some zinc-blende, iron pyrites, and galena occur. With these is a dark chloritie rock, which not infrequently shows specks of native gold. The ore is said to be remarkably rich, and there seemed to be a very positive notion that a little pocket had yielded about $100,000. In this district there are many very extensive deposits of low-grade galena and numberless thin veins carrying quite rich ore. But up to the time of our visit nothing had been done, and indeed nothing was known respecting the value of the lodes in the district. The many wild statements made, which produced so great excitement throughout the Territory, were based upon surmise, or very possibly were worse. That good mines may yet be found within the limits of the Sun Juan district is very probable, but none had been certainly proved to be such up to the middle of October, 1873, all claims being undeveloped. The mines on Rock Creek are still undeveloped. In that vicinity there are no veins but mere aggregations of mineral matter in the Carboniferous rocks. They are not even gash-veins, and are of very uncertain extent and value. The ore is present at some localities in large quantity, and consists of galena, zinc-blende, iron and copper pyrites, with some gray copper. On Mount Lincoln mining operations are carried on very extensively, but the manner in which the ore is distributed is still somewhat uncertain. As the manager of one company put it, “We all go for the ore as we do for potatoes.” When a string of ore is seen it is followed up until it disappears. The deposit is in the limestone at the base of our Carboniferous series. Though so irregular in its distribution that discoveries have been taken up in every conceivable form, from lodes to ten-acre lots, it is nevertheless extensive, and many of the companies at work have been remarkably suc- cessful. Most of the mines yield only silver, but gold occurs in some of them in considerable proportion. The ore is principally galena and sul- phuret of silver. In the mines producing gold, iron pyrites is found in addition. Along the range on the west side of South Park this limestone is argentiferous at nearly every exposure. The gypsum and salt of the Carboniferous series have already been referred to in another connection. CHAPTER XIII. MESOZOIC ROCKS. SEcTION I.—TRIASSIC AND JURASSIC. Section II.—CRETACEOUS. SEcTIon I[I.—AGE OF THE COLORADO LIGNITES. SECTION TRIASSIC AND JURASSIC. Triassic-—Rocks of Triassic age are exposed over only a small area in the district examined. Along the Rio Florida and the Rio de las Animas they are seen abutting against the lower sandstones of the Carboniferous, about ten miles below Animas City. From that line, according to Dr. Newberry, they are well exposed on the walls of Animas Park and the canon of the river below, where they show a thickness of not less than 1,500 feet. From the Animas River to Tierra Amarilla, in New Mexico, no Triassic rocks were observed along our trail, but near Tierra Amarilla, on the trail lead- ing from that place over the Sierra San Juan to Conejos, the mass of sand- stones underlying the Cretaceous shales and abutting against the Carbonif- erous is so great that it cannot all be Lower Cretaceous and must be in part Triassic.. The whole of it is so altered that nothing determinate can be ascertained respecting its relations. 5 Along the east face of the Rocky Mountains we find a coarse sand- stone mostly conglomerate, extending from our northern line to Cation City without interruption, and there curving round the extremity of the Pike’s Peak range to the western base of that axis, along which it passes north- ward. In the vicinity of Canon City this rock is not seen on the Green- horn Mountains, nor was it positively identified on Hardscrabble Creek, 378 TRIASSIC AND JURASSIC. 379 but at the southern extremity of the Greenhorn range it is again seen curv- ing round the point into Huerfano Park. South from this-I have no per- sonal knowledge, but the observations of Drs. Newberry, Hayden, and Professor Marcou show that it reaches far on into New Mexico. In Colo- rado the group shows no fossils, and no clue to its age can be obtained except from its stratigraphical relations to the Jurassic and Cretaceous. In New Mexico it is seen overlying the Carboniferous series, from the top of which Dr. Newberry obtained species of undoubted Permian age. In Eastern Colorado it underlies, unconformably, the Jurassic and Cretaceous. It is therefore Triassic to the base. It would, indeed, be impossible to separate the series as exhibited on the east base of the mountains, although some have referred a portion of the mass to the Carboniferous, and on a map recently published in the Report on the Census, vol. III, a line of Silurian is marked all along this face. The fact that this mass, as traced into New Mexico, overlies the Permian, leaves no room for any doubt respecting its relations. On Beaver Creek, a few miles northeast from Cafion City, the follow- ing section was observed descending : 1. Sandstone, soft, blood-red, shaly above conglomerate below.......--..-.--- 100 UNCP SUL MMe ai prc fareres- lem stay oan fsa cn hsis ste ieisimerr c aisicl steals Se Se Gatos e) Serie cre 100 3. Sandstone, soft, mostly deep-red, with layers of gray, somewhat micaceous, shows much cross-bedding and is entirely unaltered. It is conglomerate throughout, but especially so at the base, where for several hundred feet it contains pebbles as large as a hen’s egg and completely agatized. The coarseness of the material diminishes regularly to the top, where it is com- paratively fine in grain. Estimated thickness.... .........-.-.----.--- 2, 500 Above No. 1 there is a gap of 200 feet unexposed, after which the sandstones of the Lower Cretaceous are seen. The rocks of the section are unconformable to those above. At the canon of the Little Fountain Creek the upper portion of the section is exhibited as follows: Feet. 1. Sandstone, gray to red..............- Me cioctore sie la ea tae car at sorters Bac ARS 160 2. Gypsum and shales.-.........-.. rhs Herat wats Seochesbtwiews Selacioky sere Void. 20B 120 3. Sandstone, red. In the little park lying behind the hog-back ridge northeast from Cafion City and watered by Ute and Beaver Creeks, the red sandstone at the base 380 GEOLOGY. rests against the mountain until we reach Beaver Creek, where it fills up the valley in a succession of low hog-back ridges, and at length closes up the whole with the exception of a very narrow gorge, which is occupied by a branch of Beaver Creek and by the road from Cation City to Colorado Springs. From Ute Creek to Beaver Creek the gypsum bed is a well- marked feature of the outer wall of the park and seems to be in thin layers alternating with drab or lead-colored clays. At the crossing of Beaver Creek these shales are quite well marked, the road passing directly through the gypsum bed. The gypsum is light-gray in color and occurs in thin lamin, which are very distinct on the weathered edge of a layer, but the whole has a concretionary structure, which gives a mammilated surface to the slabs. In this respect it resembles the Carboniferous gypsums, which are always concretionary. On Oil Creek, which flows southward between the Pike’s Peak spur and the Greenhorn Mountains to the Arkansas, the red sandstone yields petroleum and salt. These are obtained from springs. Deep borings were made at one time to reach a reservoir, but were unsuccessful, and the quan- tity obtained by “skimming” the salt water is comparatively small. The oil I was informed is of good quality, and in quantity nearly sufficient to supply the local demand. Following down Beaver Creek to strike another road to Colorado Springs we find the Triassic rocks disappearing under the upper rocks, nor do they re-appear again along the road until near Turkey Creek, where, in a very extensive park, the sandstones have been entirely removed. But in the outer wall, protected by the Lower Cretaceous sandstones above, the gypsum is again seen. In the park near the wall there are several low hills covered by gypsum. The alternation as seen in this locality is— Feet 1. Arenaceous shale, fine-grained, deep-red ... -....-.-.........-------- .----- 40 2. Gypsum and: blue clays--- =.- 2 - seo eae e- eee BUR State toes ae 60 3. Shale, dark-red, with layers of gypsum...-.-..-- sos de cates: = Bet ce So asiee 40 There is evidently much variation in the character and thickness of the stratum on top, but the gypsum beds are very persistent, varying little from 100 feet at the several exposures. From the time we leave Dry Turkey Creek until we pass through the TRIASSIC AND JURASSIC. 381 canon of the Little Fountain Creek we ride almost uninterruptedly between hog-back ridges of the lower sandstone. Near the cation this sandstone is quite fine-grained and soft in the upper 300 feet, while below that it is con- glomerate, as on Beaver Creek, but contains more gray layers than at that locality. | At Colorado Springs, or rather three miles above the city of that name, on Fountain Creek, this group is well exposed in the ‘‘ Garden of the Gods,” and by its peculiar contrasts of color, as well as by the fantastic shapes pro- duced by weathering, it contributes largely to produce the weird scenery which renders that locality so attractive to tourists. The red rocks here reach well up on the mountain. Above the springs, at Manitou, six miles from the city of Colorado Springs, beds of soft argillaceous shale were ob- served below them, and under these a non-fossiliferous limestone. It was impossible, under the circumstances, to delay long enough to determine the relations of these beds. No limestone was observed in the Trias at any locality along this line, nor were any clay beds similar to these seen else- where. They may be Carboniferous. From Colorado Springs northward to Golden the Triassic rocks may be traced almost without interruption, though, owing to the increased dip in the northern portion of this line, erosion has acted so powerfully upon the un- protected gypsiferous shales that they are rarely exposed. The sandstones change materially in color, becoming gray to light-gray, but retaining the conglomerate character. Everywhere along the line from Cation City northward the Triassic rocks are unconformable to those above. Jurassic.—In the interior region no rocks were observed which could be referred to the Jurassic age, except, perhaps in the blue limestone under the Cretaceous in the Rock Creek section. At the same time no evidence has been obtained which tends to prove conclusively that they are absent, for at few localities was the junction of the Cretaceous and the directly subjacent rocks seen. Along our eastern border, however, from Caton City northward, there was observed a bluish-gray limestone, containing some indistinct fos- sils, which lies almost immediately under the Lower Cretaceous sandstones, and rests unconformably on the Trias, being conformable to the rocks above. On Oil Creek, near Canon City, we find above the oil-works an 382 GEOLOGY. -exposure of light-colored sandstones and shales, amounting in all to about 120 feet, which seem to be connected with this limestone. The same series overlies the limestone in the park between Ute and Beaver Creeks, behind the hog-back ridge, but is apparently wanting in Beaver Creek Cafion. At the latter locality the limestone is thin, very fine, compact, with flinty fracture, and almost salmon colored. The fossils are chiefly branch- ing bryozoans, though there seem to be some of the higher molluscan forms present, for some sections of those were seen on the weathered surface. The shales seen in Oil Creek again appear in the park near Turkey Creek. Near the head of West Plum Creek the limestone seems to rest almost directly on the Triassic gypsum, the intervening red sandstone or shale being absent or feebly represented. Near Mount Vernon this stratum has been used extensively in the manufacture of lime. Geologists, who have examined this region, seem to agree in placing this little group in the Jurassic. This has been done chiefly on stratigraphi- cal evidence, no assistance having been derived from animal remains. Un- derlying the lowest sandstones of the Cretaceous it cannot belong to that period, and it rests unconformably upon the Triassic rocks No decision, however, can be regarded as absolutely conclusive, until it is supported by the evidence of fossils. It is more than probable that this can be obtained by patient search, for, as has been stated, the limestone is quite fossiliferous. At all localities examined by me the fossils were unsilicified, and therefore do not weather out, while the rock itself is so compact that a fresh surface shows no evidence of fossils whatever. SHECTIONAL: CRETACEOUS. The rocks of this period are exposed over an extensive area within our district. Their line of outcrop along our eastern border is practically un- broken from Golden to New Mexico, and, according to other observers, even to Mexico. On the west side of the Front or Eastern range there is a nar- row area, of which only isolated portions remain in Huerfano, Wet Mount- i CRETACEOUS. 383 ain, Currant Creek, and South Parks. In the area of the San Juan they are the only rocks exposed between Macomb’s trail and the New Mexico line, excepting the small patch of Triassic on the Rio Florida and Rio de las Animas. The Cretaceous rocks differ somewhat in details in the various portions of our district, but as a whole the series is made up of three divisions. ‘The Lower Cretaceous is a mass of sandstone, 200 to 500 feet thick; the Middle is composed of shales and limestones, with, in the eastern localities, marls and sandstones 1,000 to 1,500 feet; and the Upper, chiefly sand- stones, with intercalated shales and lignites, 500 to 700 feet. No Cretaceous rocks were observed in the Grand and Gunnison area, west from the Blue River range, excepting at the localities along East River and Rock Creek, referred to in the last chapter. San Juan area—Soon after leaving the Rio Florida, on the way eastward, along Macomb’s trail, which is about fifteen miles north from the New Mexico line, one sees the Cretaceous rocks, but the first satisfactory exposure is on the divide between the Rio de los Pitios and the Rio Piedra. This divide is made up of the Lower Cretaceous sandstones, which there are coarse grained and in some parts conglomerate. Beyond the divide the trail leads through narrow ravines, eroded from the black shales of the Middle Cretaceous, which are well’exposed in the southwestern walls. They contain more or less fer- ruginous limestone, with some lenticular nodules of iron-ore, and are quite plastic. At the crossing of the Rio Piedra these rocks form high bluffs, capped by the Upper Cretaceous, and are visible in the mesas for many miles southward. From the Rio Piedra to the Rio San Juan the only rocks seen are those of the Middle and Upper Cretaceous; the former, dark shales, sometimes thinly laminated and fissile; the latter, massive yellow sandstones, for the most part fine-grained. As we descend to the San Juan, near Pagosa Springs, the sandstones of the Lower Cretaceous are fairly exposed for the first time along this line. At Pagosa Springs these sandstones are much altered, and in the canon, two miles below the springs, are not less than 500 feet thick. The surface of the upper stratum is covered by a mat of imperfectly-preserved fucoidal stems, which in some places is so close as to conceal the structure of the rock. In this vicinity. no dicotyledonous leaves were seen. Upon the sand- 384 ‘ GEOLOGY. stone rests a very dark-blue, almost black, shale, the same as that observed all the way from the Rio Piedra, and seen at several points west from that stream, almost to the Las Animas. Toward the base it contains many layers of very dark, fetid limestone. At the springs it is argillaceous, but higher up it is quite arenaceous, though retaining the dark color. Throughout, in this vicinity, it is more or less fossiliferous, containing scales and teeth of fish, Ostrea sp., and several species of Inoceramus, one of which is from 6 to 9 inches long, and covered with large concentric wrinkles. The cleavage planes are very distinct, and so close, that of the large Inoce- ramus no perfect specimen could be obtained, though the species is exceed- ingly abundant. The thickness of the shales, as exposed at this locality, is about 400 feet. From the San Juan to its tributary, the Rio Blanco, the road follows the shales, gradually rising so that the upper portions are exposed. These contain numerous thin layers of argillaceous limestone, grayish-blue, weath- ering light yellow, and full of Inocerami. The shales themselves are light- gray, and wear down to a whitish mud, which discolors the waters of the little stream; whence the name, signifying ‘“‘White River.” Crossing the Rio Blanco, the road passes through a somewhat romantic ravine, and rises quite rapidly, so that it soon reaches the sandstones of the Upper Cretaceous. These are mostly fine-grained, gray to yellow, somewhat argillaceous, and crumble readily under the influence of the weather. At the head of the ravine we come out into a beautiful park eroded from these sandstones. On its east side is the Cerro del Navajo, a low, mesa-like ridge composed almost wholly of the upper sandstones, bright yellow, and occasionally con- glomerate, while at the southwest in another mesa we see the same sand- stones resting on the dull shales of the Middle Cretaceous. Where the Rito del Navajo breaks through its mesa the shales are again exposed. In the park itself, exposures are few, there being none of any extent except one on a small tributary of the Navajo. The thickness of the Upper Creta- ceous, as seen in the various exposures, is not far from 400 feet, that of the Middle Cretaceous is not less than 1,200, while that of the Lower Creta- ceous sandstone, as determined on the Rio San Juan, is not less than 500, making the totak thickness of the Cretaceous in this region not far from CRETACEOUS. 385 2,100 feet. It is highly probable that the whole thickness of the Upper Cretaceous is not exposed along the line of our reconnaissance. The rocks of this upper division are, at most, sparingly fossiliferous here, for at the few exposures examined there were no traces of either animal or vegetable - life, other than a single, somewhat indistinct impression very closely resem- bling the nodose fucoid, so characteristic of the Upper Cretaceous farther east and named by Mr. Lesquereux, Halymenites major. Dr. Newberry, however, finds this species in great abundance at this horizon farther south in New Mexico. From the Ritodel Navajo to the Laguna de los Caballos, an ancient fresh-water but now brackish lake, the Upper and Middle Creta- ceous are conspicuous, there being many fine sections exposed in the mesas near the road. Crossing Horse Lake Pass, a narrow gap hetween two bluffs of the sandstone, we reach the Rio Grande area, and, at a few miles beyond the pass, come again upon the Lower Cretaceous sandstones. These are more or less altered and show no fossil remains, except on top, where several layers are covered with the ill-preserved fucoids already referred to, as occurring near Pagosa Springs. Upon these rest the shales of the Middle Cretaceous. These contain, near the base, the dark-colored fetid limestone in thin layers alternating with layers of dark shale, which prevail higher up, exhibiting only rare layers of blue limestone, weathering yellow and sparingly fossiliferous. Farther up the limestones disappear altogether and we find only dark shales, more or less arenaceous, the arena- ceous portions locally compacted into thin sandstones, while on top of all are the Upper Cretaceous sandstones, fine-grained, reddish-yellow below, and light-gray, weathering bright yellow above. The sandstones of the Lower Cretaceous closely resemble those of the Upper Cretaceous, both in structure and color, so that were it not for the metamorphism of the former, as well as for the frequent exposures of both in proximity along the route, one might readily mistake one for the other. Through this region the Upper Cretaceous is almost wholly non-fossiliferous, and the Lower Cretaceous is equally so, except in its upper layers. On the west slope of the Sierra San Juan the Lower Cretaceous rocks are traceable along the mountain-side to Tierra Amarilla, our most southern point, and are well exposed on the trail leading from that locality to San Luis Valley. 25ws ; 386 GEOLOGY. Along the line of this trail they are completely metamorphosed, many of the strata having been converted into a structureless quartzite, showing no lines of bedding whatever. Toward its base, if we take its thickness to be about 500 feet, is a conglomerate, and somewhat higher up we find a stratum containing numerous very thin seams of quartz, occupying all the planes of cleavage and giving the weathered surface a reticulate structure. Below the conglomerate there is a mass of altered rock, which, as already stated, may be of Triassic Age. The whole series rests unconformably against the Carboniferous rocks, which are seen near the summit of the pass. In the whole of San Luis Valley there are no exposures of Cretaceous rocks, everything, even on the eastern slope of the seus San Juan, being deeply buried under the eruptive rocks. Crossing the Sangre de Cristo Mountains by the Sangre de Cristo Pass, we reach the region lying between this range and the Greenhorn Mountains. For convenience sake, I include under the former name, also the western boundary of South Park and the Blue River range, and under the latter, the Kenosha range, extending up to Gray’s Peak. In this region there are iso- lated patches of Cretaceous in Huerfano Park, near the Arkansas Bridge, on Currant and Cottonwood Creeks, in South Park and on Blue River. In all these localities the character of the rocks is the same, but shows some interesting variations from that of the same series as observed in the San Juan country. The lower sandstones are variable in structure and thickness, and the Middle Cretaceous is a compound mass of clays, limestones, sand- stones, and variegated shales. Exposures of the Upper Cretaceous are not frequent, but show the rock to be somewhat coarser than where previously examined. At the lower end of Huerfano Park, where the road leading to Colfax, in Wet Mountain Valley, leaves Sangre de Cristo Pass, the Lower Creta- ceous is represented by quartzites poorly exposed and abutting against the mountains. For the most part, these quartzites are very fine-grained, almost white on freshly fractured surface, and weathering to a brilliant yel- low; but some of the layers are coarser, and weather to a dull, reddish- yellow. Near the Rio Puercos, a branch of Huerfano River, we find the CRETACEOUS. 387 sandstones of the Upper Cretaceous, which are unaltered. These rocks are moderately fine-grained, of irregular structure, and enclosing numerous patches of not very coarse conglomerate. They vary in color from gray to yellow, and are quite friable, weathering into fantastic forms. Some of the layers are quite compact and contain some calcareous matter, but no fossils were observed at any of these exposures, which are quite fragmentary. The total thickness is not less than 600 feet, but cannot be accurately determined. Of the shales below these sandstones the exposures are unsatisfactory, except of those near the base, which are well seen on the south side of the North Fork of Puercos River. There we find a series of dove-colored lime- stones, some of them dark on fresh fracture, and including a reddish arena- ceous limestone, which contains much calc-spar in very thin films. The limestones are in layers from 1 to 3 feet thick, and are separated by shales, some argillaceous, others arenaceous. The limestones are all more or less fossiliferous, especially near the reddish stratum, which contains great numbers of Ammonites, Inoceramus, Gryphea, Ostrea, and occasional fish- teeth. The thickness of this stratum is about 6 feet. Below the limestones there is a dark-colored shale or clay, in which the river has excavated its ravine. The whole thickness at this exposure is not far from 250 feet. On the north side of the river the sandstones of the Lower Cretaceous are seen underlying the clay shale. They are imperfectly exposed, but are unaltered, and somewhat shaly in structure. No rocks other than those of the Cretaceous were seen in Huerfano Park. On the east, at the base of the Greenhorn Mountains, the brilliant sandstones of the Upper Cretaceous are a striking feature, extending well up to the divide from Wet Mountain Valley, while west from the road they are seen capping the numerous mesas, and resting on the shales. They continue southeastward round the southern extremity of the Greenhorn Mountains to the plains. It is more than probable that the Cretaceous rocks once occupied Wet Mountain Valley, but the agent which scooped out that basin tore them away, and what remains of them is buried under the mass of débris forming the surface. A small area of Cretaceous rocks occurs on the road leading from Cur- rant Creek to Wet Mountain Valley, and extends from the head of Cotton- 388 GEOLOGY. wood Valley to the Dry Cation about four miles beyond the Arkansas Bridge. Where the road first strikes Cottonwood Creek we find the Lower Cretace- ous sandstones, white to grayish-yellow, and very friable, breaking down into loose sand under the influence of the weather. A little farther on the light-colored limestones of the Middle Cretaceous occur, but the intermedi- ate clay has been entirely removed from the surface by erosion. Along this valley, or rather park, the Lower Cretaceous rocks form hog-back ridges on each side, and toward the center are low ridges of the limestones, which here hold midway a reddish limestone like that already seen in Huer- fano Park. These limestones are rich in Inoceramus, and occasionally con- tain Ammonites. Near the bridge the lower sandstones are well exposed, and differ somewhat in character from those seen at the head of Cottonwood Park. A bluff afforded the following section, descending : Feet. 1: Sandstone, in thick Jayers, oray,----—2--- 2 see eee eee 20 2. Sandstone rede eas ae epee a eee SASaboanSs Sacioyssio+4 15 3. Sandstone, dark-lead color, shaly .......---.---.-.--------- volasi seh seea 8 4, Sandstone, red, soft, ripple-marked ..-.-...--.....---..---- .----.-------- 18 5. Sandstone, Vead-COLL Sie yy ae tea ota eee 13 6. Sandstone, white to grayish-yellow, soft EY, 2 SES eee 45 7. Sandstone, red, gray, and lead color, principally in thin layers, but contains a layer of coarse conglomerate, made of pebbles of quartz, granite, gneiss, and SOMO PPA GRYLE wee ois, ela ae ten a 60 179 No. 6 not unfrequently includes about midway a shaly layer, 6 to 8 feet thick. It, as well as the one below, is exceedingly friable. About a mile southward from the bridge No. 1 is seen to be light-gray on fresh frae- ture, but red on the weathered surface. It shows some cross-bedding, and contains numerous thin streaks of quartz closely crowded together, so as to give the weathered surface a reticulate appearance. A stratum of this char- acter has been seen at nearly every exposure of the Lower Cretaceous sand- stones. E At no locality in this little area were the clay-shales, overlying the sand- stones, observed. Where they should be, we see only grassy swales. About two miles from the river we again come upon the limestones, amid which the red stratum is conspicuous. This bed is about 4 feet thick, and con- CRETACEOUS. 389 tains many species, of which those of Ammonites, Gryphaea, Inoceramus, and Avicula are most abundant. Five large impressions of Ammonites were seen on the surface of a slab barely 3 feet square. Unfortunately the specimens are all in bad condition, and the Ammonites are seen only as impressions. This rock does not yield distinct specimens, except on the weathered sur- face. The total thickness of the limestones, as here exposed, is about 70 feet. They become more and more argillaceous above, and are succeeded by a gray shale somewhat arenaceous, upon which rests a bright-yellow arenaceous and thinly-laminated shale, which is the principal rock in sight as we approach Dry Canton. The Upper Cretaceous rocks do not occur anywhere in this area. Toward the cation these rocks abut against a quartzite, reposing upon the metamorphic schists. The age ef this quartzite is somewhat obscure, but owing to its position and its thickness, barely 200 feet, I am inclined to place it in the Silurian. In South Park the Cretaceous rocks occupy a synclinal trough, lying east from Fairplay, and extending from the mountains at the north to very near the southern boundary of the park. The sandstones of the lower division are traceable along the western border in a series of broken hills. The first ridge, east from Fairplay, shows them to be mostly white or light- gray, of varying degrees of coarseness, very friable, and about 300 feet thick. Farther south the South Fork of Platte has cut a cation through these strata in which they are seen resting directly on the metamorphic rocks, but are themselves entirely unaltered. The lowest stratum is fine-grained, white, quite soft, and shows thin streaks of quartz. Upon this rests a con- glomerate made up of quartz pebbles, rarely more than one-third of an inch in diameter, and cemented by material evidently derived from disintegra- tion of volcanic rocks. The highest stratum is a compact, gray sandstone, of which many layers are covered by remains of fucoids, similar to those occurring at the same horizon in the San Juan region. On the eastern border the exposures are rare. A rock resembling the conglomerate was seen on Tarryall Creek, but the exposure is too frag- mentary to admit of positive determination. At the Sulphur Springs the series is well exposed, but all parts are completely metamorphosed. A specimen of fossil wood was obtained from the top stratum. The conglom- 390 GEOLOGY. erate is converted into a quartzite of singular beauty. At this locality the group rests directly on the metamorphic schists. About four miles north- west from the Sulphur Springs there occurs a curious hill, tapering north- ward, and spreading out southward in three prongs. It is wholly covered by débris, except at the southern extremity, where a conglomerate is exposed, consisting of fragments of gneiss, granite, trachyte, quartzite, and limestone, all water-worn, and held together by sand resembling that of the surround- ing plain. Pieces of silicified wood, also water-worn, are quite numerous. The fragments vary in size from small grains to 16 inches, and the mass is more or less ferruginous throughout. This conglomerate is occasionally seen farther southward, almost to the cation of the Platte. Its age is very obscure. It certainly marks the ancient river-bed, and so is probably com- paratively recent in its origin. At the same time it bears a remarkable resemblance in general structure to one stratum of the Lower Cretaceous seen near the Arkansas Bridge. The Middle Cretaceous is imperfectly exposed in those portions of South Park visited by our party. The shales at the base, immediately un- derlying the limestone, are present in small quantity, or are entirely absent, in many localities. At the Sulphur Springs the limestones are imperfectly exposed. The rock is light-blue, somewhat fetid, variable in structure, from fine-grained to slightly crystalline. It has been affected to a considerable extent by metamorphosing influences, and breaks readily along well-defined planes of cleavage. An attempt was made to make lime from it, but the result was evidently unsatisfactory. Some of the half-burned fragments yielded specimens of Inoceramus and imperfect impressions of Ammonites. The rock freshly broken from the stratum showed no signs of fossils. Be- yond the first ridge east from Fairplay is a broad swale, occupying the space in which the lower portion of the Middle Cretaceous should be exposed, so that neither the shales at the base nor the overlying limestones are seen. But the next ridge eastward is composed mainly of the dark shales belong- ing to the upper portion of the group, which contain nodules of limestone, more or less gypsum, and nodules of iron-ore, which frequently contain fos- sils. On Trout Creek (in South Park) there are several localities which yield characteristic Cretaceous fossils in great abundance. CRETACEOUS. 391 The junction of the Upper and Middle Cretaceous was -not seen. Indeed, at no place examined by our party are the Upper Cretaceous rocks satisfactorily exposed. Near the village of Hamilton two beds of lig- nite occur, in rocks belonging to the middle division of this group. The following seems to be the section at the locality, as determined by inspec- tion of the several shafts sunk on and in search of the beds: ie Mebrisiand clay) 25 2524 5 .2\c5--.-= PSE OOS Sean ame 10 feet, Sy. TATU pace cerdc. Cec od 660 Ca a HOC OCR ROO CU ECRD Epa aCRer Epes 12 feet. 3. Fire-clay ..-.-.. Sats dae sataraine Es eater cinicle 2 ctsiancie = secs} lectiiete ae 2 feet. APU MANOSOUE) setsoa)-bisiars\ciels/cie ef Ses) = <= BPP taeyaneria(lachaye heieiote siete) stetciele 2 feet IN). [STE PA ease epee te oc 6 HONE SSD e OE RES ae Se ee a eae 2 feet 6 inches. Gs SPENDS (Aeadotednes dc Gu se Cet eo CeO nRe Ee eee eee eee 12 feet. Tip INDEGEY Gat ob eedase ocecustde Cbdo Gubo sep es pase ose paotoD. 2 feet. RMB IGAIS INCRE RItttn toy folate oe) = cS ote) he Se wiare ateene a ol ee sles nis o's oo oe EB ifeet Orne: Clay SCONe eins a sienjnee oie is he Selassie se) Sse SEO SUID ATES 2 feet. It is by no means improbable that a third bed of lignite belongs to this group, for at the grave-yard, on a level with the outcrop of No. 2, and some distance east from it, the indications of coal are very distinct, but no exam- inations have been made to test the matter. Neither of these beds has been worked sufficiently to determine accurately the quality of the coal. No. 2 is opened by a shaft directly upon the seam, which, after passing through débris and fire-clay for 10 feet, reaches and cuts through the bed, exposing its thickness. The total length of the shaft and the incline at its foot is about 30 feet. The better coal is found at the bottom, and the proprietor mines only the lower half of the bed. The dip is very sharp, nearly 40°, so that mining operations will prove very expensive. This coal, when freshly mined, shows a clean fracture and a glossy look, not unlike that of cannel, but upon exposure it disintegrates rapidly. An analysis, by Prof. E. T. Cox, shows the following composition : SIDAGITO LON Seo5! | besos aD so SSee poreroee Ba Gd Gk Be Ceson Sobre oonca sass 1.254 Weight of one cubic foot, pounds ..-..-.- .--. - 2-250. - eee eee reece ee Jgnsecide 78.37 TPE, GPT cod Hod Sede SOR eee ee Ses Ser ae Rete ei At aie 55.58 EEE Geers MEINE Press ae id res las wn gta elegans « oleic Meld aaiaute a weloe eceres 4.50 in ieKCOmulstiplermthbele. >. ose: tsar. 2% olntais oo Poleielole atcelepemareds eealecce's 37.92 BARS CS eee RE eee oo ain sooss'aiw cle’ osc 'c ate aero elwicl ere dle alsinle inte eleb/aluloraietelevevaya a’. 8) “25052 coe eee eee ee noes ores eee 4 feet. The gravel consists of trachyte and quartzite, with rarely some gneiss. The thickness of this debris, as seen on Tarryall Creek, is more than 70 feet, that being the extreme height of the terrace. From Hamilton down for two miles or more it is quite auriferous, especially near the base, and in the earlier history of the vicinity was the scene of extensive gulch-mining. The gold was derived from the eruptive rocks and the quartzites, there being no other rocks on the eastern slope of Hamilton Pass. Looking west from the Kenosha range, the southern terrace is seen to be the level of this por- tion of the park. North from Tarryall Creek, the surface is badly cut up by numerous little streams, and shows many knobs of detrital material, which of course vary much in height, but such of them as have suffered least, show a summit reaching to nearly the same level as the terrace, which stretches southward unbroken almost to the Platte. West and southwest from Fairplay a similar condition exists. From the Platte River the surface rises in a succession of terraces to the mount- ains, all bearing more or less of vegetation, and covered by fine soil con- taining much gypsum. Similar terraces are seen on the west side of the river in the southern portion of the park. On the hills the old lake-level is ANCIENT LAKES. “455 well shown, not only by the line of timber, but also by the slope, which is quite gradual from the valley up to the trees, but above that line becomes abrupt, as if worn by incessant action of moving water. Several of these hills are eroded in a manner which would have been impossible had the lower portion been unprotected, for above the lake-level they are cut down so as to resemble little ridges, while below the level they are intact. On several hills east from the Platte and southwest from the Sulphur Springs, a succession of terraces are seen marking the lowering of the lake as its waters were drained away. It seems hardly probable that this basin owes its origin primarily to glacial action. The arrangement of the rocks leads to the supposition that here there existed a synclinal trough, deepening southward, which was merely enlarged by the ice. Into this trough the great glaciers from Jef- ferson and Hamilton Passes, originating in Gilpin’s Pillars and Mount Morton, together with those from Mount Lincoln, Mosquito Pass, Horse-Shoe gulch and Stony Point Pass, with others from the Kenosha range, moved down until the whole was full. Those on the east ground the Kenosha range down to a level far below that of the mountains at the west, and doubtless aided in wearing down the partial fissures now greatly widened, ‘through which Tarryall Creek and the South Platte River find their way. The glacier could not have left the park until these gorges had been deeply eroded, for at the southeast the lake seems to have had an extreme depth of only 140 feet. The retreat of the ice was followed by the formation of the lake fed by streams issuing from the numerous glaciers. This was gradually drained as the canons of Tarryall Creek and the Platte were deepened, until nothing remained but ponds, whose position is marked by patches of alkali. The deepening of the cafions has gone on, until now Tarryall Creek flows 70 feet below the lake-bed, near the old shore-line at the northeast, while the Platte, running more nearly along the line of greatest depth, is but 25 feet below the old bed at the south. The Upper Arkansas—From its headwaters to its junction with Ten- nesseé Creek, the Arkansas flows through a deep and narrow glacial gorge. In like manner from Tennessee Pass to the junction the excavated channel-way is narrow. But below that point the valley widens, and to 456 GEOLOGY. the head of Granite Cation maintains a width of from five to eight miles, as measured at the level of the topmost terrace. From the head of Granite Canon, almost to Cottonwood Creek, the extreme width from base to base of the mountains is little more than one mile, but at the end of the canon it again expands and soon attains a width of nearly eight miles, measured as before, which continues to the South Arkansas River. The width as here given differs widely from that at first apparent to the casual observer, for the main terrace in some localities projects so far as to render the flood-plain very narrow, while in others it has been so extensively eroded that the plain below which the river flows, as near Chalk Creek, seems to reach completely from mountain to mountain. The upper basin reaching from the junction of the river and Tennes- see Creek to the head of Granite Canon, a distance of twenty miles, shows an extreme width of eight miles, measured, as has been stated, on the surface of the upper or main terrace. The slope of the basin is very slight, there being but a small difference in level between the mouth of Colorado gulch and the surface of the river at the head of the canton. The river flows almost centrally through the basin, which is flanked on each side by a magnificent range of mountains. The first terrace at the east is low, only a few feet above the present flood-plain, and extends eastward somewhat less than one mile to the escarpment of the second or. main terrace, which here reaches to a height of nearly 200 feet above the river, and presents a front unbroken for several miles, save only where some large stream has worn outa broad, deep ravine. Its upper surface rises gradually for about four miles with a grade of somewhat more than 50 feet per mile, until at old Oro City, where the terrace ends and the moraine begins, the elevation is 420 feet above the river. At one or two points near the mountains there appears to be a still higher terrace, as seen from the river, but this I am inclined to regard as the remains of a moraine, since no terrace was seen in that position, though moraines were. The composi- tion of the terrace is seen near the junction of the river road with that coming down from Stony Point Pass, there being at that locality several minor terraces formed by the tributary creek. The sorting and stratifica- tion appear in the alternating layers of fine and coarse gravel. Southward ANCIENT LAKES. 457 from this place the terrace is much broken by erosion and its continuity is soon lost. On the west side of the river the condition is very different. The first terrace is of limited extent and is soon lost in the second, rising 20 feet above it. This is the prevailing terrace northward from Half-Moon Creek. Remains of a third terrace are seen near the mountain in the vicinity of Colorado gulch, but they do not become continuous until we cross Willow Creek, where the third terrace is seen, which continues almost to Box Creek, where it has been entirely eroded by the many branches of that stream. At the lower end of this basin the mountains of the western range, the main divide, jut out into the valley and almost close it. Here we find the gorge in whose floor the Granite Cafon was eroded. The walls of the cafon are in many places vertical, rising 50 to 200 feet above the stream, while the cation itself is so narrow as to afford barely room for a road alongside of the river. The floor of the main gorge, which for our present purposes may be regarded as continuous between the mountains, is quite irregular, sloping on each side to the central line. Numerous low ridges of rock stretch entirely across and separate small level plains of five to ten “miles area. Fragments of rock, many of them of enormous size, are scattered here and there, usually without any order, all of them angular, with no signs of rolling or water-wear. The surface shows a few abrupt descents, but for the most part the slope may be regarded as comparatively regular to near Cottonwood Creek, where the cafion ends and we reach the second or lower basin, which continues to the mouth of the South Arkansas.* From the end of the cafon the basin opens out on both sides, widening as it descends, until at Chalk Creek it has a width of nearly eight miles. The terraces have been removed almost entirely over a large area in the upper portion, so that in the vicinity of Chalk Creek but one remains. This rises nearly 18 feet above the river and stretches on both sides of the stream almost unbroken to the base of the mountains. Through it several of the larger streams have worn down quite deep channel-ways, with wide flood-plains, which are sufficiently extensive to be the scene of agricultural * My information respecting the cafion is from other members of the party. I did not visit it. 458 GEOLOGY. operations. In several of these secondary terraces occur. This important terrace is persistent, and maintains its integrity to Gas Creek, near which it is interrupted. Below that stream the immediate valley becomes narrow, owing to the presence of a mass of the upper terraces, which by some means has escaped erosion. Here, beginning with the flood-plain, eight terraces can be counted, whose surfaces all slope toward the river. At one locality the whole mass is cut down and exposed in a vertical bluff to the thickness of 40 feet, showing it to be made of stratified sands and gravels with thin layers of argillaceous material, the strata varying in thickness from 3 to 12 inches. Large fragments of rock are altogether wanting, there being no bowlders more than 3 inches in diameter, and few of so large size are seen. In this respect the deposit differs much from the river bed, which is littered with large bowlders, as indeed is the whole escarpment of the lower terrace in which the present flood was excavated. From this relic of the upper terraces to near the South Arkansas only the first terrace is continuous. As we approach that stream the valley becomes very wide, and at last becomes one with that of the tributary. Where the two valleys unite three terraces are seen, which extend up the South Arkansas. They are evidently secondary and owe their origin to that stream. The material composing these terraces is consolidated into a rock of little tenacity, which yields readily under the influence of the weather. Some of the conglomerate layers are moderately compact and disintegrate less rapidly than the underlying finer layers, thus causing the rock to weather into eccentric forms resembling chimneys, urns, and helmets, very similar to the curious shapes seen along our eastern border in rocks of Cre- taceous and Tertiary ages. Such are the conditions observed in this valley. The history is clearly written. This great trough was excavated by the magnificent gla- cier of the Arkansas, which once reached, an unbroken sheet of ice, from the headwaters of the river to the Great Canon below the South Arkansas, receiving noble tributaries from the cations of California and Iowa gulches at the east, and of Tennessee, Willow, Half Moon, Lake, Clear, Cotton- wood, and Chalk Creeks at the west, together with many smaller accessions from each side. Beyond the Great Canon it never passed after it was sepa- ANCIENT LAKES. 459 rated from the mass which once overspread this whole region from the top of the main divide to South Park. From the junction of Tennessee Creek with the Arkansas, the surface, taking the surface of the upper terrace as the original plane of the glacier’s bed, steadily declines to the South Arkan- sas, so that when the glacier stretched to its extreme southern line, it rested on a rocky floor above the Granite Catton, whose level was that of the main terrace east from the river in the upper basin. The retreat of the ice-stream to the vicinity of Cottonwood Creek left the lower basin open, and so in- duced the formation there of an extensive fresh-water lake. Atasomewhat later period the glacier retreated to the line marking the southern limit of the upper basin, where it must have remained alternately retreating and advancing for no inconsiderable period, until the upper basin was excavated. Here, too, eventually, a second lake was formed, whose waters escaped into the lower lake through the broad gorge in whose floor the Granite Cation has been eroded. These lakes, fed by streams issuing from extensive gla- ciers, of which we find the traces in the cafons on each side of the river, must have existed for a long time, as is shown by the mass of till accumu- lated in the terraces, and their draining must have been very gradual, as appears from the number and gradual slope of the terraces. This drainage was effected simply by the deepening of the canons. The history of the little basin of Pleasant Valley, at the mouth of the Great Cafion, is much the same as that of the Upper Arkansas, but in the valleys of Texas and Grape Creeks some interesting features occur dissimi- lar to any already noted. These two basins pass imperceptibly into each other, and are doubtless one in origin. Wet Mountain Valley is drained by Grape Creek. It is united on the northwest to Texas Valley, drained by Texas Creek; on the northeast to a somewhat similar park, which com- municates with the Arkansas by means of the Dry Camion, while at the south it is separated from Huerfano Park by a divide much lower than the Sangre del Cristo Mountains. It is probable that the surface of the lake at no time reached above the- Huerfano divide, but that the same body of water was continuous over Texas Valley, Wet Mountain Valley, and the little park at the northeast. From this lake there must have flowed to the Arkansas three streams, Grape Creek, Texas Creek, and the third through 460 GEOLOGY. the Dry Canon. As the drainage went on, Texas Valley was at length occu- pied by one lake, and the remaining portions by another, both of which were finally drained by their respective outlets. An extensive lake at one time occupied the basin through which the Arkansas flows below Cation City, but our observations are insufficient for discussion of it, as they were confined to the vicinity of that city. Other areas, formerly occupied by lakes of glacial origin, were observed in*the interior region along tributaries of the Arkansas, but they are of limited extent and hardly deserve even a passing reference. Direct evidence respecting the glacial origin of San Luis Valley is almost wholly wanting, and our conclusions must be drawn from the physi- cal structure of the region. In eruptive rocks the results of aqueous ero- sion so closely resemble those of glacial action that one is frequently unable to determine the agent producing the phenomena in a given locality. But the whole character here seems to admit of no inference other than that the valley is the result of glacial erosion. The valley is a true basin, and its only outlet is southward through the cation of the Rio Grande. At the south and southwest, somewhat beyond the New Mexico line, the surface is almost as high as the Sierra San Juan, but from those points it slopes grad- ually toward the immediate basin until within a few miles of an east and west line passing through to Fort Garland, where it falls off quite abruptly. At the southwest, this abruptness is the more marked, owing to the erosion of plazas by the Rio San Antonio and its branches. On the west, the San Juan Mountains descend in a succession of long, low, sloping terraces, and gradually merge into the valley. At the north, the mountains break away so irregularly, because of the numerous streams, that the general slope of the surface can hardly be determined, except by very close survey. At the east, the Sangre de Cristo Mountains rise abruptly from the plain as far south as Fort Garland. Beyond the fort an interesting park exists at the base of the Sierra Rondo, or the southern prolongation of the Sangre de Cristo Mountains, and extends quite to the New Mexico line. It is from one to three miles wide, and is separated from the long, gradually-sloping surface at the west by a sharp, mesa-like wall of eruptive rock. The greater portion of this park is watered by the Rito Culebra, which breaks the wall ANCIENT LAKES. 461 at San Luis, fourteen miles south from Fort Garland. A low, terraced divide separates the RitoCulebra from the Rito Trinchara, which flows by the fort. The area of the present basin reaches westward to the San Juan Mountains, northwestward to the settlement of Saguache, northward to near the head of San Luis River, eastward to the Sangre de Cristo Mountains, and southward to a line reaching from Fort Garland to the Plaza de los Pinos, and having a rudely west-southwest direction. The original area was much greater southward and southeastwardly, reaching in those direc- tions beyond the New Mexico line. The northern portion of the basin has no outlet for its waters, and is separated from the true area of the Rio Grande by a low divide reaching across the valley and probably not more than 25 feet high, taking the level of San Luis Lake as the base. This northern portion is the true San Luis Valley, the drainage area of the San Luis River. It is divided north and south by a tongue of eruptive rock, which reaches from the main divide almost to Saguache, and separates the waters of Saguache Creek from those of San Luis River. These streams empty into the great marsh known as San Luis Lake. The soil is so porous that many of the streams from the San Juan Mountains diminish rapidly after reaching the plain, and finally sink in the sand before entering the lake. A similar condition exists in the southern portion of the valley, where the Rito Alamosa sinks before reach- ing the Rio Grande, though when it emerges from the mountains it is a very considerable stream. Throughout San Luis Valley, both in the present basin and on the elevated slope southward, the surface is covered with débris derived from the volcanic rocks of the vicinity. Near the mountains this material is a coarse gravel, with some moderately large fragments, but in the central portions of the basin it is exceedingly fine and affords a soil of remarkable fertility. From the center the surface rises in terraces to the periphery of the basin. If we examine the elevated slope at the south we find it about thirty miles wide, and nearly midway showing a broad depression, at the bottom of which the Rio Grande flows. Followed southward, this depression be- comes narrower, and at length disappears in a deep, gloomy caflon beyond 462 GEOLOGY. the New Mexico border. Northward, it is separated from the main basin by a short canon, which begins where the surface falls off abruptly toward the valley. These general characteristics show beyond a doubt that this whole region, as far south as the New Mexico border, and as far north as the head of San Luis River, was at one time occupied by a great fresh-water lake, covering an area of several thousand square miles and fed by streams com- ing from the mountain glaciers. To me it seems not improbable that the glacial mass was of equal extent, and that in its retreat northward it delayed for a time, its foot occupying the line marked by the abrupt wall forming the southern boundary of the present basin. The lake must have occupied the subordinate park under the Sierra Rondo, as its outer wall is lower than that portion of the slope directly west from it. The broad trough in this slope marks the narrowing limits of the discharging stream, as the lake-level was lowered by the deepening of the cation southward. The main supplies for the lake must have come from the Upper Rio Grande and from the southern portion of the Sangre de Cristo Mountains, while the accretions from the Saguache and San Luis portion were com- paratively small. The Rio Grande has been persistent throughout, and the slope everywhere in the southern part of the basin is toward that stream. When the deepening of the Rio Grande Cation lowered the surface of the lake below the almost imperceptible ridge now dividing the valley, the amount of water coming from the north was not more than enough to over- come the loss by evaporation, otherwise a channel would have been cut through the divide and the northern section would have become tributary to the Rio Grande. As it is, no great lake exists in the northern portion. The supply of water has been so small that the lake has contracted to the limits of the present swamp, its waters having been removed partly by absorption into the ground, but principally by evaporation, as appears from the large proportion of alkali in the soil, and from the frequent occurrence of alkaline salts in white patches upon the surface. The basin of the Laguna de los Caballos, though possibly ‘tht due to glacial action, is of interest, as the lake has not entirely disappeared, and as it illustrates directly the drainage by deepening of the outlet channel. It ANCIENT LAKES. 463 is on the main divide and only a few miles south from the northern line of New Mexico. A short narrow passage through a wall of Upper Cretaceous sandstone, forming the Horse-Lake Pass, leads from the basin to the area of the Rio Chama, and the lower extremity of the lake reaches quite to the pass, which is but little higher than the surface of the lake. Through this pass the surplus waters were formerly discharged and found their way to the Rio Chama. The basin is not large, and is surrounded on all sides by low hills, which are deeply covered by débris and have a mammilated surface, as though made up of fragmentary terraces. This structure reaches up to a level with the top of the sandstone wall, through which the old outlet passed. The surface of the lake is now barely 10 feet below the summit of the pass. There being no longer any outlet the water is exceedingly alkaline, and the soil surrounding it is impregnated with salts. At no very distant period it was inhabited by fresh-water mollusks, of which the bleached shells are still to be seen on the shore as well as at various levels, 15 to 20 feet above the surface of the lake. Along the Rio de las Animas we find a series of parks, whose origin can hardly be accounted for on any hypothesis other than that of glacial erosion, though here, as in the case of San Luis Park, the eruptive rocks predominate, and all direct evidence is wanting. From the Rio Grande Pass, of which mention has been made in another chapter, we come down through Cun- ningham’s gulch into a small park on the Las Animas, about seven miles long by half a mile wide. At its lower end this is closed by a canon, through which the river flows into a somewhat larger basin called Baker’s Park. In this lower basin the river is joined by two large streams, Mineral and Cement Creeks, and afterward enters a close, narrow caiion, said to be impassable, which continues for not less than twenty miles to Las Animas Park. The Rio de las Animas rises in a deep amphitheater, not far from the source of the Rio Grande, North Fork, and flows southward to the Rio San Juan. At ashort distance from its head it enters a close cation, choked with débris, in which the stream is almost lost. At the mouth of the cation the river re-appears in the upper park. Unlike the cation of the Rio Grande, this park and its neighbor, Baker's Park, are shut in, not by ridges with regular crests, but by mountains, whose irregularity- is almost 464 GEOLOGY. indescribable. These terribly rugged hills show no terraced slopes, but only successive cliffs, sometimes 1,000 feet high, and almost vertical, between which little streams dash down along narrow ravines, their beds sloping at from 30° to 80°. The crests of these mountains are rude knolls, or craggy cones, reaching to a height of 3,000 feet above the river, and in some cases to 13,500 feet above the sea. At the mouth of Cunningham’s gulch there is a grand cone, about 13,600 feet high, scarred on all sides by deep ravines, and surrounded for half its height by a vast talus, above which steep bluffs render the top inaccessible to the ordinary traveler. About one mile below Cunningham’s gulch the river enters a narrow canon, whose walls rise about 50 feet to the old floor of the glacier, which descends with gradual slope, though the surface is irregular, to Baker’s Park. Here the mountains are hardly so harsh in outline as those of the upper park, and erosion has so separated them that the scene is more open, and one is less oppressed by the painful feeling of confinement. But the true con- dition is no better, for both basins together form as terrible a trap in autumn as one can well imagine. Shut in on all sides by mountains 12,000 or 13,000 feet high, with no pass lower than 11,500 feet altitude, this region is prac- tically closed against ingress or egress early in November, and so remains until late in the spring. Midway between the parks, a stream comes in from Little Giant gulch, an imposing amphitheater, whose walls rise nearly 1,500 feet above the floor of the cup. At the southern extremity of Baker’s Park the river enters a deep cation, whose walls are close, and almost vertical to a height of about 200 feet. At that distance above the stream the gorge widens and presents an appearance similar to that of the country between the two basins of the Upper Arkansas. Of the relation of this cation to the main Animas Park below, it is impossible to speak, for the oldest wanderers in this region are unanimous in declaring that it is utterly impassable for either man or beast. There can be little doubt, however, of the persistency of this broader portion for a considerable distance, since, two miles below its head, a fine amphi- theater is seen, whose western wall rises 1,800 feet above the floor, while its eastern wall is crowned by as fine a nest of crags as was observed during the whole season. Other amphitheaters exist farther below, as far as one can see, ANCIENT LAKES. 465 so that from the general character, I am inclined to suppose, in the absence of all direct information, that this floor of the broader portion of the cation reaches quite to Las Animas Park. An examination of Baker’s Park, and the one adjoining it, shows at once that the history of this region differs but little from that of the Upper Arkansas. In both parks we find terraces, which mark the gradual draw- ing off of the waters. The glacier which, as I take it, at one time occupied the broader and higher portion of the great camion, halted, in its retreat, at the head of that cation long enough to admit of wearing out Baker’s Park. During the farther retreat of the glacier, the lower basin was filled with water. This retreat was slow, for we find much débris upon the rocky floor above the small canon separating the two basins. In a similar manner the upper park was eroded, and, after the glacier retreated to the long canon above, was filled with water. The lakes were drained, as were those already referred to in connection with other localities, simply by the deepening of the cafons. Their existence was of short duration, as compared with that of the Arkansas lakes, for the amount of débris is small, its extreme thick- . ness, as shown above the stream, being barely 60 feet. Crossing the high divide from Baker’s Park we reach a wide canon with long, gradual slope, descending southward, and flanked by sharp mesas. At a short distance from the summit a broad camion opens into the first, from the west, at a small angle, and so likewise farther on, a second, a third, and others, until, at length, we find ourselves in a beautiful park, thirteen miles long, by about one wide, which is Las Animas Park. Continuing south- ward, the condition is reversed. Low ridges, rudely parallel, and terminat- ing northward en échelon, are thrust from the eastern side into the park, so that the open space becomes less and less until it is finally shut off by an abrupt wall at the south. Through this the river passes in a grand cafion, whose sides rise 1,500 feet above the stream, (Newberry.) Looking northward from Animas City, near the head of the park, one sees a broad floor at a considerable height above the bottom of the canon and sloping rather gently toward the park. The great canon, bounded by jagged mountain walls, really terminates at the junction of the river and Cascade Creek, several miles above Animas City, but the broad floor 30 WS - 466 GEOLOGY. becoming wider reaches quite to that settlement, and is everywhere littered with water-worn fragments of rock. The bed of the river is paved with bowlders of granite torn from the mountains through which the camion is cut. At the head_of the park two well-marked terraces are seen on the east side of the river, the first rising 5 feet and the second 15 feet above the stream. On the west side these have been removed by erosion so far that small fragments only remain. Following the trail on the east side, we soon rise above the second terrace, and at the height of 80 feet above the river find the surface strewn with fragments of granite, syenite, quartzite, and limestone, mostly water-worn, and resting on unaltered rocks, showing that the river must have flowed at this elevation. Farther down the upper ter- races have been entirely removed, and there remains only a long slope stretching from the mountains on each side to the river. Here is the true Animas Park, whose agricultural value has been so highly extolled by those interested in the San Juan mining region. Its surface is covered by strati- fied sands and gravels, which are exposed in gulleys to the thickness of 20 feet. About ten miles below Animas City, the trail turns off sharply east- ward to strike the wagon-road leading to Tierra Amarilla. On this trail we find water-worn fragments of granite and gneiss resting on the dark shales of the Cretaceous, and somewhat more than 200 feet above the river. The origin of this park cannot well be explained by our observations, which were made in haste. Whether or not the glacier of the Animas reached to any distance in this basin I cannot say. It certainly reached to near its head, for its former existence in the cafion is quite evident. Along Cascade Creek and the other cafions leading into the park no evidences of glacial action could be found. It is very clear, however, that this whole basin has been occupied by a body of water in motion, whose bed originally was many feet above the present stream, as is amply proved by the pres- ence of transported bowlders. The successive depressions of this bed and the consequent narrowing of the channel are shown by the several terraces, on all of which transported fragments, water-worn, and of comparatively large size, were seen. The many canons, almost parallel, which by their union form the park at its head and the similar series at the lower end, seem to militate against the hypothesis that the basin owes its origin to glacial ANCIENT LAKES. 467 action. Though somewhat in doubt, owing to imperfect information, I am inclined to regard the whole as due to ordinary erosion by running water. Similar instances, though on by no means so large a scale, occur along the Rito Florida and the Rio Piedra, and are beyond all doubt the result of simple erosion by running water. The cafion of the Rio Grande, extending from the head of the river to San Luis Valley, is due in its present shape almost equally to both glacial and aqueous erosion, and so should most properly be referred to in this con- nection. The river is formed by the union of three main forks, each of which flows through a deep cation. That of the Middle Fork is much broader than the others, and has a somewhat irregular surface marked here and there by small basins connected by shallow cations. Its walls are ex- ceedingly abrupt, and rise 1,500 feet above the stream, and their crests are weathered into architectural forms of the wildest eccentricity. Toward the junction of the forks it widens and becomes a park, whose surface slopes each way toward the river, which flows near the southern wall. About a mile below the junction the river enters a magnificent canon, twelve miles long, whose south wall is abrupt, densely wooded, and rises nearly 2,000 feet above the stream. The north wall is equally abrupt to a height of from 75 to 300 feet, beyond which it rises with a slope of 20° to 30°, 400 feet higher to a rude terrace reaching back to palisades, the true wall. The south wall is broken but three times, and then only by tributary streams issuing from cations as gloomy as the one which they join. Twice the gorge opens out into a very narrow park, occupied by a marsh, through which the river meanders in a succession of horse-shoe curves. It is by no means improbable that at one time the river-channel occupied a depression immediately north from the cation and rudely parallel to it, through which the wagon-road passes. Of this, however, I am unable to speak positively, as no opportunity was afforded for careful investigation of the matter. At the mouth of the canon, the river, turning sharply southward, enters a beautiful little basin known as Antelope Park, which possesses a some- what melancholy interest, as it was the scene of Frémont’s disaster in 1849. It is rudely oval in outline, the longer diameter, two and one-half miles, being in a north and south direction. The river, entering about the middle, AG8 GEOLOGY. hugs the western wall, and a little stream meanders sluggishly through the plain from the east to the river. North from the river the western wall is low and somewhat broken, while southward it is high and very abrupt. There seems to be little room to doubt that in ancient times the river entered the park at its northern end by means of the depression, already referred to, which is traceable to the park. On the eastern side the surface rises grad- ually from the plain to a height of nearly 350 feet in a distance of not more than halfa mile. The face of this ridge-like hill, separating Antelope Park from a long narrow cafon at the east, shows a series of confused benches, evidently the remains of terraces, but now so disguised by erosion that the surface is simply mammilated. In the park itself two distinct terraces exist. This basin is closed abruptly at its southern end by a tongue extend- ing from the eastern wall, and the river flows out under the western wall through a short narrow gorge into another park, where its course is turned sharply to the east. The southern wall is deeply indented by a broad trough, which is itself cut up into severai smaller troughs by low narrow ridges. This trough, covered by water-worn fragments of rock, was form- erly the bed of the river. On the east side of the trough we find the east- ern wall of Antelope Park, which gradually descends to the park below. Along this portion we find its surface eroded into hummocks, among which are many oval depressions without communication, which at certain sea-° sons of the year are filled with water. When we passed through, the ponds were dry, and the only evidence of their previous existence was the saline incrustation covering the surface. Everywhere along this ridge, the body of which consists of voleanic rocks, one may see the most satisfactory evi- dence of depression of level in the river-bed, for the surface is covered with water-worn fragments of trachyte, gneiss, syenite, and quartzite, varying from 6 inches to 2 feet in diameter and mingled with gravel and fine sand. None of these is angular, as if transported on a glacier. Many of them must have been brought from the headwaters of the river, as is manifest from the character of the rock. The cation lying east from Antelope Park is one of the gloomiest of the many gloomy canons opening into that of the Rio Grande. It enters the park just below the Little Antelope basin. The principal interest attach- ANCIENT LAKES. 469 ing to it lies in the fact that the stream by which it was excavated has changed its channel, and no longer flows through it to the mouth. This stream, which is a very powerful one, has broken through the western wall of the cation and now empties into the Rio Grande a few miles below An- telope Park. Below Antelope Park the river valley is for the most part a succession of broad beautiful parks until it reaches the Twenty-nine-Mile ranch, twen- ty-nine miles above Del Norte. Throughout this distance the surface is quite level and deeply covered by ordinary gravels, which are arranged in only two terraces, both of low height. Thirty-eight miles above Del Norte we find the yellow sandy shales, formed entirely of detritus derived from the voleanic rocks in the vicinity, and reaching up the side of the northern wall for more than 200 feet above the river. This deposit, which is purely local and of fluviatile origin, has been described in a previous chapter. Above the Twenty-nine-Mile ranch the park is very wide, and the mount- ains on each side rise from the plain with a gradual slope, and for the greater part are free from that abruptness which characterizes the walls above this locality. From the ranch the valley is a canon for sixteen miles, seldom more than one-eighth of a mile wide, and with harsh abrupt walls rising from 300 to 1,500 feet above the river. At the junction with the so-called * South Fork, the valley begins to widen and gradually opens up until at Del Norte it merges into the San Luis Valley. Beginning, then, with the Middle Fork (Deep Creek) and following the river down to Del Norte, we find the following conditions: On Deep Creek, a broad canon, becoming a park with irregular, more or less hummocky surface, and closed by a deep narrow canon, on whose north side is a ter- race covered with water-worn fragments of rock. Below this cation is An- telope Park, the first of a succession, its boundaries terraced and bearing many transported fragments. This line of parks is closed by a deep canon, which continues to San Luis Valley, which has been described already. The close resemblance of these conditions to those observed along the Arkansas and the Animas would lead one at once to suspect that this great gorge originated as did those of the rivers referred to, especially as there is no room to doubt that glaciers existed at several localities along the north- 470 GEOLOGY. erly side of the north wall as well as on the Animas in the immediate vicinity of the Rio Grande. I have already stated that glacial and aqueous erosion were equally concerned in the formation of the valley. An exam- ination of the details, however, shows that it is impossible to explain every- thing without much difficulty. Thirty-eight miles above Del Norte there is found the local deposit of leaf-bearing arenaceous shales. Possessing an eastward dip of about 3°, and being distinctly non-conformable to the unconsolidated gravel terraces which they under-run, they must date back beyond the existence of the lake on whose bed the terrace materials were distributed. The purely local nature of the deposit, as well as its composition, shows its origin to be due to fluviatile action. The character of the flora, containing, as it does, many specimens of Platanus, a genus utterly unknown in the whole region, and, under present circumstances, unable to exist at the altitude where the shale occurs, shows that the time of its deposition must be quite ancient, reaching certainly into the Tertiary, and far anterior to the existence of glaciers. It is evident, then, that during the Tertiary period the locality where these shales are found had been eroded, and that it was filled by a lake into which these leaves were washed or blown from the land. That so exten- sive a basin could be eroded during the time required for cutting out the cation below is by no means improbable, for the voleanic rocks surround- ing the basin are, for the most part, friable, and yield readily to the weather or running water, while those forming the walls of the canon below are exceedingly hard. The present park is due solely to the erosive action of running water, which has removed these soft shales. To my mind it seems quite probable that the glacial agency was not active, or at least long continued, below the junction of the main forks. The gorge above Antelope Park is undoubtedly due to glacial erosion; but if a glacier ever reached to Antelope Park, its stay there and in the long canon above was of short duration, and left no traces behind. The whole region is covered with bowlders, evidently coming from the headwaters of the river, but in every instance distinctly water-worn, as they would not have been had they been brought down by glaciers. At the same time I feel hardly justified in positively asserting that gla- EROSION, 471 ciers did or did not exist throughout the whole length of the gorge. My opportunities for examining those portions of the country lying off our trail were exceedingly limited, so that, beyond all doubt, many facts of cardinal importance in this connection never came within the range of my observa- tions. | SECTION III. EROSION BY RUNNING WATER AND ATMOSPHERIC AGENCIES. In our examination of glacial phenomena we have seen that the ice- stream wore out boat-shaped troughs, usually broad, and with walls more or less abrupt. These troughs expand and contract, frequently showing neat little parks or meadows. The distinction between erosion by ice and that by running water is very well marked. The stream of water becomes less as the erosion goes on, the drainage becoming more rapid, so that the cation resulting from its agency is wide at the top, and gradually contracts toward the bottom, having a section much like the letter V. This form pre- vails almost without exception. It is true that where several streams are in close vicinity the walls separating their ravines are thin, and in process of time are worn away so as to produce a basin, especially if the rock be such as to disintegrate readily under influences acting conjointly with that of the moving water. But, even in cases like this, the original V-shaped troughs can be traced without any difficulty, except occasionally among volcanic rocks. In previous portions of this chapter instances have been given, which show the activity of running streams in modifying the conditions left by the glaciers. Of these, probably the most marked are the Granite Canon of the Arkansas, and the cations of the Rio de las Animas, all of which sink below the old glacial floors, which form, as it were, terraces above them. In this section reference will be made to only a few well-marked camions, in con- nection with which will be given some illustration of the modification of mountain crests by water and frost conjomed. Eagle River—The North Fork of this stream has its source in a narrow basin confined between abrupt, rather low walls, and separated from the 472 GEOLOGY. North Fork of Ten-Mile Creek by an almost imperceptible divide. For nearly a mile the surface slopes gradually, and the basin shows many fea- tures common in glacial amphitheaters. It soon falls off, and the stream descends quickly, nearly 300 feet per mile, forming a deep, close canon rarely more than 30 feet wide at the bottom. The left-hand wall rises sharply in a succession of very narrow terraces, which continue almost to the mouth of the cation, where they disappear, and the wall becomes an unbroken, almost vertical escarpment, about 1,500 feet high. The right wall differs. It rises very abruptly to a height varying from 200 to 300 feet, and there forms a broken, sloping terrace, reaching back several hun- dred feet to the main wall, whose crest is level with that of the opposite wall. This terrace, whose slope is about 20°, is covered deeply with sand- stone debris, which is cut into ridges by the many little streams pouring down in early summer. At first I was inclined to suppose that the gorge was of glacial origin, and that this terrace had been the floor, but, examina- tion of the rock in which the cafion has been excavated showed that ordinary weathering is sufficient to account for the terrace. This sandstone, which belongs to the very top of the Carboniferous, is a moderately coarse con- glomerate, almost without cementing material, much cross-bedded, and bear- ing much resemblance to the ordinary terrace material exposed on the Ar- kansas River. It shows extensive jointing, so that, taken altogether, it is one of the most friable rocks seen in our whole area. Large masses were seen separated by narrow crevices from the main stratum, and crumbling into gravel merely under the influence of the weather. This close canon ends suddenly about six miles from the head of the stream, and changes into a narrow valley, whose sides slope sharply, so as to form a broad V. Here, as in the canon above, the left wall is the steeper, showing that during the whole time of excavation the stream flowed closely toward that side. The valley continues for about six miles, and opens into a broad trough of glacial origin at a distance of about eight miles above the junction with the South Fork. The total descent of the stream within twelve miles is 1,900 feet. ‘The coarse sandstone covers the crest of the walls at this point, and has been cut down so deeply that the wall resembles a long row of great buildings, 2,000 feet high, surmounted by Mansard roofs. EROSION. 473 The canon on the South Fork of the Eagle River is about five miles long, and, owing to the harder material of its walls, is much more abrupt than the one of which we have just spoken. It separates two portions of the gla- cial trough, as is done by the Granite Canon on the Arkansas, the portion above being broad and deeply excavated like the Upper Arkansas basin. Here it may be well to note that there is no reason to suppose that a lake ever filled this upper basin, but everything tends to show that it was long occupied by the glacier, which remained there, alternately retreating and advancing, until after the cation had been eroded by its river. The gorge is exceedingly narrow, and its walls rise at a very sharp angle, though per- ceptibly separating so as to form a compressed V. The height of the ab- ‘rupt portion is not less than 800 feet, while above this the sides rise with a slope of 35° for nearly 2,000 feet more. The cation itself is utterly impas- sable, and the narrow trail on the steep slope above winds along, in most places, not far from the brink. A few tributaries enter the stream in the canon, and break down the wall. Elsewhere it would be impossible to get down, or, once down, to climb out. The whole of the Grand and Gunnison area is marked by cafons. Lying, as it does, on the western slope of the main region of upheaval, and stretching westward to the low table-lands, the general slope of its surface is quite rapid, so that deep ravines are formed by the Grand River, and deeper, or, rather, more abrupt ones by its tributaries. The most imposing of the cations, which owe their origin entirely to the erosive action of run- ning water, is that of Rock Creek, to which indirect reference has already been made. The following sketch by Mr. Young represents the entrance to it below the embryo city of Elko. This stream is very rapid, descending 2,500 feet in less than eight miles. From the beginning its bed is a succession of falls until, at a distance of three miles, the valley, previously narrow, closes suddenly, and becomes an awful cation, whose left and right walls rise at angles of 55° and 70° respect- ively. The direction is nearly northwest for abouta mile, where a tributary stream, flowing in a similar gorge, enters from the east, and the course is turned almost westward for a short distance, after which it again changes to northwest. Eight miles from the head of the creek the canon opens out into a 474 GEOLOGY. narrow valley. The bed of the stream descends with great rapidity, there being merely falls and rapids, varying from 10 to 40 feet in height, until, four miles below Elko, the creek plunges at one leap almost 150 feet, forming a cascade which, in the middle of summer, when the volume of water is Fic. 142.Entrance to cafion of Rock Creek. greatest, must be quite imposing. Throughout, the cafion is narrow. For two miles it varies in width, at the bottom, from 10 to 30 feet, and is so choked with large fragments of rock, polished by incessant action of the water, that it is almost impassable. No person has succeeded in traveling through it, though several have made the attempt. Once in, one would find the utmost difficulty in endeavoring to scale walls which rise almost 2,000 feet near the head of the canon, and in many places are precipitous, or even overhanging for hundreds of feet. BROSION. 475 The divide between the headwaters of Rock Creek and those of the Roaring Fork is a remarkable example of weathering, and its southern ex- tremity exhibits an eccentricity of outline nowhere excelled within the area of our survey. The crest of this exceedingly narrow ridge resembles a line of ancient castles. Indeed, standing in any of the enormous cavities under this ridge, from which issue the many streams which form the Roaring Fork, one needs little power of imagination to conceive himself within the = = Fic. 143.—Whitfield’s Peak. ruins of some majestic cathedral, whose towers, surmounting the massive walls, still remain to attest its pristine splendor. Two of the peaks rise almost to 14,000 feet. One of these I had the honor to dedicate, with the consent of my associates, to Mr. R. P. Whitfield, the distinguished palzon- tologist, of Albany, N. Y. This remarkable peak, of which the eastern 476 GEOLOGY. aspect is represented in the following figure by Mr. Young, rises to a height of 13,985 feet, as determined by triangulation. It is pyramidal in outline, composed of sedimentary rocks, varying in color from dark gray to dull red and maroon, and almost horizontal along the face, so that, taken in con- nection with its surroundings, it is probably the weirdest object in this por- tion of the chain. On its southern side a similar pyramid reaches almost to an equal height, while adjoining it on the north a long, arched comb grad- ually rises, stretching to within a hundred feet of the level of its summit. Its northeasterly face is hollowed out so as to resemble a huge pointed scoop, rising 2,000 feet above the glacial cup below. On its western side the mountain shows itself a noble pyramid, whose face rises sharply and unbroken at an angle of 40°, for 4,000 feet above the wondrous crateriform excavation beneath. ‘To complete the ascent of this peak was impractica- ble. Our indefatigable topographer, Mr. Young, climbed to within 200 feet of the summit, but was compelled to return, as any attempt to move farther along the narrow crest was evidently mere recklessness. This magnifi- cent peak is the most conspicuous object in the whole region, and served as a distinct triangulation point, even so far south as the summit of the Rio Grande divide, eighty miles away. In the southern portion of this area, and beyond, where the only recks exposed are of volcanic origin, the conditians are somewhat different from those which we have been considering. The tendency here is to form basins by the rapid wearing away of the walls separating the shallow troughs of the streams. Such we find on Cochetopa and Los Pinos Creeks. There the several cafions have come together, as is evident from their existence now around the basins. But the jointed condition of the rock rendered it very susceptible to the influence of water and frost com- bined, so that the walls of the canons have been removed over extensive areas, and the basins are the result. In these, however, the several troughs can still be traced. This process sometimes leads to perplexing conditions, and in the higher regions not infrequently causes the formation of an am- phitheater very like those of glacial origin. This is neatly exhibited at the head of a small stream emptying into the Rio Grande about thirty-three miles above Del Norte. There several streams have worn out narrow can- EROSION. ATT ons beginning at the very headwaters. These unite within 400 yards and form one deep, broad excavation, which, were the numerous tributary gorges concealed, could hardly be distinguished from a glacial amphitheater. In course of time the partitions, still separating the narrow canons, will be worn away, and the form of the excavation will be complete. In such cups, however, one usually finds means to show that they are not of glacial. origin. The benches are ordinarily absent, the general form of the floor does not so closely resemble an elongate shallow scoop, and the undulations so characteristic of glacial action are for the most part entirely wanting. The shales of the Middle Cretaceous, in the San Juan region, have suffered greatly by erosion. The readiness with which they yield induces the formation of many sharp V-like troughs, such as are seen on the tribu- taries of the Rio Piedra. Such troughs are widened by the joint action of running water and the weather, until they finally become broad, grassy swales, or even parks, with an undulating surface. This erosion must have begun very early in Post-Tertiary timeg, for most of the broad swales or parks certainly attained almost their present extent before the great canons of the Rio San Juan or the Rio Colorado were very deeply cut. The deep- ening of these valleys depended on the deepening of the Colorado Cation, to which that of the San Juan is tributary. As the result of this deepening and the resulting increased rapidity of drainage, we find the fine terraces along the Florida, Piedra, and Los Pitos, and possibly the extensive park along the Rio San Juan above Pagosa Hot Springs. The soft sandstones of the Upper Cretaceous, in the same region, have been affected scarcely less than the shales. The whole country along our trail, from the Rio Blanco to the Laguna de los Caballos, is a succession of beautiful parks eroded from these sandstones, which appear on all sides in the mesas, where they rest on the black shales. At the eastern base of the Rocky Mountains, we find a series of “hog- back” ridges five to fifteen miles wide, and extending along our whole line from Golden almost to New Mexico. CHAP Rae Xavi, MINERAL SPRINGS. Pagosa.—On the San Juan River, near the crossing of the old wagon- road which leads from Animas Park to Tierra Amarilla, the cloud of vapor arising from the Pagosa, or the Great Hot Springs, at once arrests the atten- tion of the traveler. The locality seems to have been an interesting one to the Indians from ancient times, for numerous trails, all deeply worn, con- verge toward it from all directions, and the main trail from New Mexico northward to the White River passes directly by it. The springs are situ- ated at the end of a beautiful park, which extends for several miles up the river, and is closed by a narrow éafion beginning just below the springs. On both sides of the valley the hills rise several hundred feet, and are coy- ered by a dense growth of pines, while northward beyond the park the Rio Grande divide rises gradually to upward of 12,000 feet, and merges at the east into the rugged mountains of the Sierra San Juan. Southward, the surface rises sharply in all directions, and nothing can be seen except the bluff walls forming the cation through which the river flows. Here and there in the vicinity of the springs are low mesas with steep escarpments, and composed entirely of the deep, black shales of the Middle Cretaceous, the prevailing rocks north from the cation. Around the springs themselves, is a great stalagmite deposit, whose dull gray color offers no violent con- trast to the gloomy black of the shales. The numerous springs issue from orifices scattered over an area of little less than thirty acres, which is covered by a deposit consisting chiefly of calcium carbonate. In its full extent, this deposit reaches over nearly fifty acres, passing to the opposite side of the river, whose channel has been cut through it. The great mound about the springs is more or less cayern- ous throughout, with many small openings through the upper layers, from 478 MINERAL SPRINGS. 479 which sulphurous vapor escapes. It is surrounded by a plain, encrusted by calcareous and other salts and bearing a rich growth of grass, which is said to remain green throughout the year. Reaching well up on the mound, this grass conceals many of the openings in the outside crust, and renders the approach to the main springs quite insecure, as these small openings are frequently only ‘‘blow-holes” to large cavities roofed by a very thin shell of stalagmite. The principal mound is double. In the lower division no springs were observed, nor indeed was any evidence of activity visible. Fig. 144.—Basin of the Great Spring at Pagosa. At its summit there is a crevice several feet long, 5 feet deep, and 18 inches wide, which no doubt at one time was the crater of an extensive spring, though now it contains much débris. From the margin of this division southwest to the river, the surface is undulating, and holds several patches of hot water 10 to 25 feet in diameter, in which the bubbling of the springs 480 GEOLOGY. is quite energetic. These springs have surface outlets which carry the water directly to the river. In the upper or northern portion of the mound is the Great Hot Spring. At the summit we find an irregularly oval depression, or crater, 25 by 35 feet, and about 3 feet deep to the surface of the water. It is divided trans- versely by a partition of stalagmite, reaching up barely to the level of the water, into two areas, one 5 feet by 2 feet, and the other rudely circular with a diameter of about 25 feet. The depth of the larger basin cannot well be determined, owing to the craggy character of its walls, shelves of stalagmite reaching all the way to the center. At one point no bottom was found at 50 feet. Everywhere columns of bubbles are seen rising continu- ally, and the number of the larger columns is more than one hundred. Near the center of this larger basin there are nine principal columns ar- ranged triangularly in three groups, with a low cone of stalagmite project- ing above the water near one of the angles. The surface of the smaller basin is like that of a boiling pot, bubbles escaping regularly and continu- ously over the whole. Around the margin of the crater there are numer- ous openings in the mound, 3 or 4 feet deep, some of which contain only still water covered by a green scum, while others are actively emitting vapor. The action of the springs in the larger basin is intermittent. The three groups of columns referred to are continually in operation, but at in- tervals of from three to five minutes the ebullition becomes explosive. In the northwestern group the water is thrown for a few seconds to the height of 1 foot, and so in the eastern group, which is close to the cone. In the southwest group the ebullition extends over a greater surface, and when most violent produces a flattened cone about 4 feet in diameter at the base and 6 inches high. Near the margin of the crater the temperature of the water is 140°F., but is doubtless.much higher near the center. This latter point could not be determined, as the party was not provided with self- registering thermometers. The water is strongly impregnated with hydric- sulphide and carbon dioxide. The solid constituents are carbonates and sulphides of calcium, sodium, and potassium. The water of the springs in the crater is drained away by subterranean MINERAL SPRINGS. 481 outlets leading to the river, and evidently flowing upon the Lower Cretaceous sandstones on which the mound rests. The outlet farthest up the river is a little rill, 8 or 4 inches wide. The main one is a rapid stream, 1 foot wide and about 4 inches deep, and flows out nearly 5 feet above the level of the river. The volume of water poured out by this stream is very large, but no estimate of the quantity was made. One can easily trace the course of this outlet from the crater to the river bank by means of a line of openings in the surface of the mound, from all of which vapor constantly issues. , Some of these holes are simply tubes, 2 to 4 inches in diameter, while oth- ers are large cavities several feet wide and almost entirely closed at the top by a roof barely 1 inch thick. Below all the outlets the river is discolored by sulphur, separated by decomposition of the sulphureted hydrogen. The spring is undoubtedly very ancient. The mound was not less than 12 feet high before ever the river began to excavate its present channel, for such is the thickness of the deposit on the west side of the stream, opposite the springs. How much higher it has been one cannot conjecture, but there ‘is every reason to believe that the whole mass has suffered greatly from erosion. The main portion of the mound long since ceased to increase in height, for the water no longer poured over the rim of the crater after the opening of subterranean outlets. Near to and rudely parallel with the river several large crevasses are seen, beyond which the separated portions lean toward the stream. It is evident that the river is making inroads upon the mound, and it is much aided by the erosive action of the many little streams carrying the water from the crater. Somewhat less than a mile below the Great Hot Springs, and on the west side of the river, there is a small mound, about 100 feet long, and rising five feet above the surrounding plain. Its surface is almost flat, and shows three small basins, rudely circular, each about 20 feet in diameter, which are arranged along a north and south line. In the center of each of these a small spring issues from an orifice surrounded by stalagmite. These springs do not overflow and the amount of water is inconsiderable. No outlet was observed. The temperature is quite low, barely exceeding 60°. The composition seems to be similar tq that of the Hot Springs, except in that the proportion of sulphureted hydrogen is less and that of the alkaline 3l Ws: 482 ; GEOLOGY. salts somewhat greater. All of the springs in this vicinity evidently hold more or less of iron in solution, as the deposits about them are invariably of a dingy gray color and frequently have a deep ferruginous tint. At the exit of the main outlet from the crater of the Great Hot Spring the rocks, over which the water flows, are covered with an incrustation, white and mammilated, and with a porcelaneous surface. Small hand spec- imens can be obtained greatly resembling the paved floor of a drum-fish’s Jaw. On twigs or jutting portions of rock this sediment is seen in the earlier stages of deposition, moss-like, in tufts of flexible fibers, one or two inches long, which eventually become united by a reddish substance, after which the deposit becomes compact. In the crater the process is somewhat different, and then the successive steps are more clearly shown. A thin scum forms on the surface of the water in small patches, seldom more than one- eighth of an inch wide at first, which combine to form pieces of varying size, sometimes an inch thick and several inches broad and long. This material seems to originate in the films-of the bubbles, and occurs in thin, almost transparent lamine. The larger pieces are porous, the laminz being loosely packed, so as to give the mass a spongy structure. This scum forms for the most part around the border of the basin, where the ebullition is less violent, and the bubbles do not burst so quickly as they do nearer the center. In the vicinity of the principal groups of columns I could see no formation of such scum during an hour; though no doubt it does form there, but in fragments so small, that they do not appear until, approaching the border, they unite to form pieces of larger size. This material is reddish- brown in color, very soft and of pulpy feel. It probably consists largely of sulphur. Being much lighter than water, it floats on the surface, continually receiving accretions from the bursting bubbles. At length, fastened to the shore, it acts like the twigs seen at the outlet ; calcareous matter is deposited on it and through its pores, until, becoming heavier than the water, it sinks and forms part of some craggy shelf projecting from the sides of the basin. Under the water this pulpy matter is always present, but elsewhere in the substance of the mound it seems to be absent. If present, it is so mixed mechanically with the caleareous material as not to be detected by physical MINERAL SPRINGS. 483 signs. Sometimes large fragments of pulpy matter become cemented together, and, hardened by the deposit of calcareous matter, may form the lid-to a cavity several feet wide. Such a mass is seen in the southeast cor- ner of the crater, and has an area of nearly 60 square feet. The material composing the mass of the mound is compact, as though deposited not in this manner, but rather by overflowing of the water in thin sheets ; and some layers are seen closely resembling the beautiful calc-tufa so plenty at Niagara Falls and along the Genesee River in New York. At, the lower end of the mound, where the many springs are drained by super- ficial outlets, the process by which the mound was formed is clearly exhibited. The water running here over the surface has been entangled among the grass, which in many portions is very prettily incrusted. Such incrusted branches soon form little bars, over which the water flows, and the little pools back of them are gradually filled up with the calcareous deposit. The water is thus spread out over a broad surface in a very thin sheet, and is compelled by every obstacle to deposit some sediment, until at length a succession of broad shallow steps is produced, like that made by the flowing of a thin sheet of water over a regular surface during a very cold day. In this direction the mound is rapidly extending, and eventually it will cover all the swamp to the river bank. From the marked resemblance of the deposit at Pagosa to that observed at the Mound Soda Spring, I am inclined to believe that the spring comes from the metamorphic rocks. The sulphureted hydrogen is doubtless obtained during the passage of the water through the underlying Triassic and Carboniferous, several limestones belonging to the latter being exceed- ingly fetid. Mound Soda Spring—Nine miles below the head of Currant Creek, a tributary of the Arkansas, this spring is seen in a little canon on the north side of the stream. The mound surrounding it is rudely elliptical in section, with a longer diameter of 60 feet and a height of 20 feet. The lower layers are composed of white travertin and are loosely packed. Some of them have a surface bearing some resemblance to brain-coral. Toward the top the rock becomes less compact, and shows several extensive cavities reaching for a long distance into the interior, which may have been outlet channels 484 GEOLOGY. in earlier times when the spring was probably much more energetic than now. This upper portion is not white, but is deeply colored by iron. The spring issues from an orifice on the summit of the mound, about 3 feet in diameter at the surface, but rapidly contracting below to about 15 inches. The only outlet for the water is a small gutter leading from the edge of the orifice along the surface of the mound. The amount discharged at the time of our examination did not exceed three gallons per hour, and, judging from the size of the gutter, it is probably not greater at any time. Though the quantity of water is so insignificant, the ebullition is so violent that one would suppose the discharge to be very great, and be led to suspect an outlet below the surface. This ebullition, however, is due solely to the escape of carbonic acid gas, which comes off in immense quantity. No analysis of this water has been made. The proportion of carbonate of lime is evidently large, and iron peroxide is present certainly to the extent of one-half of 1 per cent. Some soda or potash is held in solution, as is evident from the slightly alkaline taste. The temperature isthe mean. The flavor is agreeable, being much the same as that of the carbonated waters of the shops. In many features the spring closely resembles those at Manitou. The spring comes from the metamorphic schists, there being no other rocks in the vicinity. Hot springs occur on Chalk Creek in the Upper Arkansas region and in the northern portion of the San Luis Valley. These were not visited by that portion of the party to which I was attached, and no notes were taken by members of the other division. South Park—The Sulphur Springs are near the road.leading from Fairplay to Colorado Springs, and are about five miles above the cation of the South Platte River. They are resorted to by many invalids during the summer. In August as many as two hundred persons have been encamped in the vicinity seeking benefit of the baths. Doubtless were there satisfactory hotel accommodations, or proper conveniences for bathing, the number would be greatly increased. The springs or rather orifices are eleven, but clearly proceed from one stream, for the proprietor stopped up six, and the remaining five discharge as much as eleven did. The water is strongly odorous of sulphureted hydrogen, and has a strong alkaline taste, so that MINERAL SPRINGS. 485 the predominant salts are probably the alkaline sulphides. The little stream running from the springs leaves the ground covered with sulphur derived from decomposition of the salts. The springs issue from the lower portion of the Middle Cretaceous. On the South Fork of the South Platte, and about two miles above its junction with the river, a strong hot spring occurs in the bed of the stream directly under the bank. The temperature is about 130° F., being kept low by the influx of water from above. Held directly amid the escaping bubbles the thermometer indicated 160°. A slight odor of sulphureted hydrogen is noticed in the vicinity of the spring, but none is perceptible when the water is held to the nose. The water is tasteless and odorless, so that the gas escaping in bubbles must be only vapor of water. There are nearly forty orifices from which bubbles issue. The quantity of water dis- charged is very great, and so elevates the temperature of the stream that in winter it remains unfrozen to a distance of more than half a mile below the spring. The Salt Springs have been noticed in another connection. Idaho Springs——These are on a small stream entering South Clear Creek near the village of Idaho. Owing to the romantic scenery in the _ vicinity, as well as to the cleansing properties of the water, they have attained no inconsiderable reputation, and are resorted to during the summer by many hundreds of visitors. There are three important springs, all of which have a temperature above blood-heat. The upper one is a carbonated spring, with an appreciable proportion of iron and a temperature of 98° F. The water has an agreeable flavor, and is much employed by invalids for drinking. The lower springs show temperatures of 105° and 107° respect- ively. The water is strongly alkaline, and is especially for bathing pur- poses. It was analyzed by Dr. J. G. Pohle, of New York, with the follow- ing results : Me PELIIETESROHESOIV AMET ie occa ae coe Oak Fae oa uas scaeiss neato sce ce one ere 30. 80 RRM per bere tl moh oS S320 ects ve dk ve 3 Ss bab evo Ls Ropeaeeeed 9. 52 COSTES Ge 1ST E ae peepee SpOB Se ene Seo BOeRSae Se aacrsar oo = Saorn asec 2. 88 WAT HOUALETOl TOMS ot - . <.cie'eeisie ses aes 5, Shay ataysynilsevate euayer oe wine erate mageidates &s 4,12 SRM ALEOMSOMIMIN ES Satna 2 Sets clea a aheele ce) salle Se Se ees ees Sere A oe 29. 36 Sulphate of magnesia ...-.. ONS Pen OOOO OSE Le SOS aae ho eee Oe nae 18. 72 486 ’ GEOLOGY. Sulphate Of MIME L's... 2.02.02 pypeie yb aie peielele eee ee Bee neiee eee eee 3. 44 Chloride\of Sodimm oo... rae ere ee elseiee EP eieiee eis eee eee ne eeeneee 4.16 NilicateOl Soda... —. S. -:c ere c= olaisee clei ees ae eee Se ee eee eee 4.08 @hloride of calcium: .. 525 Saco. sere ere eee er eer ana ee eee eee Trace Chloride of magnesium. s: .s2s2oceer cone eee see oe Ee cee oe eee Trace Total grains solid residue per gallon... 2. /.- 22; 12-220 -eeeeene wee -ee 107 These springs issue from the metamorphic rocks. Colorado Springs-—These springs, situated on the Fontaine qui Bouille, near the village of Manitou, and six miles from the city of Colorado Springs, have long been celebrated for the magnificence of the surrounding scenery, as well as for the medicinal value of the waters. They attracted the atten- tion of Captain Frémont during his second expedition, and received a some- what glowing description in his report. There are five springs above Manitou, which readily arrest the attention of the traveler. The upper two are small, one of them much used for drinking, and the other, a chalybeate spring, not used for any purpose. A few yards below the latter, which is on the right bank of the stream, are two large springs, one on each bank. That on the right side is close to the road, and is surrounded by a mound of stalagmite several feet thick. At the summit of the mound is an oval opening through which the operations of the spring can be observed, for the water no longer overflows the mound, but passes by an insignificant outlet below into the creek. The ebullition is exceedingly violent, but the small amount of water discharged shows that it is due entirely to the escape of gas. The spring on the opposite bank is surrounded by a similar deposit, but evidently yields a much larger quantity of water. The fifth spring is opposite the post-office, and is surrounded by an extensive deposit reaching quite to the bank of the stream. The ebulli- tion is quite violent, but I was informed that the quantity of water discharged is comparatively small. In Frémont’s report the following analysis of the deposit about the springs 1s given: Carbonate OFM rl... sea se rca reiete ciate tetetstotate tte = Paiatetsiete stele tate tates ate ttt ees ne ".. 92.25 Garbonate of magnesia... 2. scjeete) teeta ae ed eee ete ete hte terete eee 1.2 Sulphate of lime ) Ohloride of MAPNESIUM > - Soe erento tere wale nate tee ate tele ieee ate tee 0: 28 Chloride of caleium j MINERAL SPRINGS. 487 STIGD 6b 258 C600 COCCI Reena eee Ce AS GAS SS Orns acre or eee wetee 1.50 VWEGIRII OTe nit 6GGoeneeeEe Ome O Ce DOC OC or CORec4 AC AGn Oe Cre bOdd 4 STOO 0. 20 URE. S6dche Sho ce qUEEURIE GEE Eee rns OUI Sc ar SEI C orc orioetro cn perrict aces 4.61 100. 00 In a circular obtained at Manitou I found the following analysis of the solid residue obtained from the water of one of the springs: CHUDGR GRU MIT Babee: SO a5 eee ne Dein ern ts eee eee ere 7 36. 69 OhlorideokipotassiiMmes. 2 Sas - sesh we sciocn iis. or. Pi SS 10. 01 Bicarbonate of soda.....- ...-.. Ss eeRcits ot tose ence ase Cee mete 24. 01 TEAS WITS RON? SOE CSS So8e oS G5= hc AUN OU BOCA SEes Oe ADeaiCn saicciace. sae 44S Srna waherG ee limes See eee ee oe eo ce wicca ice case ee veed ee lenedeieoein ace 15. 62 @arhonatel Ota ONO he sais pols ess iciiele cin ecShienidiso eo dleeie GoW sinh olde Saaebioes 8. 89 100. 00 Though issuing from the unaltered rocks, these springs bear such marked resemblance to the Mound Soda Spring, both in their action and in the character of the deposit, that I am inclined to believe that they are of deep-seated origin, and have-their sources in the metamorphic rocks below. CHAPTER 2 Vat: STRUCTURE AND AGE-OF THE ROCKY MOUNTAIN SYSTEM. In this chapter much must “be said which may not fully bear the test of investigation, (complete in all its details.) The area in which my obser- vations were made is little more than two hundred miles in length north and south, and at no pojnt is wide enough to include all the axis of elevation. While it is sufficiently extended to embrace all but two, and these, in one sense, the least important, still it reaches northward only a comparatively short distance along the chain, so that no information was obtained north from the parallel passing through Denver, and only the southern extremity of most of the axes could be carefully examined. For this reason I shall give only my own observations and such conclusions as seem most naturally to flow from them, leaving to others to collate my observations with those which may be obtained hereafter, in order to elaborate fully the structure of this remarkable chain. STRUCTURE OF THE SYSTEM. From the Missouri River westward the whole country gradually rises at an average grade of barely 10 feet per mile until west longitude 105° 30’ (approximately) is reached, when the Rocky Mountains rise abruptly from the plain. From this line the ranges extend to somewhat beyond west longitude 108°, where they rapidly fall off to the great plateau, separating the Rocky Mountain region from the broken ranges of Utah and Nevada. . The ranges composing the great system under consideration appear to be in two series; the first comprising the two complex axes of elevation, the front or eastern and the Sangre de Cristo, whose trend is from north 10° west to north 30° west, while the second is made up of the San Juan, Los Pinos, La Plata, and San Miguel, which have a trend of north 30° west to north 45° west. Each series shows a parallelism of its ranges, and the “whole system terminates en échelon southward, most of the axes ending 433 STRUCTURE AND AGE OF ROCKY MOUNTAIN SYSTEM. 489 ithin Colorado. The observations of Dr. Newberry and Mr. Gilbert show that minor axes occur in New Mexico. These are apparently independent of each other and of the main axes in Colorado, but it is by no means im- probable that future examination will disclose some more intimate relation than has been suspected. The Eastern range consists of several subordinate axes, closely packed together, and almost accurately parallel to each other. It rises sharply from the plains and attains its greatest altitude near our northern boundary, where several of its peaks rise to a height of more than 14,000 feet. The axes within our area are seen terminating en échelon at Colorado Springs, Caiion City, and Huerfano Park. The Kenosha range, the eastern boundary of South Park, is evidently only a portion of the western axis, which, under the name of Greenhorn or Hardscrabble Mountains, extends to Huerfano Park. This group is cut by the Arkansas and South Platte Rivers. The former breaks through only the western axis, while the latter passes through the whole group and reaches-the plains about twenty miles southeast from Denver. Near our southern boundary the width is not far from forty miles, at the cation of the Arkansas it is barely twenty, while southward from that line it dwindles rapidly to its termination. The several axes terminate abruptly, and the unaltered rocks are seen in each instance curving round the base. This range is composed of metamorphic rocks, which are badly fissured by dikes of lava, and not infrequently capped by overflows of the same material. The schists are much torn and faulted, and sidethrows of mineral veins are by no means uncommon. In some of the canons which cut deeply into the flanks of the mountains a compact granite, more or less syenitic, is seen, which seems to prevail along the median line of the axes, having been observed near the head of Clear Creek Cafion, as well as in the walls of the amphitheater containing Chicago Lake. The sedimentary rocks occur as ‘“‘hog-backs” along the eastern base and curve round the southern termina- tion of the several axes. They pass round the Greenhorn Mountains into Huerfano Park, where they are more or less concealed by the great overflow of volcanic rocks. Along the eastern face of the range the disturbance was variable in its 490 GEOLOGY. effects. Toward our northern border it was so violent that one can obtain no satisfactory information respecting the stratigraphical relation existing between the rocks of different ages, but as we go southward beyond Colorado Springs the conditions are better defined. On the Little Fountain Creek, where it issues from the “‘ hog-backs,” we find the red sandstones and gyp- sum marls of the Trias inclined at an angle varying from 40° to 60°, while against them abut the Cretaceous rocks dipping from 10° to 20°. Far- ther southward, toward Cafion City, the Jurassic and Cretaceous are seen resting unconformably upon the Trias, while at a little distance beyond Canon City the Cretaceous overlaps and conceals all the underlying forma- tions. On the western face of the range the Trias and Cretaceous are un- conformable in Huerfano Park; farther north the Cretaceous abuts against sharply inclined quartzites of undetermined age, its own dip being barely 5°. Still farther north the unaltered rocks are wanting, and the axis becomes a great fault, for the sedimentary rocks belonging to an outlier of the next range west abut against the schists of this at the northern boundary of South Park. The dips in the metamorphic rocks of this range are, for the most part, northerly, either northwest or northeast, and no satisfactory anticlinal or synclinal structure could be made out. Between the eastern range and the one next westward, there occurs a series of parks separated by outlying spurs from the mountains. In South Park the Cretaceous rocks rest directly upon metamorphic rocks, and are themselves more or less altered. At no locality were they seen resting upon any sedimentary rocks older than themselves. In Wet Mountain Valley the unaltered strata are concealed, and in Huerfano Park the Cretaceous rocks are the only ones observed, except around the border, where they abut against the Trias. The second range, which may be termed provisionally the Sangre de Cristo axis of elevation, is in the main almost parallel with the Eastern range, but is much more complex in its structure. It is divided longitudinally by the Arkansas River, which, turning eastward, breaks through its eastern slope. Northward, beyond our area, it is eut by the Grand River. In its northward extension, within our area, it is known as the Blue River range ; STRUCTURE AND AGE: OF ROCKY MOUNTAIN SYSTEM, 491 farther south, where it forms the western boundary of South Park, it is the Park range; in its southern extension it is called Sangre de Cristo and Spanish range; while beyond our limits, to Santa Fé, where it ends, it bears several names. The portion lying west from the Arkansas River and cor- responding to the Park range on the east may be termed the Arkansas or Saguache range. Owing to the effects of erosion upon the topography the intimate relation of these several ranges is not at once apparent, but with a little care the whole can be traced out quite readily. Beginning at the New Mexico line with the Spanish range, we follow the ridge to Sangre de Cristo Pass, beyond which to Poncho Pass it is known as Sierra Sangre de Cristo, the whole forming, within our area, the divide between the Arkansas and the Rio Grande. If now we follow the eastern slope along Wet Mountain and Texas Valleys we reach the Arkansas at Pleasant Valley. Ascending the river from this point we soon enter the cafion cut through the east face of the Sangre de Cristo Mountains. Passing through this long caflon we emerge into Arkansas Park at the mouth of the South Arkansas and on the west side of the Park range. No break occurs in the cafion, so that the Park range is merely a continuation of the east slope of the Sangre de Cristo. In this park the continuity is clear. _ On the west side of the park a line of broken hills stretches to Poncho Pass, where they are broken down completely. Beyond Poncho, however, they again begin and soon develop into that grandest of mountain ridges, the Arkansas or Saguache range. To one standing in the park there seems to be every probability that the Park and Saguache ranges are one with the Sangre de Cristo; but, fortunately, one is not left to reason upon probabili- ities, for the evidence from structure is ample to prove the unity of the whole. On the eastern slope of the Park range the Paleozoic rocks reach quite to the crest, and are traceable from the Sangre de Cristo to our north- ern line. Underlying these are the metamorphic schists and gneisses, which - are seen in the deep cations along the eastern face, while on the western slope they extend from the river level almost to the crest, and are exposed all the way from the South Arkansas to the mouth of Tennessee Creek. - Beyond that point the natural range is divided, as will be shown hereafter. 492 GEOLOGY From the mouth of Box Creek to near that of Cottonwood Creek, the valley of the Arkansas is very narrow. This is the place of the Granite Canon. Here, granite and gneiss, both metamorphic rocks, are continuous from the park to the Arkansas range, being broken only by the close camion. Starting from the west base of the former range, we go by the side of one of the many high ridges of metamorphic rocks until we reach the river. Crossing the stream and climbing the steep granite wall of its cafon we follow a similar ridge until beyond Twin Lakes, where we find the porphy- ritic syenite, which forms the heart of the axis. Passing the crest, the metamorphic rocks are again seen on the west side, and on them rest the _ ancient quartzites dipping sharply westward. The high ridges of metamor- phic rock, thrust out from each side of the Arkansas gorge, demonstrate the continuity of the whole and give a satisfactory succession, unbroken any- where, save by the cafion. Let us now ascend the Arkansas a few miles, to the mouth of Ten- nessee Creek. At about this latitude a great fault causes a bifurcation of the original range. Following Tennessee Creek to Tennessee Pass, upon the eastern slope of the spur produced by the great fault we see, on the eastern side of the stream, hills covered by sedimentary rocks, which are traceable across the Arkansas, and are seen to be continuous with those covering the eastern slope of the Park range. If, instead of proceeding directly to the pass, we ride westward across the moraine of the ancient Tennessee glaciers to the amphitheaters at the head of the creek, we find strewed over the moraine numberless fragments of Silurian quartzites with some of. Car- boniferous limestone. These must have come from the west, where now only metamorphic schists occur. Itis impossible to suppose that they came from the East, for the transporting agent moved from the West. It is clear, then, that the paleozoic rocks, the same with those found on the Park range, at one time reached unbroken from South Park to the Arkansas or Saguache range. How terrible was the erosion which not only cut away these rocks but also tore out and removed the metamorphic rocks to a depth of 6,000 feet along this valley of the Arkansas. If we cross Tennessee Pass and go down to the Eagle River, into a region where only narrow canons have been eroded, the succession of the rocks is clear at a glance. Beginning with STRUCTURE AND AGE OF ROCKY MOUNTAIN SYSTEM. 493 the mountains, a continuation of the Arkansas range, the Silurian rocks are seen resting on the schists and succeeded by the Carboniferous rocks, which reach within our area to the edge of the great fault along Ten-mile Creek and the upper portion of the North Fork of Eagle River. It is evident, then, that the Sangre de Cristo and its extension, the Span- ish range, are but the southern portion of a magnificent group which once covered the whole region from East River to South Park. The width from South Park to Taylor River is about twenty-five miles, but southward it diminishes, being barely twelve miles at Sangre de Cristo Pass. Beyond that pass the range becomes broken and irregular. As it passes beyond our line into New Mexico it is so involved in eruptive rocks that it can be worked out only with some difficulty. In the Sangre de Cristo portion no spurs are set off, but northward from the South Arkansas River the general structure becomes very complex. Near the head of Chalk Creek a very important spur sets off, with a trend at first almost west, but soon changing to northwest. This extends almost to our northern line and is the divide between Taylor and East Rivers, as well as, farther north, between Roaring Fork and Rock Creek. From this are thrown off the strangely complex spurs, if they may he so called, form- ing the Elk Mountains. Near the head of Taylor River, another spur strikes out from the main range, and apparently unites with the one just referred to. A third spur is produced by the great fault, and becomes well defined for the first time near the head of the Arkansas. The first and third spur seem to extend to about the same distance northward and to dis- _appear before reaching our northern line, so that the country there is merely a broken table-land. The intimate structure of this group is very complicated and exceed- ingly difficult to unravel. No exploration of this region has yet yielded results sufficient to give even a partial solution of the problems involved. Only a few isolated facts, therefore, can be given here. The Sangre de Cristo portion, in its southern extension, is made up apparently of several axes of fault, most of which have a northeast and ‘ southwest trend, but’ these seem to disappear northward, as they were not observed in the long deep cafions opening into Wet Mountain Valley. In 494 GEOLOGY. the Park range the faults are very numerous, there being two seen in the canon of the South Fork of the South Platte River, and one very extensive one occurs in Horse-Shoe gulch. These have a northwest and southeast trend. Another, with similar trend, is seen farther north, which is traceable across the gorge of the Arkansas River, above the junction with Tennessee Creek, and becomes more extensive as it goes northwest. On the east side of the cation of Ten-Mile Creek is a wall of metamorphic rock more than 2,001) feet high, while on the west side the very highest strata of the Car- boniferous form the wall. For the most part the dips in the Park range are toward north of east, but near the head of South Park there is a strange spur, which includes some of the grandest peaks in the whole chain, among them Gilpin’s Pillars and Mounts Lincoln, Bross, and Morton. Here the dips are sharply toward the southeast. In the spur produced by the great fault, the dip is toward the fault or northeast. In the Arkansas portion no dips or faults were satisfactorily made out in the metamorphic rocks, but over the crest, on the Taylor River side, the dip of the quartzites is toward the south of west. The first great spur on the west side is very perplexing. It is clearly an anticlinal from Chalk Creek to the head of Taylor River, but is badly broken by extensive faults. In this portion, on the eastern slope, as seen in Taylor and Beattie’s Parks, as well as on the divide between Taylor River and Tumichi Creek, the dip is eastward in a succession of faults, some of which are very sharp, the dip in two instances being reversed. The spur is quite narrow here, not more than six or seven miles wide, the whole structure being exposed on the West Fork of Taylor’s River. Near the junc- tion of the forks the dips are all eastward, but near the head of the west fork they are all westward. At the latter locality the rocks are very sharply curved, the rate of dip changing from 70° to 10° within less than fifty yards. Along the “Old Miners’ Trail,” from Taylor to East River, the faults are well exposed, and the Carboniferous limestone is seen three times standing almost on edge and dipping westward. In the portion lying be- tween Rock Creek and Roaring Fork the derangement is excessive. Prob- ably no other portion of our continent shows such cross-faulting as does this little area. The rocks dip toward all points of the compass, and one STRUCTURE AND AGE OF ROCKY MOUNTAIN SYSTEM. 495 whole group is compactly folded on itself and pushed over. Enormous dikes and overflows of igneous rocks are numerous and do not aid in sim- plifying the conditions. In the main portion of this second group no rocks occur of later date than the Carboniferous, which, with the underlying Silurian, may be traced along the eastern face to the Blue River. In the southern portion the rela- tions of the Cretaceous to the Paleozoic rocks was not ascertained, but along the Blue River they are unconformable. In no portion of the main axis do we find any rocks more recent than the Carboniferous, the Trias being entirely absent. Nor do any occur until in the Elk Mountains we reach the ancient synelinal trough which lay between the second group and the next one westward. There the Cretaceous rocks are involved in the great fold exhibited near the head of Rock Creek. This fold evidently deepens northward and disappears southward. Near Elko, on Rock Creek, the dark shales of the Cretaceous are folded upon themselves so as to be but one stratum, and are inclosed by Carboniferous rocks, which are not only folded but faulted. Followed southward along the wagon-road across the divide to East River the fold rapidly disappears, so that, before reaching the mouth of the cafion on Upper East River, the shales are resting uncon- formably upon the quartzites below, and are dipping at only a small angle. In the narrowest part of this cafon, through which the road winds on a shelf, the quartzites describe two shallow curves, which do not involve the shales above. At the junction of the forks of East River the shales are almost horizontal, and at the mouth of East River the Lower Cretaceous rests on the metamorphic schists, with almost inappreciable dip. This whole line of Cretaceous marks the northern portion of the ancient synclinal val- ley between the Sangre de Cristo group and the San Juan. Between the second and third great axes of elevation, we find at the south the San Luis Valley, a broad, open plain, extending from the New Mexico line northward to Poncho Pass. It shows no rocks except those of volcanic origin around the border, and the surface of the valley is deeply buried under volcanic sand. Followed northwestwardly, the intervening region is so filled with eruptive rocks, that were it not for the occasional ex- - posures of the underlying strata, one would hardly suppose that this had 496, GEOLOGY. been a great synclinal trough. The eruptive rocks describe broad curves, both anticlinal and synclinal, as though they had been subjected to great lateral pressure. In several localities they are seriously faulted. The third great axis or line of elevation is the San Juan, so named because in its southern prolongation it forms the Sierra San Juan. It reaches into New Mexico, and ends not far from Abiquiu, somewhat farther north than the termination of the Sangre de Cristo axis. 'To trace out this axis is no simple task, for, excepting along its western flank, near the New Mexico border, it is almost entirely concealed within our district by an enor- mous deposit of volcanic rocks. By means of a few fragmentary exposures, it was followed northwestward to the one hundred and seventh meridian. It is cut by the Rio Grande dyke about thirty-three miles above Del Norte, . and reaches the one hundred and seventh meridian on one of the forks of Lime Creek, and almost due west from the Indian agency. Not far north from Tierra Amarilla, in New Mexico, a spur sets off in a northwest direction, which is cut by the Rio Navajo and the Rio San Juan. How far north- ward it extends was not ascertained. It was not seen along the Rio Grande, and north from that river no observations were made west from the one hundred and seventh meridian. It makes an angle of about 12° with the main axis. As already stated, the main axis is, for the most part, buried under a great mass of volcanic rocks, which conceals those of sedimentary origin. In Northern New Mexico the western slope is bare for a number of miles, and near Tierra Amarilla the exposures show very marked unconformability between the Carboniferous and the overlying rocks. The older formations are inclined at a very high angle, while the Cretaceous and Triassic (?), which are conformable to each other, have a very small dip. The spur is crossed by the Rito Navajo within two miles of the wagon-road, (Macomb’s trail,) and by the Rio San Juan at a short distance below the Pagosa Hot Springs. The extent of the spur is unknown. Its dip increases somewhat in sharpness northward. As far as followed this sub-axis involves the Cre- taceous rocks, which describe a beautiful curve where the Rito Navajo breaks through. The dip is somewhat steeper on the west than on the east. No rocks of older date than the Cretaceous were observed along the spur. STRUCTURE AND AGE OF ROCKY MOUNTAIN SYSTEM. 497 The next great axis toward the west is the one termed by Dr. New- berry the Los Pinos (apud Macomb, ined.) and is in part the divide between the Rio de los Pinos and the Rio Piedra. It is crossed by the Rio Piedra near Macomb’s trail, which follows along the southwestern slope for several miles. The line terminates quite abruptly a little way south from the trail, and before reaching the southern line of Colorado, the whole country southward being a broken mesa, whose strata have a barely perceptible dip. Followed northward, it is found crossing the Rio Grande near the head of the Middle Fork, and is cut by the Rio de las Animas in the long cafion leading from Baker’s to Animas Park. The trend is almost due northwest. The dip is comparatively sharp near the southern extremity, being 10° toward the northeast and 12° to 15° toward the southwest. Farther north it seems to be much less. The only rocks seriously involved in this anticlinal are the Carbonif- erous and probably the Silurian, though the latter were not satisfactorily recognized. On each side of the fold, which is not more than five or six miles wide, the Cretaceous rocks are seen forming mesas and dipping only two or three degrees. The next axis, termed La Plata by Dr. Newberry, forms in part the divide between the Rio de la Plata and Rio de las Animas. Our route fol- lowed for barely twenty miles along its northeastern slope. For the most part, it lies wholly west from the Animas River, but is cut by that stream in Animas Park, near the middle of which the axis terminates quite abruptly. Along the trail from Baker’s to Animas Park one rises twice to the altitude of 11,500 feet, whence the general structure can be seen. The course of the uplift is almost northwest and the dip is very gentle, not exceeding 5° where the strata have not been locally disturbed by the bursting forth of lava and the consequent formation of dikes. The only rocks involved are the Paleozoic, against which the Triassic and Cretaceous abut at an angle of barely 2°. This anticlinal, as well as the Los Piios, has been much broken by eruptions of voleanic rocks, which in many places have over- flowed and formed a thick cap on the hills. According to Dr. Newberry there is another axis still farther westward, which he terms San Miguel. This terminates farther north than the La 32ws 498 GEOLOGY. Plata, and, like it, involves only the Paleozoic rocks, those of Mesozoic time forming mesas around it. Beyond this, as appears from a section made by Dr. Newberry, the country is a plateau of Cretaceous rocks, which separates the Rocky Mountain System from that of the Great Basin at the west. In general, respecting the dips, it may be said that the prevailing direction is east-northeast and west-southwest, and the western dips are for the most part somewhat steeper than the eastern. The most extensive faults are on the eastern slopes and cross the easterly dips. The most marked effects of the convulsions occur in the eastern lines, the first and second axes, which are characterized by extensive faults and sharp dips. Crossing westward or southwestward, the dips diminish in steepness, until in the La Plata they are comparatively slight. Of the several axes, the Sangre de Cristo extends farthest south. Those lying west from it have their terminations successively farther and farther north, while the eastern group ends at a considerable distance north from the New Mexico line. AGE or THE Rocky Mountains. From the facts given, it is sufficiently evident that the Rocky Mount- ains are not the result of one grand upheayal,* and that the several axes are not wholly synchronous in origin. Indeed, one cannot resist the conclu- sion that the area now occupied by this great system has ever been made up of lines of weakness in the earth’s crust, along which at varying intervals there have occurred elevations and depressions of the mass. The sections obtained in the deeper gorges of the Eastern, Sangre de Cristo, and Los Pinos axes of elevation show that along the median line of each there is a peculiar syenitic granite, more or less porphyritic in structure, upon each side of which the metamorphic rocks lie. There seems to be no room for doubt that the doctrine of granitic axes is a good one in this region, though it may or may not be satisfactory elsewhere. The general diminution in disturbance westward, as shown by the * Dr. J. L. Le Conte came to this conclusion respecting the eastern group in 1868. See his notes on the Geology of the extension of the Union, Pacific Railway, Eastern Division, 1868. STRUCTURE AND AGE OF ROCKY MOUNTAIN SYSTEM. 499 diminishing steepness of dip, together with the general trend of the various axes, shows that the disturbing force was propagated from the east or east of northeast. The relations of the strata of the several periods give us the story of successive elevations, and enable us to determine the era and comparative energy of each upheaval. Along the Eastern range no Carboniferous rocks were exposed at any locality visited by me, but they have been seen elsewhere by others. They must be quite unconformable to the Trias, as it overlaps them very greatly. The unconformability between Trias and Cretaceous is extreme, there being a difference of about 40° in the dip. The Tertiary rocks in the same region rest unconformably upon the Cretaceous, and have a dip of not more than 5°. It is worthy of note that the Tertiary. rocks on the Rio Grande have nearly the same dip. In the interior no rock of more recent origin than the Carboniferous is involved in the main axes. The Paleozoic strata occur high up on the flanks of the whole group, and the Cretaceous (the Trias being absent) every- where abut against them around the base of the mountains. The one exception to this is found in the Elk Mountains. In the southwest, around the southern extremity of the system, we find the Trias and Cretaceous forming mesas abutting against the Paleozoic, and perfectly conformable. One instance, the spur from the San Juan, has been referred to as involving the Mesozoic strata. Everywhere throughout our area the Silurian and Carboniferous are conformable. The conformability between the Silurian and Carboniferous seems to imply that during the long period of their deposition the conditions must have been the same, either comparative quiet or continued subsidence, while the marked want of conformability between these and the Mesozoic rocks is ample evidence that elevation began at the close of the Carboniferous. ‘The fact that these Paleozoic rocks alone occur on all the interior axes of eleva- tion, with no Mesozoic rocks either overlapping or resting directly on them, shows that the elevation there was permanent, but the extensive overlapping of the Paleozoic by the Trias along the face of the eastern range is proof of a subsequent depression along that line. The first great epoch of accelerated disturbance in the Rocky Mountain region, resulting in permanent elevation of the MGs 6h i | - . ‘i | : n | hae Aas ee % Fubeens ‘wba 4 langle rere a iter ieee ed gin sia) = << ‘ | re a> 4 af re > aa Ty f WaAP th ok: 2 ite Tey AT TEY ad - , | | . APT o : i ; . : et - e 3 | 2 4 ‘ % = ~~ =a 2 aol a ee ae REPORT ON THE GEOLOGY OF PORTIONS OF NEW MEXICO AND ARIZONA, EXAMINED IN LS 7-se re G. K. GILBERT, A.M. COMPRISING CuapPrer XVII.—THE RANGE REGION; XVIII.—THE VOLCANIC REGION; XIX.—THE PLATEAU REGION. 503-504 ar e Rs, 2 Borie a : ~ ON is y - 7 ie. - 5 ; aay 2 ’ . : ee 5) hey Fee | 7 S ' . ah \ . \ . E ; ; ; PORN ST ES OE La Pp ¥? , Tt Aa, ? e : ¥ ¢ ‘ 3 iS Shas hates a ee aK Sey = 4% a) ey © ste. 44 : eg _ ng ‘ ; vi} u ~ +4 eee 19 Mt gba? a i F t Pass Sdh'tu'e ge) ahd ted fee): |}? bs - 4 4 ‘ i dyntee: et q ° ot ¥ > % > id 2. Thy pa roe ‘ vet 104 t J 2 Wasuineton, D. C., October 19, 1874. Sir: I have the honor to submit to you my report of geological exam- inations in the field-season of 1873, together with drawings for illustrative wood-cuts. It includes, besides the result of my own work, a portion of the information gathered by Mr. E. E. Howell, and by Dr. O. Loew, in the same year. My first examinations were made in the vicinity of the Fort Wingate rendezvous in the latter part of July. Thence, to Camp Apache my route was the usual wagon-road, with the exception of an excursion to In- scription Rock, and a detour of three days, eastward, from the bridge of the Colorado Chiquito. From Camp Apache I. made three side-trips; the first with your own party to the Sierra Blanca country, the second up the North Fork of the White Mountain River, and the third to the junction of the main forks of the river. Thence to Camp Bowie, the most southerly point touched, my route was identical with that of Lieutenant Tillman and the topographer, Mr. Schmidt. We diverged from the traveled road to explore the South Fork of the White Mountain, and the Prieto and Bonito Rivers, and to ascend Mount Graham. To Camp Bayard we followed the road via San Simon and Ralston. At that camp I joined the division under Lieutenant Russell, for the sake of uniting my route more closely with that of Mr. Howell, and with him I followed, first, the Mimbres, and then the Gila River to its source. Continuing northward, by way of Luera Spring, the Tres Hermanos, Acoma, and Cebolleta, we reached Agua Azul, not far from the point of starting, late in November. The notes of that portion of Mr. Howell’s route which lies within this circuit were placed by him in my hands, and his material has been combined with mine so intimately that it has been impracticable to give him full credit in the places in which it has been used. The invertebrate fossils gathered in the progress of the work, and which have now been intrusted to Prof. C. A. White for thorough study, were previously inspected by Mr. F. B. Meek, and upon the authority of 505 en 506 GEOLOGY. his determinations are based the names which I have enumerated in describ- ing the relation of the fossil§ to the stratigraphy. The subject matter of the report falls naturally into three categories already recognized in the report of my earlier work, and it happens that, in this field, the areas characterized by the several types of geological consti- tution are so massed that, in adopting a logical division of my material, I have at the same time chosen a geographical division. I am confident that the omission of details will meet with your approval. Wherever the facts at hand have appeared to warrant a general statement, that has been given in preference to the individual facts, in the belief that, even though it shall require future modification, it will be more readily available and in every way of greater service to geological science than the enumeration of the local details that were the subjects of direct observation. Very respectfully, your obedient servant, G. K. GizBert, Lieut. Geo. M. WHEELER, Corps of Engineers, in charge. GEA. PILE Bi deVi dL: THE RANGE REGION. In a former report (Part I of this volume) I have had occasion to dwell upon the distinction that is marked in Utah and Northern Arizona, between the plateaus of the Colorado Basin and the ranges of the Great Interior Basin. The explorations on which that report was based showed the persistence of the distinction as far south as Middle Arizona, but left doubt whether the plateau belt ran southward into Mexico or found limit within our own territory. In 1873 the southern extremity of the belt was ascertained to be approximately in latitude 33° 30’, and the entire border, at the south, between the areas of great and slight corrugation, was found to be blanketed with lavas. These facts have led to the discrimination in the description of the region explored in 1873 of three provinces, which form the topics of as many chapters. The present chapter considers the ‘mountain ranges visited in Southeastern Arizona and Southwestern New Mexico; the next, the broad area of volcanic rocks everywhere encountered in passing to the north; the last, the plateau country which stretches from the lavas northward beyond our field. In the region of mountain ranges we intersected the route explored by Lieutenant Parke in 1855, and I was enabled, by direct comparison with my notes of a number of localities, to recognize the fullness with which Dr. Antisell, the geologist of that expedition, has described the phenomena of his route.* Entering the field from different sides, and with different pre- conceptions, and closely coinciding in route for but a short distance, it is not surprising that we fail to agree in our generalizations, but at our com- mon points of examination I have almost no amendments to propose to his descriptions. The majority of our differences of interpretation it will be unprofitable to discuss until the array of facts shall be less meager. *Vol. VIII, Pacific Railroad Reports, Part I, chapters 20-23. 507 508 GEOLOGY. In latitude 32° it is possible to group the mountain ranges of Arizona and New Mexico in two systems, distinguished by difference of trend. In the vicinity of the Rio Grande del Norte the ranges trend nearly north and south, and their northward prolongations swerve somewhat to the east. One hundred and fifty miles to the west the Chiricahui range trends north- west, and its prolongation in the Pinaleno, Pinal, and Mazatzal ranges holds the same direction for nearly two hundred miles. The space between these divergent lines of structure is filled at the north by plateaus, and at the south by a series of ridges parallel to the Chiricahui, but disappearing northward under the lavas that fringe the plateau region. West of the Chiric ahui Mountains are others with the same trend. In a general way, we may say that east of the Mimbres River is a mountain province, in which the trend of the axes of corrugation is north, and west of that river another province, in which the trend is northwest. The mountains of the eastern province are the southward continuation of the Rocky Mountains of Colorado, and with them constitute the eastern boundary of the Colorado plateau region. When the western mountain system is traced northward it is found slowly to lose its northwest trend, exchanging it for a more north- erly, and finally coalescing, without discernible break, with the Basin Range System of Nevada and Western Utah. Regarding it as one with that sys- tem, it constitutes the western and southern boundaries of the Plateau region. Whether this classification, based upon trends, corresponds with, and will lead to a classification based on the more important character of age, cannot yet be told.. The general tendency of the evidence at hand is to give the principal uplift of the western or Basin Range System an earlier date, but there is no final proof. In Nevada, Mr. King announces fossil- iferous Triassic strata older than the Basin ranges, and refers the birth of the latter to Jurassic time; but in Arizona and New Mexico there are not grounds for equal confidence. The newest rocks there recognized by fos- sils are Carboniferous, and these are folded components of the ridges. In the valley of the San Pedro, (Southern Arizona,) Antisell found strata newer than the adjacent mountains, and which he regarded as Cretaceous. If it could be proved that they belong to that system, the age of the mountains would be locally established as between the Carboniferous and the Creta- THE RANGE REGION. 509 ceous, but the only evidence adduced is lithological, and such proofs, always untrustworthy, are in this case especially questionable, from the fact that the beds pertain to a small estuary, or perhaps lake, where the character of deposits must depend on local causes, and be independent of such wide- spread conditions as alone can give value to lithological coincidences. West of the Mimbres, on the other hand, the facts gathered by Messrs. Marcou, Newberry, Shumard, Jenney, and Howell, though not entirely concordant, appear to show that, while the north-trending chain had a pre-Silurian existence, its present proportions were acquired, after a long period of quiet, in post-Cretaceous time. But, whatever the value of the distinction as an element of ultimate classification of mountains, it is convenient to recognize it in the description of the ranges touched by the season’s exploration, and those of northwesterly trend will be first mentioned. Taking them up, in order, from west to east, the first to consider is a long line (for which there is no comprehensive title) of ridges, succeeding each other in the same trend, and known in different portions as the Mazat- zal, Pinal, Pinaleno, and Chiricahui ranges. Of the geology of the Mazatzal nothing is known. The Pinal Mr. Marvine crossed in 1871, and found to be constituted of granite, overlaid in part by sandstone and limestone, that are probably Paleozoic, and in part by acidic lava. The Pinaleno includes three titled peaks, Saddle-back, at the north, Mount Turnbull, and, at the south, Mount Graham, the highest point of the region. Atand in the vicinity -of Saddle-back Peak, Lieutenant Emory (Reconnaissance of 1826-47) noted the occurrence of granite, sandstone, and limestone ; and in the same vicinity Carboniferous fossils were discovered by Lieutenant Whipple, (quoted by Mr. Marcou in his “ Geology of North America.”) In the same neighborhood, and especially to the southeast, about the mouth of Aravaypa Canon, the sedimentary beds are overlapped by great eruptions of trachyte. In the vicinity of Mount Turnbull Dr. Loew noted granites and schists as predominant, but with some quartzite and limestone, and lava. Mount Graham I ascended from the northeast, finding upon that face only gneissic rocks, and a syenite that, viewed in large masses, betrayed a trace of structure. The chief mass, and not improbably the whole of the mountain, is metamorphic. It is of imposing proportions, rising 6,000 feet from its 510 GEOLOGY. eastern base (and nearly as much from its western) so abruptly that it is difficult of ascent. To the southeast the crust gradually descends, until in Railroad Pass it is buried by the valley detritus. The Chiricahui Mount- ains, beyond the pass, are inferior in magnitude to Mount Graham, and less simple in structure. My examination of them was confined to the northwestern extremity, from the peak Dos Cabezas to a point six or eight miles beyond Camp Bowie. In this region they are constituted of syenite, schists, Paleozoic strata, and porphyry. The relation of the syenite to the schists was not made out, but they are both overlaid (the schists unconform- ably) by the Paleozoic. The syenite is not uniform in kind, but a large portion is characterized by crystals of orthoclase from one to two inches in length. The schists are thoroughly foliated, and, in large part, fall under the denomination of gneiss. In the vicinity of Dos Cabezas they contain magnetic iron ore, probably in quantity to give it economic value. The Paleozoic strata, where best displayed, show 3,500 feet of limestone, shale, and sandstone, with Carboniferous fossils near the top of the series, and Lower Silurian near the base. The porphyry overlies all the other rocks, and is probably inferior to all in mass, although it constitutes Dos Cabezas, the highest peak in this portion of the range. The break between the Archean schists and the Paleozoic beds is strongly marked. The Archzean sediments were foliated, were tilted, and were lifted above the ocean and eroded before the Paleozoic were laid down. Or, to give the data instead of the inferences, the contrast in degree of meta- morphism of the two systems is conspicuous at their contact, the one show- ing complete foliation, while the other retains ripple-marks and fossils. The angle of discordance in dip is as great as 65°; and the lowest bed of the upper system is a coarse sandstone, spread over a plane and originally level surface. If the syenite is older than the schists, then the degradation of the Archzean mountain was carried so far as to expose the former also to the waves of the Paleozoic shore. Later revolutions have thrown the rocks into a new system of ridges, in which the Paleozoic strata are inclined at all angles, even passing the vertical. Subsequent denudation has so far removed them, that their areas of outerop are now inferior to those of the Archean; and their metamor- iF J \ ie i y 4 & “ae . tas ® ; t ‘ - > ™ ee , & . ay 3. * » a i. ; i 3 . aa # ie | gee id at aS onde Peat) VP — i . } i bee | f ake pee pA OTIS Sy Sa a ~e2 ua eee i | A he Lar ieee a ‘ ‘ y by i oes 4 A * : » a wr, i iii! thee : A i | i gna . . = ; i 4 . 4: ’ . 7 ur bse, a « _ a et ho Agi \g? sd ts Pad L 4 ; {>a oa ; hi “ = ‘ = ! os “ge mye ty anit il “ : . oS J ] 45° 3% i t i f > ' h et 7 ea ft oR, fd i 2 ties site) 2b ) a@t = Oras é 4 dita QI Y 44 4 IZA Tae oe woe ei 1 ait reMs Ta hu ’ ha 511 THE RANGE REGION. phism, though far less than that of the older system, is marked by the crystallization of hornblende and andalusite in certain shales, and by the e fossiliferous, to marble. The elsewher ion of limestones, iS) local conver Fia, 146. Fic. 147. x 56a GO Fier, TC C a i ee rea ON eS i oS VISES EIA CUT A AEG UES ASO Fo Ml, a ee vay: Via. 148, C. Taig ee eats 7, DS~), Ay VED WN VRS SSS, Ws Sections of the Chiricahui range, Ariz. Scale, yz}py. Base line=sea level. Fig. 146, section nine miles east of Cainp Bowie. Fig. 147, section three miles east of Camp Bowie. Fig. 148, section at Camp Bowie. JU.S., Ewell’s Spring. D.C., Dos Cabezas Peak. C.B., Camp Bowie. trend of the structure lines of the later corrugation is north 65° west, and g ’ the original strike of the schists was determined, at a single point, to have 512 ' GEOLOGY. been due north.* The structure of the range is exhibited in figures 146, 147, and 148, which give sections transverse to the strike at intervals of three and six miles. The rocks are divided into two principal monoclinal bodies, ab and a’b’, by a fault; and each of these bodies displays a belt of Archean at the north, and one of Paleozoic at the south. Camp Bowie stands close to the line of fault. The Paleozoic rocks of the northern belt are there little inclined, but in tracing them northward they were found to gradually increase their dip, until, in the vicinity of Dos Cabezas, it is more than 90°. The porphyritic overflow constitutes the crest of the range from Dos Cabezas eastward nearly to the line of the second section, and near it the strata are more altered than elsewhere. The southern Paleozoic belt exhibits two parallel ridges, that figure as southern, and in part outlying, foot-hills of the range. From Ewell Spring they run east-southeast, with constant form and trend, for six or eight miles, and then sink out of sight. In the opposite direction they curve toward the north, and are less persistent. It will be seen by the following sections that both Lower Silurian and Carboniferous fossils were found, but the horizons were not sufficiently numerous to define the relative thickness of the two formations. If the upper horizon of the Ewell Spring section be regarded as Subcarboniferous, then the Silurian does not exceed 1,000 feet in depth. Section of strata exposed at Ewell Spring, in the Chiricahui range, twelve miles west of Camp Bowie. The lowest bed rests on Archean sye- nite. Feet. 1, Massive gray limestone, with little chert, [| Pentremites, (like P. melo,) Syring- opora, Zaphirentss, Favosttes| 2-2 o-oo > - == See eee ee 125 2. Unseen 5. S086 5.) c 2 s:2iss.0 5.5 oni ho a so ee ae 450 3. Dark, bedded, arenaceous limestone, with much chert, [Huomphalus (like £. trOCRASCUS)] .'5 Boje eo oiw dsc wae Ske Sere se ot pede eee ae ee eae eae 325 4, Vitreous, bedded sandstone; gray, weathering brown; conglomerate at base. 260 * At a point two miles northeast of Camp Bowie, where the junction of the strata is clearly seen, the Archean strike north 20° east, and dip at 60° to the east; and the overlying beds strike north 70° west, and dip at 30° to the south. Assuming that the last flexure had its axis parallel to the strike of the upper beds, it follows mathematically that when the upper beds were horizontal, the lower had a strike north 4° cast, (approximately,) and a dip of 64° to the east. WG} dy IUUE (Ga (OCONEE JE LAINE, IS PRBBLES CARVED BY HELIOTYE bat] ig] THE RANGE REGION. Dis Section of strata exposed at Camp Bowie, in the Chiricahui range. The lowest bed rests on Archzean schists. Feet. 1. Massive limestone; dark blue to white, in places changed to marble, [Pro- ductus semireticulatus, Athyris subtilita?, Spiriferina, Zaphrentis]........-- 850 2. Quartzose rocks: J a. Quartzitic schists, alternating with black slates, the latter Containing andgaluUsiken-s2os- 2 <5) sees (eicnseeniele n= = 525 feet. 1. 325 b. Quartzite and quartziferous slate, bedded and of dark colors. 600 feet. ec. Dark gray, calcareous, vitreous sandstone or quartzite ..... 200 feet. | 3. Limestone: a. Arenaceous limestone. .....- EG inaton cease a boteeede? b. Massive, sectile limestone, laminated with blue and white .. 15 feet. | Ga WIE Ganoce Rede koh cnccadwouseme red ocosmonos ake Sees 80 feet. d. Bedded, rust-colored limestone, with geodes of arta and | 420 calcite, and obscure fossils, | Lingula]......-.---..-+..-. 75 teet. | e. Bedded limestone, dark on fracture, but superficially banded With plue-cray and ashi <2. coe a= <2 eee ne mie oe 100 feet. 4. Shale: a. Pale gray, argillaceous shale.......-.........s----..-. «. 55 feet. b. Black, argillaceous and calcareous shale, interlaminated with 1é blackalim cstonen sents etre aor tae asa sey sae 150 feet. aoe c. Pale blue, caleareous shale.........----------+--.--.----- 10 feet. \ MaSSIVes Pale Cray IEMCSGONO 1 .)192 ais ssisyetalateie'=!S{eje cele sis 3-50 vane ocles ec cnne 35 oo Massive limestone; mottled with gray and ash-color. The mottling is in part coralline in form. Fitty feet below the top is a zone of chert, from which the bed is otherwise free. At base is a gradual transition to the next 7. Dolomitic beds: a. White, massive rock, composed of dolomite and some quartz. 20 feet. b. Gray, caleareous shale :.5.--:-..--. 22. .--5.2.-0-2-----50- 80 feet. 160 c. White, massive, crystalline dolomite .-...---.-..---.--.--. 60 feet. 8. Bedded quartzite and quartzitic schist, gray to brown.-.-.-..---...-..--.-- 310 Moataleree... 2oal dsecen Oe One d dome nee dod HORE RE Ee eC Ae Aree terrae 3, 620 The Peloncillo range, next northeast of the Chiricahui, is of less mag- nitude. Its trend is northwest, and is prolonged beyond the Gila by the Gila range, (the “Sierra Carlos” of Emory.) It is built chiefly of trachytic lavas, but at the two points.at which I crossed it a sedimentary nucleus was detected. Opposite Pueblo Viejo the southwestern base of the Gila range is of quartzite, in which are cupriferous veins. Over this is a gray rock, made 33 WS 514 GEOLOGY. up chiefly of feldspar and hornblende, and possibly of eruptive erigin. Above are nearly 1,000 feet of trachytes and trachyte conglomerates, un- evenly bedded, and surmounted by basalt. These are all exhibited in sec- tion on the southwestern face, which is steep, while the opposite face is con- stituted by the upper lavas, which, dipping in that direction, are continuous to the Bonito River, five miles away. The range is at this point a mono- clinal mass of bedded lavas, whose eruption took place before the disloca- tion that produced the ridge, and the same structure probably continues to the northwest for fifteen miles. Forty-five miles in the opposite direction, at Peloncillo Peak, (Steen’s Peak of some maps,) Antisell noted only vol- canic rocks, but at Gavilan Peak, ten miles beyond, the sedimentaries are once more exposed. They comprise limestones and sandstones, and are probably of the Paleozoic series observed in the Chiricahui range. Car- boniferous fossils were seen in their debris. The strata dip at a high angle toward both flanks of the range, and upon their upturned edges rests the granite which constitutes the peak. The circumstances admit of no ques- tion that the granite in this case is eruptive, and was extruded after or during the disturbance of the Paleozoic strata. The limestones, at their contact with the granite, are converted to white, coarsely-crystalline mar- ble; and the same metamorphism is to be seen along the margin of a heavy dike of granite in the vicinity. The granite is fine-grained, and consists chiefly of quartz and albite. Its body is traversed in one place by a dike of quartz-porphyry. In the Pyramid range, of which we visited the northeast end, I failed to discover any save eruptive rocks. Basalt and trachyte flank and overlap a more ancient lava, which is proably referable to the propylite of Richtofen, and which contains the quartz veins of the Virginia (Ralston) mining district. The whole range has an appearance of great antiquity, being reduced nearly to the level of the surrounding plain by an erosion, the present progress of which is of exceeding slowness. The appearance is doubtless due to the easy disintegration of the ancient lava. The purest quartz veins, resisting the destructive agents by which the country rock is degraded, project above the ground surface in long,ragged walls. Other veins less conspicuous, but more attractive to the miner, contain, in the quartz, argentiferous ores of lead and THE RANGE REGION. / 515 copper, and, with the building of the Southern Pacific Railway, may become of economic importance. For the present, however, all mining operations are suspended by the proprietors of the veins, because too expensive for profit in so sterile and remote a place. The Burro Mountains are of greater magnitude, and are comparable in structure with the Chiricahui. Mr. Howell, crossing them in a northeasterly direction, from Ash Creek to Silver City, found their chief mass Archaean eranite, lying in two bodies, the first and smaller of which bears bedded tra- chytes with a northeast dip, while the larger is overlapped by Paleozoic strata with the same dip. The range is thus, in a general way, monoclinal in structure, the inclination of the rock masses being to the northeast, and the latest disturbance haying occurred after the extrusion of the trachyte. The Paleozoic limestones and shales contain the argentiferous veins mined at Silver City, and have likewise been intersected by dykes of a peculiar gray feldspathic porphyry. From one of the limestones, in close proximity to silver mines, Mr. Howell gathered a suite of fossils of Cincinnati age, includ- ing Leptena sericea, Strophomena, (type of S. planumbona,) Rhynchonella, (like R. subtrigonalis,) Fenestella, Favosites, and Stromatopora, and from the same vicinity Lieut. A. H. Russell brought a block with several specimens of Zaphrentis, marking the presence of Carboniferous rocks also. Fifty miles northwest of the Burro Mountains, and possibly in the same line of trend, the parties which descended the Prieto and San Fran- cisco Rivers found islands of Archzean and Paleozoic rocks—the crests of a mountain almost completely hidden by the deep floods of the lava-field. The most conspicuous rock is a deep red granite, against which rest a system of sandstones, limestones, and shales, lithologically similar to the Silurian and Carboniferous rocks of the neighboring ranges. The only fossils dis- covered are of Carboniferous age, but it is nevertheless probable that the base of the stratified series is Silurian. The chief of these islands, lying between the two rivers, contains the Clifton mines. It is possible that other peaks of the same character jut through the lavas on the line between Clif- ton and the Burro Mountains, but none of them were visited. Next east of the Burro Mountains lie the Santa Rita, a range defined for only a short distance. In the vicinity of Fort Bayard and the Santa 516 GEOLOGY. Rita copper-mine its axial rocks are displayed for a few miles, but to the south they are covered by the rhyolite of the Kneeling Jesus mesa, and to the north by the similar lava of the Diabolo range. The axial rocks are 5 \ \ of strata with a northeast dip. I visited only the more easterly ; but, from the descriptions given me by gentlemen engaged there in mining, I am led to believe that the rock series of the whole is identical with that of the CC, Carboniferous. Base line = sea level. Scale, rzbo0- 2, Santa Rita copper-mine. Fic. 149.—Section of Santa Rita range, New Mexico. Archeean schists, and Silurian and Carboniferous sand- stones, limestones, and shales. The schists were seen only at the northeastern base, near the Mimbres . River, and at their contact with the Silurian their dis- M, Mimbres Valley. A, Archean, S, Silurian. cordance of dip is 75°. Resting upon them are, in order, sandstone, limestone, with Silurian fossils, shale, and limestone with Carboniferous fossils. The strike of the whole is northwesterly, and the dip gently to the southwest. The weathering of the shale has opened a valley between the outcrops of the two limestones, leaving the lower as the cap to a line of hills near the Mimbres River, and the upper as the crest of the main ridge farther to the west. The sur- face of the western slope of the range is made up of the Carboniferous limestone and a feldspathic por- phyry that has risen through it, and in part overrun it. From the foot of the slope, westward to the Burro and Bear Mountains, the foundation of the plain is of this same porphyry. Fort Bayard stands upon it, and the roads thence to Pinos Altos, Silver City, and Lone Mountain cross little else. Pinos Altos Peak is a granitic, and presumably Archzean, island, bounded on one side by overlapping porphyry, and on the other by the still newer eruptions of the Diabolo range. Lone Mountain, also an insular butte, is bathed at - foot on three sides by valley gravels, and to the north ‘by the porphyry flood. It consists of two principal ridges, both short, trending northwest, and composed THE RANGE REGION. Sy Santa Rita range, the Silurian outcrop being, in this case, at the west instead of the east. The eastern ridge is of limestone, with Carboniferous fossils, including Productus semireticulatus and Spirifer lineatus. Porphyry, such as floors the country at the north, breaks through the limestone in dykes, and in the same neighborhood are calcareous veins and deposits, with argentife- rous galena. The section of strata exposed in the eastern face of the Santa Rita range is as follows, beds 1 and 2 being estimated in thickness, the others measured by barometer : Feet 1. Gray, massive limestone, [Spirifer cameratus, Productus, Orthis]........-.... 200+ PRCA PATO ACROUS SH AIC) o.2 aye a) fo! apo) e\ a sshe in) oraietsys o/s" sea} ore) afann ayai« arerate leicleseigys siete 100+ 3. Gray limestone; massive and bedded, with much chert, [Strophomena (alter- nata,?) Orthis lynx (var.,) O. (like O. testudinaria,) O. (type of O. sinuata,) Rhynchonella (like hk. subtrigonalis,) Murchisonia,? Modiolopsis, Favosites].. 90 ay UIRSROD.S SNUG >: cary sou ces Sop Ue a eps SHOE Om Oe DECI ape Ae ae Comer ea erie 25 Sa Gray Sanasuone, in part CalearcOuUSs 2. 2. = veeccis ew sew Mined se ecisse cece 10 PrepUITISCON era eases fees Nae ee ye So mas ee sides bie ae anit DSS RSL tees web 30 7. Heavy-bedded limestone, with coralline mottlings; in part arenaceous, [ Cono- GIUA| socorcdes Seeckab eS at ss SOC eb oD Oo Spee ROE DOSS EE SOE sone Reena ee 200 8. Vitreous sandstone and conglomerate, red and white, resting unconformably ONVANCH LAN SCMISES Ha sf ale steele sfaranin S aetns pewlae cts bathe sie saee a ocbewel 22% 80 Oba re woe ae eats i950 pRECSOER SC aC SS aot DORGOdO DO aueb DOE per. 7354+ This closes the list of ridges with northwest trend. It may be said of them, in general, that their axial rocks are Archean and Paleozoic, there being no evidence of sediments newer than Carboniferous before their up- lift. Their age can be defined no more closely than is expressed by the term post-Carboniferous. There is proof of an antecedent—pre-Silurian— corrugation of the same region, the axes of which did not accord in trend with those of the later disturbance. The ridges of earlier formation were mostly, if not all, obliterated by pre-Silurian and Silurian denudation, and the existing ridges are referable to the later—post-Carboniferous—action. Our examinations have demonstrated no anticlinal structures, except as minor features. The usual structure is monoclinal, demonstrably due to faulting in the Chiricahui and Pinal ranges, and presumably so in all the others. Taking the ranges in order, from southwest to northeast, the 518 GEOLOGY. inclined masses dip as follows: (The ranges given on the same line are considered continuations of each other.) Chiricahui, SW. Peloncillo, at Gavilan Peak, synclinal. Gila, at Pueblo Viejo, NE. Pyramid, unknown; axis not seen. Burro, NE. Clifton, SW.? Lone Mountain, NE. Pinos Altos Peak, unknown. Santa Rita, SW. In this succession no symmetry is discernible. All the ranges show post-Carboniferous eruptive rocks, and these have no common character, unless it be the preponderance of feldspar. They include granite, feld- spathic porphyry, propylite,? trachyte, and rhyolite, with basalt, quartz- porphyry, and other rocks in minor masses. The geological distribution of the metalliferous veins warrants no gen- eralization further than that it is not narrowly restricted to rocks of par- ticular age or composition. In the Chiricahui range a siliceous vein in syenite has been wrought for gold. In the Gila range are cupriferous veins in Archzean (?) quartzite. In the propylite (?) of the Pyramid range are quartz veins with argentiferous ores of lead and copper. Near Clifton, gold and copper have been obtained, the former from placers, the latter from lodes in limestone of Paleozoic, and probably Carboniferous age. At Silver City, argentiferous galena in calcareous gangue is taken from Silurian lime- stone and shale. At Pinos Altos are mined quartz veins, traversing Archean granitoid rocks, and containing compounds of iron, copper, and lead, together with an economic percentage of gold. At Lone Mountain, calcareous veins and deposits, with argentiferous galena, are found in Carboniferous limestone. On the western slope of the Santa Rita range, in the Santa Clara mining district, plumb-argentiferous ore is obtained from Carboniferous limestone ; auriferous and cupriferous, from veins in feldspathic porphyry. The cele- brated Santa Rita mine, near the crest of the range, lies on the contact between the Carboniferous limestone and the porphyry. The Upper Mim- bres mines, on the eastern slope, are in Carboniferous limestone, and afford argentiferous galena. Passing now from the ranges of northwesterly trend to those of northerly, THE RANGE REGION. 519 we pass, at the same time, from the southern border of the Plateau region to its eastern border, and have to consider a chain of ranges of remarkable persistence, that coalesces northward with the Rocky Mountains of Colorado, and southward, crosses the Mexican boundary. Through the labors of Messrs. Marcou and Newberry, in the vicinity of Santa Fé, and of Mr. Shumard and Mr. Jenney in the El] Paso Mountains, it is established that this chain, while it consists mainly of Archzean and Carboniferous rocks, with Silurian at the south, bears upon its flanks Cretaceous and other Meso- zoic strata, which have shared in the disturbances that produced the chain. A comparison of the Cretaceous strata upon both sides of the chain, as described by those authors and by Mr. Howell, suffices, when taken in con- nection with the manner of their disturbance, to indicate that the Cretaceous sea occupied the present site of the chain, with the exception, at most, of a few islands, and possibly without exception; so that the last great upheaval of the chain cannot have begun before the end of the Cretaceous epoch. The discovery, by Dr. Loew, of a Pliocene deposit in the valley of the Rio Grande, at San Ildefonso, assures us that the data for the closer determina- tion of its age are accessible. If these Pliocene beds shall prove to be undisturbed and non-conformable to the Cretaceous, the date of the first uplift will be defined as early Tertiary. If they prove to be conform- able, then they ante-date the birth of the Santa Fé Mountains, and presum- ably of the whole chain. The Mimbres range, in the portion that I examined, belongs to the great lava field, but as its sedimentary nucleus is not entirely concealed, it may be mentioned here, also, as a member of the ridge system. From the town of Upper Mimbres to the Canada Alamosa, a distance of sixty miles, its western slope is a continuous sheet of trachytic lava, of wonderful uni- formity of texture and habit. The opposite face I did not see, but it was skirted by Lieutenant Tillman and Dr. Loew, and from their descriptions, taken in connection with my own observations, I am led to consider the range a great monoclinal uplift, with westward dip, composed in chief part of lava, which constitutes the entire crest, but revealing the underlying sedimentaries (Paleozoic) along the eastern base. Farther south the sway of the lavas is broken, and the sedimentaries rise to the crest. 520 GEOLOGY. The San Mateo and Ladrones Mountains were seen only from a dis- tance. They are huge piles, that would rank among the lofty summits of the land, if they stood on some high plateau, instead of springing from the low valley of the Rio Grande. Their shapes are jagged and alpine, con- trasting strongly with the lava forms to the west of them, and inditating a complex structure, with certainly stratified, and probably Archean, rocks predominant. ; Of the mountains that lie east of the Rio Grande, the only ones touched by our parties are the Zandia and Santa Fé, and our observations add nothing to the knowledge of their general geology. The collection of Coal- measure fossils made by Mr. Keasbey, near Santa Fé, is of value to the paleontologist, not from new forms, but from the exceptionally good condi- tion of its specimens, which will enable an intimate and thorough knowledge of some species heretofore but partially described. The spectacle presented by the Zandia Mountain is a peculiarly impressive one. It overlooks the Rio Grande from the east with a bold, mural front, even and straight, and little gashed by cations. From the water to the crest the rise is 7,000 feet. Except the crest, the whole front is Archean, but from end to end there is a cornice of Carboniferous lime- stone a few hundred feet thick, that by its continuity shows the whole was raised in a single unshattered mass. The eastern face is of easier slope, but is less regular. The limestone band that forms the persistent and almost level line of the crest, is the edge of an eastward dipping bed that is succeeded in that direction by superior Carboniferous and Mesozoic strata, all dipping from the mountain. But going westward from the Archean belt the unaltered rocks are not found in the same order. The tough Carbonif- erous limestone, that holds its own so valiantly on the summit, does not appear at the west, as it should if the structure of the mountain were anticlinal; but the first strata seen after passing the valley gravels, which bury the base of the Archzean wall, are of Cretaceous age, and they dip toward, rather than from, the ridge. I conceive that the mountain is a great, but simple, monoclinal mass, bounded on the west by a profound fault, along the line of which is the river valley. The difference of level between the Carboniferous strata on the crest of the mountain and the i THE RANGE REGION. 51 dissevered fraction of the same strata, buried far below the Cretaceous rocks in the valley, is not less than 11,000 feet, and something greater than this must have been the throw of the fault that separated them.* There are two general facts in regard to the geological history of the great West that deserve especial mention, for the reason that, while some of the individual instances on which they depend have long been known, it is only recently that they have been announced in such number, and with such distribution, as to dissipate all doubt that their meaning is general rather than local. The first is that the pre-Silurian stratigraphical break is as complete and as universal in the West as it is in the Eastern States and Canada. Its existence has been determined in Nebraska, Montana, Idaho, Wyoming, Colorado, Utah, Nevada, Texas, New Mexico, and Arizona, and its general features are everywhere the same. ‘There is, first, a wide non- conformity, demonstrating the tilting and erosion of the Archean beds anterior to the deposition of the Silurian. And, second, there is always, at the contact, a contrast of condition as regards metamorphism, the Silurian rocks being, usually, merely indurated, and the Archzean invariably highly metamorphic. These two characters of the break serve to show that it represents a vast chasm of time, a chasm, the duration of which may have been greater than that of the ages which have since elapsed. _A third character of the break, one that is supported by less evidence, but is negatived by none, is that the lowest of the superposed rocks are conglomerates and coarse sand- stones. The lowest Paleozoic rocks are Primordial, and the basal portion of the Primordial is everywhere siliceous and of coarse texture. Where the Primordial is absent, and the Carboniferous rests directly on the Archean, a limestone has been observed at the contact; but this is a local phenome- non, the meaning of which is that certain Archean mountains were islands in the Silurian sea, and were afterwards covered, or more deeply sub- merged, by the Carboniferous sea. The conclusion to be drawn from the coarse, fragmental nature of the lower deposits is that the water which * See J. Marcou’s profile from Fort Smith, Ark., to Los Angeles, Cal., in the “Geology of North America ;” the same by W. P. Blake, in Vol. III of the Pacific Railroad Reports; and Mr. Howell’s section, Fig. 122 of this volume. 522 GEOLOGY. spread them was an encroaching ocean, rising to possess land that had long been dry. The recognized interpretation of a wide-spread sandstone is continental submergence, or, what is the same thing, an advancing coast line; and where the formation is important in depth, as well as breadth, we must suspect, at least, that the shore waves sorted, not merely the detritus which they themselves tore from cliffs of indurated rock, but other debris, which they found already ground, and which needed only redistribu tion. The Tonto sandstone of the Grand Canon, and its equivalent in other Territories, may fairly be regarded as the coarser of the débris accumulated by subaerial agencies on the Archzan continent; the continent, that is, which immediately preceded the Silurian sea; and the Tonto shale and its equivalents, as the finer and lighter part of the same debris, sorted out by Primordial beach action, and deposited in the stiller water that followed in the wake of the advancing shore. It would, perhaps, be out of place to controvert here the familiar presentation of eastern Paleozoic history as an emergence, beginning with the uplift of the Laurentian highlands, but it may confidently be asserted that western Paleozoic history is the reverse of this. There was a time when Archean highlands constituted islands in a Paleozoic Sea, but this condition was produced, not by the emergence of these islands, as the nuclei of a growing continent, but by the submergence of the surrounding area, and the consequent abolition of a continent. And, so far as we can judge of the remoteness of shores, and of the depth of water, by the relative importance of calcareous and earthy—soluble and insoluble —deposits, the general movement of land through the entire Paleozoic age was a subsidence. Of the extent of the pre-Silurian continent we know absolutely nothing. No portion of its shore is determined, nor the posi- tion of any reservoir for the reception of its waste. The break which its existence made in the sedimentary history of this portion of the world appears to be absolute ; and with its extinction as a continent and division into islands by the Primordial Sea, begins our acquaintance with the early limits of land and water. The second general fact to which attention is called is the meager representation of the Upper Silurian and Devonian formations, both in fos- sils and in strata. The geologists of Lieutenant Wheeler's surveys have THE RANGE REGION. 523 discovered Lower Silurian fossils at twenty-two different points, and Car- boniferous fossils at about seventy-five points, without finding a single specimen of intermediate age. Others have been more successful, but the showing is still meager. Of Upper Silurian localities one is announced by Dr. F. V. Hayden, near Ogden, Utah, upon the strength of a single speci- men of Halysites catenularia; and some fossils from the Hot Creek mining district, Nevada, are referred by Prof. J. D. Whitney, ‘without much doubt to the Niagara limestone.” Devonian fossils were discovered by Mr. H. Engelmann at Eureka and White Pine, Nevada; and another locality in Nevada, Pinon Station, has been incidentally announced as discovered by the Fortieth Parallel Survey. Dr. J. S. Newberry has received Devonian fossils from Hyko, Nevada, and Mr. R. P. Whitfield refers to the Devonian some specimens collected near the Emma mine, Utah, by Prof. 8. Tenney. Trilobites, that indicate either Upper Silurian or Devonian, were announced by Prof. Whitney, from Silver Peak, Nevada, and by Mr. Engelmann, from Egan Canon, Nevada. To compare with these ten localities of the two faunas, there are known at the west more than thirty localities of Lower Silurian fossils, and probably one hundred and fifty of Carboniferous. . Of the absolute thickness of these beds nothing can be said at present, _as their limits have nowhere been definitely ascertained; but there is indi- cation that they are thin as compared with the other Paleozoic formations. _ At White Pine the Devonian fauna is said by Mr. A. Hague to extend through ‘“‘several hundred feet” of strata, (Geology of Fortieth Parallel, Vol. II, p. 415.) At Ophir City, Utah, the interval between the lowest Carboniferous fossils and the highest Silurian is 350 feet; and in the Grand Cation of the Colorado it is not more than 1,000 feet. In the Santa Rita range of New Mexico it is less than 500 feet from the Carboniferous to the Cincinnati horizon. Considering the broad distribution of these localities, and that any of these enumerated spaces, which may be filled by middle Paleozoic rocks, may possibly be chiefly filled by higher or lower beds instead, it is safe to put the general thickness of the two formations at 400 feet, and compare this with the 2,000 feet and 3,000 feet that may be called the average depth of the Lower Silurian and Carboniferous, respectively, in the same region. 524 GEOLOGY. ‘the paucity of Devonian and Upper Silurian strata is not to be ex- plained by supposing that the region was lifted above the ocean in those ages. But a single non-conformity has been recorded within the Paleozoic, and that was seen by Mr. W. P. Jenney in Texas, near the Mexican bound- ary. tall of the localities enumerated in the preceding paragraph there is apparent conformity, and in the Grand Canon so many miles of outcrop were examined that the fact of conformity is placed beyond question. In each of the localities, excepting the Santa Rita range, the rocks between the recognized Lower Silurian and the recognized Carboniferous are lime- stones uninterrupted by shore deposits. Of the main divisions of the Paleozoic system, the best developed all through the great West is the Upper Carboniferous, and it is characterized by limestones. The Subcarboniferous is unknown in the southern Terri- tories, and has been most frequently noted in Montana; but no one has at any point determined the thickness of its strata. 'The Devonian and Upper Silurian are known only in Nevada and the adjacent half of Utah; and the Lower Silurian, while universal in its distribution, has its greatest develop- ' ment along the boundary between Utah and Nevada. CHAPTER XIX. THE VOLCANIC REGION. Prior to the expedition of 1873 it was not known that within the borders of Arizona and New Mexico there lies one of the great lava tracts of the world, a continuous area of volcanic products, second in magnitude in our country only to the great northwestern lava field, and fifteen times as large as the classical district of extinct volcanoes in Central France. The geologists who have accompanied the various public and private railroad surveys, have passed, on the thirty-second parallel, to the south of it, or, on the route of the thirty-fifth parallel, have missed the main body and touched only its extended arms. Messrs. Marcou and Newberry, who saw Mount Taylor and Mount San Francisco, two hundred and thirty-five miles apart, had no means of knowing that by a detour to the south they could pass from one to the other almost without walking on other rock than lava, and yet such is the fact. In the rectangle contained by parallels 32° 45’ and 34° 20’, and the meridians 107° 30’ and 110°, more than nine-tenths of the surface is of volcanic material, and from this main body there stretch two chief arms; the one going north-northeast, eighty miles to Mount Taylor, and the other west-northwest, one hundred and seventy-five miles, in Ari- zona, to the San Francisco group of volcanoes.* At the present stage of completion of the maps of the survey but little beyond the above general statement of the geography of the tract can be made. A general idea of its form and position may be obtained from the crude sketch in Figure 145. Its total area is more than twenty thousand, and probably nearer twenty- five thousand square miles, or about half that of the State of New York. The lavas which go to make up this district are conveniently classed, for present purposes, in three divisions, trachyte, sanidin-dolerite, and *The San Francisco group and the belt with which it is connected were examined in 1871, and their description will be found in Chapter VI of this volume. 525 \ t 526 GEOLOGY. basalt. The variety of trachyte most widely distributed is of light color, the characteristic hue being pale-yellow, and is usually of light weight. Imbedded crystals of feldspar are nearly always visible, and occasionally quartz, mica, and hornblende. I have rarely detected an iron oxide, but the rock is usually magnetic. The name “‘sanidin-dolerite” is used, for merely temporary convenience, to designate a rock of considerable importance in Arizona, which seems to fall without our present nomenclature and deserves the careful scrutiny of the lithologist.. Its habit and color are identical with those of the basaltic or doleritic family. It spreads in broad, sometimes thin sheets, and is apt to be vesicular, the bubbles, in such case, being large, and the partitions which separate them, thick. In typical specimens the matrix is dark iron- gray, and the imbedded crystals are of sanidin. It is by these sanidin crystals, which are often a half inch in diameter, that the rock is separated from dolerite. It is further distinguished by graduation, through a change of matrix, into a true trachyte. It is quite possible that when, by the determination of the constitution of its matrix, it is fully defined, it will not appear lithologically entitled to a specific appellation, but the recognition of its individuality finds geological warrant in Arizona. Under the term “ basalt” are included, after Richtofen, all the more recent basic lavas. *~ The invariable order of superposition is: Basalt ; Sanidin-dolerite ; Trachyte. In many places beds of the lower lavas have been faulted or folded by subsequent orographic disturbances, but this has not been observed (except in a single instance) in the case of basalt. The earlier basalts, however, have a considerable antiquity as measured by erosion. The trachytes have at once the greatest mass and the greatest superficial extent. The basalts are, perhaps, least in mass, but stand second in area. The main body of the district is characterized by trachyte, the arms by basalt. Sierra Blanca has an imperfectly conical form, and, for a mountain of its magnitude, a remarkably low angle of slope. Standing alone upon a 7 i THE VOLCANIC REGION. 527 high plateau, it is a conspicuous peak, but the maximum depth of its lava is probably less than 3,000 feet. Its summit has no crater, but is composed of massive eruptions of trachyte—a variety of trachyte affiliated with, and passing into, sanidin-dolerite—and comprises a cluster of rugged knobs. From it there stretch, in every direction, long slopes of sanidin-dolerite, that appear to have flowed from side fissures, and spread in successive sheets over the plain. To the east these sheets extend for ten or fifteen miles, and to the west for thirty miles. To the south and southwest the same material is continuous for forty miles, to the borders of the San Carlos and Bonito Valley; but there were probably independent eruptions of it in that direction. Scattered over these broad sheets are rounded cinder cones, not exceeding a few hundred feet in height, and with some of them are associated coulées of basalt. North of the main peak is a dense clus- _ter of these cones, associated with basalt flows, that have completely covered the sanidin-dolerite, if, as is probable, it extended there. The line of eruption, of which this cluster is the culmination, runs northwest- ward toward Mount San Francisco, and is the Sierra Mogollon. Many of the cones are so fresh as to have perfectly rimmed craters, but none so recent as to be ‘bare of vegetation. The depth of the water-worn gorges upon the flanks of Sierra Blanca, attest the antiquity of its chief mass, and in some of these gorges have run streams of basalt. In the valley of the White Mountain River, near Camp Apache, are vestiges of three distinct lava flows, which entered at as many different epochs in the progress of the excavation of the valley, and have been successively cut ‘through by the stream. The Natanes Plateau is the southern continuation of the Sierra Blanca sheet of sanidin-dolerite, to which allusion has just been made. It is imperfectly tabular, narrow, and elongated in a northwest and southeast direction. Its northeast face, looking toward the South Fork of the White Mountain River, and Prieto Park, is abrupt in its general character, but is broken by numerous canons. The southwest face, overlooking the head- waters of the San Carlos and Bonito, is an abrupt escarpment, exhibiting in section the lava-beds that constitute the plateau. The series consist of : 528 GEOLOGY. Feet. $ 1. Typical sanidin-dolerite; in beds 20 to 50 feet thick, 3 and remarkably continuous...........-..----- 1,000 & 2. Silicic trachyte, (rhyolite :) US % a. Pale pink to white, lithoid, light, Nw 3 somewhat brecciated......----. 110 feet. ra . 2 b. Dark brown, brecciated and amyg- 460 XX 3 daloidal = -/..-2c24.,2oe-er esa ste 30 feet. ee S e. Purple, hard, fine-grained, brecciat- S Es ed; base not seen .........-..-. 320 feet. 5 \ ° ys e MOtAL > 2202 252.2 222. ee ee 1, 460 \ t Al The same trachyte was seen at the opposite base, and is doubtless continuous underneath, as repre- sented in the diagram. The southwest escarpment of the plateau is not the work of erosion. Lava- topped tables, with precipitous edges determined by the erosion of softer substrata, are of frequent occur- rence in the vicinity of Sierra Blanca, but their contours \ / Gas 7/ \\ P. Prieto Park. re Base-line =sea-level. yz BONEN INVA be y i Scale, rzbvv: B. Bonito and San Carlos Valley. “~N \ have a peculiar character, thatis hereabsent. Instead iS) of the scalloped figure, made up of convex curves, 4. \\ rN\e that results when erosion controls, we have a straight +\ Si\/ IN) line, interrupted only by angular embayments, where it is intersected by water-ways; and the steepest cliffs, instead of overhanging the points of most rapid present erosion, are along the rectilinear front, which faces a broad, streamless valley. This character main- DN s\ =TINYI y S ANY. Section of Natanes Plateau, Arizona, tains for twenty miles, and is unquestionably due to a fault—a fault of not less than 2,000 feet throw, and which has occurred since the eruption of the sanidin- dolerite. The strike of the fault, and of the plateau, is northwest, strictly parallel to the Gila and Pinaleno ranges, which lie ten and twenty-five miles, respectively, to the southwest; and the plateau should perhaps be regarded as a member of the Basin Range System. If it is so, then it is, in longitude 110°, the most northerly member. Fria, 150. The valley which lies between the Gila range and the Natanes Plateau, deserves mention as an anomaly. A portion of its water, ramming north- THE VOLCANIC REGION. 529 westward, reaches the San Carlos, and the remainder, running southeast- ward, is the Bonito. The portions of the valley in which the streams flow are rugged and rocky; but the headwaters of the two are not separated by aridge. The interval is an open plain, level and grassy, of the full width of the valley, ten or fifteen miles long, and drained at its two ends by arroyos leading in diametrically opposite directions. So exact is the equi- poise between the erosions of the two water-channels, that the plain, which may, with no strained metaphor, be called a lake of detritus, maintains two outlets. South-southeast from Sierra Blanca, and twenty miles distant, is a tabular mass of lava, to which the name “San Francisco” (with unfortunate duplication) has been attached. It rises a thousand feet above its base, is ten miles broad at top, and terminates rather abruptly on all sides. It was not ascended, but its débris to the northward was found to be basaltic, and a distant view from the south showéd a horizontal bedding of its material. From the base of this plateau the Prieto River runs southward in what appears to be an anticlinal valley of trachytic lavas. A rude and unequal bedding, discernible only when a great area is seen at once, betrays a dip in each of the adjacent ranges (ranges without known names) away from the river. In places the valley has been choked -by the subsequent eruptions of basalt, and further south the structure proved too intricate to be appre- hended in our brief transit; but all the valley and its bounding ridges are volcanic to the junction of the river with the Gila, except that at one place the narrow crest of a granite ridge juts from the tumultuous sea of lava. The same ridge is continued eastward to the San Francisco River at the mining town of Clifton. ? Sierra Escudillo, a conspicuous rounded summit upon the common boundary of Arizona and New Mexico and due east from Sierra Blanca, was ascended by Mr. Howell and ascertained to be a massive eruption of trachyte—-a cryptocrystalline variety of earthy texture, containing in its larger cavities crystals of quartz. Its summit, although showing no crater structure, has something of the form of a crater, and opens a large chaldera or gorge to the east. From this point eastward to Fort Tulerosa, a distance of fifty miles, the same observer found the country floored with rhyolite, 34Ws 530 GEOLOGY. horizontally bedded and overlaid in places by basalt, and the same holds for twenty-five miles to the northward, with an increase of the basaltic ele- ment. Southward, along the San Francisco River, he detected a great anticlinal fold of bedded trachytes and rhyolites, a fold of which the axis is followed by the river, while the flanks constitute the bordermg mountain ranges. The trend of the axis is southwest, or at right angles to the nearest structure-lines of the Basin Ranges, but the Tulerosa mountains, which are constituted by the eastern of the inclined masses, change their trend south- ward for a more southerly, and finally, in their prolongation the Sierra Diablo, acquire a southeast trend. This entire range, if a mountain mass so irrecular in form can be called a range, through the hundred miles of its length, exhibits only volcanic materials. Its chief components are trachytic, and basalt, which is present at many points, is, as usual, in small quantity and superposed. Eastward, to the Mimbres range, a distance of fifty miles, the same lavas are found, and with the same relative position and importance, but they form no great ranges. The country is elevated and rolling, and intersected by deep narrow gorges of the Upper Gila and its tributaries. The building of the Tulerosa and Mimbres ranges separated the basin of the Upper Gila from the lower valleys of the stream, and the way which the waters opened for their escape is a profound cafion separat- ing the Diablo range topographically from the Tulerosa. Before the cutting of the cation to its present depth that part of the basin which lies nearest the outlet was filled by erupted and transported materials to a great depth and a lake-like plain produced, the proportions of which can still be grasped by a bir®’s-eye view. It was about fifteen miles by twenty-five in size, and sloped very gently toward the outlet. By the deepening of the draining cation, an excavation probably connected with a broad continental oscilla- tion to which further allusion will be made in the sequel, the water-ways have been carried below the floor of this plain, and a system of narrow gorges, 500 to 1,000 feet in depth, now traverse and exhibit the filling of the valley. The filling consists of basalt, tuff, and gravel, with nearly hori- zontal bedding. At bottom are basalt and tuff in alternation, and above, a gravel of basalt and trachyte, in places capped by basalt sheets. In some localities basalt has run into the intersecting gorges since the beginning of THE VOLCANIC REGION. Hod their excavation. The tuff is, usually, simply a yellow sand, the volcanic origin of which would escape a casual observation. At the mouth of Dia- mond Creek it can be seen in a bluff 200 feet in height—a homogeneous, slightly coherent, feldspathic sand, without lamination or bedding. At one point, near the mouth of Gilita Creek, the continuity of these beds is broken by a vertical fault of a few hundred feet, affording the only instance with which I am acquainted of the occurrence of a fault or fold demonstrably subsequent to a basaltic eruption. 13 Sierra Luera, a mass of some magnitude at the northern extremity of the Mimbres range, is composed, like the Tulerosa Mountains, of trachyte and basalt. It overlooks the desert plains of San Augustin, and from its foot a low ridge of more ancient lava runs northward across the desert to Sierra del Datil. The desert is by this partitioned into two parts, the eastern of which is drained (in part at least) by the Canada Alamosa, while the western is not known to have outlet. Across the low barrier runs a narrow water channel, now long deserted, but once carrying the surplus water of one plain to the other. An attempt was made by Lieutenant Russelland the writer to determine barometrically the direction of the descent of this channel, but without success. A faint trace of an ancient shore-line, how- ever, on an isolated butte near by, marks the western plain as the one that has been covered by water, and records the former existence of a lake that must have been hundreds of miles in area, where now is an absolute desert. If, as the topographical results of the expedition indicate, this lake did not escape by cutting a barrier southward and draining into the San Francisco or the Gila, but lost its water by evaporation, then its record is the record of a climate far more humid than the present—a climate comparable with, and probably contemporaneous with the climate which flooded the basin of Great Salt Lake seven degrees farther to the north. The Sierra del Datil and its eastern continuation, the Sierra del Oso, are the northern edge of the great trachyte district; the lavas which occur farther north are, with the exception of Mount Taylor, basaltic. At the - pass near Todo el Mondo Peak the Datil range consists of yellow trachytes, of which hornblende is a constant though small factor, rudely bedded, and dipping to the south. The trend of the range is east and west, and the 532 GEOLOGY. northern face is precipitous, exposing the edges of the trachyte beds, and showing their relation to the underlying sedimentary beds, which form the foot-hills and extend northward. The escarpment is a cliff of erosion, en 2 recording the fact that destructive agents, which the trachyte has been able to withstand, have, beyond its margin, degraded the country more than 1,000 feet. During the progress of this degradation floods of basalt have occurred, which have sufficed to arrest it locally. One of these, arising from the Datil range, a few miles east of the pass before mentioned, has run northward and N. 1, Trachyte; 2, Soft strata, preserved a spur to the range, and it is probably from this source that the lava was derived, which caps in the vicinity three detached buttes, known as the Tres Hermanos. Farther north the con- fluent lava from a number of vents has mantled Base-line= sea-level. a much larger area, and, by preserving it against denudation, given rise to the Acoma plateau, a table thirty miles long, (north to south,) with an extreme width of fifteen miles, and with an average height of more than 500 feet. Similar tables of Seale, zzho0: (Tertiary ?); 3, Cretaceous. unknown but probably smaller dimensions lie to the east of this, between it and the Rio Grande. From the Alamocito Mountains, a volcanic group visited by Mr. Howell, and lying west of the Datil, there extends, in a north-northeast TH yell ah \ direction, to the base of the Zuni range, a line of nity thor basaltic cones, thickly set and marking vents, the lavas from which have flooded hundreds, perhaps a thousand, of square miles. or these cones col- Fic. 151.—Section of Datil range, N. Mex. lectively I propose the name of Marcou Buttes, in honor of the veteran geologist who first made record of them.* They must be several hundred in number, and are comprised in a belt of moderate * Jules Marcou: See foot-note to page 22, Geology of North America. THE VOLCANIC REGION. 533 width and fifty miles in length. The principal lava flows have run east- ward, but some remarkably long coulées have found their way westward. One has reached and passed the Arizona boundary, fifty miles away, follow- ing the valley of the Zuni River in the vicinity of Ojo de Benado, and causing a curious duplication of the valley, which has been deepened by later erosion on both sides of the lava, (Fig. 152.) Another coulée, which ends near the town of Zuni, is referred by Mr. Marcou to the same line of vents, and must be nearly as long. A third fills the monoclinal valley, which, along the southern base of the Zuni uplift, marks the place of the soft Triassic clays between the Carboniferous limestone of the main mountain and the Triassic sandstone of El Moro and companion cliffs. Eastward, the lava-flows cover a continuous area not less than ten miles broad, and bounded by the foot of Acoma plateau. Follow- ing the general line of drainage, they have passed, in a broad sheet, northward, around the southeast end of the Zuni range, and eastward, through ten miles of the nar- row pass at the head of the San José. It is evident that the entire phenomena of the Marcou buttes are of later date than the Acoma plateau, and some of the coulées are certainly very recent. That which passes El Moro is almost bare of vegetation, and is too rugged in most parts to be crossed in the saddle. East and southeast of Old Fort Wingate is one still fresher, and which com- pels a wide detour of the road from that place to the old Spanish fort at Cebolleta spring. It is a tongue of this which passes the source of the San José, and the con- volutions of the viscous torrent, preserved as perfectly as though cooled but yesterday, afford there a wonderful and impressive spectacle. At one point the lava is crossed by a stream of running water, which has not yet removed an inch of its substance. Mount Taylor was ascended by Mr. Howell, and is described in his ‘opeuag op ofp 4v AaT[BA 1unZ Jo uoIyegG—ZGT “OW qour 7 ‘apeag an ona 09 Lavqnqig ‘Seye a Saq ‘q faeary wong ‘7 ! teary yung ogy JO poq yuaroue Sarddnodo ‘yyesvg ‘gq “JeaF 00B‘T 534 GEOLOGY. report. It is, in nearly every particular, the counterpart of Mount San Francisco—a massive, solitary cone of trachyte, steep-sided, and craterless, and bathed at foot by basalt. Its summit rises 1,000 feet above the timber- CC, Cre- taceous strata; A, Basalt of Acoma plateau; T, Basalt of Taylor plateau; M, Basalt from the Marcou buttes. sea-level. Base-line Scale, rzbn0: Fic. 153.—Section at the head of the San José River, New Mexico. line, and is 4,000 feet higher than the floor of Cretaceous sandstone on which the lava rests. On all sides the general surface of the country has been lowered by an erosion which the more en- during lavas have resisted, and the peak, with its surrounding basalt sheets, is left upon a table of circumdenudation, limited in nearly every direc- tion by steep cliffs 1,000 feet high. Judged by the amount of subsequent erosion, the Taylor plateau is of earlier date than the Acoma; and the Marcou lavas, which follow the present sur- face, are almost incomparably newer than either. The accompanying diagram gives a general ex- pression of the relation of the three, although it does not present a section which was actually measured. About the base of the Taylor plateau are several localities of later eruption. Near Agua Azul there have run, from a single vent, a number of streams, one of which has reached so far to the southeast as nearly to meet a sheet from the Mar- cou region on the opposite side of the Zuni range. In the valley of the San José is another lava bed, which, measured by the subsequent lowering of the stream bed, is less recent, and others, of similar character, follow the valley of the Rio Puerco. At Covero, on the San José, is a small butte which affords an epitome of the Taylor plateau. It consists of a lava cone on a pedestal of sandstone and shale. Since its eruption a hundred feet of strata have been removed from the - Covero plain, and whatever sheet of basalt surrounded the cone has been THE VOLCANIC REGION. 535 undermined and destroyed up to its very base, where the increasing thick- ness of the cover has retarded the work.* Several miles to the north of this stands another butte, which represents a later stage of the pro- cess of destruction. It is not far from the foot of the Taylor plateau, and its summit is lower than the plateau edge. I conceive it to be the vestige of the flue through which an erup- tion reached the surface at the time of the flood- ing of the plateau with lava. The last contents “4[eseq Ot} JO WOIJOs parojsad B OAL ‘9MIUS OY} JO WOI}D9S-sso10 [VAPJ—*ZGT ‘DIT ‘OST ‘DIA ‘QUIVS OT} JO 101}D08-S8010 [OPI —'Gu] “HIT *XOW ‘N ‘O1OAOD AvVoT O9yNG VAVI—FCT ‘OT “PSL “OMA ‘XO ‘N ‘O19A0D Jo YVAN 099Nq Aovjq—9gcT ‘1,7 of the flue, congealing within it, formed a pillar of trap, that opposed a stubborn resistance to the atmospheric agents which have destroyed the surrounding strata. It is a cast, in lava, of which the mold was the “LST “STA ‘g[vYs pue ouojspues snosovjorQ ‘g { y[useg ‘q ‘auojspaes puv orgs snooororn ‘g {y[useg ‘gq “SST ‘SIA conduit of a volcano, ~ now not only extinct but demolished. In offering this explanation, it is proper to state that the butte was not directly visited, but that Mr. Howell and the writer, passing it on opposite sides, arrived independently at the same interpretation. In the same way we ~ sau, peyop oq, * Query. Did not the name Covero arise from the resemblance of this butte to a pot-lid ? 536 GEOLOGY. would account for the Cabezon and other similar pinnacles on the opposite (northern) side of the Taylor plateau. Each exhibits a compact mass of lava, nearly as deep as it is broad, and possessed of neither the form nor Fic. 158.—Diagram to illustrate the manner of disintegration of basalt-capped tables. the structure of a surface eruption. A group of the same character, the largest of which is entitled Keily’s Butte, stand in the valleys of the White Mountain River and its tributaries, west of Camp Apache, and are overlooked in similar manner by basalt-capped tables; but in this case the soft strata, by the excavation of which the flues have been laid bare, are Upper Carboniferous instead of Cre- taceous. The survival of these pinnacles, and the conservation of plateaus by basalt cloaks, depend upon the superior durability of this lava, as compared with most other rocks. Since the lava of the Acoma plateau was extruded, the sur- rounding country has been stripped of Cretaceous free- stones and shales to a depth of more than 500 feet; but the only effect of the elemental warfare that has for the same period assailed the level lava of the plateau, has been to alleviate the rugosity of its surface, and give it a thin soil, adequate to the growth of trees, but hardly to the use of the plow. For the same reason—the endurance of the lava—the undermining of the plateau edge is a slow pro- cess; since the lava, when displaced, is not destroyed, but, lying upon the slope, still guards the substrata against atmospheric attack. The manner in which the reduction of such cliffs is effected is worthy of note. The ordinary structure of the lava is a subprismatie, vertical cleavage, due to shrinkage in cooling; and, determined by this, a vertical face is maintain- ed at the edge of the lava-bed. Exceptin extreme cases, as where its foot is worn by a stream, the slope below the lava is so gentle, that the fragments of the latter, which are successively detached, do not roll to the base, but slowly settle, without notable horizontal shifting, as the sub- l| - : Oe a, at i . . @s ‘ eo a Y he 4 o 7 . vy . i a. a an ‘ Re ae Brae as “ieee (lt of pero tie seu. “inch Tig Ae & if -= NTs ste! * 2, wy ~ phage Sip cad re Seed ROERRY PI: hah seta *: : Se eae a | ee . 4 a a s ‘5 - * SiON Sez. Sig oh ot fat, s ey ‘ ape Cowal ee ais A eree is 3 a 7 s +3 = bb. El a LET Sy rae i oy see utes ks eh Lae ae he 7. < Ty . > > b co ting? t > \ fe i ¢ a er sd -< ayy as . ele ‘, jh . ; a , cy . gt? r rk sill 5 mF ’ a bhige ini ee rr) 2) 2 ee Sess LIBRARY ; : eis (' Sars os ~—yyVERSITY OF EEINOIS A t= leg s igh ag Whien ia tera Ae era er ie a . : teers ga 44a3e2' 4 ~ \ ; = 4 ~ > » z) J ‘ ‘ THE VOLCANIC REGION. Bou jacent material is eaten away by percolating waters. Usually, the basalt does not fall away in small fragments, but. parts in large masses, which, in the order of their detachment, lie upon the slope. Once separated from the parent bed, they lose somewhat their individual coherence, and become subdivided into smaller angular blocks; and these, in wave-like heaps, make up the surface of the slope. The uniformity with which these undu- lations succeed each other, where the underlying material is homogeneous, is not exaggerated in the illustrative diagram, (Fig. 158,) and its explana- tion is an illustration of the principle of rhythm in nature. As, in the proc- ess of undermining, the support is gradually removed from the edge of the lava-bed, the force exerted by the weight of the unsupported portion increases, and the point of its application is carried farther from the edge, until, finally, it suffices to overcome the coherence of the bed, and this always occurs, in a given locality, at about the same distance from the edge. Thus arises a rythmic uniformity of result, as nearly perfect, perhaps, as that of the analogous waves of the sea. The size of these rock-waves depends chiefly on the depth of the bed from which they are derived. Behind each of them, on the slope, is a comparatively level spot, usually covered with soil, and, where the phe- nomena are on a grand scale, containing a fertile swale, or even a lakelet. Upon the East Fork of the White Mountain River, not far from Camp Apache, a number of such swales are under cultivation by the Indians. Other localities, at which the phenomena were observed upon a larger or smaller scale, are: at Ojo de Benado, twenty miles south of Zuni; on the headwaters of the Colorado Chiquito; at Cave Spring, between Zuni and Camp Apache; on the South Fork of the White Mountain River; at the Tres Hermanos, north of the Datil range; at Cebolleta Spring, under the Acoma plateau; and at Covero Butte. In this brief sketch of a great lava district an endeavor has been made to render the description as general in its character as the facts at command would permit; and, with this end in view, the presentation of local details has been avoided. The field-notes, however, afford a few special facts which are worthy of record, and these, with the mention of a few others, not 538 GEOLOGY. of voleanic order, but pertaining to the volcanic district, will complete the chapter. ; Buried cinder-cone.—At the junction of the Prieto River with the Gila, their carions are cut in bedded basalt to the depth of 1,100 feet. On the right bank of the Gila, just below the tributary, stands the ruin of a cone of scoria. It has been so unevenly excavated that the relation of its parts would not be detected by one who stood near it; but a comprehensive bird’s-eye view, from the cliff of the opposite shore, revealed its character. It was formed after the compact lava had accumulated to a height somewhat above what is now the level of the water, and was founded upon it. Its height was probably 600 or 800 feet, and it appears to have been completely buried by later outpourings of lava. The erosion of the river has once more brought it to light, and displayed its structure in a rude and uneven section. At a point on the Prieto, ten miles farther north, a similar scoria was seen in the river-bluff, but its manner of occurrence was not recognized. The subsequent discovery of the cone on the Gila led to the surmise that it too might belong to a buried volcano. Lakes.—The field of this year’s exploration is not a region of lakes. A number of playas at the extreme south are inundated in periods of rain, but the list of permanent lakes is exceedingly small. Allusion has already been made to the little basins that arise incidentally in the peculiar, slow process of the demolition of some basaltic tables. Many of these hold water for a short time, and a few of them permanently; and it is supposed that in sucha basin lies Apache Lake—a pond near the North Fork of the White Mount- ain River, that was visited and photographed by Mr. O’Sullivan. The salt lake forty miles south of Zuni, on the shore of which is gathered the salt used by many Indian tribes, was visited by Mr. Howell. He found its basin anomalous in character, and, with present data, its origin is inexpli- cable. The basin is 100 to 200 feet deep, and is surrounded, on nearly all sides—apparently on all sides—by horizontal Cretaceous strata, over which, for the most part—the chief exception being at the north—there is a cap- . ping of recent basalt. A cinder-cone stands at the margin of the lake, and has a crater so deep that it contains water at the lake level. If the basin THE VOLCANIC REGION. 539 be really a cup hollowed from undisturbed Cretaceous strata, it is difficult to account for. Reservoir Lake, at the eastern base of Sierra Blanca, occupies a shallow basin, floored and walled by lava, which lies in the form it assumed in cool- ing, with little modification by erosion. The water is shallow, and weeds grow to the surface over nearly its whole extent. The area draining to it is small; there is no permanent inlet, and no visible outlet. That the lake is permanent, is indicated by the life it contains; and that it has a subterran- ean outlet, by the perfect freshness of its water. At the time of our visit, August 22, the area of water surface was about fifty acres; but its maxi- mum is a third greater. Its maximum height is marked by a well-defined beach, three feet above the water-stage which we found. Ten feet higher is an ancient beach, that appears to have been abandoned for centuries. Siredon, Limnea, and Physa were found in great abundance; and the presence of fish was announced, though none were obtained. Prairie mounds.—The grassy plains that diversify the pine forests at the eastern base of Sierra Blanca, are dotted with a system of low mounds, in a manner independent of the nature or slope of the soil. They are usually one or two rods broad and less than a foot high, and separated by interspaces several times as broad as themselves. There is frequently a notable difference of soil texture between the level ground and the mound, the mound being, in some instances, the more gravelly, and in others, the less so; and there is some difference ofuality, that the eye detects only in its effect upon vegetation. The grass upon the mounds is distinguished by a ranker growth, and, as we saw it in August, by a deeper green. Viewed from a commanding position, the effect is peculiarly beautiful, the green spots dappling the plain like the figure of a carpet. These are not consid- ered geological features, and they are mentioned in this place only to distinguish them from the prairie mounds of California, which, according to Professor Le Conte, are phenomena of erosion.* There is little question that they are the vestiges of hammocks thrown up by prairie dogs, or other burrowing animals. The manner of their distribution first suggested this * American Journal of Science and Arts, April, 1874, p. 365. 540 GEOLOGY. explanation, and it appears to accord with all the observed facts. The subsoil, brought to the surface in the excavation of the burrows, produces the superficial difference of texture; and the looser aggregation of the earth, together, perhaps, with the presence of animal manure, gives the grass a stronger growth. None of the mounds are inhabited, and no burrows, or other sign of recent occupation, were seen. I am acquainted with no colo- nies of prairie dogs at such an altitude—7,0U0 feet—and, if the mounds are the work of that species, they may point to a climate, in very recent time, of even greater warmth and aridity than the present. Some of the mounds were seen upon, and on the slope below, the oldest of the Reservow Lake beaches, showing that the race which built them has given way since the diminution of the lake. The Gila conglomerate.—A system of valley beds, of which a conglom- erate is the characteristic member, are exhibited in section along the gorges of the Upper Gila and its tributaries. The bowlders of the conglomerate are of local origin, and their derivation from particular mountain flanks is often indicated by the slopes of the beds. Its cement is calcareous. Inter- bedded with it are layers of*slightly coherent sand, and of trass, and sheets of basalt; the latter, in some cliffs, predominating over the conglom- erate. One thousand feet of the beds are frequently exposed, and the maxi- mum exposure on the Prieto is probably 1,500 feet. They have been seen at so many points, by Mr. Howell and myself, that their distribution can be given in general terms. Beginning at the mouth of the Bonito, below which point their distinctive characters are lost, they follow the Gila for more than one hundred miles toward its source, being last seen a little above the mouth of the Gilita. On the San Francisco they extend eighty miles; on the Prieto, ten; and on the Bonito, fifteen. Where the Gila intersects the troughs of the Basin Range system, as it does north of Ralston, the conglom- erate is continuous with the gravels which occupy the troughs, and floor the desert plains. Below the Bonito it merges insensibly with the detritus of Pueblo Viejo Desert. It is, indeed, one of the ‘“‘ quaternary gravels” of the desert interior, and is distinguished from its family only by the fact that the water-courses which cross it are sinking themselves into it and destroy- ing it, instead of adding to its depth. It is in its relation to the rivers that it _ THE VOLCANIC REGION. Al is chiefly interesting ; in the accumulation, and subsequent excavation of the beds, there is recorded a reversal of conditions, that may have a broad meaning. The base of the series in its deepest parts is not exposed, and if we go back to the beginning of its deposition, we have to picture the val- leys as deeper than they are revealed at present.* During the accumula- tion the altitude of the drainage lines steadily increased—their altitude, that is, in relation to the surrounding mountains—and it attained its maxi- mum when the top of the conglomerate was laid; since which time it has as steadily diminished. There is no difficulty in comprehending the present action, for it is the usual habit of swift-flowing streams to cut their channels deeper ; but to account for the period of accumulation there must be assumed some condition that has ceased to exist. Such a condition might be, either a barrier, somewhere below the region in question, determining the discharge of the water at a higher level than at present, or it might be a general de- pression of the region, in virtue of which the ocean (now three hundred miles away) became a virtual barrier. With either hypothesis, a change of more than 1,000 feet must be considered. *The postulate is not absolutely tenable, since the corrugation by which troughs are produced, and the filling of those troughs by detritus, go forward simultaneously ; but it introduces no fallacy in its present use. CHAPTER XX. THE PLATEAU REGION. Since the Plateau region differs from the Range region only in the degree of disturbance, the determination of their common boundary is neces- sarily to some extent arbitrary, and the difficulties in the way of concise- ness are increased in Southern New Mexico by the great lava cloak, which conceals for many miles the structure of the buried strata. But, as the only object for the drawing of the boundary is the graphic presentation of the general distribution of certain structural features, it need not be regret- ted that the position of the line is indefinite at points, where, in nature, there is a transition from one grade of structure to the other. In 1871 the bound- ary was traced in Arizona from Music Mountain southeastward to the Natanes Butte, passing to the north of the Black Hills and Sierra Ancha. From Natanes Butte I have drawn it eastward, past the south edge of the San Francisco plateau, and then, east-northeast, over the uncommunicative lava, to the Sierra del Oso. Thence it passes between the Ladron range and the Lucera plateau, to the Rio Grande Valley, and follows that north- ward to the Nacimiento Mountains. The general contour of the southern part of the boundary is shown in Fig. 145. The portion of the Plateau prov- ince included in Arizona has an area of forty-five thousand square miles; and that in New Mexico, of twenty-five thousand. Of Utah it includes fifty thousand, and of Colorado, perhaps, twenty thousand miles; making a total extent of one hundred and forty thousand miles. Of the voleanic mountains, noticed in the last chapter, the San Fran- cisco group, the Mogollon, Blanca, Escudillo, Alamocito, Datil, Oso, and Taylor, and the Marcou Buttes, are based on the level strata of the plateaus. The plateaus explored by Dr. Loew and the writer in 1873 are built of Tertiary, Cretaceous, Triassic, and Carboniferous rocks. The presence of Tertiary strata was demonstrated by fossils at but a single locality, and 542 THE PLATEAU REGION. 543 their horizontal and vertical extent are unknown. Dr. Loew, who visited the locality, says: ‘‘A mile and a half north of Ildefonso, in some hills of alluvial drift, fossil bones of several mammals were found. These bones were much broken and scattered, leaving no doubt that this was not the origi- nal locality where the petrifaction took place.” A collection had previously been obtained from the same place by Gov. W. F. M. Arny, and was, by his gift, added to that of the expedition. The joint collection has been placed in the hands of Prof. O. C. Marsh for study; and, in a preliminary examination, he was able to recognize the presence of Mastodon, Rhinoceros, Equus, and Procamelus. He pronounces the fauna Pliocene, the equivalent of the Pliocene of the Niobrara region. 'The bones are well preserved, and the fact that they are not worn by rolling, shows that, if not found in the place of original deposition, they, at least, had not been far removed. The adherent matrix is a coarse sand, closely resembling, according to Professor Marsh, the formation in which the same fauna occurs on the Plains. Among the more interesting of the specimens are a large head of Rhinoceros, proba- bly referable to no known species, and a pair of Mastodon tusks, character- ized by a ribbon of enamel upon one side only, in place of the usual com- plete envelopment. The Cretaceous is in area the chief of the formations. Underlying the lavas of the Taylor and Acoma plateaus, its exposure forms a belt around each of them. Overlying the Trias and Carboniferous, which appear in the Zuni uplift, its exposure encircles that also, except where covered by lava. In like manner it flanks the Nacimiento uplift on the west and south. North of the Zuni range and the Taylor plateau, and west of the Nacimiento range, it covers the country to the limit of our survey. South of the Zuni range and Taylor plateau, and thence to the great lava field, it is the only sedimentary formation, except the Trias, by which its continuity is inter- rupted at two points. West of the Zuni range it forms a belt fifteen miles wide, and with a north-northwest trend—a flat synclinal, limited east and west by the Nutria and Defiance folds. Going due east from the Taylor plateau to the Rio Grande, Mr. Howell found the Cretaceous only, but, both north and south of that line, it yields in part to the Trias. Three islands of Cre- taccous were discovered among the basalts of the Mogollon Mountains— 544 GEOLOGY. one at Mineral Spring on the road from Zuni to Camp Apache, a second five miles farther west, and a third sixteen miles north of Camp Apache. Not far from the last is a coal opening that is presumably referable to the same formation. The Cretaceous rocks are an alternating series of sand- stones and shales, in which the sandstones are yellow, and the shales gray and yellow, with bituminous layers and coal. In the upper part of the series, the sandstones incline to green, and are soft; in the lower, they incline to orange, are harder, and form heavier beds. The coal occurs through the entire series, but, so far as is known, is of economic importance only near the middle. None of the sandstones are known to continue over large areas, but the lower are more persistent than the upper. With the utmost variability of the individual beds, there is combined a marked uniformity of the series as a whole. Characterized by sands, by coal, by rapid alternations, by ripple-marks, and by oysters, it is evidently an off-shore deposit. Lithologically it is a single series, offering no criteria for subdivision. In its entire depth of 2,000 feet, fossil animals have been found, in this particular field, only in the lower 850 feet. The highest fossil horizon, near Stinking Spring, yielded Inoceramus problematicus and Ammonites. The most prolific localities are near the base. From one of these, a point at the western base of the Acoma plateau, near Cebolleta Spring, were obtained Ammonites, (of two species,) Turritella, Gyrodes, Anchura, Cardium, Ostrea, and Lingula, with vertebre and teeth of sharks, (Otodus and Lamna Texana.) The same horizon at the Mesa Redonda, near Quelites, New Mexico, yielded, besides a portion of the above, Cucullea, Gryphea, and Pinna. A locality sixteen miles north of Camp Apache, and probably near the base of the series, afforded Ammonites, Gyrodes, Anchura, Scalaria?, Cardium, Avicula, and Inoceramus ; and another twenty-five miles farther north, gave Anchura ?, Camptonectes, Pinna, and Gryphea. In the local sections, which will be found a few paragraphs beyond, the top of the uniform lithological series, to which, with our present know]- edge, we must apply the title Cretaceous, is found only in the first. At that locality the famihar Cretaceous characters cease, in the ascending series, with number 3, (section A,) and the upper 1,000 feet of strata are so distinct in character as to permit an easy stratigraphical discrimination. THE PLATEAU REGION. 545 The superior beds (No. 2) were seen only at this point, and are of so per- ishable a nature that they would have disappeared but for their volcanic shield. The trachyte that covers them must have been spread before they were greatly lifted above water. They afforded no fossils, and showed no stratum that suggested the possibility that such would be yielded to care- ful search. The only beds with which I am familiar that resemble them in lithological character are the barren Jurassic clays and sands of Northern Arizona, but they lack the visible gypsum of the Jurassic. They rest, with seeming conformity, upon the Cretaceous. The base of the Cretaceous is included in each of the sections, and there is little uncertainty as to its position. The barren, bright-hued sandstones and clays, that are, by com- mon consent, called Triassic, are known in Utah to be separated from the Cretaceous by strata with Jurassic fossils, and Mr. Howell, tracing the beds by almost unbroken exposures, from Utah to Fort Wingate in New Mexico, has demonstrated the continuity of the Cretaceous and Triassic, and the thinning and disappearance of the Jurassic. His determination defines the base of the Cretaceous as at, or very near, the great lithological change from the heavy homogeneous sandstones to the variable lignitiferous series, and proves—what Dr. Newberry surmised—that the abrupt transition marked a historical break. The lowest Cretaceous bed is, in section A, No. 11; in B, No. 7; in C, No. 8 or No. 10; in D, No. 6; and in E, No. 4. The best display of coal seen by the writer is near Stinking Spring, twelve miles west of Fort Wingate. It includes four seams of workable thickness, (4 to 53 feet,) three of which are probably of good quality, (1 x, 1 p, and 1 ff, of section B.) Their position is not here the most desirable for working, as they dip at 70°, and are probably deteriorated by leaching to a considerable depth; but, toe the north, south, and west, the same hori- zon must reach the surface with a gentle inclination, and intelligent search will readily discover favorable localities. The Cretaceous region is char- acterized by innumerable mesas, or tables, the tops of which are sand- stone, and the bases, shale. The coal beds are included in the shale, and are usually concealed by débris, unless lying close to the sandstone. Hardly an escarpment can be examined without the detection of thin layers of coal, and any of these may develop, at some point, to economic thick- 33 WS 546 GEOLOGY. ness. Whetiever there shall be a market for it, coal will be developed in all the indicated areas of Cretaceous outcrop. About the Zuni range the Trias forms a belt, inside the Cretaceous, and without the Carboniferous, (except where covered by Javas,) and upon the flanks of the Nacimiento range it holds the same position. Southeast of the Taylor plateau it appears in the valley of the San José, as described by Messrs. Marcou and Newberry, and the same exposure extends south and west to the Indian town of Acoma. It is possible, also, that an outcrop in the valley which lies east of the Tres Hermanos and of the southern end of the Acoma plateau, is connected with the same. West of the Marcou Buttes, Mr. Howell found a belt, with east-west trend, passing under the Cretaceous at the north, and separated from it at the south by a lava-stream, and probably a fault. From Fort Defiance, southward and westward ; from Zuni Village, westward; and westward from the lower course of the Zuni River, there stretch tracts of Trias, that are probably confluent with each other, and with the belt through which the Colorado Chiquito flows, which is overlooked by the Moquistowns, and which was followed by Mr. Howell from Utah. Lithologically the “Trias” is a definite system, sharply distinguished from the Cretaceous above, and the Carboniferous below. In Southern Utah it is not sharply distinguished from the superior Jurassic, and, if our stratigraphic nomenclature had been first instituted there, the term “ Trias” would probably not have received its provisional use; but, in the absence of fossils, there is no reason to depart from the practice of Messrs. Marcou and Newberry. With reference to the subdivisions there has arisen a variety of nomenclature, dependent on the localities at which different observers have first analyzed the series. Mr. Marcou, who saw it on the Plains east of the Rocky Mountains, made three divisions, to correspond with European formations, as follows: Feet. Upper division, (Varie- § 500 feet of sandy calcareous clay of brilliant colors. 1.500 gated Marls.) 1,000 feet of massive, white gray sandstone. : Middie division, (Muschelkalk.)—Red clay, with gypsum, salt, and magnesian limestone © ”.i5:4..: «celeb sta e atin ate wnat lah es eee lea hem ninis sss ti age 1, 500 Lower division, (Bunter sandstein. )—Red sandstone, over red and blue clay .. 2-3, 000 ROtANS «scence ~ Bim, a ets ety eae eles Rie )-o ae hee oes eee =n 25 feet. e. Purple and white clays-----..-----..-.------------ Totes a 125 feet. 975 Ff. Red and purple clays.-------.-- Be Seat cte miata ie inte oie rete 50 feet. g. Coarse brown conglomerate.-....---------+-----+------++-- 10 feet. h. Red, purple, and white clays.........-...---+-----.-+---- 90 feet. 4. Gray sectile sandstone <2: - --.--.- 2. ~~... <2 --- = --0- oe - 10 féet. j. Red, purple, and white clays ...-..-----------.--------.-- 50 feet. RIC OF en SA NE So = conbee cocece es Geen Se aco seacn cee SbadocaasStoces: 25 16. Massive gray limestone, [Productus semireticulatus, Bellerophon, Bakevellia, Schicoaus, Aviculopecten| = =< me .el= ime teenie = ee a on alee ie 40 17. Caleareous, cross-laminated sandstone; gray on fracture, but red in escarp- ment; base not seen ......-.-- 0. +22 eee eee ee ene ee ee eee Sete 75 Motal ...--. .ccwen voce cee nee a5 ee tow ee eee nec en en ence enewnn seen 2,738 Section D. Near Nutria Pueblo. The strata are upturned at the western base of the Zuni range. “eet. 1. Yellow sandstone-o--<0 (--sester esac = eee ene ee we tee ae Rte Re neistasene 25 2. Unseen; shale? -.... . . ene cnn wc we see cece en meee nn nase ssawee ese emcees 50 3. Massive, orange sandstone .-...-..-- S NURAOREES Sein cc wks noes wo wea De 20 4. Soft recks, unseen, (this'is the position of the main coal series)..........-- 600 b. Massive, red-brown: sandstones -cesere << eee eee ee eee aCe 20 6. Clay shale, with thin coal, changing below to red, arenaceous shale.....-.- 110 7. Massive, cross-bedded sandstone, red and white, and weathering brown..-. 535 3. Conglomerate -*..2 6. -... ae ee Seer eee een een eee 10 9. Red, arenaceous shale .............- gyn ibaa Gr wiktareon ie WSS aii piace is a 240 10. Purple, brecciated limestone Se ee ee ee ee ad THE PLATEAU REGION. Feet. 11. Variegated clays, with sandstone beds: a. Purple and variegated clays......-...--. 800 feet. { b. Pale red, sectile sandstone.........-..---. 5 feet. | CRoREGuclay= hiss 2k osceces see Bien eae eaeae 70 feet. & 1,585 d. Pale red, sectile sandstone.....--... --- . 10 feet. Creve satem. ClaySems eae - ee acon vere oi 7100 feet. } 12. Massive limestone, [Athyris subtilita, Productus, Euomphalus, Nautilus, Aviculopecten, Archceocidaris|....-.....--..---- 55 ERO teal bape Btn ete SPP S ae sl SL Cee sale sie a ete tae boce 3, 252 The variegated clays (11) have apparently a greater depth at this point than at Fort Wingate, (section C, bed 14,) and the difference (1,585 less 975 feet) is so great as to suggest that it is apparent only, and arises from the imper- fect facilities for measurement. The strata have in each case, but more especially at Nutria, a considerable inclination, and the position of the clays is marked topographically by a broad flat valley, interrupted only by the ridges that are produced by the interbedded sandstones. Measure- ments were made horizontally by pacing, and the dip was measured at each of these hard beds; and from these data the thickness of the series was computed. It is possible that the clays, which are here laid bare and relieved from the pressure of superincumbent beds, have, at the surface, expanded, after the manner of the ‘‘creeping” of underclays in coal-mines, and, by their expanse, tilted the included sand- stones, and thus vitiated the only data available for meas- urement. The accompanying diagram shows the relations of the beds at Nutria. Section E. Near the pueblo of Acoma. 1. Massive, cross-bedded sandstone; yellow, stained superficially with red and brown 2. Gray and yellow, gypsiferous shale 3. Sandstone with fucoids *q uorqo08 ‘XO ‘N ‘VINNY Avou VpvIYs Jo dip Aoys 0} WILInLIq—09T “OMT worydvasy4v148 0} Ioyer somnsy puv s12}49[ ONT, i i it i ii i i i eis i ee i ni ee areas Feet. 554 GEOLOGY. Feet. 5. Massive, friable, cross-bedded sandstone : a. Pink, weathering: browni sett... -..-s--4eeeeeee eeee 30 feet. b. Yellow and firm; pebbly and banded with white near top.. 250 feet. | ce. Soft; olive-green, with brown band 100 feet below the top.. 250 feet. = d. Softs 20d 2k aestpersinn ce ones 2 = eee ee 150 feet. | ToOGAL. J on eis ccs cnt, Meise oe eponie See see ee Peli es ee 900 Some general laws of erosion are well illustrated by the region under consideration. The conditions under which meteoric agencies produce the sculptured forms of land are complex, and in special cases difficult of analy- sis, but there are two general principles everywhere manifested. The first is, that soft material is worn more rapidly than hard, and the second, that high points are worn more rapidly -than low—or, more strictly, that steep acclivities suffer more than gentle.. The tendency of the first princi- ple is to variety of surface; of the second, to uniformity; and the two are complementary. Insomuch as the Cretaceous areas are, in a general sense, plains, with no conspicuous elevation, and insomuch as the series consists of a quick alternation of soft sandstones and softer shales, the areas are, in detail, variegated with low sandstone tables. Moreover, where the series is covered by lava, the vastly superior hardness of the lava has enabled it to protect the strata, and given rise to such “hills of cireumdenu- dation” as the Taylor and Acoma plateaus. These facts have resulted in obedience to the law of hardness, but it has, at the same time, followed from the law of altitude, that the areas not protected by the lava have been denuded evenly, instead of being deeply scored along the chief lines of drainage. The Cretaceous field southwest of the Acoma plateau has been reduced nearly or perhaps quite a thousand feet since the eruption of the Acoma lava, but it has been reduced so evenly, that its surface is now as near level as that upon which the Acoma lava was spread. And the same may be said of the field north of the Taylor plateau, which has been degraded even a greater amount. Standing upon the edge of one of these tables, and viewing a broad stretch of country, from the entire face of which it is demonstrated that a thousand feet of rock have been razed since it has been notably modified by any movement of orographic corrugation, one can appreciate the fact that erosion is the great agent in the production VOL, Li PRAT Rex : ROCKER CREEK. ARIZONA THE PLATEAU REGION. 555 of all details of surface, and that the disposition and hardness of rocks are only modifying conditions. The antagonism and the concurrent result of the two laws of erosion are illustrated by the Zuni range, which is an elongated quaquaversal uplift within the Cretaceous area. From its sides and summit the soft Mesozoic strata have been removed, exposing the tough Paleozoic rocks, and even the Archean. If the law of hardness only had been potent, the Cretaceous strata would still cover the arch, and the range would rise 6,000 instead of 3,000 feet above its base; if only the law of altitude were obeyed, (which would have been the case if the Paleozoic and Archean rocks were no harder than the Mesozoic,) there would be no mountain at all, and the up- lift would be marked only by concentric annular outcrops of the several strata. There could hardly be found a simpler natural illustration of these familiar principles. The site of the village of Acoma presents a curious result of erosion. The streams flowing eastward from the base of the Acoma plateau have first opened channels in the Cretaceous, and, farther east, in the Triassic strata. At the point of their descent, where they traverse the clays of the Lower Trias, the yielding of these clays has undermined the overlying sandstones, which are there massive, but rather friable, and opened broad valleys. At the same point the water-courses approach each other, but they recede again as they continue eastward. The lateral extension of the valleys has pro- ceeded so far as to remove, for several miles, the barrier of Upper Trias sandstone, producing, in effect, a single, high-walled valley, traversed, in the wet season, by two streams, which do not unite, but leave it by separate outlets. The removal of the sandstone partition has not been completely effected, but it has been broken through at a number of places, and the intervening fragments, which still stand, are precipitous pinnacles, as diffi- cult of access as Pompey’s Pillar. The most westerly of them, and one which is not yet quite isolated, but, by a narrow neck, is joined as a penin- sula to the Triassic escarpment, has been chosen as the site of the Indian village. Upon every side except one the spot is surrounded by sheer pre- cipices 200 feet in height, so that for defensive purposes there is need to guard but that single side. At the neck of the peninsula, communication is 556 GEOLOGY. afforded with the valley below by a natural pathway, no less curious than the citadel itself. The soil of the valley is sand, freed by the destruction of the sandstone; and a portion of it is so dry as to be shifted by the wind. _ In favored places it accumulates in dunes or drifts, and one of these drifts, 150 feet high, reaches to a point on the neck, from which the summit can be gained.* The upper surface of the peninsula is naturally very uneven, but a portion of it has been partially leveled for the village, and one of the cavities has been improved so as to constitute a cistern, the water of which may serve in time of siege. Folds.—If the reader will refer to the first chapter of this volume, he will find there a description and discussion of the folds and faults of the Plateau region, as observed by the writer in Southern Utah and the adja- cent border of Arizona; and additional material by Mr. Howell will be found in the ninth chapter. What I have to add, as the result of my examinations in 1873, is a mere supplementary contribution of facts,—facts which do not differ in kind from those that have already been adduced, and which, partly from the nature of the country in which they were noted, are less susceptible of generalization than those gathered in the previous year. Only a single fold—the Nutria—was traced for any considerable number of miles, and observations upon others were so scatterred, that the system to which they belong was not shown. But of a class of facts so novel it will be profitable to record even isolated examples, and a description of each locality will be given, for the benefit of future investigatorsin the same field. The Tres Hermanos buttes stand south of the Acoma plateau and north of the Datil range. Between them and the latter there runs eastward a water-course tributary to Tres Huerfanos Creek. The diagram, Figure 161, represents the structure of the Cretaceous and Triassic strata, as shown on the left bank of the water-course. The proportions were not submitted to measurement, but were estimated and sketched, by the writer from the saddle. ‘ | ' , ’ pod a ‘ s r, So ’ ’ : d : ~ rT af re va . -. Yee es SF ee S NA Z, : Se) G—_ pull AN DUE HK S GS QT, Y =x YG ys o™ 4 YY, 2s ip ———— — ees t-asi2a4 06, SOL, 431 Galllwillec. sot, SC 4y_ Seater ae 86 Cafion City -.320, 322, 341, 342, 356, 378, 380, 381, 393, 395, 396, 398, 399, 400, 401, 404, 406, 407, 423, 460, 489, 490 Canling?- Ses. ot center eee eee 25, 121, 179 Cebollita: .2.22de2. 222 noo eoaeeee ees 505 CedariC ity, 22. -2<525.c see. ae ate 59, 278 Circlenille) an oie sence oss aden ae 142 Clifton = 22s 2s.- 25 -sepee eee eee Oed Coalville)... << - soo eel aoe ane, aod Mantie: Sir oet. neseane 49, 50, 175, 236, 267, 272 WG i ieee eres ote tacs: 256 MINGISVIO cos tock ne eee eae 233, 256, 257 MGEN NO aoe eee eee 281, 299 Monroe . 22. - oo todas poeooe nec oe 116, 296 Montezuma---- -=2---+ sc-52--->-->—=> 518 Soldier’s,>- 2 = 237, 252, 272, 273, 274, 276, 294 Silver Bed minint.-->--->.--=+-4- 2" 248 South Clear Creek, South -........---. 429 Star mining .....---- ee eee 179 Sonth Platte, North... ....321, 329, 345, 350, 428 Virginia (Ralston) mining.-.--.---- 514 South Platte, South......-...---. 433, 485, 494 Wellow Pine =24 - 225225222 ceseeceee 179 Spanish casts se aaee ee Ecc 58, 235, 251, 257 POLIO WT REONE rennet ee eee 149 Taylor River, West .--2------222- 2-=- 365. 494 . of the Ten-Mile Creek, East-..--...--.. 324 = of the Ten-Mile Creek, North....-. -..- 472 Wl Moro - ~---<- --22sene nes woe onan aaa 533 of the Ten-Mile Creek, West - ---- 324, 368, 447 Erosion ---.63,72, 126, 132, 135, 187, 427, 471, 539, 555 Virgin; Bast. 2 it ee ee 45,77 Eruptive rocks. .-.-...--------------------- 411 |" Virgin, North .. ..---- 78, 158, 266, 272, 273, 278 F of the White Mountain Creek, East....218, 537 ‘ of the White Mountain Creek, North ..217, 218, Faults ....33, 38, 40, 44, 48, 54, 55, 57, 70, 196, 238, 289, 505, 528 291, 296 of the White Mountain River, South ..505, 527, Pane Grant ash o.com seas es oce ene 47 | 537 Hurricane 22-252 ses. eos ee 54,285 || Wort Bayard --222-2---02--ee 2e-sencectineee 515, 516 Kaibabe 222220: Be ose eee 46, 76, 291 Cedkr nee enn e eee eee 237 of Long Valley .-.-...----.---.------ 45 Defiance (old) ....51, 274, 275, 277, 286, 287, 289, Sevier Valley -.. ....48, 49, 56, 77, 128, 132, 296 291, 299, 546, 560 Wortweayeedene< eae nee ae 155 Garland. .osceeest eee tee 323, 422, 460, 461 Fillmore group of cones .....--.-------.---- 136 Rock ee ee ee ee ee 206 Volds?:---=> 22-2222 os 289, 290, 291, 294, 295, 556 TEED cee enc ee ee eee 521 Mold Wafinnas=-22. 222. sees an ee 543, 560, 565 TIBRORE ee 6520 ee te eee 529 East Kaibab .-....-.--- 56, 176, 291, 295, 558, 559 ingate..... 51, 286, 505, 553, 545, 550, 559, 563, Nutra... ---—-— : 543, 556, 557, 560, 561, 562, 565 565 Paris {oe eee 51, 53, 56, 291, 295, 558, 559 Wingate (Old)! 2. ---n2 naan een 563, 565 West Mariah ssn 2=- ese eo eee aera 559 Winhipp leno ao- ono ence aes eee 19L VAT bees eeeen mae MCR E CERISE OOS 286, 565 | Fortification Rock ........-....---.---- ----84, 206 Fork Arkansas, Be RIC oi ta es 309 | Fossils (animals) : 1) Sconce ace eetericcer maa nccias 291 ADNORGUB | Sas2en sean Sones 167, 182 Bill - Wiliams: -s2sso-< eee ce Se 60 RUIORISINIA cc one ce onae See oan coe eee eee 164 Bouche: 2222 ese eae eee eee 2 2G Ammonites ....-.. 271, 387, 388, 389, 390, 392, 399, Fork Eagle River, North..-..----- 324, 362, 368, 376, 407, 403, 544, 551 471, 493 Tohatus =... 0+ ~ cee eee 406 Eagle River, Sonth.. ... .324, 360, 362, 368, 447, TBOGIN SLAY cee oe ance ee 406, 407 : 449, 473 percarinatos................ 271 Fast River) Mast2- 2-5 -cccer «neneeeees 367 Amnicola cincinnatensis...-....---..--- 99 Bast River; West=<=2* <8" sheneecemeneet ale AION iii an Getta hee nme Same Se 406, 554 RR Sl ys eS 322 AYIOVIOUGISN = seo eee oe cenk Gene oeeeeee 271 Montezuma ......... 2-202 o- oe BAD, SA, 429 TA YSti Oh Gc once ac esce ka on ca veel 101, 103 Paria Crook; Waet-c---o- eee een eet eee 291 Oregonensis .. ...--..--------- ~ 100 Paria Creek, Weat .:...2. sesese -5-- -- 109, 240 Archmocidaris .........--- 62, 164, 165, 178, 553 Platte, North's... c5552 aeee eee nee eal, ane AVOITIINBUON = 220 poe ene oe ote ane 237, 238 Platte; South <<-::.:.ctce cen e 317, 372, 389, 416 ARODNUN cece. ya enn coen en ose anes 167, 168 Puerco Rivet; North ~ 22 .cae sen seeees 387 AGRE. cco cc cece eony senate 181 Gryphiea -271, 281, 383, 387, 389, 392, 399, 544, 551 INDEX. 575 Page. Page -Fossils (animals)—Continned. Fossils (animals)—Continued. Astartella vera...---.-----+--2-2------- 362 Gryphea Pitcheri ...-..---------------- Q71 Athyris. ..-.------------------ 166, 180, 362, 3C9 Gyrodes ..---------- ------ -----7 --- 77° 544 subtilita ..161, 164, 166, 177, 178, 234, 238," Hamites. ccc ss cesseacaeteeensee a= = 271 243, 287, 369, 375, 513, 553 Halysites catenularia..---------------- 522, 523 Atrypa ..---- ---- ----25 222-2 rere 169 Helix. 3:0 ee-42e se seene == eee eee 270 [Sa Aoeeos Saocos eee coo aeeenenS 166, 389, 544 Hemipronites . 161, 166, 177, 178, 180, 234, 238, 243 Aviculopecten -...---- 166, 177, 271, 281, 552, 553 Inoceramus -- 157, 269, 271, 275, 367, 384, 387, 388, interlineatus -.-.-------- 164, 178 389, 390, 392, 399, 406, 408, 544, 550, 551 occidentalis -.----.------ 161,178 problematicus --------- 159, 271, 544 IBaonlites:. 2 0: -cteeee ]-)-p sec sene === 399, 407, 408 Lamna Texana-.--.---------------------< 544 aNCepS.--- ------ ---- ---------- 271 Lepteena sericea .. -.-.-- -- -------- ---- 356, 515 Balcevellidesse sie 4 see- sna 161, 177, 552 Thine chew oe Ene ee eee ee Bathyarellus Wheeleri ---- ------ -- 167, 181, 182 Toil eee eee eens Doo) Bellerophon .-.---- 163, 165, 167, 178, 363, 369, 552 Limnzea desidiosa ..---- .----------- 99, 100, 141 carbonarius .--------------- 362 palustris. ..-.------------------ 100 eos) Aooseeeloone oseoroes 164, 287 Lingula ..---. .----- ++ 0--- -+++ +2222 >> 513, 544 B. montifortianus .-.----- ------+-------- 369 Lophophyllum..--.. ------------+-+----- 364 Brachiopoda. ..---. -------------------- 359 proliferum ..---- be oe ee 362, 369 Calymene ..-- ----- ------------------- 168 Wc d ceeeses cose ones cee = 271, 406 Blumenbachii -----. ---------- 181 Tenabiaises sees se oes se eater 406 Camptonectes ..--.------- 159, 236, 271, 281, 544 Maclures) ....ce.c-ses-semee ese == 181 bellistriatus ...----.------ 174 Macrocheilus -.------- ---- ----- -..164, 166, 178 @ardinm(ss. soca se ~ 92 ©=s=--1tR = 271, 275, 544 Mactra alta ...--..--- .----- ---- ---- 9+ 406 speciosum ..-.-.----- ---------- 406 Warrenana -.----.---------- 406 Carnifex Newberryi ---- .--------------- 100 WMastod0ne. ha. - ce csess cst asoceessre = 543 @hetetes<:=---------- 161, 166, 168, 184, 234, 375 WMepkellactess cof cases sa ee sas— ees 161, 166 milleporaceus - .--------------- 375 striato-costata.-----.--------- 101, 177 Chonetes . ..-.---.---- ---- 162,166, 180, 362, 364 Modiolopsis-.------ -----+-------------- 517 Conocardium ......-.-..---------- 166, 180, 238 Murehisonia -.ccectssso- = =e 164, 178, 517 Conocoryphe (conocephalites) -166, 169, 181, 517 Myalina .....--- .-------------0-" --- 166, 178 Conocoryphe (conocephalites) Kingii- .-167, 182 Naticopsis .....------ ----+-----+2-+---- 166 Gurbiedlass 2224-9 e— 28 <2 ae as 271, 275, 278 Nantilussceceuceos] scse=s= 2 Re ese 553 Davk@le cesses s\-=- = 9 -5-,~=h 159 occidentalis2-----rses- ee 164, 178 Gorbulayescseeee sane siesta i 159, 271, 278 INenibin gees: tes sacee anes seer emeece = 271, 275 Gunzianaecete feet ees ae ceoe nena eel O3, 180, Nuculla cancellata -..------------------ 406 @ueulliea -222---s s2-- ==. a-ne = s 225-2 =-< 544 Olenellus Howelli.... .---------------- 182, 183 Cypris?....---. -.-- ------<<------++---- 99 Olenus Gilberti -.------------- ----167, 181, 182 Dikellocephalus...-.-.------------ 166, 181, 238 Wermonlana. <2 caeSceeaacpees 182 DISC INamee en eae eae aoe Sete 167, 234, 238, 357 Orthiseesee eee. 161, 162, 168, 181, 357, 517 Equus-..---. --------++ +--+ ---2 2-0 220-- 543 lynx ....--------- ------ 168, 181, 356, 517 Euomphalus.--. .--. ---- --164, 175, 238, 512, 553 Orthocerasis.o- see: sae a ese 163, 167, 168, 357 subrugosus -.--------------- 362 Ostreaacee o- oases 159, 367, 384, 387, 399, 544, 560 Exofyra ponderosa .----.---- ---------- 271 congesta. .---- Aik are de eee 71 MWargOBlteSe ve eseme seria aio <= =< 512, 515, 517 Virginiana-...--.---------------- 271 Menesteliai-.<--- -<--<+ s------- 161, 164, 180, 515 (ALTE bees cacooe Roeeoe 32 oe Oa 406 Fusulina cylindrica ..------------- 239, 242, 245 OtodUs tes heen. tes soasais eee rat eee 544 GlanCOHOMG os. 6-65 o~ 0 so cicea~ een ene 164, 178 ParndoxiGe@s-2s ose sesee eae ee .- 167, 182 GG OMIGUABISeEE eee neice sae oe w= 267, 258, 269 Pentacrinus asteriscus ---------------- 174, 236 Nebrascensis- ..---- ---- -157, 173, 268 Pentremiteseee tenes ees ees ease 512 tenulcarinata ..---..-.-- Beeeloveas Phillipsia-...--..-..---------- 166, 178, 180, 238 Graptolithus bicornis. ....-.------------ 180 Pholadomya -.----- ---- ---- -----+------ 406 DUISIS ato larw ete m = latetetininln a= 120 Phyllograptus -- ----- Ne tee Nee 167, 182 ramosus. -. -- - Bea 9. LSD (Physic ceases 157, 267, 268, 269, 270, 271, 272, 539 Bridgerensis -- --- SEAS oaeRo 270, 272 576 INDEX. Page. < Page. Fossils (animals)—Continued. ' Fossils (animals)—Continued. Physa heterostrophia -....-.. .--...---- 100 | WANA DANUIB on = ane 157, 267, 268, 269, 271 Pinna .-----.----+ ---+++ +--+ +--+ +--+ 159, 544 trochiformis ...... ...--- 157, 173, 268 PIBNOCDIG ean eee 157, 267, 269, 272 Aaphrentis 22222822 5ee 161, 238, 512, 513, 515 Platysomus\.-- <<. - <9 = See eee ee 178 Zagerinus 2 25 ets Se ae 362 lento poses aes = eae 161,177 | Fossils, (plants :) Plenrotoniania). 55.2 et oe aceseee 164, 178, 362 PNUTORSS 2a eicuc ne Nene ae eae 403, grayvilliensis .........2-. 362 BU a ais ae = tke ea inn as) a ees 100 Polypord sacers ee ence eee 166 PVP E Ree ee A ee SRL = Bane 100 Pomatiopsis lustrica.....---...-...--:+. 99 | Artbrophycus Harlani. -.-..-.--. .---.. 246, 409 Procama@lusse assess ate aos eee aes 543 | Cardiomorpha -....--,.- sa=%---5 -=seasaee 366 Productus -..-. .. 1638, 165, 166, 180, 237, 239, 364, Chiara n.-.o..sa2o45cs ane ee eee 157, 263 365, 517, £53 Halymenites major- . .385, 394, 396, 397, 404, 405, Productusicostatus: <..2-- .--- --2- see 287 406, 403, 409 UN este eg en lh PE ICG amellibranchy 222 -2.--5 «= 2aoee ee ee 366 muricatus ......------..----362, 369 (Pecopteris 2.2.6 sae eae ee 180 Nebrascensis -.......--: 178, 366, 375 PINUS <2 25 ee ooo ee Prattenianus <- 222 Seees- 369, 375 Platanns .- <2 <2 cose=ceqieeen a= n i a punctatus ------.----_- __--_- 243 G. semi-reticulatus -.-.161, 164, 166, 177, y 178, 234, 243, 287, 366, | Garden of the Gods.... --..-.----.381, 400, 402, 500 371, 375, 513,517,552 | Geological age of the lavas. .----. -.....---. 134 Pseudomonotis. ........--.---- ered 161 | Gilpin’s Pillars...........--.- 309, 310, 311, 455, 494 Piylodictyanscscwea- vec ccc cc eeeaeeee 166, 180 | Glacial epoch... ..26, 97, 104, 116, 3C0, 403, 426, 436, Receptaculites ........--..-.-- 167, 169, 181, 182 449, 452 ATC a a oon eee OS. 243 | Glacier... -87, 103, 300, 420, 426, 427, 428, 429, 430, 438, Momoniiss oosese os. nn ce obo ons, S09 440, 443, 444, 446, 448, 455, 465, 470 Rbinogeros ..--c 3-H Seee so 2 = === 543 of the Animas .-25-5---eeee = 466 Rhynchonella. .._. -.---- ---.--180, 239, 515, 517 of the Arkansas:_---.---<_-- eae 458 CAPBX <<< cscs ene eens 157, 173, 268 Devonian. --- 407 | Homestake group -----------------++------- 312 Gila Conglomerate ----------+ +----+---- 540 Jurassic, (Jura).24, 29, 45, 59, 63, 76, 82, 174, 187, I. 233, 236, 247, 271, 276, 280, 381, 402, 490, 508, 545 | Tnseription Rock..--.. 280, 282, 297, 505, 557, 561, 562 Mesozoic rocks.-.--- ---------- 499, 519, 520, 555 Monument Creek group ---- ------------ 402 J. Aor limestoneste-isee eee saan LTS ; Tienctel HERAT Se 546 | Jicarilla Apaches ---.---------+-++++ +--+ 7>-- 337 Paleozoic .. -25, 54, 59, 121, 122, 186, 231, 499, 509, 510, 512, 515, 517, 521, 523, 549, 555, 562 L. Permian ..----2-2---s-z-25 2557257" 178, 213, 233 | Laguna de los Caballos.. ..---. 316, 323, 385, 462, 477 Permo-Carboniferous. ----------------- IZB6 213) lap aiken os cay ten oases eee 111, 248 Pliocene .-.. -- ------ -----2 *--207 te-oo* 265,519 | Lake Apache ...--------------+--+--20 00-77: 538 Potsdam group ---------- e----2 27507 185 Beaver .----- ------------ -----* 277777 112, 113 Post-Tertiary .--.---------------- 77777 47 Bonneville .-.-88, 89, 1, 93, 95, 95, 97, 100, 101, Primordial ..---.---- ---- +--+ ---°-" 26, 180, 521 102, 103, 240, 250 Quaternary ---------~---- +--+ -+7-7- 24, 172, 540 Chicago..---.--------+ +--+ ----7> 349, 411, 489 Red-wall limestone and group ..69, 77, 178, 184, Bishi mc cce socio ne oasis eine 112, 128, 300 185, 199, 209, 218, 219 Great Salt.---26, 30, 65, 66, 67, 88, 89, 90, 92, 96, Shinarump bed, (Trias) -.176, 215, 248, 283, 285, 98, 99, 100, 101, 102, 105, 111, : 547, 548 113, 114, 115, 238, 249, 250, 263 Silurian -24, 26, 27, 28, 30, 31, 34, 37, 179, 180, 181, Klamath ...--..----s--------- ---22--° 101 187, 235, 238, 243, 356, 423, 432, 499, Little Owens ---------- ---+ ----+- +--+ 103, 112 510, 512, 516, 518, 519, 521, 523, 524 Little Salt ......-------------------- 112, 263 Subcarboniferous --------------------- 178, 180 @wenseeee os 93, 25, 101, 103, 111, 112, 118, 124 Tertiary -.-..-+-- 24, 45, 57, 58, 59, 63, 75, 82, 172, Pabranagat ...--.-------+ +--+ 2------ 112 173, 236, 247, 265, 271, 402, 403, 405, Pauquitch ....-.------ +--+ -222-7 0077 112, 113 409, 410, 423, 470, 499, 501, 519, 542 GCs oe oe Cee eae mw nici 200 Tonto shale and group-. ----69, 70, 163, 184, 185, Reservoir. .------- -----+ e202 - 539, 540 186, 198, 199, 200, 219, 221, 522 Shee aes oe ate ees comic 112, 113 Triassie, (‘Trias)- -- 45, 51, 52, 53, 56, 68, 76, 77, 81, San Luis.----- ---- -----------"-° 313, 323, 461 82, 175, 194, 213, 215, 233, 235, 247, 272, 2e2, Sevier ----25, 2%, 67, 88, 92, 98, 99, 100, 101, 102, 378, 409, 490, 499, 501, 508, 533, 542, 543, 545, 108, 111, 113, 114, 115, 119, 134 548, 555, 560, 561, 562 Spring ---------+------ 00-7 9-77 112 Variegated marls -. .----------- 546, 547, 548, 552 Stockton ..--.. ----------------- 112, 113, 249 Volcanic rocks - ---- 93, 63, 118, 119, 253, 297, 412, Trine eee eo Aad anes 444, 445, 492 418, 422, 423, 500, 514, 525 Witsh6. <5 22s ewaeto= == #8, 90, 92, 111, 113, 237 Gulch California-.316, 317, 359, 361, 424, 439, 440, 458 | Lakelet Mountain. .--.----------- 112, 113, 154, 158 Colorado. .----. ----312, 317, 331, 412, 456, 457 | Last Vellaiiey cases 266, 270, 272, 273, 275, 291, 294, 295 Cunningham’s---.---------+----- 376, 463, 464 | Lode Coldstream..----- ---+-----+----*7777 353. 354 Homestake..---. ------------ +--+ ==, 438 Colorado Central. ---------- -----+---- 352 Horseshoe.----------------- 432, 433, 455, 494 Comstock.--.--------------""-°°7" ---257, 359 Tow assess <=> FES SR 359, 371, 439, 458 Equator -.-.--------- ¢+-e-2 e222 08-07" 353 Little Giant.----. ------++----+0+---- 464 Little Giant -.---------------+-------- 376 McNulty’s.-----------+-------25 7°77" 320, 447 Pelican. -g2<2 eee 2s3--22--2=-- == =ae~ 353, 304 Mount Vernon..----- ---------+------ 348, 351 Printer Boy .-----------!----+ 00777777 424 Gulf of California .----------------------- 225, 308 Schaffter ..---- .----------- crs 57-777 351 Gunnison wagon-road --.-. -------------+-+-7- 314 Seaton ae ee eaexscs se ceeanilanz ool, sue Senator .----- --- soemccsthecee sss ae 425 i Silver-Wing .----- ------ ----27 07-77" 354, 355 Hills, Black...23, 36, 48, 125, 147, 186, 208, 209, 211, 542 agri blots mone oa eases oe ase ene Sem 353 HIRVIEG ae. oo. e -parReReseo pr oae =n SoOee 39 Victor..---. ------ 2-22 eee ee0 ree 351, 352 578 INDEX. Page. Page. M. Minerals—Continued. McGlare Honse\.s-+=-2---> +s-22-seecnnce—== 399 Propylite<-<- + -acastan-2 2s saa eee 127 Mavom)'s trail-2---~ -225cs—-e5e esa 383, 496, 497 Quartzites ......-. 38, 234, 241, 245, 248, 261, 361, Mareou ‘repion +~—---.---..=-2= shea Rea ase! : 363, 386, 423, 513 Meadow Creek Chimney..----.----- - Sesas 143 Rhyolite-..-.--. 33, 38, 119, 127, 132, 133, 202, 205, TO WOG sae no eee a eet 103 . 255, 516, 518, 529, 530 MCRa AGO = on cloce ee ~ eae aeee eee ea 298 SE iaceeee ca saee aageee sa: 263, 372, 380, 538, 547 Blick sseo aces nee ees 47, 212, 215 Sanidin-dolerite (sanidopbyr) - .525, 526, 527, 528 Cathedrals 26526. e sa sea aoe 135 Silveri=-.-—-- 352, 353, 354, 361, 371, 377, 425, 515 Kneeling Jesus ...--. ---- escc0--sencne 516 Syenite.. ..35, 201, 208, 346, 411, 413, 509, 510, 518 Mopollon:=2222seseeeac onsen sans 47 Trachyte..35, 120, 127, 129, 132, 247, 255, 288, 412, Redonda... —- eee 544, 557 413, 414, 415, 416, 419, 420, 422, 443, 509,514, San Francisco 2>.0 22. =-s6seeeneastene = 529 515, 518, 525, 527, 528, 529, 530, 531, 584, 564 Shimaruwi psc s.ce sess sa sea- aoe ae ee 46, 84 LNG Cee eae ee ean Se 415 IVGrui HON poe seen e Sena ean eee & “inc-blende.- ~~ -.'-=--=---leoee Soe 353, 354, 377 Mine Clifton..--..---. ---...-.. -..--- wae—-- 515 | Mineral springs...-..---.---.----------.--- 47 Lprr) rrp yeas Se ES Sse 523 | Moraine.... ..---- 300, 431, 433, 434, 438, 440. 444, 450 Freiberg ....-.--..ss-s2. s-e2+-------- 37] Mount Bill Williams .. ....-. ....25, 46, 130, 132, 163 HOomestakG>..---5a.-se- = esse 438 ROSS soe steele nee eos 310, 320, 348, 494 Tuternational . ==. .22-2=%!-.22<<-61- <5 354 Canmelitase=sne =a een eae eee 25, 45, 50,77 Raymond & Ely--...-.--. seep eee ess 244 UO) heh Fes aoe = Bn Sn oe 312 Santa Rita Copper..---.-.---.-------.516, 518 IVE MIR = 255 3 = S552 ee on ae a5: 46, 411 Washington and Creole.-.--..-------- 245 Woyd (eas ee eee 25, 130, 132 Minerals: CEG UNE ee Re RR ee 206 Arragonite.....-.------------..--- ---- 363 (Grahan)aeeee ee ee eee 505, 509 Basalt .....-.. 36, 120, 128, 132, 203, 205, 248, 253, IB eee ee ace = pent 288, 413, 414, 419, 420, 422, 514, 518, 526, Kendridk:, os -.-55-as- eee es 46, 130 527, 529, 530, 531, 534, 537, 538, 557, 562 BEING oe seein ae eee no wine me tee et 372 |. Brine of Sevier Lake (analyzed) -.. .----- 114 Calonrecus tite 3-2 2--enn a ees eee cee 97 GhalGeuOny saa sass ee eee eee 419 Conlesecece see 157, 173, 174, 278, 279, 391, 392, 396, 407, 544, 550, 551, 553 | COD PRt cee ane eee cee ae ae 377,518 | Crystalline schists and rocks... ..24, 56, 54, 186, | 194, 246, 343, 549, 563 Fresh-water limestone and deposits - .--. 45, 265 Galenhe-_ceeeea-oerene n= 353, 375, 377, 517, 518 Gneisa"=...~-.--4-6 35, 248, 343, 347, 443, 492, 509 Gold escee ene 351, 361, 372, 423, 424, 432, 518 Granite ..23, 29, 35, 98, 201, 206, 240, 28, 343, 345, 411, 443, 492, 509, 514, 515, 516, 518 Gypsum ..... 264, 271, 251, 363, 364, 371, 372, 374, 379, 380, 394, 454, 547 Tron noses. 252, 261, 361, 375, 377, 390, 394,424, 510 AON von uie deen dele ome ene oh see tee 263 Lava ....118, 124, 127, 134, 197, 201, 211, 298, 413, 509, 513, 515, 529, 534, 536, 543, 557, 564 GO axe uals ses cate rtrete tak aaa ee 518 1S feel (7: Bee ee ao 391, 394, 396, 404, 408 Metamorphic rocks......-..-.. 206, 234, 343, 346 Obuldiat:.. .V.dveadcsstcoan camtakentee 415 PetwOlOM 2. Fics cancas dna ndlensin a ureen OCU OLY RY anc te ein as wnccoecs 510, 515, 516, 517, 518 Lincoln... -310, 311, 316, 220, 348, 349, 357, 358, 373, 377, 416, 429, 435, 455, 494 Mary.n5 o-oo ee ee eee eee 316 Morton. = .-.-2--os5 309, 311, 320, 374, 455, 494 Nebo... ..2.23, 58, 59, 84, 231, 233, 234, 236, 264 Picacho -.-..---. .-.--- ----130, 179, 246, 255 Dayton 1 ee SRR ae 312 Quandary ---.......-....-- 311, 320, 324, 374 LSE YS ag SS SS =e + 428 San Francisco. 25, 46, 47, 49, 81, 112, 129, 130, 131, 132, 135,136, 211, 213, 214, 215, 216, 299, 525, 527, 534, 542 BShendans-....-2-a5-F ease eee 316, 433 RGeTERWAR = one ee one oceans . ----46, 130 Taylons eaasn 279, 281, 289, 297, 298, 299, 525, 531, 533, 542, 559, 56: TOLD O au eap = pacceeeee wreens se eee 509 U(r a a eee eer a 312 MeROM eat oon eet weweee eee ss ae 382 WG o8-e nce nd nae Sane one cere Wala) scene Eee oe Cee 312 Mountain Antelope .....----.-------------- 256 pT, No a tee a 32, 33, 124 BROOME cet Gtelaies wa cies Sime 25, 121,132 1208 eR eS ee 2 ear a 516 RAD. on atin Sawn tbeeke huemee 123, 181 RIGOR age swan von cs Seeeeee eee 35 Brow . 2.6 wn nnas cous wemadaulSonawe 349, 353 INDEX. 579 Page. Page. Mountain Burnt Rock.....----------------- 135 | Monntairs, Kern..------------- 30, 123, 240, 241, 242° Colorado....-------------+------- 35 Mogollon - ..46, 49, 129, 130, 214, 215, 217, TOSS een iceee es acter elle 206, 207 542, 543 19) ) ee pscenee Secor 324, 193, 495, 499, 500 Nacimiento ..---- --------+----- 542, 549 Escadillo -..-.----+-----+-+---- 299, 542 Panamint ..---- .---------+----- 125 Fourth-of.July - .----------------- 316 Peacock .----. ------ -----+-----° 205 Glacier .----- -. ---+ ------------- 324, 429 Pinal 2242-056 92s 221, 222, 225 Granite..----. -------+----++ ---- 40, 97,119 Pine Valley ----23. 121, 182, 135, 195, 247, Greene ee eee Sek aaa ctoesset 397 954, 256, 266, 272, 273, 299 Homestake. ..---- ---------------- 447 Pinos Altos ..---. --------------- 516 Hualapais.-----------+----------- 205 Placer--.------- ---- eae ete 277 (meon,cesse sete ee- == 59, 232, 248, 256 Raton socacc see ecee see seeeeelm= = 406 . Leavenworth -..--.--------------- 349, 352 Rocky - --21, 87, 97, 103, 193, 220, 207, 311, TWO cg os Seer seers 516, 518 312, 314, 317, 318, 330, 375, 378, Arc @lellanieeoseeeeeeE -ceecree e== 310, 321 403, 404, 405, 442, 477, 488, 498, TPAD Ollie: SosSSasecdsemcoereces 40 499, 501, 508, 546 Massive..---- ---- e----2 eee ene 312 Gal hi-eceecn eo ee ae =e 264, 296 Meadow .«...--+------- <---> -=--° 256 Sam Pitch...--..--2---------"-- 129 Music .. ..23, 47, 186, 199, 200, 201, 205, 542 Sangre de Cristo -. -87, 318, 322, 333, 334, invajO .aeeconc a sero cee StH 294 343, 361, 371, 386, 416, 419, 422, 426, 434, Noticheectececoece- emeaacs-ee- 27, 28 442, 453, 459, 460, 461, 462, 488, 491, 501 Old Baldy .--------------+- +7777" 318 San Juan..-.------ 315, 422, 460, 461, 488 Pilot ..---- ------ s-2--" ------ 25, 124, 185 San Mateo and Ladrones --.-- ---- 520 - Red ..-.------------ 324, 369, 418, 445, 449 San Prieto...--- ---------+-+---"- 125 Republican .---------------- 349, 353, 354 Suntaphé .uleexteseacs seeeese= 519, 520 San Antonio .-..------------+---- 422 Sheavwits ..---------------+ <<" 46 Spring----------- 31, 124, 166, 174, 179, 180 Tulerosa .---.----------------- 530, 531 Steamboat .--------+ +--+ ----- +777 45 Uinkaret .----- 4G, 70, 80, 82, 129, 135, 177 Superstition .----.--------------- 224 TWintalce=se- <2 s-—ee 43, 173, 231, 266 Thirty-nine-Mile ..---------- 317, 318, 415 Uncompahgre------------------ 322, 326 Thousand Lake.-.------- 291, 295, 299, 301 Virgin...--. ---------+----- 194, 195, 196 Wet ..---- ------ +--+ +----- wees 319, 382 Wabsatch. --22, 23, 24, 57, 65, 66, 129, 174, Worthington ..---------------- 37, 41, 122 179, 231, 233, 244 Tionicsecereet eee wea =e ese ane se 244 Wheatstone ...------ ---------- 591, 597 Mountains, Alamocita .----------+---+----- 532, 542 Wichita ..---..------------"---- 147 Apache ...---- --!--++ ---+---- 93, 220, 221 Wihitesce: cece Se S-e 2 60, 217, 218 Aquarius ..----------+-----+---- 206 Wiantdien <2 22 -\222 22 asia 289, 520, 549 Ball Valley ------------ 121, 247, 251, 255 Zuni -.274, 283, 286, 287, 289, 297, 298, 299 Burro ..---.----------* ---- 515, 516, 518 ; Cascade .--. ---- ---- ------+---7- 87 N. Codarrececenasas5 40, 233, 239, 244, 254 | Narrows, (The) -------- “Seeeee coon eees rere 78 (REA ee ee Eeee 9096 | Natural sand-blast ---- ------+---2-7 +70 777° 82 Champlin .-----.----- -------77" 119 oO. “CIS SRe ae 507, 508, 510, 515 | O55 de Benado ....-------++----+27077* 15, 533, 537 Colorado --------------- ae tee 125 Gl O80 ce oo cee ae lena saa nase 551 El Paso..-.-------- 124, 135, 142, 143, 519 ATUL MAGE ee ear eeseEcoReae-obso 494 peer SITE EE OEE Ae me = Le Old river bed ....---- ------ ------ 77707777" 98, 120 Gosi-Ute.--.----- ---- +--+ 72-77 123, 240 Spiers mieatch use tn este dy 2 22a scene 61 Hardscrabble or Greenhorn .---319,321, | Orology ...---------22e--2 eo a1 - t=) - 322, 333, 334, 335, 356, 378, 380, 387, 400, 401, 415, 422, 424, 489 Pp. Henry ..----------+-+----- _274, 291, 295 | Paradise of the geologist ..-------+----+---- 43 Humboldt -..-.------------------ 65 | Park Animas- .--- 315, 316, 337, 374, 375, 378, 421, 463, eon gess ae oe gades eae SSS 232, 248, 256 464, 465, 466, 469, 478, 497 Juniper .----. ---------- 2000007 207 Antelope.----------- 314, 322, 467, 468, 469, 470 580 INDEX. Page. Page. ParkvATKGNRAS! 22 =o. ww ec eee eceesesaceaeeee 491 | Pass Uiyabi ...............--......30, 241, 242, 244 LOS TCT ee Se ee 376, 463, 464, 465, 497 Wiles essa ceess dasens 22 eee 318 OR UHO Et to. 2. oshcooe eee 344, 366, 152, 494 Wialkerain 3 ssa seek owoc- st 87, 103, 124, 142 Cottonwood...- «22. tonne ee oe $83 | Pay moekic os seo occ See ee 354 Huerfano.. . ....320, 333, 335, 371, 379, 382, 386, | Peach Spring Wash ......---. 22-22. -2---.-- 79, 80 387, 388, 415, 426, 459, 489, 490 | Peak Bald...........----..... 357, 358, 359, 360, 373 Middle - 2-2. epee sebanenn eee «----310, 320 ET AG KP RRR S Sea ee 112, 133, 231, 256, 422 Novth>? 25 3Ssasseen eos Ge concn eee 320 Basalt s.ns56.2- S035. 058 317,414 Prigtoctecoce se eae awe cos seco o 527, 528 Belknap, .2scsaniecssenssaeses 88, 112, 133, 141 Sar Luis ssi se cence ee eee a 419, 463 Buffalo 2. -.2 255 sos ee el ear South .. -87 307, 308, 310, 311, 316, 317, 319, 320, Cabezon:5.=-.55-22552eeeeeee ee ee 536 327, 328, 329, 343, 348, 350, 356, 357, 361, 371, Cilebrance 55 assess esac ese eee 318 372, 377, 383, 386, 389, 390, 403, 412, 413, 415, Dos Cahezas:..-.;.22--s2ssneseeee 510,511,512 + 417, 422, 423, 426, 453, 484, 490, 500, 501 HVONG nc eccincosteer ee en ery F525) 2 309, 321 Maylorss2.55.i54 360, 366, 451, 452, 459, 493, 494 Gavilan...--.-: c22e<.cne0 seneeneee DIA Is Mexag st... Soccs « oss ac cee eee 415 Goats osc 2 oh Sos 2 eee ee - 316 WDION 5 oho nw mpg cies 3 Cee 452 Granite .-.... Sie eet Une SS AbS Ee 125 Wet Mountain..-............ 319, 322, 382, 415 Gray’s..--.. 309, 310, 321, 324, 349, 354, 386, 429 Yellowstone... oo)22. 5452: 2 Seceseee- 149 Unies s 2 cose eee ae 312, 367, 370, 419 Pass Argentine or Grizzly Bear .....-.-. 310, 311, 429 McClellan) <2. 2-=-— 2a beet Se 321 Arkansas)< 22. ... 45-25 eee 509 PR WN BY a a asennad oie 27,119 SIV OE = 2 asec eons olan 155, 181, 523 Mainfiel d= 52 26 5 eee wees he 25 SUES VC} eae eee eee 5 5 422 Burémont’s sn cnc cows eee 142, 232 UC: ae AR eee on os Se 514 Frenchman or French Gnieh._... ..---- 311 UGLONG = 5 canela nee eee os pao Georgia or Jefferson .. 121, 310, 311. 319, 324, 455 Timpahote..---. onan sabes 39, 122, 123 GOL: sao 3 aden eee ee 324 Modo.el'monda |= .-. -----«c..neacsen eee 531 Hamilton ....311, 314, 321, 374, 417, 424, 454, 455 | DLOUEOY pamnaeninnee panna ie sO 309 LEV TL apres ahee rere sate se 50 318 ranchers s<5 22) a. oan =n easaeee eee 318 HOO OD. 3560 ncn nnen mann eeeees 311, 314, 417 yO. sas asn akan ts ee eee 121 Horse Dake: . soc Coinannas cae sieneeo lo; Gen, 400 it: ee Ses eee cere 422 JeMOIson cocscisc seca rsswass saeco 417, 455 Measles 2 2 eS 30, 88, 112, 184, 241, 242 Kievl0shis 2. .-\Snnm acc ceme see eee 319 Wihite’s =~ ~'=.-<-. 5.505 een, 31, 88, 167, 184 (aks Creek nn cd. an eb a aeeaeeee 451 WHIMEld s <2. cap eren mamma ceneee 449, 475 uD eg NER aE Po ea i ya ny 38;'39,'123 || Pioche wein..-25-.22 22256 e.. conten ect 258, 261 MGsGn 52) 2 - om ancidaacccaecwane tee eee 319 | Plants of medical and technical use... ...--- 607 Mosquito). -<.<0 << concer scep eee 316,455 | Plateau Acoma .. 532, 533, 534, 536, 537, 543, 544, 546, Ponaho = 3265 nccannnosGes 318, 319, 416, 491, 495 554, 555, 556, 557, 563 Matlroad < -< .cannca sco ceees sails See 510 Aquarios ..--..---.--. --.. 292, 293, 294, 299 Rio! Grandess. < a.cdsscace ee eee 463 Colorado. .... 22, 43, 56, GO, 147, 154, 193, 201, Bacraments «6 cece cduaccncasdWecs eee 241, 242 212, 251, 278, 280, 284, 289, 407, 408, 508 Sang Fil) soo ocn nae mactes we sae Renato 319 Kaibab nce scans 46, 47, 51, 52, 56, 57, 70, 291 Sangre de Cristo .. ..317, 318, 319, 323, 371, 386, PRAUOU Geecne heanantéheneds vancadenee 47 422, 491, 493 UB C0) [Sek a ee eS Se 5 M7 Stony Point .................358, 359, 455, 456 TG DRBES Fcemcrnane sans cient 542, 557 Tennessee ...... 312, 324, 356, 359, 360, 370, 437, Nata Ga chs ncn ocak tinea ee §27, 52. 455, 492 Sai Pate cemene anarin sine eeteenee 157, 175 Trout Oreck ew ces nack 316, 317, 358, 359, 372 | Ran rantintt..<:0naccantctecan 109, 116, 542 INDEX. Page. Plateau Sevier ......-.--- Sale Dwar ioe eee 88 Sheaywits\ sees. 2s eee ss ceeee 47 Paylor?=------ 534, 535, 536, 543, 546, 554, 559 FERIASSI Gg stan cer ctcickacede eile Sasa see 52 Plateau system or region... 22, 24, 128, 131, 134, 187, 220, 231, 252, 265, 542 ln yas sees ee we aces occas catiesce weed 107, 111 Plazaide tos: Pinos. 22.2). sowie e ete eee 461 OMG Y AEA oa terial wee et ee eeee 555 Ponds, Stockton and Cedar Valley .--.--..--- 113 ROO! SACOD She Soh. toons once eee ee keeteecses 46, 160 Pai Noles eases see sm ceascoce cree ct eerste 7 HopvloWoloradas 22.5 -2< 0-1 sabes oa) oes 281 INO son ainisaecitcaeecseeeseseea “OBR NOP cise am pea sacs see peewee 513, 518 PUM Ra oar ene mate hake eee cists tewisecs 155 “Purgatorial” wave-work.-.---..----.-.---- 98 R. Railroad, Central Pacific ......-.-.2--...--- 92, 121 Denver and Rio Grande. ..-..----- 397 WmTOnPP ACH Ceca reo sien eee 172, 276 UtahySonthern: ..4.-- soc seas s 90 aU ARe OI pUNner sect nase aiecisees wren 84 Pam chipAay aves aeesam is gam iiorrciniacive cease soe 158 Banl@yis perenne cero is a1 cece's woe cloe 345, 350, 428 ID ESN ae seeBee Pao nese sa ee eee 443, 444, 445 JONNBONIS eran soso casas ee tees 25 PI POR Seat ememinsooeweerewiccinccem eee 34 IPOS Gal Slaseeae jamie tec seek te See 125, 132 WRENN CW Sica se anes secieeten cers aeeaicae 25 Thirty-nine-Mile ............--.-.--- 414, 469 Young’s .---- eas coon seers ae 25 isp nyo <2 eee ess SESE SS Ss 507, 508 AMPs lost sme no eae 123 Amargosa.....-.----- 33, 62, 124, 169, 181, 184 DATA see ee ea 412, 491, 492, 493 BOA Gl S2ccco. osenrorige ee dewtioe 120, 133, 141 Beaver Creek -..-.. 28, 39, 40, 120, 133, 141, 296 Belted’ Mountainy-s25-265~--- eee 123, 181 BHC Saeko s site e socte =o eerie ees ae 74 Blue River --..320, 324, 350, 368, 383, 386, 426, 429, 447, 448, 490 Bart Rock. 220.522 ss22-2 Pe (CHINO EH 2 Oe Deseo see ee ionesao 44 @Cedarisecccs cease tee 39, 119, 136, 239, 255 Chiricahui---- -.--- 508, 509, 511, 512, 513, 518 Chitown co- so ee ao eee tne - 1018 Gowmtosioneess- 26 s2oe) 25 ST 40, 120,179 MSN area iaet a -aems tor a tiororm( shat a tat one 103, 112, 124 TONES S 2S Se ee eee aes 531, 532, 549, 556 Draholowecss-ter spams eee ten 516, 5380 Tire eps oe a a a ae 123 Bochiticationy.<<.-1sss2 oceslo-- seo O= c= 242 Giles eso 2 Alec stele 0513, 518) 528 581 Page. Range Greenhorn ........-.---.---.--. 376, 379, 428 Hawahwahl so. .e. ss. 'soceces ces 120, 247, 255 Highland ...........-.- 179, 243, 244, 255, 257 Hot'@reeks 22 oe ssecavk een 121 House. ..-. 27, 28, 39, 40, 42, 65, 90, 94, 110, 120, 167, 181, 245 Humboldt .. 2265 soscce ew ose eceeee 87 Hy KO wate scott den cote CER 39, 123 In y Oupe see eee 34, 39, 103, 111, 124, 169, 170 Tron’ Mountam: 222222252. s..seeecece 59 Kawichisi-4 Goce Ree ee es 122, 319 Kenosha -. 320, 321, 329, 386, 417, 428, 454, 455, 489 La Plata 3222522 eee Rare Sen SS 488 Pind row Pes 0st ue se cae een ce een 42, 563. Talei(Utah)eeeeeeneeees 179, 237, 238, 244 LOS Pin08 were cn etrocersee ChE 488 Mazatzal: nec. ccocwesttiheteey 209, 508, 509 Mim brést.0 4 soethucaeeeea 519, 530, 531 Mineral 25232 29, 120, 174, 179, 233, 246, 254 Mogollony.ss..0 gee SUC eee ae 549 Monitorssce-cedesccerasrencdun ieee 121, 122 Na&CIMIentO ae oer ee 543, 446, 563 Needle antic oe sce cece en tecc ence J 1205247, 255 Onaqui - ---- 26, 27, 39, 40, 65, 238, 244, 254, 255 Oquirrh. -- 25, 26, 59, 98, 166, 179, 181, 237, 254, 245, 251 Pahranagat.. ..-.-- 37, 38, 59, 42, 128, 168, 181 Pahvoe reece a deseceacm ioe teee 123 Pahvant..23, 59, 93, 120, 136, 141, 179, 231, 296 PanaMmints2 soccc sasen rset sees 34 Pancake, 252 S2 rete so See reese 122 Park Act sl eeloetersheeneee tk. 415, 491, 492, 494 (PalOW ADs sects coco rire eons sees 296 oo Peloneilosss Ss. Sat Soceee seen ake 513, 518 IPicachOs wk oe set Seuee eee Yous w228,129 Pike's Peak 2s. cachet eon ez 376, 378, 428 Bintalisecae te sade au, wn asee ates 508, 509, 517 Pinaletiosss cs0-ca6s52 2225 228508)509, 528 Pine Walleye ssa- nesassss cose eeeeee 59 Pyramid = sae seme See cma osetaaceee 514, 518 Quin Canons. = 5-5 251-2 a eee 122 IReveillatccs atoceaevects. 37, 122, 123, 179 Robert's. Creek: 22.25 $5226. ses eaee ee 180 SamyPiteh tet aeonrscns sad eee toes 273 Sangre de Cristo ...------------ 323, 491, 493 Santachitanssce-ss-see- 515, 517, 518, 523, 524 San) Jiaamyee= sees ee eee 438 Mignelispe assesses nee eee 488 Sevier 500 tse al 2 hetict SAB Rees 299, 301 Schell Creek.--... 30, 88, 123, 167, 179, 182, 184, 242, 244 Shoshoness= tee occa eee SSeS 121 Snake <. 22-0252 30, 42, 123, 182, 240, 243, 244 Spanish s-tss7 sce) see 318, 323, 422, 491, 493 58 2 INDEX. Page. Range Spring Mountain .31, 32, 42, 124, 166, 174, 179, 120 Stansbury)... -<-s-s-<<-- 40, 119, 179, 181, 238 THOMAS Seo aeons 27, 39, 40, 65, 119, 181 Timpahute.......-. 38, 39, 41, 42, 123, 169, 181 DiNGie | Socices ¢4ioeemwces ese eee eee eee 119 DONMUIN Binns aealeweeeala= a5 sere 36, 121, 245 TPOYADG one oan cone enn e ann Ol gely led, 245 (Uintalie beset. oe cane incemeeeeee 87 Virgin... ..35, 51,54, 121, 179, 184, 186, 232, 247 Wabsatch ....22, 23, 25, 30, 59, 87, 89, 103, 129, 175, 233, 238, 244, 251 AZangiais. soos siercces ccs see ee aoe 563 Zuni. .290, 532, 533, 534, 543, 546, 549, 552, 555, 560, 562, 563, 565, 566 ou Reservation of the Ute Indians-..---......-. 337 RioiGrandeidyke--- 2 een eae 496 AMOR Scie aoe nae ae pene anaes eee 323, 461 de las Animas (Colorado and New Mex- ico)... ..315, 322, 326, 337, 374, 375, 376, 378, 383, 384, 412, 421, 423, 453, 463, 469, 470, 497 Blanco). 35 Sacsesc nase snneccemesseeeeeee 384, 477 Bonito <<<n a6 43, 45, 49, 75, 109, 247, 297 Page. RiowWMivers .2. ~ 55-2 eksasns sca oc geet eee 243 iver Apish pa... o-ccenptaaaancomessul aes 322 Arkansas . .308, 310, 311, 312, 317, 320, 321, 324, 340, 342, 343, 347, 348, 359, 380, 397, 398, 400, 402, 403, 411, 413, 416, 418, 423, 429, 435, 438, 440, 442, 444, 445, 446, 453, 460, 472, 483, 4n9, 490, 494 ATM APOBR ano n5 Saas aaiane eeeieee eas 123 Uff Mae a5 BRE PRS ia e 66, 252, 273 Blue... -310, 311, 320, 324, 351, 358, 374, 386, 392, 417, 418, 423, 424, 429, 495 BONITO A= siscnee on ee eee 505, 514, 540 Colorado. .25, 35, 43, 44, 46, 47, 51, 52, 54, 67, 72, 77, 79, 80, 83, 91, 107, 109, 125, 129, 130, 155, 173, 176, 193, 195, 196, 198, 232, 251, 274, 275, 280, 282, 289, 291, 294, 296, 308, 477 (Columbiagess seeease aaa eee 103, 133 Dirty Devil.. ...-... 109, 128, 174, 271, 280, 281, 283, 286 Eagle........-- 312, 313, 356, 371, 418, 447, 448, 471, 492 East... .325, 338, 339, 344, 366, 367, 383, 418, 450, 493, 495 DOG UGIES 6 Sac SSeS ea 174, 281, 286 Fontaine qui Bonille ........---.---- 322, 381 Grand -.43, 308, 312, 323, 324, 325, 338, 343, 412, 473, 490, 501 (Ohi Weseaeouerc ssresescncscascese se 43,173 Gunnison -.308, 312, 313, 314, 323, 324, 325, 338, 343, 361, 412, 418, 452, 501 derman0ecncs seces ees cee eae 319, 322, 335 Tn Gs eee eA Sse 8 179 SP Rt SAS ens SS Se 2 66, 90, LIL WN eyo ea ea RS 505, 508, 516 AIBSOUT cena gee ea nea ake ae ae WEN ES Rasa seein sae ce Bae 202 (OVS Ae SESS a sn 5 BS Se 103 Platte....-% 308, 310, 311, 317, 324, 340, 413, 454 PIA Se cite Rinne ain i ae oie oe 265, 269, 272 TOTS RSS SSE SERS 505, 515, 529, 538, 540 ENTS eteb ne nea Sac 58, 250, 251, 256 Purgatoire....... Sees ere 322 RR GPEEY race ath al keine on aoan se eal a a aloes 121 Salt or Salina..........<.<= G0, 219, 220, 264, 266 San Juan ...43, 274, 279, 308, 315, 316, 326, 327, 343, 375, 383, 384, 407, 421, 463, 477, 478, 496 Santa Olurareencurancneass ered aeknae 194 Sevier . ..22, 43, 44, 48, 59, 65, 100, 109, 112, 116, 158 Snake. ccatesss 65, 91, 102, 251, 324, 351, 374, 392 South Arkansas ....309, 321, 325, 330, 332, 344, 347, 358, 489, 453, 456, 457, 458, 459, 493 South Platte. ..308, 310, 311, 316, °17, 319, 321, 342, 400, 402, 406, 429, 430, 433, 442, 455, 424, 459 INDEX. 583 Page. Page. River Spanish Fork .....-.-...-...--...-.--- 251 | Springs Cébolleta......-.....-....-...---.533, 537 : SWalssstesasecosessenics sess. colic: 310, 324 Colorad oper ese scans sce 149, 319, 486 Taylor..... 313, 325, 338, 344, 346, 360, 366, 367, Cnystali er set yak ttt oes bee ece 179 371, 373, 411, 449, 450, 452, 493, 494 Deop trace sae et eee este tede 3 Virgin - .. 46, 83, 109, 110, 112, 129, 174, 194, 195, Deer 2.) 7.- Ned Seis Sue ace oS eke 290, 297 : 247 Desertec-as252+'2 seep eeess 247, 251, 254, 255 WWiODOR ta enacn ce. nee sons cece ewes: 66, 252 Dinoaeh 2.252: 52540 se aesso reece 198 WRIt@URIVGI swam sas 75 octeinectelne sciass 478 EWE ss czcaesdace Secuee ones 511,512 White Mountain -..-.....---. 60, 135, 527, 536 Bishio. s2occsessaceraeeas 25, 27, 94, 110, 167 MMM eee ot aeseosietsemt oeee eee see ee 533, 560 Fontaine qui Bouile ..149, 399, 400, 401, 486 Roaninp: Hapldmecr sennccs eae ¥ % d ey 44 "994, 301 174, 175, 176, 179, 191, 193, 229, 231, 222, 248, ae ‘Rocke eee a onan ee 4G 53 350, 254, 261, 265, 275, 278, 281, 283, 285, 300, Hushutats Seota = pr ear 200, 202 205 404, 405, 408, 488, 521, 524, 542, 545, 547 Joe's 5 ree paced 2 yea aa "068 Washington Territory ....-...-..-..-.-- 149 aienae PE RR OE Oe 949, 957 Wy oIning saceee occk oe eee 404, 405, 408, 521 inate: Ses ae Pape coter Station Desert Wells.... ....-.-..-------.-- 143 Little Zion CT Caan Sa are as oa : : 79 SESEANIOU: 5 2-<525=oe Sac cana ha Long sacs sare eoee45, 46, 49, 50, 56, 136 Greeniand:--ceesseeeeee see eee 397 Sih a eee Orne ay a2 hoe ee Men coos. a22- sece aoe ee oes eee 25 Owbhnt2Aes ce io see ee 169 EUBOUIS = ais aebt a niman nosing ae Parcwan: ae Sa a een 120 ie quid heiiahagetaeb ind Antes oe i> wipe Pleasant... .30, 241, 242, 244, 255, 332, 342, 371, Stratified roaks\; - 22.2.5 ss0ceses< peers 156 415, 459, 491 Sirens (Gc cscs cen cncce wens eee eee 106 Quin’s River : 101 Structure and age of the Rocky Mountains... 488 Ralhike te ee ee 132 Gr ICP OR eee eee eee 40 Balaton 02: 121 Supset. Crossing <<<. pec eeeen ana ponstuseeeeee 214 of ‘the Rio Grande’... ...-- ....265, B19, 542 Bnnset Tanks... -.. scasseeceeaven-weewe 81, 213, 214 Rone: se tee a ee 255, x bs DT ea Sg Sa Ay Se 90, 112, 238, 249 Tabernsele Cluster :..2 assonehone cece eeaee 137, 140 Sali Diakosot 2.52 43-0 2-55 see $0 Table-land Markagunt ...-.. .......-....--. 45 Sam Pitch ...25, 49, 50, 236, 267, 270, 273, 278, Powneapneg.--. ss nonce eee 45 294, 295 Table showing the correlation of the sections. 171 San Carlos--<- <5. --- <3 219, 220, 222, 527, 523 Territorics. (See States.) of Mig Rinloge no coc ne case ae aos 534, 546 Thermal springs in the United States..118, 145, 150, BAUR scone Ss cnee aaa see 175 151, 152, 153, 256 Towns. (See Cities.) ino Dome. sis os ceca eee ee eee 825 San Luis - ..307, 308, 315, 318, 322, 323, 335, 385, 386, 419, 420, 422, 469, 461, 467, 469, 484, 495, 501 INDEX. ' 585 2 . Page. Wallen es anered iG renee le see es <= irc -e,0< 5-2 508 | Valley Wet Mountain .--.318, 333, 334, 335, 348, 371, Snead cqcs ee eee 270 386, 387, 422, 426, 434, 435, 459, 490, 491, 493, Suit (ON ie? se eas hcaod eeseseroeooe 254, 255 : 501 Sevier. .-.---- 25, 50, 116, 128, 135, 264, 295, 296 WALT he ee ya a oe a ee ee 155 Ste) SCS a6 So Sooee aeeeeeeecoscos 249, 251, 264 | Villages. (See Cities.) SnakeyiVelyesssess=) 4. oscce-as-oo~ = 102 | Water of Lake Bonneville...--. ...-..------ 101 SHENG ene eaeee a Sens pee eae 242 | Wells, Desert .....-..-- physnion ie eepenuate ees 25 Sammiti-eces=csses-fe eee te~ Se 299, 301 Tn dian sacocerenc scars oo eetn eee aoe eee 103 SPM ooo scp osecosacbe soseees ee 223 INE we Unapeer Poca seboes coaccccneece 46 exagesee ceca a aes apenas sic 459, 460, 491 Vanpin) Saltee.-cea-cdeeeer easter see L09; 110 TG psoas ovencaobabse0 eaSSre QOS U9 249) Willows GLONG) oo. x CORE tet ves ti Bai 7 fuga ha re td x Unitep States ENNGINEER O€FFIcr, GEOGRAPHICAL AND GEOLOGICAL EXPLORATIONS AND SURVEYS WEST oF THE 100TH MerrrpiAy, , Washington, D. C., May 20, 1874. Dear Sir: I have the honor to present herewith a report upon the chem- ical investigations of soils, minerals, mineral waters, rocks, coals, and plants of parts of Colorado, New Mexico, and Arizona, traversed during the expe- dition of 1873. The report is divided into four chapters. The first contains a descrip- tion of the agricultural capacity of portions of New Mexico and Arizona, with analyses of soils and plants, and remarks on several cosmical condi- tions; the second treats of the composition of mineral waters and minerals, and contains, also, an investigation of a previously undescribed fossil-resin, which I have taken the liberty to name after yourself,—“ Wheelerite ;” the third consists of a general geognostical and chemical description of the vol- canic rocks of New Mexico and Arizona; the fourth comprises a list of minerals, embracing not only those collected last year, but also the mineral- ological data of the two preceding years, by Messrs. Gilbert, Stevenson, Howell, and Hoffman, of the survey. The tables are arranged after the system of Dana, thus deviating from the usual alphabetic enumeration, which is not well adapted for a scientific report. Permit me, in submitting this report, to add that, since so many impor- tant and interesting questions can find their proper solution only by chemi- cal investigation, it is to be hoped that, as you have been the first to recog- — nize the importance of chemistry as a branch of natural history operations in explorations for survey, its claims will continue to receive favorable con- sideration at your hands. Respectfully submitted, : O. Loew, Mineralogical Assistant. Lieut. Grorcr M. WHEELER, Corps of Engineers, m charge. i i {tar Jud eee — 7 - _ = ol te ” > ae eee > uthiteatan eee \ ; 2 ~4¢ dif Waly Phe : ‘ ' 7 ¥ * th A 7 “ 2 . P . 37 » : Phi eI . ay C 1? ‘ f * Al ity : Ps a - : * 4 - Ss. ‘. - by A * . . > ‘ “s . ts he . 1 .* J * ~~. ‘ . * o P is 1t ah - : ti hs) Tapa CHAPTER XXI. AGRICULTURAL RESOURCES: SOIL, VEGETATION, COSMICAL PHENOMENA. SEcTION I.—GENERAL REMARKS ON THE AGRICULTURAL CAPACITIES OF ARIZONA AND Nrw MEx1co; THE VALLEY OF THE R10 GRANDE, NEw MEXICO; SouTu- WESLERN NEw MExico; NORTHWESTERN NEW MEXICO; COUNTRY OF THE Moguis, ARIZONA; BOTTOM LANDS OF THE COLORADO CHIQUITO AND CHEVE- Lon’s Fork; THE MoGoLLon Musa; THE SAN FRaNcIsco Mountains; Bot- TOM LANDS OF THE R10 SAN PEDRO; PLAIN OF CAMP GRANT; BOTTOM LANDS OF THE RIO GILA, ARIZONA; GENERAL REMARKS ON THE RESULTS OF SOIL INVESTIGATIONS. SECTION II.—THE CLIMATE OF THE GILA VALLEY; OZONE REACTIONS OF THE AT- MOSPHERE; GEOGRAPHICAL DISTRIBUTION OF PLANTS; List OF PLANTS OF MEDICAL OR TECHNICAL USE; ANALYSES OF YUCCA BACCATA (SOAP WEED) ; OF AGAVE (MESCAL); AND OF EPHEDRA ANTISYPHILITICA. eC TLON: i. GENERAL REMARKS ON THE AGRICULTURAL CAPACITIES OF WEST- ERN NEW MEXICO AND EASTERN ARIZONA. The extent of agricultural lands in Western New Mexico and Eastern Arizona is not very considerable, by reason of scarcity of water-courses and deficiency of rain, on the one hand, and on the other, of the rocky, irregular character of the country. A large part of this irregular region, however, is suitable for stock-raising, but a portion, at least, appears doomed, ‘until a change of climate effects an abundant rain-fall. The sections suitable for farming are situated either on the Plateau region at an altitude of more,than 6,800 feet, or along the river and creek bottoms. Many of these streams, however, are of but little use for agricultural purposes, being partially or wholly inclosed in deep caftons or flowing through rocky and mountainous regions, termed in New Mexico “mal pais,” the “ mawvaises terres” of the Northwest. Among themare White Mountain Creek, Salt Creek, Rio San Carlos, and Rio Bonito, tributaries of the Gila in Arizona, and Rio de las Animas, and Rio de las Palomas, in New Mexico. The Rio Francisco, in Arizona, is flanked here and there by small strips of arable lands, compris- 573 574 GEOLOGY. ing a few acres. The river, however, is chiefly inclosed in a cation. The Rio Gila, Rio San Pedro, Colorado Chiquito, Chevelon’s Fork, in Arizona and the Rio del Cuchilla Negra, Rio Mimbres, and Rio Alamosa, in New Mexico, are bordered by larger belts of good bottom lands. A number of Mexicans have settled on the Rio Mimbres and Rio Alamosa. Several rivers and creeks, on reaching the lowlands, sink or run dry during the sum- mer season, among which are the Rio Puerco of the West, Rio Puerco of the East, Rio Galisteo, and the Pojoaque. The Rio de Santa Fé and Rio Tesuque are small bodies of water capable of supporting but very limited areas by irrigation. I have not seen the San Juan or Zuni streams, nor Lithodendron Creek, nor the head of the Gila, in New Mexico. The region about these streams is said to be suitable for agricultural and pastoral pursuits. The White Mountain district, in Arizona, was not visited by our division, (No. 2.) Since a report on agricultural lands is not at the present day complete, if unaccompanied by the results of investigations of the respective soils, good average specimens were collected from all the agricultural sections visited, being taken from a depth of one foot, and preserved in sealed bottles or well closed tin boxes. THE VALLEY OF THE RIO GRANDE DEL NORTE. The bottom lands of this river, which has not unjustly been compared by some writers to the Nile of Egypt, undoubtedly form the best portion of New Mexico in an agricultural point of view. Four-fifths of the population of New Mexico live upon the banks of the Rio Grande. These settlements are traversed by acequias, large irrigating ditches, averaging two feet in depth and three in width. The water of the river carries with it large quantities of a reddish-gray matter, which settles when the water is left in repose for several hours, and supplies the only fertilizer used, the soil yielding fruits, grain, and farm-produce of every description in abun- dance, notwithstanding it has been under cultivation for over two hundred and fifty years. Here onions weighing over two pounds, cabbages of sixty pounds, turnips of enormous size, peas, watermelons, squashes, beans, Indiar AGRICULTURAL CAPACITIES OF ARIZONA AND NEW MEXICO. 575 corn, and figs, are grown in great profusion. ‘These bottom lands appear well adapted to grape-growing, and already the El Paso wine has gained a great reputation. It was currently reported that, although every effort had been made to raise potatoes in this region, none had been grown; the cause, however, was ascertained to be carelessness on the part of the Mexi- cans, who neither hoe the ground sufficiently nor remove the numerous caterpillars from the herbage. Careful Americans have succeeded in raising potatoes of fine quality. Notwithstanding the excellent properties of these lands, one would be disappointed who here expected to find a paradise; since this bottom, in average two miles wide, shows upon the mesas embracing it hardly a sign of vegetation, save sage-brush. Wherever water does not border the soil, or is not carried there by ditches, there even grass is absent; vegeta- tion being defeated by scarcity of rains and the sandy, porous nature of the soil. Well-watered ground and a perpetually dry atmosphere form a union of circumstances exceedingly favorable for splendid development of crops of all kinds. This fact can be observed not only in New Mexico along the valleys of the water-courses, but also in Colorado, where by means of irriga- tion the most abundant crops are developed. Here, in 1872, three times as much corn was raised to ‘the acre than in neighboring Kansas, where a moist atmosphere and occasional rains do not necessitate irrigation. The splendid growth of firs and pines, above an altitude of 7,000 feet, in New Mexico, may be attributed to the above-mentioned fact; the soil contains sufficient moisture for the trees, while the air is mostly dry and the sky seldom covered with clouds. Thus the reduction of carbonic acid is rarely retarded by absence of direct sunlight, the circulation of the sap is greatly increased by the more rapid evaporation from the leaves, and all moisture necessary for the body of the tree is supplied by the roots. With reference to the water of the Rio Grande, a chemical investiga- tion appeared of great importance, since, if it could be proved that the virtues ascribed to it existed, many hundreds of thousands of acres now lying bar- ren near the banks of the river could be profitably converted into the best farming lands. For instance, just west of Fort Craig theré is a wide level plain, which would afford 5,000 acres of good farming land could the water of the Rio Grande be carried to its level by being lifted about 100 feet. 576 GEOLOGY. The analysis of the water naturally divides itself into two parts, viz: (1.) Of the matters in solution. (2.) Of the matters in suspension. During our stay at Fort Craig, six gallons of this water were evaporated and half a pound of the sediment from the river-shore was brought away for analysis. In order to a more concise idea of the composition of the dis- solved matters, the analysis of the Rio Grande water is here placed along- side that of the water of the Isar—a stream of Southern Bavaria, possessing no fertilizing properties. In 1,000 parts of water are contained: Constituent. Rio Grande del Norte. River Isar. Ghloride/ofsodinmpesse see == aes ae ae eee 0. 05938 0. 00163 SI Dual Of SOH8 . sees anal = ae eee eee eee 0. 02736 0. 00569 Sllplate Of potasSae ees n= nee es ee eee ere een eae 0. 00140 0, 00982 STUNG) NT en Eo one ona-spsco gore Sanbes seco oneeenctee 0. 03928 0, 01788 Garbonate‘of dime fo -- 5-2 ee se eclesne eee ee Saeecaesee eee 0. O1195 0. 07830 Carbonate lofimarnesia ten oa. aaa eee se acae eee eee eae 0. 00431 0. 01574 @arbonateof Soda o.escicnae eee atte a ee ee ieee Trace. < 2225. conn. eee PHOSPHO WC) ACO hace sneer ae eet eae Wery famt trate ——----=|2eo eee eee Dilicie dcid .. 52 oo. Seen ne cawacs ance ease cu asee anes seeneeeyan ee SACRE pea eee ee Traces. INITIOMCIG S22 2 cia Pusu np aot Adee ear Goonies aan cage 0.072 @arbomateroty MMe pees torsion ole = = wie ye pair lofage =e ioie fo lee == wre lnimte tol =i= 2.970 (lime =1.665) Hos phonicracl@ees asets-yato= alot onl = cise ele sinle le’ Mee Sora Se 0.031 Soda... ee er ee aac 2 ren 2s oss traces Alumina ..... Oko) Gy TRON. Specks sbeedounepeod DouooDeU eo ooubecoeee ObCdc 2.327 Magnesia. .... Total extract by hydrochloric acid = 5.40 per cent. Insoluble = 94.60 per cent. THE BOTTOM LANDS OF THE COLORADO CHIQUITO AND CHEVELON’S FORK. The bottom lands of the Colorado Chiquito are barren in the extreme, with but little grass, some grease-wood and sage-brush to relieve the monotony of the dreary landscape. . The condition of the valley of Cheve- lon’s Fork is somewhat better, cedar and grass being abundant, yet these bottom lands present nothing attractive or inviting. There is no doubt, however, as to the fertility of these areas, since a most vigorous vegetation may be seen along the margin of the river. The shores of both rivers are fringed with trees of various kinds, and also tall grasses in a flourishing state. Chevelon’s Fork has never run dry within the memory of the whites. It is 2 to 4 feet deep, about 18 feet wide, and abounds in otter, beaver, tur- tle, and fish. The Colorado Chiquito, however, is dry every summer thirty miles below Sunset Crossing—the intersection of the road from Fort Win- - gate to Prescott. The altitude of this locality is 8,700 feet above sea level. These bottom lands are not inclosed by high mountain ranges, as are those on the Gila. Here the country is mostly a wide plain with occasional low hills, hence the temperature does not fall during the night as low as on the Gila. During our stay from August 8 to August 13, the temperature ranged as follows: At sunrise, 62° to 64° F.; at 2 p. m., 82° to 85°.5 F.; at sunset, 71° to 75° F. During three days it rained twice. Before the rainy season sets in the temperature will probably reach 95° or 100° during the atter- noon. Cedar grows within eighteen and pine within seventy-five miles in a westerly direction. There is, however, an abundance of cottonwood along the margins of the river for local wants. The water of the Colorado Chiquito contains a little gypsum, the taste of which could be easily removed by “filtering through sand. 586 GEOLOGY. With regard to Chevelon’s Fork it may be mentioned that the river was visited at three points; at its mouth, thirty miles above, and at its head. Near its mouth the altitude of the country is about 4,000 feet, the land somewhat broken and irregular, but on its upper course where it traverses a region of from 4,600 to 5,200 feet in altitude are many flats suitable for farms. The head of this tributary of the Colorado Chiquito is situated on the southern extension of the forest-clad Mogollon Mesa. From the crossing of the Camp Apache road up to the pine region, some thirty miles, the country is excellently adapted for grazing purposes. Although this soil is sometimes rocky, sometimes coarse, and but a few inches deep, itis covered with a fine growth of grama grass. In this region the sandstone is super- seded by basalt. A specimen of the soil of the bottom lands of Chevelon’s Fork at the crossing of the Apache road was taken for analysis. It had a reddish color and was devoid of humus, and was derived from sandstone, (Triassic.) The locality was covered with juniper and some grass. Re- action neutral. It consisted of : . . : Per cent. CE eae emnn Mae: Pomme ens Sy reco a spam asticcce asso coes- 53.10 SS UE oan oe ae conarce danmdcebe aSotondc oobochorign Sadsscasse- Sis: 43,55 Eby ELOSCOPICAMOIRGURG fete ala ee eis eet ele otal ele ale ale fei ale ania hel eee eee 1.89 Chemically-bound water and trace organic matter ...........--...-.-.--..--- 1.46 On treatment with hydrochloric acid was obtained: Per cent. POtASSa) x2 cbs, isto = Oo i tea ie Sine ace ee etre otal ae aa ee eS eect 0.092 S008 q. nno- ceccls cite sam gab nos nde cle opine sigs aise Sap Ea eee eer 0.010 IU tr eee Seer OSS Oar eo.cGed Shdcbe Goomra cats Sok ac aNSSRASoSs - 0,319 Phosphoric acid 22% .% 2 ccc seele ete piel a aster (oetetetetetatala/olelnieletelateielette hai er 0.070 Sulphurie acid . « 24 Gen nwee . eee vs py lett. Saeed 8. Mii. at a Ree veces 2.559 Oxide of iron .. 5 Insoluble in hydrochloric acid, (chiefly quartz sand) ..--.....-..----..+-----: 93.55 With proper irrigation this soil would suit for crops of every variety. In view of the wide extension of the plateau of the Mogollon Mesa, south and west, it is highly probable that on sinking wells water would be found at a moderate depth in the valley. AGRICULTURAL CAPACITIES OF ARIZONA AND NEW MEXICO. 587 THE MOGOLLON MESA: This timber-covered plateau extends from the vicinity of Camp Apache in a northwesterly direction to the vicinity of the southern extension of the San Francisco Mountains, and is of an average width of ten to fifteen miles and an altitude of 7,000 feet. It was the source of former grand rivers as testified by cations of gigantic dimensions. The cation of the Big Dry Fork, for instance, is over seventy miles in length, and from 200 to 400 feet in depth; the walls are principally sandstone, with here and there limestone, and descend in terraces, sometimes, however, quite vertically. Around the small ponds or little rills on the bottom of this remarkable cafon an extra- ordinary vegetable life has been developed. Nothing of the cafion is noticed until one stands on the very margin where a pathway to the other side is looked for in vain. It was a tributary of the Colorado Chiquito. Its head at the present time is formed by. a small creek that sinks when it reaches the juniper region. Numerous creeks head in this plateau, among them Chevelon’s Fork, Cedar Creek, andCarrizoCreek. The Tonto Basin, a deep depression, borders this plateau on its south side. The carboniferous strata predominate, but the southern extension is covered by basaltic eruptions. Here are many forest meadows and fine valleys suitable for farming and stock-raising. From August 16th to the 20th the average temperature at sunrise was 54° F.; at2 p.m.,76°; at sunset, 63°. Although this climate may be unfavorable for raising Indian corn, the hardier vegetables would grow with ease. A specimen of the soil was obtained from a grassy meadow cov- ered with luxuriant vegetation and bordered by gigantic pines in the vicinity of Big Dry Fork. Its analysis resulted as follows: Physical condition : Color, dark; consistency, loose. Per cent. Sandler ere. era Ss ,0.2 SN 6 seg ie ctteeatretlae Sena ve vesuoat Sacets a /arai€ ajate whales alaiers siete 42.20 STU TIG! CER So AES See ae ee tere SS AUR ne een ate nee ye ees ee ee 37.98 ERVETOSGO PICMNOINOUTOH =n. scee ates ott tae seem siecle shoe e teins cincinnees one 10.97 Humus and chemically-bound water .......--- 2. 2.22 ee cees cee e cece eases 8.84 Chemical constituents : WBOUASSAimea tee se Seite ta « = ioe Be OREO OS ee eS SO SOC DOSS CSN CSTE 0.115 Soda... pee Bo Goethe) OSG GUOQO CO ROGOT Pe GADOMC OE SM OGD CChH So Be DOORS a OnEe traces NOME Sager air roetteieya ¢ e:bia's(e.4,0 2 Sie Sats aca S biad watemie saleleneree sete vs as east .< Sh 0.028 588 GEOLOGY. Per cent. VM. occ nc enc n cence emncn seennn hwacns nen wstninisie\- "envio wis \aje rmie'= wpemisinwiia =e 0.153 Phosphoric acid... ....-.- veceee oe ee cece eee cece ee cece e ent cee ee cen ene n ee 0.058 Oxide of iron... Alumina .-...--- phi WR Aen Shh oto dae ano oo aScp Geisanoo not tone noeedaces 2.013 Sulphuric acid. . Total, soluble in hydrochloric acid, water included ............--..... 22.188 IME MMOL Eb HAM LOES PE Sao aa 55 snodesase 8 Senn oon > FbecS=sSe5e5aq oon 77.812 100.000 Not considering the rather small amount of lime, this composition cor- responds to a fair average soil. The rock from which this soil is derived is a red sandstone. The par- ticles of quartz are cemented by ferruginous clay. On analysis, the rock gave 0.007 per cent. of phosphoric acid probably present in the cementing clay as phosphate of iron. As shown by the above results, the soil made up from this sandstone contains over eight times more phosphoric acid than the original rock; the clay and silt are also considerably increased. The latter fact is due to the action of the water in floating the lighter particles of the crumbling rock farther than the coarser ones. The increase of phos- phoric acid and potassa is, however, proportionately greater than the in- crease of silt and clay, which is due to the extraction from the depths of these nutritive materials by the penetrating roots of the trees, providing the leaves, by capillary attraction, with these substances; upon the decay of the leaves these mineral substances remain to enrich the surface-soil for sub- sequent vegetation. THE REGION OF THE SAN FRANCISCO MOUNTAINS. This is a well timbered region, in the heart of Arizona, of an average altitude of 7,000 feet, some peaks being over 10,000 feet high. The pre- dominating rock is basalt; here and there the strata of underlying lime- stone (Carboniferous) are exposed for some distance. On the way from: the Dog Buttes, via the Cosnino Caves, Flat Top Mountain, to Rancheria Springs, we crossed a number of little valleys and open glades, splendidly suited for farming homes, here and there encountering springs and fine grass. The climate is very moderate and is similar to that of the Mogollon mesa. The specimen of soil collected was from a small valley in the vicinity AGRICULTURAL CAPACITIES OF ARIZONA AND NEW MEXICO. 589 of Point Lookout and Rancheria Springs, about six miles north from the road to Prescott. Like many other valleys we had passed in this region, it was covered with a luxuriant growth. It being the rainy season at the time of our visit, much importance cannot be given to the amount of hygro- scopic moisture found in the specimens. Physical condition : Color, black; texture, loose ; reaction, neutral. (Cima ylenGlepnilSS Ssonsosce so sour conse mesos ee Hae ear de ier ee ITS 15.95 Pita Rillipas Sac coq eo bobo uae a GOnSC SE OO OU DOD a SOs oo O Renter so eCe cm rane 62.97 Hygroscopic moisture .....----.---- ------- oREOD eer si= eases saoeiainie se espsioets 12.83 Chemically-bound water and humus .........---------------+ 22-00 ---+---- 8.25 Chemical constituents : DP LASN aes eee er etter s clots Soeisecem seek Ss seleleecicete © esos sc a--- 0.130 Sodanwithe trace otwlitiiae ss ses oerstoese arses alm = aimee wine «iste lai elation = 0.017 ING cand be Sods na do TSU ORO Oot HOM OCROUIS COC AES EOC rice ame nema rm conmaic sic 0.684 Magnesia.. --.- shina rs 225 ROE R Ae enor ae ener aE traces Phosphoric acid. .--...- 2.2... -- 0-0 e ee cece cee cence cee ee tenet cece nese 0.284 Alumina ..--~ : ; zs etaise aon boy GiihS to de pau ace, bOCUne On toro SO nrocS come Oe ase arsic tr ate 9.720 ‘Insoluble in hydrochloric acid, basaltic particles and some humus --.---.------- 71.09 This soil is comparatively very rich in phosphoric acid, and therefore most excellent for grain and corn; for beans, peas, and lentils an addition of gypsum would be an improvement, these requiring more sulphur. Gyp- sum is found some thirty miles east, at the Sunset Gap mesas. THE BOTTOM-LANDS OF THE SAN PEDRO RIVER. The Rio San Pedro, in Southern Arizona, tributary of the Gila, which rises in the mountains of Sonora some thirty miles south of the boundary- line of Mexico, is flanked by broad belts of bottom-lands capable of nriga- tion. The river is on an average 12 feet wide and 2 feet deep. Several small settlements are found along its margins, among them San Pedro and Santa Catalina, two stations of the Southern Overland Mail Route. Below Santa Catalina, the river traverses a wide valley flanked on the west by the Sierra de Santa Catalina, and on the east by the Caliuro Mountains. A good deal of timber exists in this valley, principally mesquite and juniper; it is well grassed over. According to Leopold de Beau, a settler of Santa Catarina since 1857, the river never fails at that place; but during the last 590 GEOLOGY. fifteen years ran dry twice twelve miles below. We are indebted to this gentleman for valuable information with regard to farming in this region. He informed us that the soil here yielded, per acre, 2,000 pounds of corn, valued at 3 cents per pound; 2,200 pounds of barley, valued at 3 cents per pound; 3,000 pounds of wheat, valued at 34 cents per pound; 8,000 pounds of potatoes, valued at 10 cents per pound, the last mentioned being 7 cents near the close of the season. From this it will be seen that un- usually high prices for farm produce rule in Southern Arizona. But if we take into consideration the occasional Indian depredations, the annual dam- age by large flocks of blackbirds in spoiling one-third of the crops, and the absenee of competition, this condition of things may be easily accounted for. But little damage has been experienced from grasshoppers; bugs and worms, however, do great harm to beans and potatoes. Watermelons and beans are often killed by “rust.” The planting of corn is done in the mid- dle of April, and by the beginning of October the crops are ripe. Manure has never been used by Mr. Leopold de Beau. The chief market is Tucson, forty miles to the westward. With regard to the climate, the gentleman in question remarked that there had been no snow during the last six years; late frosts, however, have been experienced on several occasions, and as late as May 29 the past year, necessitating replanting of the corn. It has heretofore been impossible to raise cattle on account of Indian depredations; the Indians, however, are now nearly all on reservations. Irrigation is carried on once in twelve days. There are over 5,000 acres of land in the immediate vicinity of the settle- ment that could be brought under cultivation. Similar information was obtained at San Pedro, ten miles above. The soil of these settlements is derived from the detritus of the Catalina and Caliuromountains. On the former are encountered granite and Carboniferous limestones ; on the latter rhyolite, basalt, and volcanic tufa. The soil is a reddish-gray color, of fine grain, neither heavy nor clayey, and of a weak alkaline reaction. Physical condition : Sands ..55..S.5.hat Acie bre ig noeemaiege ede yn ee ne Rear ate eaten o:a'e | lle s Aa cl a 14.00 Silt, with littloiclay,.< 2.2. a rs) a | a ro Ss) ow Predominating rock......... .....| Granite .! Rhyolite.| Sand-|Sand- Sand-| Basalt.| Granite and | Granite .) Basalt and stone.| stone.) stone. rhyolite. thyolite. STNG: cere miscues cto cece veicnneci'e 32.14 87-97 | 72-04 | 53-10 | 42.20 | 15.95 14.00 (SheZan 4 baneeodaan Silt, with some clay............. 58.09 12.05 | 27.96 | 43-55 | 37-98 | 62.97 75-40 34.07 92.26 LG) SS 5 Sponecidaprarcsuscans 0.184 0.074 | 0.072] 0.092! 0.115 | 0.130 0.401 0.131 0.242 SECS JARS GS ngOUDE COC EDO peneBbS 0.012 o.ort | Traces} o.or0 | Trace.| 0.017 0.051 0.014 0.039 LIME ...... eee c cece eee eeeeeeceeee 3-169 0.152 | 1.665] 0.319 | 0.153 | 0.684 4-356 1.998 1.798 Magnesia cin cccccscescs ses cscees 0.214 | Trace... | ©.0a9 | Trace. I.019 9.203 0.570 Becr TT|f ene] om lft A lhl) seas] ea) ast noe Phosphoric acid ............--+- 0.101 0.029 | 0.031 | 0.070] 0.058 | 0.284 0.213 0.095 0.214 Sulphuric acid.................. 0.002 | Trace...| Trace.| Trace.| Trace.| Trace.| Trace....... o.oro | Traces.. Hygroscopic water ............. 5-20" 1.351 | 2.221 | 1.89 | 10.97 | 12.83 6.09 2.80 4.98 Chemically-bound water and 4.56 3-633 | x.529| 1-46 8.84 8.25 4.51 1.93 2.76 organic matter. , 2 insoluble in hydrochloric acid...| 79.90 02.15 94-60 | 93-55 | 77-8 | 71-09 71.10 87.52 84.85 598 GEOLOGY. SECTION II. CLIMATE OF THE GILA VALLEY; OZONE TESTS IN NEW MEXICO AND ARIZONA; GEOGRAPHICAL DISTRIBUTIONS OF PLANTS; LIST OF PLANTS OF MEDICAL AND TECHNICAL USE. THE CLIMATE OF THE GILA VALLEY. In this valley several noteworthy peculiarities of climate may be ob- served which are equally true as regards other regions of a similar character and of dry climate. Our party was twice in the Gila Valley, crossing the Gila River the first time at the San Carlos reservation, leaving the valley in the vicinity of old Fort Goodwin. The second visit was on our return, when we crossed the Gila near the mouth of the Rio Francisco, (a tributary.) We remained in the valley three days. The differences of temperature per diem were very great, on several occasions amounting to 60°; while in August and the beginning of September the daily temperature ranges from 50° at sun- rise to 105° F. at 2 p.m. In the beginning of October it ranges from 30° to 90°, and at the close of this month from 15° to 60° F. The hygrometer generally, the rainy season—July and August—ex- cepted, indicates a great degree of dryness of the atmosphere, and the wind, if any, blows generally from the southeast. Thus, with only rare excep- tions, the temperature of a number of consecutive days is found to be the same at the same hours. But little inconvenience is experienced by this great change of 60° in temperature, since dry air is a poorer conductor of heat than humid air. Such extremes in an atmosphere charged with humidity would doubtless be very sensibly felt and prove injurious to health. Humboldt tells us that in Cumana, where the air is always charged to its utmost capacity with aqueous vapor, the sinking of the temperature for but 5° Celsius (9° F.) causes a feeling akin to that produced by frosty weather. The great differences observed in a dry climate compared with a humid one are partially due to the differences of the calorific capacity of air and aqueous vapor, and partially to the barrenness of these mountain-ranges which do not reach the altitude of timber-growth. A barren spot when exposed to the sun naturally becomes hotter than a spot covered with vegetation. A humid CLIMATE OF THE GILA VALLEY. 599 atmosphere, on the contrary, will rise comparatively slowly in temperature during the morning hours; the dew on the ground will absorb the calorific rays of the sun until it has assumed the gaseous state, while during the night the rapid falling of the temperature is to a certain degree retarded upon reaching the dew-point. Thus water prevents the extremes that would otherwise occur. But all these considerations, true as they are, are still insufficient to explain peculiarities observed in the Gila Valley. The Gila River, for in- stance, at sunrise has a lower temperature (57°.5 F., on the 16th of October) — than the Rio Francisco, a tributary, (63° F.) The Gila River for the most part flows through a depression from five to ten miles in width, bordered by ~ continuous mountains-chains, while the Rio Francisco courses through the rocky slopes of the Gila Range. In the Gila Valley, at sunrise on the 17th October, the temperature was 28°F. while at the base of the mountain-range, about ten miles off, itwas40° F. On the 18th October, when again encamped in the Gila Valley, about fifteen miles above the former camp, the temperature at sunrise was as low as 14° F,, yet no change of wind or of any other atmospheric condition had occurred; there was only a change of locality, the contour of the valley being triflingly different, while the barren mountain-chains inclosing it appeared somewhat higher. On the 19th of October we were encamped on a wide plain adjoining the Gila Valley where it leaves New Mexico and, bending to the westward, enters Arizona. The atmospheric conditions with regard to wind and moisture were the same as before, but the temperature was as high as 40° at sunrise—a great contrast with the previous day. On the 20th October we camped on the foot of the western slopes of the Burro Mountains, where the temperature was even 2° higher than that of the day previous. Still the altitudes had been steadily increasing during the march, as will be seen by. the following table: Temperature. Date. 4 Altitude. At sunrise. | At sunset. Feet. le = q Mctolerir Sees ee eee etaciae eo le tint asin ane cele pee vane e eee tenes 4, 500 14 53 October 19 -.----- ---- 2-2-2 enn nee ee eee eee cet eee cee eens 5, 200 40 56 Olotoentic epee see Sere ae ots a= Se ok dasa be eee eee toner 6, 100 42 57 600 GEOLOGY, From this it will be seen that although not differing essentially at sun- set, the temperatures present a marked contrast.during the night. This fact is characteristic of a dry climate. In a valley inclosed by mountain ranges or Via. 170,—Ideal sketch of air-currents in interior mountain valleys. chains, the night temperature will sink lowest where the depression is greatest. This may be easily understood when it is recol- lected that the surface of the barren mountains heated by the sun’s rays must in cooling off during the night necessa- rily produce a motion of the atmosphere from the strata of the upper regions down to the greatest depression, as here illustrated : Thus the point a will be the coolest place, and b the warmest; the descending cur- rent having arrived at a, in proceeding to b, takes up the heat of the ground. Imme- diately after sundown a cur- rent sets in from the mount- ains toward the valley, caused by the sudden contraction of the air of the latter region, which is naturally hotter dur- ing the day than the air of the mountain; but about two hours after sunset a reverse current takes plaee as above illustrated. The cooling-off of a wide plain during the night evidently takes place under different circumstances. The air ascending from the warm ground meets resistance in the descending cool CLIMATE OF THE GILA VALLEY. 601 air, and while a slow mingling thus takes place the falling of the tempera- ture will be retarded. The loss by radiation is insignificant compared with the loss by atmospheric circulation. Another instance of the considerable falling of temperature in valleys was observed at Eureka Springs, the greatest depression of the valley adjoining the western slopes of Mount Graham in Arizona. Here the temperature, at sunrise on the 22d of Sep- tember, was 44° F., while at Camp Grant, twelve miles east, and immedi- ately at the foot of Mount Graham, it was 53°F. The altitude of Camp Grant is 5,400 feet, while that of Eureka Springs is but 4,900. We have therefore a lower night temperature notwithstanding the lesser altitude. Recognition of the above elucidated law may prove of value in estab- lishing farms in the dry regions of the West. Many plants growing along the slopes of a mountain-chain will not thrive in the adjoining valley, a marked example being the Giant Cactus, (Cereus giganteus.) This plant cannot bear a very low temperature. It can easily be understood why in other climates the temperature, ceteris paribus, does not, in basins surrounded by mountain-chains, sink as low during the night as in the dry regions; the falling dew would counter- _act the upward movement of the air along the mountain sides; moreover, a country well covered with trees and grass does not admit as free circula- tion of the air as do the bare, rocky slopes of mountains. OZONE TESTS IN NEW MEXICO AND ARIZONA. Few substances have for the past twenty years awakened such interest in the chemical world as ozone, particularly that of the atmosphere, to which many noted investigators have devoted special attention; indeed, the sub- ject has developed a voluminous literature. The air of forests and deserts, of mountains and valleys, of cities, mines, and factories, of healthy and sickly regions, of hot and cold, and of wet and dry seasons, have been subjected to careful tests; but the general conclusions. arrived at by different observers thus far do not perfectly agree. Among the latest contributions on this subject are communications from M. Eber- mayer, “On Atmospheric Ozone and Spread of Diseases,” (Moniteur Scien- tifique, October, 1873,) and one by Houzeau, (Chemical News, November, 602 GEOLOGY. 1873.) The latter concludes, as the results of his inquiries, that the chief cause of the production of ozone in the atmosphere is electricity. There is no doubt, however, that a certain portion is produced by the oxydation of vegetable matter. Ozone was found to act as a strong disinfectant by its energetic power of oxydation; hénce it was inferred by some authors that the atmospheric ozone could arrest infection by destroying the germs of ma- larious disease. But it must not be forgotten that the ozone operated within the laboratory was at least a thousand times more concentrated than that found in the atmosphere. Dr. Mitchell says: ‘No sound conclusions can be deduced from the comparison of the fluctuations of disease with ozone observations as at present made.” Dr. George Baird says: ‘‘ Summing up in a few words, we may say that atmospheric ozone is more abundant during the winter and spring, because in those seasons there is much rain, snow, hail, and wind, a low tempera- ture, and a maximum of electricity. In the summer and autumn, ozone is least abundant, because during these seasons there is no snow or hail, less wind and rain, high temperature, and a minimum of electricity.” Further, in relation to disease, he says: “A deficiency of ozone in the air prob- ably bears a certain relation to epidemic and chronic diseases. Deficiency of ozone invites disease, debilitating the system, and thus making it less capable of contending with morbid influences.” ” During our trip, numerous tests were made for ozone, from June to November, in various altitudes, of from 4,000 to 10,000 feet above sea-level, in well-timbered regions and in deserts, in healthy and unhealthy, or ma- larious places. The tests were made with papers impregnated with iodide of potassium-starch, which were freshly prepared for each test. The papers were generally exposed during the night; for tests during the day, they were well protected against the direct rays of the sun. The following conclusions were arrived at: (1.) There is no difference in the amount of ozone between healthy and malarious places. At old Fort Goodwin, a place noted for fever and ague, and abandoned on this account by the military authorities, ozone reactions of the same intensity were obtained September 15 as at Camp Apache Sep- tember 5, a place not affected by malaria. GEOGRAPHICAL DISTRIBUTION OF PLANTS. 603 (2.) The dryness and uniformity of the climate of New Mexico and Arizona are the cause of the insignificant changes in the quantity of ozone. Even in the barren region of the Painted Desert the usual intensity was observed. A moderately strong wind was blowing during the night of ob- servation. (3.) No marked differences could be observed between the intensities of the reactions of September, October, and November. (4.) A very marked increase of ozone was observed in the well-tim- bered plateau region of Valle Grande, June 30; in a small side-valley filled with the perfumes of flowering plants, Menthene and Terebene were particularly prominent. THE GEOGRAPHICAL DISTRIBUTION OF PLANTS: In a country where the altitudes are subject to repeated and great variations—where low bottom-lands continually alternate with plateau re- gions—a favorable occasion is presented for close study of the geographical distribution of plants. A botanical specialist, with the material derived from such a regiom, could produce a most interesting volume. The facts here presented as the results of observations during our trip, though mere outlines, may serve as a basis for further study of this interest- ing subject, which is undoubtedly of considerable value in an agricultural point of view. The regions of the Southwest may be divided into four distinct zones, (according to altitude :) (1.) Zone of Cactus, Yucca, and Agave; altitude, 3,000 to 3,500 feet; grass is scanty. Where there is water, a most luxuriant vegetation springs up. (2.) Zone of Obione and Artemisia, (Greasewood and Sage-brush;) altitude, 3,500 to 4,900 feet. Grass is poor, with few exceptions, on granitic and volcanic soil. The Cactus species are diminished in number. (3.) Zone of Juniperus occidentalis, (Cedar ;) altitude, 4,900 to 6,800 feet; Cactus species few. (4.) Zone of Pine and Fir, 6,800 to 10,800 feet, (highest points.) These limitations are subject, of course, to some variation through various local causes; they descend more on eastern and northern than on southern. and western slopes. Above 8,000 feet nightly dews fall. Thus a flora may 604 : GEOLOGY. exist in many respects resembling that of our eastern forests as well as of the forests of Central Europe. Below the pine regions the flora becomes more scanty, and assumes quite a distinct character, corresponding to the dry climate. Glancing at the flora of the pine region in Arizona and New Mexico, we find in the more elevated portions the Quaking Aspen, (Populus tremuloides,) a tree seldom occurring below 7,500 feet; the same may be said of the Fern, (Pferis aquilina.) Quercus alba (White Oak) accompanies the pine from 7,000 feet upward; it is not found, however, to any great extent, and is principally in small patches, or groves. 23 A peculiar species of juniper, r of tree-growth, is here and there met with at an altitude of 7,000 feet. Rubus ideaus and Ribes cy- nosbati (Raspberry and Goose berry) occur at the same height. We observed them, however, only at Point Lookout, in the San Fran- cisco Mountains. Cerasus (Wild Cherry) was not met with. Quite a number of species of pine and fir was encountered; the former pre- dominating, and occasionally so vigorously developed that branches ramify in a descending direction to such extent as to resemble a Fic. igi! Bpesinted of secondary tre etcelil Colorado widely diverging root. Sometimes Elateet a branch was seen converted into a secondary tree, with roots, trunks, and branches. Splendid forests of gigantic pines were traversed, wherein no young trees were noticed. At an altitude of 10,000 feet, in the Valle Grande, fifty to sixty miles west of ‘Santa Fé, the following-named plants and trees were observed: Viola canina ; Tormentilla erecta ; Gnaphalium sylvaticum ; Ceras- tium arvense ; Taraxacum dens-leonis ; Achillea millefolium ; Sambucus nigra ; Vicia ; Geranium ; Lithospermum. GEOGRAPHICAL DISTRIBUTION OF PLANTS. 605 At an altitude of 7,500 feet, in the San Francisco Mountains, we en- countered, in August, Solidago virga-aurea ; Linum perenne. On the Mogollon Mesa, in an altitude of 6,800 feet, were found, in August, Epilobium angustifolium ; Rosa; Myosotis palustris; Acer; Ra- nunculus acris ; Humulus luputus ; Brunella vulgaris ; Cherophyllum ; Allium ; Valeriana. ; , Of the cryptogams were noticed the genera Equisetum, Dicranum, Barbula, Usnea, Polytrichum, Mnium, Parmelia, Hypnum, Fontinalis, but never Sphagnum ; all efforts to find it proved futile. This moss is unable to live in absence of abundant water. The zone of Juniperus embraces that of the Pinon, (Pinus edulis,) which is found at an altitude of 5,700 to 6,800 feet. Scrub Oak and Live Oak, (Quercus acrifolia and Q. emoryi,) especially in Southern Arizona, are asso- ciated with the Juniper. Yucca baccata (Amole, or Soapweed) forms an essential part of the flora, and is the only Yucca of this zone. Here and there Opuntia arborescens occurs. Other plants, found occasionally here, are Achillea millefolium, Ephedra antisyphylitica, Solanum, Mentzelia albicaulis, Pectis angustifolia, Aplopappus. We find along creeks Epilobium montanum; Juglans nigra, (Black Walnut;) Humulus lupulus, (Hops;) Platanus occidentalis, (Sycamore ;) Populus monilifera, (Cottonwood;) Schrankia uncinata, &e. The latter plant was found but once, namely, at the head of Caton Diablo. Campanula rotundifolia was encountered only once in this zone, and then near a spring in the Navajo reservation, (July 26.) In the Pine region, however, it occurs at an altitude of 10,000 feet, near the summit of Mount Graham, (September 28.)° Thus this plant appears to range through wide altitudes. A peculiar Mistletoe vigorously vegetates upon the Juniper- bushes, often entirely covering them. The species of Cactus increase in number as we descend and become more numerous at an altitude of 3,000 to 4,000 feet. Opuntia bulbispina, O. grahami, O. emoryi, Cereus giganteus, Cereus stramineus, Echinocactus septispinus, and many others are limited to the 606 GEOLOGY. southern part of Arizona. The species of Yucca also there increase to six. Cereus giganteus can hardly be found above an altitude of 3,500 feet. This plant appears to depend also considerably upon the nature of the ground, inasmuch as it favors calcareous soil: The Mesquite-tree (Algaro-- bia) is found in three species, in altitudes of 3,000 to 4,500 feet, but rarely occurs north of the Gila, except in a low bush-like species. The Mesquite- tree, Cactus, and Yucca are the representatives of a dry and hot climate. . It is clearly shown by the structure of these plants that it is necessary they should by every means prevent the loss of water by evaporation from their surface. The leaves are either very small, (as in Mesquite, Stinkweed, Grease- wood,) or they are covered with a thick, dense layer, (as in Yucca, Agave,) or they have no leaves proper, the function of these being performed either by the trunk, as in Cactus, or by the branches, as in Ephedra. A further peculiarity is the large amount of mineral matter they have accumulated, which yields protection during long drought. Of the grasses, the grama-grasses Chondrosiwm and Bouteloua are the most important. They exist in altitudes of from 4,000 to 7,000 feet, and are partial to granitic, rhyolitic, and basaltic soil, avoiding that derived from limestone, clay, or sandstone. They are frequently accompanied by the mesquite-grass, (Sesleria dactyloides.) Beyond 7,000 feet, various other grasses occur. The peculiar growth of the grasses in ‘‘bunches” is characteristic. The cause is evidently this: the seeds of the grasses can rarely germinate on account of the dryness of the surface, coarseness of the soil, and absence of aqueous precipitates. Sweeping winds earry the finer particles away from the dry surface, leaving only the coarse ones. The grasses therefore mainly spread by their roots, thus causing the “bunch” growth. Hence a New Mexico prairie is in striking contrast to our eastern meadow, where the grass forms a net-work so dense as to render the surface of the ground invisible to the eye. Among other grasses may be mentioned Arundinaria, growing in swampy places, and the so-called Sacaton grass. Around salt-marshes, the peculiar Bryzo- pyrum spicatum is frequently found. PLANTS OF MEDICAL USE. 607 LIST OF PLANTS OF MEDICAL AND TECHNICAL USE. Numerous valuable plants are indigenous to Arizona and New Mexico, but more time would be required for a detailed study than a hasty trip through these Territories affords. We mention the following: Yucca baccata, (Amole, Soapweed, Spanish Bayonet.) This and related species form a conspicuous part in the flora of those Territories. Their pecu- liar leaves are provided with strong fibers well suited for rope, cloths, strong paper, &c. The roots, especially that of Yucca baccata, are used by the Mexicans and Indians as a substitute for soap, which is said to be excellent for cleansing woolen goods and hair, to which it imparts a peculiar glossy appearance. The pounded root is reduced to a pulp by adding water, when it is ready for use. The fruit of Yucca baccata is of excellent taste, resembling that of the Banana, but unfortunately the plant seldom flowers. Agave, next related to Agave decipiens—Maguey of the Mexicans, and Mescal of the Indians—The undeveloped leaves (or the ‘“heart”) of this plant are used as an article of food, and also in the manufacture of an alco- holic beverage. For further particulars see page 610. Arundinaria is a grass of 10 to 14 feet in height, of strong fiber, well suited for paper making. A specimen of paper-pulp was prepared from this fiber. It could easily be bleached by the application of a diluted solution of permanganate of potassa and sulphurous acid. Algarobia, the Mesquite-tree, occurs in three species in Southern Ari- zona. It furnishes a valuable gum, undistinguishable from genuine gum . Arabic. Algarobia glandulosa occurs in dense forests here and in Western Texas, the gum of which has constituted an article of commerce for some years past. The beans of the tree are rich in grape-sugar, containing as much as 30 per cent., and furnish a valuable food for cattle. The taste, though sweet, is disagreeable, which renders them undesirable as food for man. Indians of the Comanche tribe prepare an alcoholic beverage from the beans. The wood of the tree, which is dense and hard, is an excellent material for cabi- net-work. The charcoal prepared from it is unsurpassed for metallurgical and smelting purposes. 608 GEOLOGY. Opuntia—The fruit of this Cactus contains pectin, grape-sugar, and tartaric acid; it is an article of food for Indians as well as for bears. Pectis angustifolia—A small yellow Composite, growing in Cedar-woods, possesses an intense odor of essence of lemon. It may be worth while to experiment upon its cultivation, since the essence of lemon is a valuable article. Another and larger species of Pectis has a peculiar action on the salivary glands. Juniperus occurs in several species. In the vicinity of Santa Fé, a balsam is gathered from it by boring a hole into the lower part of the trunk, and is used in various urinary diseases. Mr. A. Krummeck, apothecary in Santa Fé, recommends the following formula: Balsam. junip., 1 dr.; alcohol, 1 0z.; manna, 2 drs.: dose, two drops three times a day. This gentleman asserts that this substance is far superior to Canada balsam. It is of strong aromatic odor, of light-yellow color, perfectly transparent, and imperfectly soluble in alcohol. It has also been found to be valuable in the preparation of varnish. Populus tremuloides—The bark of this tree is used by Indians as a rem- edy against feverandague. On analysis, populin and salicin, known constitu- ents of the Poplar family, were found. No trace of quinine could be detected; and the febrifugal properties are probably due to the salicin and populin. Ephedra antisyphilitica is used in form of a decoction against venereal diseases, which are said to be peculiarly wide-spread in these regions. Angelica, a peculiar species of the umbelliferous family, grows upon the Sierra Gorda, and furnishes a strongly aromatic root, used for weakness of the system. Mr. Krummeck considers this root more effectual than that of our eastern Angelica species. Among plants used for bathing purposes in rheumatic affections, the so-called Creosote-bush, Larrea Mexicana, (Stinkweed or Etiontio,) may be mentioned. The branches of this plant are often found covered with a red- brown exudate,* caused by an insect; the leaves are rich in a peculiar resin. The alcoholic extract of the leaves on evaporation yields a greenish- brown residue of a specific and somewhat disagreeable odor, more strongly perceptible on boiling the extract with water. This residue is only to a small extent soluble in water, and the solution has an acid reaction. It yields a *A red coloring-matter can be extracted showing all the reactions of cochineal. ANALYSES OF PLANTS. 609 light-yellow precipitate with acetate of lead. |The part of the alcoholic ex- tract that is insoluble in water is easily soluble in alkalies. It also dissolves in nitric acid: at a moderate heat, whereby oxydation takes place. On addition of water, a yellow, brittle mass is precipitated. For bathing purposes, an infusion of the leaves is made, which is said to be of excellent service. THE CHEMICAL CONSTITUENTS OF THE SOAPWEED. The root of Yucca baccata is used, as before mentioned, as a substitute for soap. The froth produced on shaking the pounded root with water resembles the foam of soap. The root is cylindrical, 2 to 3 inches thick, branching, and covered with a brown, brittle bark. The taste is at first sweet, afterward bitter and scratching. Ether extracts but little, consisting of resinous and fatty matter. The alcoholic extract of the root on cooling deposits a flocculent precipitate; on evaporation,.the filtrate leaves a resid- uum, containing, among other substances, sugar and resin. The aqueous extract of the root has an acid reaction and behaves as follows : Ammonia or potassa—no precipitate. Baryta water—flocculent precipitate. Acetate of lead—precipitate insoluble in excess. Fehling’s copper solution—red precipitate on boiling. The reaction is much stronger after boiling with dilute acids. Chloride of iron—greenish coloration. About a pound of the root was cut into small pieces and. extracted with warm water; the extract was evaporated to a sirupy liquid, and this treated with alcohol. One part remained insoluble—chiefly gum—while another was dissolved, consisting partially of grape and cane sugar. The alcohol was distilled off, the resi- due dissolved in water, and precipitated with neutral acetate of lead; the precipitate filtered off, washed, and decomposed by a current of sulphureted hydrogen filtered and evaporated ; thus a body was obtained easily soluble in water, less in strong alcohol, of burning, scratching, bitter taste. On shaking, the aqueous solution produces a voluminous foam; it has an acid reaction, and gives a precipitate with baryta water, insoluble in excess of it. 39 Ws 610 GEOLOGY. All this agrees with the qualities of saponin, a substance contained in many other plants, as Agrostemma githago, Silene inflata, and Polygala senega. The property of the Yucca root, to produce froth on agitation with water, is therefore due to the presence of saponin, and the cleansing of goods may mainly be attributed to the froth. THE MESCAL. 7 In Southern Arizona, some parts of Utah and New Mexico, a peculiar species of Agave occurs, (most related to Agave decipiens,) called Maguey or Mescal, which is used by Indians as an article of food. The undevel- oped leaves, folded one into another like a bud, are perfectly white and soft as long as they remain protected against the sunlight by the exterior leaves. They are of a slightly sweet taste at first; afterward, somewhat biting. These leaves, the so-called ‘‘heart” of the plant, assume a very sweet taste, which is, at the same time, somewhat sour when exposed to heat for several hours, when it becomes sufficiently soft to enable the fibrous parts to be easily removed. No peculiar smell is perceptible. In such localities where the plant grows abundantly, stone-hearths have been erected, upon which the Mescal is subjected to roasting; the charcoal fire is kept up about six hours. A large hearth of about five feet in diameter was seen by us on the south side of Mount Turnbull, in Southern Arizona. On trying the experi- ment of roasting the Mescal myself, I was somewhat surprised by the thor- ough change that took place,-and endeavored in vain to trace such a beha- vior to a known substance. We are aware that starch will yield sugar on being boiled with diluted sulphuric or muriatic acid; or, also, on being digested at 60° with diastase. We know, also, that there are many gluco- sids that are split up, on treatment with mineral -acids, into sugar and various other compounds. But with the Mescal the case is different, the sugar being formed without aid from mineral acids. There is no starch present in the plant; iodine does not reveal even a trace of it; neither is there present any known isomer of starch, as inulin or lichenin. I was therefore led to the conclusion that we have either a new isomer of starch, or a new glucosid before us, and took a sufficient amount of the raw, dried . material for investigation. If the finely-pulverized Mescal be treated with “ANALYSES OF PLANTS. 611 alcohol to remove the trace of adhering sugar, the substance, upon boiling with water for a few minutes, yields grape-sugar in abundance; this also takes place on treatment with a large quantity of cold water, and it appears to be an impossibility to separate the new substance from the cellular tissue without simultaneous formation of grape-sugar ; all attempts to this end were in vain. If the substance was a glucosid, another product besides grape- sugar would be formed in the decomposition; and if this product could be isolated, the nature of the original compound in the Mescal would be revealed, inasmuch as it represents a glucosid of this secondary product. Such a sub- stance was, indeed, found; it is contained in solution, together with sugar, when Mescal is boiled with water; it yields a precipitate with neutral acetate of lead. This precipitate, after being well washed, was decomposed by sul- phureted hydrogen, and the filtrate from the sulphide of lead evaporated. Thus an acid was obtained of an agreeable taste, easily soluble in alcohol and water. A close examination proved it to be Citric acid, easily recognized by the peculiar behavior of. the lime-salt, which is more soluble in cold than in hot water. Oxalic, succinic, malic, aconitic, and fumaric acids were absent; tartaric acid was present in small quantities. The nature of the original substance is thus revealed, and proves to be a glucosid of citric acid—a compound heretofore neither found in nature nor prepared artifi- cially in the laboratory. This glucosid forms an exception to the usual behavior of this class of bodies, as water alone can bring about its decom- position into grape-sugar and citric acid. The rational name for this com- bination is Citro-glucosid. INVESTIGATION OF EPHEDRA ANTISYPHILITICA. This plant, as above mentioned, is largely used by Mexicans as a remedy for venereal diseases, and it is claimed that it possesses all the virtues ascribed to it. Were this confirmed by our medical men of. experience, another step toward the knowledge of our medical herbs and shrubs would be made. With this view, chemical examination was made. The mineral constituents of the air-dried leaves amount to 5.58 per cent. The aqueous extract of the leaves has an acid reaction, and an astringent taste, resembling that of tannin. - Lime-water produces a greenish-black precipitate. 612 GEOLOGY. Chloride of iron produces a black precipitate. Acetate of lead produces a light-yellow precipitate. Basic acetate of lead produces an increased light-yellow precipitate. Fehling’s solution undergoes reduction. Preliminary experiments had convinced me that there was no body resembling an organic base or alkaloid present, and that the active principle, if any was present, was of either a neutral or an acid character. A large quantity of aqueous infusion was precipitated with basic ace- tate of lead, and the precipitate, after being well washed, decomposed by sulphureted hydrogen. The filtrate had an astringent and strongly sour taste: the former due to tannin; the latter to tartaric acid present in the plant. Besides these combinations, there is Pectin in the filtrate, as is indi- cated by the jelly-like precipitate produced by the addition of alcohol. The whole filtrate from the sulphide of lead was concentrated in the water-bath. In this operation an interesting phenomenon was observed, consisting in the separation of a dark-red, insoluble powder, the develop- ment of the characteristic odor of crude pyroligneous acid, and the forma- tion of glucose. This decomposition was no doubt due to the action of the tartaric acid upon the tannin. It is known, from recent investigations, that there are quite a number of bodies showing more or less the properties of “tannin ” formerly supposed to be one identical substance in many different plants, and that there are two distinct groups of tannins; the one yields green, the other blue and black precipitates with salts of oxide of iron. The latter are glucosids, furnishing sugar on treatment with acids and various other compounds, and, upon dry distillation, pyrogallic and carbonic acids, while the former yields, on dry distillation, pyrocatechin. The “tannin” of Ephedra antisyphilitica is evidently a glucosid; on treatment with acids, it splits up into sugar and the red amorphous powder above mentioned. I took this red powder at first to be “rufigallie acid,” but subsequent tests proved this opinion erroneous. It is not soluble in water and alcohol, easily in alkalies, yielding brown-black solutions. It is quite a distinct body, and I name it Lphedrin. The principle which in Ephedra antisyphilitica may prove of medical -action would be due to the peculiar kind of tannin it contains. CHAPTER XXTITf. ANALYSES OF MINERAL SPRINGS AND MINERALS. THE MINERAL SPRINGS OF OJOS CALIENTES AND SAN Isipro, N. Mrex.; THE HoT SPRINGS OF THE R10 SAN FRANCISCO, AR1Z.; THE MINERAL SPRINGS OF CANON Ciry AND MANITOU, COL0,.; PARNASSUS SPRINGS; WARM SULPHUR SPRINGS ON THE NAVAJO RIvVHR; CARLISLE SPRING; SPRINGS OF WAGONWHEEL GAP; Las VEGAS SPRINGS AND HOT SPRINGS OF ABIQUIU, N. MEX.; SPRING NEAR Rio Pasarito; PAGosA Hort SULPHUR SpRING, CoLo.; SALT FROM A SALT LAKE EAST OF THE SANDIA Mountain, N. MEx.; SAL’ EFFLORESCENCES FROM OJo DE Tao, N. MEx.; SUNSET CRossinc, SANTA CATARINA, AND CROTON SPRINGS, ARIZ.; INCRUSTATION FROM THE ALUM CAVE ON COOK’s PEAK, N. MEX., AND FROM COSONINO CAVES, ARIZ.; “ WHEELERITE,” A NEW FOSSIL RESIN; THE COALS OF NEw MEXIco anD CoLoRADO; COMPOSITION OF VARIOUS ORES FROM NEW MEXICO AND COLORADO; COMPOSITION OF KAOLIN FROM ARIZONA AND UTAH. THE MINERAL SPRINGS OF OJOS CALIENTES, NEW MEXICO. These far-famed springs of New Mexico are situated twelve miles above the town of Jemez, on the Jemez Creek, and are inclosed in a deep spacious cation. (See Plate XIII.) The slopes of the canton are formed by strata of limestone and sandstone of Carboniferous age, often changed from their original positions by protruding volcanic material. There are two distinct groups of warm springs in the valley, two miles apart. The springs of the lower group consist of: (1.) A geyser with a surface of 60 square feet, and an aperture of 1 square foot; the temperature is 168° F.; large quantities of escaping car- bonic acid keep the water in violent agitation; thick deposits of snow-white crusts are formed, consisting chiefly of carbonate of lime. This spring yields about fifty gallons of water per minute. (2.) One spring with a surface of 6 square feet and a temperature of 130° F.; it contains free carbonic acid and forms a red-brown deposit. (3.) Three springs, with a temperature of 119° F., covered with a vig- orous growth of a peculiar alga. Dr. Schaeffer, of the Army Medical Museum, 613 614 GEOLOGY. who kindly exainined a specimen of this vegetable scum of intense green color, pronounces it as filaments of Oscillatoria, 0.005 of an inch in thick- ness. Globular Gonidia were also found.* When this vegetable scum is left to stagnate in the small pools near the springs, a black deposit of sulphide of iron is formed. This is the result of the action of the sulphureted hydrogen upon the carbonate of iron in the water and the oxide of iron in the alga-plant. The sulphureted hydrogen is a product of the reduction of the gypsum contained in the water. (4.) One spring of 110° F. (5.) Two springs of 108° F. (6.) Several small springs of 94° to 102° F. The water of the geyser contained in 100 parts— Ohloride:of sodium. 2.52.9 s soe sateen poe cess selnesnt see sche ee ee eee 0.1622 Sulphate of soda. ss.0525eccac. space Sane ee + ge ele ee ee eee 0.0035 @arbonate‘of limes saa-2-e pease ote oee Se eeweiibcs Cosh bea eee 0.0641 @arbonate ol Magnesia seer ance = sees oleracea eee eee 0.0103 Potassac. 4 Sivas. 2. Benen aoe et eee oe eee i 11) Can A eee Ries iGo GA ah ae BOB.s iH eA Ioan rae Gia Silicie-acidgcsenscc eters 6 Es Bee at Oren oe me fen ne ey A ea eo aad ooo om 4 J p , ‘ j Tee it 4 A Tory | bifve Lite deep + ‘ _ arn ani) She pee ale AT Wis began NT a thet Oden) Mal") +)! yet Yoder ate helive ANALYSES OF MINERAL SPRINGS AND MINERALS. 617 THE MINERAL SPRINGS OF CANON CITY, COLORADO. A number of mineral springs exist in the vicinity of Canon City, Colo., which hitherto have not been chemically analyzed. As I had no oppor- tunity to visit the locality, Lieutenant Marshall, who explored this region, provided me with specimens of the waters through the kindness of Drs. O. B. Bryan and T. L. Prentiss, of Caton City. The springs are named Tron Duke, Big Ute, Little Ute, Aqua Vida, Congress, and Hot Spring. There is still another, called “Mills Sulphur Spring ;” the amount of its mineral salts, however, is exceedingly small. The analyses of the six springs above mentioned is given in the following table, from which it will be seen that the Congress and Hot Springs are inferior to the rest. All the springs contain, the same constituents, varying, however, in the proportion. Slight traces of iron, potassa, and lithia were detected. These waters, no doubt, possess valuable medicinal properties; the most effective constituent is evidently carbonate of soda. The waters are saturated with free car- bonic acid; the taste is very agreeable. * The mineral waters of Canon City, Colo. In 100 parts water. Mineral springs. Constituents. Iron Duke. | Little Ute. Big Ute. Aqua Vida. | Congress. | Hot Spring. Chloride of sodium .............+.05- 0.137236 0.195648 0.225810 0.207060 0.065221 0.030162 | Sluphate Of SOUR. -=--)| Skacesee-eeee | Traces. Lithium ..--.. ------ ---- <<< 650.2. -200- --25------------| Strong traces_| Strong traces.| Strong traces- STO Be ee ee ne ae ees BEn ect eses tees 1.04 Wraces—- == —2. 2.51 Total! solid constituents .. sc. esos seeesa-otoe serene eee 53.22 | 52. 10 62. 53 ' These springs are doubtless weaker than many other hot springs of New Mexico and Colorado. There is another, but a cool mineral spring, three miles northeast of Las Vegas and two miles east of Green’s ranch. It issues from the strata of Cretaceous limestone, and possesses a strong odor of sulphureted hydrogen. It showed the following composition : In one hundred thousand parts of water are parts as follows: Sedinum: carbonate: <: ac lac 08 Scns oxo Sater $a 5 Say" ta SRE eee 120.00 Calcium carbonate, <<...) <5+..6-nee ste ee ee ee Fp, RL A pee ‘ 13.75 Magnesium carbonate ....... .-.-- eA tan ta ener) a Sehr eS Sodtam! sulphate “7-2-2. o2 2 ccee Soe ee g tere coer eke ae 5.26 Sodium ehlonidews..2<«ossca4 nee eee PeeieS So Toktee et Cee eee 6.41 Silicie acid .........- one esgic eS Soke Wie eat reac ee i ee Trace. 145,42 Gases: Carbonic acid and hydrogen sulphide. HOT SPRINGS OF ABIQUIU, NEW MEXICO. Fifteen miles northwest of Abiquiu is the Mexican village Ojo Caliente, in the valley of the creek of the same name. One mile above the village four warm springs issue from the foot of a hill) While the surrounding region consists of sand-hills, and voleanic dykes, and mesas, the hill in ques- tion is composed of gneiss, through which run veins of a very coarse-grained ANALYSES OF MINERAL SPRINGS AND MINERALS. 625 eranite, the feldspar and quartz forming masses of several cubic feet, and the muscovite large plates several inches thick. An American, who here built a few bath-houses for visitors, stated that last summer from forty to! fifty invalids were there using the waters for medicinal purposes; the ma- jority of these suffered from rheumatism and syphilis. The waters are of good quality. Where they evaporate on the rocks, a white residue is formed, erroneously called there “borax.” Three of the springs have been widened and otherwise improved. No. 1 has a basin 20 feet long, 9 feet wide, and a temperature of 114°.5; a reddish deposit is formed, containing a trace of iron. No. 2, basin 10 feet square ; ‘temperature, 108° F. No. 3, basin 5 feet long, 2 feet wide; temperature same as No. 2. No. 4, basin 6 feet square; unimproved; temperature same as No. 2. The taste of all these springs is saline and alkaline. In one hundred thousand parts of water are contained parts as follows: Constituents. No. I. No. 2. OMIM CATON ALG ene mst = eelaweeta sate 11S atevem vente storm Store eee te sweet ras se ele 196. 95 184. 29 Doma CATDONALC tas sap sate ce were neeteaiveniciclaeis ea mieacjocseacaesan dees tans acd 0. 21 0. 16 (Cal ciomeeannonnbeyss a. se. ose secs sacle esee cece aoeecine celta: sen eisssccaeeeec sce s ? ME RTOS iFIA GAN OTES B65 Seon eccsoenne Seno soe A -eanid ocho Uso sSH eee eC omcsborens § 6.25 SFE Iron carbonate....... eee natn afc toe se wens Cae fe SS Peal Gsu of sects aah afeeedate Trace....} Trace. Gt ASSIUMONSH plate gam eyenawe shes Seeaicale sisiainialacomracloaisisacic, cacnisiesces osseucce sc 5.17 5. 34 Soudiommpsutphateres yee a eens sae see aac Solad sioke ees aac etee aces cecesSeces eens 13. 60 19. 33 Soup Chon Gee cmc sa ese tae el anak esac? saacae)aauea ocasceacemeasc ee ceta 38. 03 39. 78 SIN GICH ClO er ynep tsa amarante amine Calne nintaicioc: elsioe clanaa wiecinssteicueisens wise oat Trace...-| Trace. shotals colidkconStuentsi setts parame es csac. scene = sian clehecclgcwcn sein uscees cece 260, 21 254. 30 Gases: Carbonic acid. SPRING NEAR RIO PAJARITO, NEW MEXICO. This warm spring was visited by Lieutenant Birnie, who has kindly furnished me with information regarding it. It is situated not far from Rio Pajarito, a small, and for the most part dry, creek, in the extreme west of New Mexico. Its temperature was found to be 68° F.; smell and taste strongly of sulphur. The water is in constant agitation, here and there breaking through the sand, all the openings occurring within a circle of 5 feet in diameter. The rock of the region is basalt. 40 Ws : 626 GEOLOGY. In one hundred thousand parts of the water are contained parts as fol- lows: Sodium -carbonatezs ce ha ere eee a eee ae NPR): ( Galeium carbonate. =, i522 tepcisshe Some eee cet eee em fee ee eee 7.19 Magnesium carbonate’. -22 15. = se ace ere wie ele ea eet ae or Sodiumtsul platens sc in AE See ee ie tee eee Cre cine see cee 14.60 Sodium’ ,Chloxid@.c so -s-0 vax oeeee Se ooo ta Sees Se ice Pee aee been oe eeres 9.11 PS UTA RCO tt Ok an ne Se ReGen sas OF CN ROAD BOGE ASS AO Sloss eosatsonc+- Trace. Potassinm): <2 cere so eee Lyrakis ein tetanatan 2S shaa SRES SoREine Ss SESE S Trace. ithtuma 2:ss) oS nhs ces sbrains= mie le = ints remot elo sc eee ee Trace. ~ Total solid constituents: na-cieeaes DOSBO OBESE 4. 70 BGR \leeooss cool lacreboesbe Heithimm\ car bOnabelte cas e'sa0 Fac cares ciate ace me See kcae Sess asi 0.71 | Trace.-:.| Trace....| Trace. Calcium carbonate...... ...=..=-.. Seeds ms ahh bate ox toe Co: 59. 00 59.50 54. 51 58. 73 Maenestam carbonate: <= =-2s ssceea trae cereus coneteeceneteses 4.85 3.92 3. 68 3.59 LASSE NSU INNS sono soneer Sse cocess can posses cneSse sede Tol3 6.98 6. 63 7.10 Soyehinie Sil peeks Ae So os ees ASE <5 SeSeeen acer to sBane eee!) mee aD 220, 20 223.92 224.59 Sodium»chloride2c a. co ccc asc este seed nericceeee tates s week 29. 25 29. 36 31.21 29. 81 Silicicacid’ee — 4 Sab sosech sc srds ceases a mileaes eaceee wee 5.70 5. 21 5.53 3. 82 Wreanic matter caacu. ane teenn as oaeaaee cease cece asoses Airace=---|/lrace=---|suxace=- —-|| brace, Dotal’solidiconstituentS== ~~ sens eee hoe ase ceice see eo=e|), 333.00 328. 50 325.48 327. 64 Gases: Carbonic acid; hydrogen sulphide. SALT FROM A SALT LAKE SEVEN MILES EAST OF THE ZANDIA MOUNTAINS, NEW MEXICO. This salt is used in Albuquerque and Santa Fé as table-salt. Some people are of the opinion that it contains saltpeter, because of its peculiar sharp taste. Although convinced to the contrary, I subjected it to a chem- ical investigation, and found it to contain in one hundred parts— Chloride of sodigm 4 hits cwsseaje sels aie said aie Bsr dts! B6a cratic faye tas MS is rae 82.57 Sv EUGNGTE S0vd ty) Bone ep oe Saou SHOR HEe tee Oot Se Cee AAR ES Cares Serene 6.89 @hanid Gro DIAC HESLUM Ps sae see cae aes seen se aioe ieloe scis S ce slat einem aletatee sie als 5.88 MAC Es 45) SERN LEM TTS AES 3 Ua Ce RE ER Le es tk) Ea 2 ala zines 2 SNE AE 4.66 RSEUMPA ete O LUNTIMOY «a= hare o a) cis. = Si petteeyen ieee orsinactoy opel tec atersia atel= © Gaeta eaistscce Traces. 100.00 As the medium table-salt of commerce rarely contains above 1 per cent. of chloride of magnesium and sulphates, this salt must be considered very impure; still there is no serious objection to its use. SALT EFFLORESCENCE OF OJO DE TAO, NEW MEXICO. There are three springs in the Valle de San Miguel, about four miles 628 GEOLOGY. north of the Cerro de Alesna, New Mexico. Their temperature (in July) was 59°.5 The taste was weak salty. The surrounding ground was coy- ered with a white saline mass of the following composition : Sesquicarbonate of sodasti:. 12 see oe ee ee en ee eee 88.01 Sualphate.of: soda. ss <..2:<,22 ats hoses Se oe ee Oe ee ee 10.60 Obloride of'sodinmy.. -...3. 355 s288 bees oso seeecs ee eee eee 0.9L Dracesof lime; magnesia, andi lOSs:= 22. +2. sos pee eee oe enee eee eee 0.48 100.00 SALT DEPOSIT AT SUNSET CROSSING, ARIZONA. At the time of our visit to the Colorado Chiquito, this deposit was a salt pond, caused by heavy rains. Chemical analysis of the evaporation residue gave— Chiorideofsodiamys>. 2. -- ust. tse seeee eters Seog ased Sa EobnoSteS 78.79 Chloride ofcal@inm 22% 2-..0-.0 arene ERE Ae oe cae ee 5.48 Chioride ofmagnesinm's...- 2 5: aee aeons toe ace ee eee eee 12.16 Sulphaterof Timter<..o1-e2 co eee he kee cee nate Serie Sneek ee ae a 3.07 Traces of alumina, oxide of iron, and loss.............--. SG be Ga OS NGO a SNe 0.50 100.00 The quantity of this salt is not large, and in taste it is disagreeable. SALT EFFLORESCENCE OF SANTA CATALINA, ARIZONA. Santa Catalina is forty miles east of Tucson, and a station of the South- ern Overland Mail Company. Several small areas in the vicinity are covered by salt efflorescences, apparently remnants of former salt springs. The efflorescence was composed of— Snlphateot soda O24. 5.52557 Tae eres eee re eet ores eta 94.04 Chiloridevof sodiani 2" 55 2. cece aero eis eee eer eee aac 5.93 Traces of lime, magnesia, and loss .-....--.2.-..2ccces-e- Beco acr _ 0.03, 100.00 SALT EFFLORESCENCE OF CROTON SPRINGS, ARIZONA. A’wide plain extends between the Dos Cabezas Mountain range and the Dragoon Mountains in Southern Arizona, several square miles of which are covered with a thick salt deposit. There also exist two small ponds, whose waters are completely saturated with the salts, and on whose shores are deposits of white crusts. Although this water has a decided taste of ANALYSES OF MINERAL SPRINGS AND MINERALS. 629 carbonate of soda, ducks were seen in great numbers on these ponds. On analysis, neither borates, nitrates, nor iodides were found, but decided traces of lithia, potassa, and phosphoric acid. Specimens of this salt deposit, as well as of the crust, were analyzed, with the following results: Salt deposit. SER mIeaTbonaLe Of SOGM, <----.-) sos -0+ = 9 S-o2cerr esses see eee oe cecmey ams 15.51 “Sil DIM ARG Dap onosc0ee HOG oC OSC SCORcne Ulan od cee mR DOGO IO ASOD oNa 74.66 Cininin® ar ainhitia anon sete cae eseee cao meee remn a Neen a elie oe cies ate ri 8.85 Traces of silicic acid, phosphoric acid, potassa, lithia, lime, magnesia, aud loss. 0.98 100.00 Salt crust. esquicanbonatejor SOdar a... = <2 se ee es sie is elaine is ole “els ws = nim a= 26.25 ulphatelon Soda .--. 20 c= scenes sees as ele ate a= en ceein i afm nin sailors - = ans 60.03 CHIU O! Soshihiwososre svovos Gueebumosobetssausind on volo oaccHomoReaT 13.14 Traces of silicic acid, phosphoric acid, aes lithia, lime, magnesia, and loss. 0.58 100.00 INCRUSTATION FROM THE ‘ALUM CAVE” ON COOK’S PEAK, NEW MEXICO. This cave is 5 feet high, 10 feet wide, and about 8 feet deep, and is situated on the mouth of a cafion not far below the summit. Until quite recently, it was inhabited by savages. The walls are covered by a white fibrous incrustation, of alum taste. On adding potassa, these crusts evolve an ammoniacal odor, with a decided by-smell of tobacco-smoke, undoubtedly due to the absorption of the alkaline products of combustion of tobacco by the acid wall crusts. The composition of these crusts corresponds nearly to that of alunogen: Alumina ....-.. ab Sor ono Haocde GOGH Sen Se BES GCC OB Oae ICO ONES CON ador 18.11 Sulphuric acid .........-.----- Si IG eG HERO Enon HEAD OSE Coogee 30.90 ViVi peBkece cod osenScceds noc opdso.cop Modes, Guan, coeueo oo Ge acdo0 CHUSlr abe 48.38 Traces of ammonia, oxide of iron, protoxide of manganese, lime, lithia, potassa, and loss....---- SREB EMA Eb CO00S0 500: Gace Ga pOSCONeS GDC ORE DEED DO Coor 2.61 100.00 INCRUSTATION FROM THE COSNINO CAVES, ARIZONA. These caves, fourteen in number, are situated about twenty miles east of Humphrey’s Peak, the highest point in the San Francisco Mountains, on a steep slope; their walls formed by flows of basaltic lava. They are partly 630 GEOLOGY. side by side and partly above each other, and were formerly dwelling-places of Cosnino Indians. From their rear, narrow and low tunnels lead some distance into the hill. Some of the caves had evidently served as sheep- corrals. "The dung is many inches thick, and gives out an intense odor of ammonia. Here and there the walls showed white incrustations, which consist principally of nitrate of potassa, (81.4 per cent.) The remaining constituents are nitrate of ammonia, nitrate of lime, nitrate of magnesia, nitrate of soda. The nitric acid is undoubtedly derived from the oxydation of the ammonia evolved by the sheep-dung, while the fixed bases were fur- nished by the wall rock. INCRUSTATIONS OVER PYRITIFEROUS ROCKS IN COPPER GULCH, BURRO MOUNT- AINS, NEW MEXICO. The well-dried substance contained— Protosulphateiofaron (22 - - 42 2. Sas eiele ete ee telnet iteletn een 95.31 Sulphate of copper .-..-. .-.----- +--+ ---- 2-2 eee ene woe ene wenn on one 4.69 100.00 INCRUSTATIONS OVER BASALTIC ROCKS. In a great many instances in New Mexico and Arizona, white crusts were observed covering basaltic rocks. These crusts proved to be carbon- ate of lime. It is still an open question how these crusts were formed. The hypothesis that they are the result of the action of calcareous springs is untenable, since they may be seen even on the very summits of hills, where the spring could not possibly pour its waters. A NEW FOSSIL RESIN—‘‘WHEELERITE.”* In the Cretaceous beds of Northern New Mexico, a yellow resin is fre- quently found, filling the fissures of the coal, and interstratified with it in thin layers. On the way from Nacimiento to Willow Springs and Fort Wingate, more of this substance was encountered than in any other section of our journey. Fibrous gypsum not unfrequently accompanies this coal. The behavior of the resin toward reagents, as well as a chemical analysis, proved * This article was published in the “American Journal of Science and Arts,” June, 1874. ANALYSES OF MINERAL SPRINGS AND MINERALS. 631 it to be a compound heretofore undescribed. The principal part is easily soluble in alcohol, while a small portion, another distinct combination from the hot alcoholic solution, separates in flocculi in cooling off. If, after the separation of this compound, the alcoholic solution of the resin is evapo- rated, a yellowish-brown body is obtained, very brittle and strongly electric on friction. It melts at 154° C., and at about 200° C. begins to decompose, emitting an aromatic odor. It burns with a smoky flame; the residuum being a voluminous coal. The resin is also somewhat soluble in ether; less so in bisulphide of carbon. Concentrated sulphuric acid dissolves it in the cold with a dark red-brown color. It may be again precipitated by water. It is easily soluble in potash, and acids precipitate it from these solutions in an unchanged condition. It is readily oxidized by strong nitric acid evolv- ing nitrous fumes. The final analysis gave the following results: (1) 0.106 grain yielded 0.284 carbonic acid and 0.076 water. (2) 0.101 grain yielded 0.270 carbonic acid and 0.071 water. These data give us the formula C; H, O. Theory. Experiment. (OBTIDO CS GSEe Oe ce Ree Cea REe DU Oa e Ret sa aren ye ee 73.11 73.07 72.87 HEMirelO Olas ame icisteaiais cl arcice Cixioreicvato isles a sosaevewzeral ete 7.3L 7.95 7.88 Oe AWG, «5 SSeee oes AB ORe SPEC U SS 2 Seen GAPCme eR ara 19.58 ce 100.00 The molecular formula of this resin is probably more than six times as high as the empyrical formula indicates. No one of the investigated fossil resins is identical with this. The retinic acid of Johnston, which he obtained by extracting the retin asphalt from Bovey with alcohol, is the only combina- tion bearing any relation to it, and this only in a few particulars. This retinic acid has the formula Cy H,; O,, and is little soluble in alcohol, freely in ether; its melting-point lies at 120° C. In honor of the officer in charge of the survey, this new fossil resin has been named “ Wheelerite.” THE COALS OF NEW MEXICO AND COLORADO. While numerous deposits of coal are found in these two Territories, there are but few in Eastern Arizona. They belong principally to the Cretaceous age; in some exceptional cases, however, to the Carboniferous. These coals differ widely in composition and appearance in different localities ; 632 GEOLOGY. they often bear impressions of leaves, particularly the brown-coal stratas in Northwestern New Mexico. COAL FROM THE PLACER MOUNTAINS, NEW MEXICO. This bed is between slate and limestone on the northern slope of the Placer Mountains, thirty miles south of Santa Fé. The coal is compact, massive, not friable, nor intumescing. Color, jet black; luster, brilliant; fracture, conchoidal, uneven; specific gravity, 1.45. The coal is probably of Carboniferous age, and ranges among the semi-anthracites. Its composi- tion is as follows: Walter itso se toes POE pe ere ae aoe ant ee ee ee a4 2.10 Volatile. combustible matters <<. wos nce Sees eee eee 6.63 Pixedcarbony2: ~020b a2 =. oto. see eer cee. cor eae eae 86.22 AGL 5 oe .0 SS rare Sess yatore o SES ooo e eee Berrie e mete ee Ee ae 5.05 100.00 COAL FROM THE RIO PUERCO OF THE EAST, NEAR NACIMIENTO, N. MEX. The strata of brown coal are freely exposed in the perpendicular walls of the mesas, and are accompanied by shales, slate, clay, and sandstone. Their thickness varies from 6 inches to 8 feet. In some instances, the strata have been partially destroyed, and undoubtedly by fire, as evidenced not only by, the accompanying clay being tumed into brick, but also by heaps of slag composed of silicates of iron and alumina. This brown coal fre- quently contains a yellow resin, which has been subjected to analysis, (see article on ““Wheelerite.”) It is bituminous and of Cretaceous age, not coking, very brittle, somewhat laminated; luster, dull. Wate cis eye. 1 Gia win cassie aaron Sic ee Sls eo 6.00 Volatile matter. co... +o. oso oa S ee etniee ace t ec etn ee So es renee Fixed carbon 2.22.02. 2. SO ee ee eee 52.28 ABB oo asa e ninins 6! Sb,ac Sc ie oo cate ee tee T a ee eee ee eae 4.23 100.00 COAL FROM SILVER CITY, NEW MEXICO. This bed is said to be of moderate extent. I did not visit the local- ity in person, but obtained a specimen of the coal at Silver City. It is ANALYSES OF MINERAL SPRINGS AND MINERALS. 633 compact, massive, very hard, not intumescing; luster, metallic; fracture, conchoidal, splintery. It belongs to the semi-anthracites. Its composition is as follows: \WV IRE cig ere DG ee er Ce a ee ei aR ie heh ce ot gral oa) oy Re Bee ie 2.13 Wicd eile mb UOE ees oats eee ree eee eT Sta yee en _ Sr ee Sok eee es 4.86 I isco OTe ps len es ae ncn ay ECE, See eae OR tee eee Reese eee eae 86.56 JASN GH pop DES ONES Sh Bay SOE SE AA ee ey CEN ant aie Pe oe Se sei rE 6.45 100.00 COALS FROM GOLDEN, BOULDER, AND CANON CITY, COLORADO. These coal-beds are of Cretaceous age, as indicated by the fossils con- tained in the accompanying clay-strata. The composition of the coals of the three localities does not differ essentially; they are of a bituminous nature, friable, of brilliant luster, and not coking. | Coal of— Constituents. Golden. | Boulder. | Canon City. NWidbe re ce tee een alec eee ea aensice sees cecebieca cine coe cneeaes 8. 32 11. 81 5-37 io latilavmettensee = sneer eer cee ecient acme sacsateeseesce secre 29. 92 31.40 35.08 nusedicanbOnecs esas aa aee sels as csiesyde eee Seceed aace apa 58. 25 53-38 56. 66 IAS Dike eee peen) sae enone ase eo nisnawiee oo coe cetea cseeeviceedte ces 3.51 3.41 2. 89 100. 00 100, 00 100, 00 . ANALYSIS OF COAL-SPECIMENS FROM COLORADO. ~ (1.) Coal from Colorado Springs, Colorado. Within the last year there have been two coal-deposits discovered in the vicinity of Colorado Springs—one nine miles to the east, the other nine miles to the northwest of the town. These are bituminous, friable, free- burning, non-coking coals. The latter is the better gas coal. Ashes white or light-gray. Composition as follows: No. 1, 9 miles east. No. 2, 4 miles northwest RV EL ieee etna ae Lit dhs ciccaa ite aie Sere ioe ese 7.14 8.12 CASS eer Sea eee AE Se so enoS 24.56 37.09 I RGOKCAT VON Serer ac cs- 2 =< s s a ecierw inate sole 52.27 47.29 AST eg aniicon geod BASE GSB OB HDB eSondaaa- 16.03 7.50 100.00 100.00 634 GEOLOGY. (2.) Coal from Trinidad, Colorado. Near the thriving town of Trinidad are extensive beds of iron ore and coal. The latter is of excellent quality, and yields about half its weight in gas, is of coking character, brilliant luster, and contains an exceedingly small amount of moisture. The Denver Gas Works pay $12 per ton for the freighting only of this coal by ox-teams from Trinidad to the railroad at Pueblo; although there is a large supply within easy reach of the railroads in the vicinity of Denver. The Trinidad coal, however, is of the very best quality for gas purposes. It contains— ; Water ere Mats.. 8550 fo LE eRe Pero eacta ae ene eterna ate caine Cn eRe ee eer ree 0.80 GQaGie tire o bisectomr tose JAR socio ae ge a eters oe Beare ae ee ed eee oes 50.32 IPG d Carbo (2.2. (5G a estore. oetale reps eke yates et yer at orare ain ous Sheet Sete eras oe ee aes 40.18 PSR esi ta toes cose bse an tear ala Sree Cara ree ae by aia ae raln OT Eee eee ee 8.70 100.00 (3.) Coal from Red Creek. Near Elizabethtown, on the Red Creék, some twenty miles below Cos- tilla, in Southern Colorado, is a bed of bituminous coal 10 feet in thickness, non-coking, dull luster, ashes yellow. The following is its composition : Water =. 260 So «oes aSas a oils tordocias nie DER CORO: RiGee EE eee 2.70 MOS Fae Siar sisi ors crea ewe pore Saetdiaieln Slots eke eo ose s a aR eee eee eee 24.44 Mixed carbon! = fas.0c ces eae ereitics 6 See ae e oe ace eR Oe meine eee tre eee 59.36 INS ais eine a .235 ore fw Fale a" Revers ace Swine la vials a cies Mae ele ea A ETE se oe COIs 13.50 100.00 COAL FROM THE LOS CERILLOS AND PLACER MOUNTAINS, NEW MEXICO. From the Rio Santa Fé and Rio Galisteo to the Placer Mountains, the country is broken into hills and cafions; in some portions, however, it is nearly level. ote a The principal rocks in the northwestern portion are basalt and sand- stone, with hills of gypsum, called, in New Mexico, “ Hasped” or “ Yeso.” The Los Cerillos Mountains are made up of granite, trachyte, and quartzites, and partly, also, of quartzite schist, while the southeastern portion of the region consists of strata of clay, coal, shales, and sandstone, which are well exposed in their succession in the cafions and in the narrow channels, or arroyos. The thickness of the coal strata varies from 4 foot to 5 feet, and, ANALYSES OF MINERAL SPRINGS AND MINERALS. 635 as traced, is one continuous bed through Canon de los Ojitos, Cation Chu- padera, and Canon de la Chapina; the croppings extending over an area of fully 20,000 acres. Island-like hills of primitive and volcanic rocks jut out through the sedimentary beds. The original horizontal position of the strata has been changed in several instances to an incline. In the southeastern _ portion of this region a trachyte dike of considerable dimensions has pene- trated the strata of coal and sandstone, and changed the horizontal position to such an extent that they now dip at an angle of 25° west. The stratum of coal at this place is fully 5 feet thick, and is overlaid by sandstone about 28 feet in height. The coal is hard, dense, of brilliant luster, and resembles anthracite in every respect. Its specific gravity is 1.43. Indeed, chemical analysis of this coal shows the same composition as that of anthracite. Its best application would be for blast-furnaces and smelting purposes gen- erally ; and since there has thus far been no anthracite coal found west of the Mississippi River, the bed in question is of particular interest and highly valuable. Although the statement may be superfluous, it may be said that this coal contains no injurious pyrites. Three specimens were examined—one from a short tunnel in the south- western portion of the tract, where the coal was dug, or mined, forty years ago; another from Cafion de la Chapina; and the third from the Canon de los Ojitos. Constituents. No. 1. No. 2. No. 3. No. 4. Water -=2->- BA seed Be ose eet eno = ge6es le 5 SSC rSCOC EE CO UATE 2.10 2.12 HAGi |[jasseccece= (Gas) stam cee elas aasene aectelaee are ermeaetas siete tee see 6. 63 7.20 II. 74 3. 84 Bixed carhon) 2 Se,o5 a4 soso see ase eee eee eeeic- eaten si sse 86. 22 84. 33 "70. 52 87.45 ING Ve Sen yas creat oes Bee cnce ee aesae Bese eee aoe 5.05 6.35 16, 46 O84) No. 4 is Prof. W. R. Johnson’s analysis of a specimen of Pennsylvania anthracite, for which see Dana’s Mineralogy, p. 758. The specific gravity of true anthracite coal varies from 1.32 to 1.7. The amount of carbon varies in Pennsylvania anthracite from 85 to 93, and in the anthracite of France, from 80 to 83 per cent.; further, the amount of volatile combustible matter (gas) varies in different anthracites from 2 to 8 per cent. 636 GEOLOGY. In consideration of these facts, we must pronounce the coal in question a true anthracite coal. * This coal-bed belongs to the Mesita Juana Lopez grant, which is the more valuable on account of fine pastures, good pine-timber, and presence of water in springs, and the Galisteo Creek. ANALYSES OF ORES. The ores analyzed were fair average specimens of a mine, or a number of mines; generally a large piece, weighing several hundred grammes, was reduced to powder, and from 2 to 5 grammes taken for investigation. Copper-ore from Springhill district, New Mexico. Copper-f1anes . < vnacccn ee ee a ee sieeea 46.56 DUlCAte LOL COPPCl a. 449 ce eco ae a ee tt eee eee ce Lo esttecteess 3.52 Silver... ... OA au eh ee a ae yl Meee re Hoe 0.28 Gangue, (quartz)........---. Binh sie felsic) 1S ays ise [alain ot ete ionl lee See a 49.05 99.41 A ton of this ore would contain $90 in silver. Copper-ore from the Rio Francisco, Arizona. No silver was found in this ore. Its composition was— Herrnginous sulphide of copper... «i s2-cs-- sasaee Soe ee eee eee 53.41 (Green carbonate.of copper’ 2<<./522 22252 sooo rae nee eee eee ee 8.55 Quartz, (by difference) 222 2. )...2..42 22 oe aeee ee BE PORS Soph s Sane Rast ecaess 38.04 100.00 Zinchlende from Gilpin County, Colorado. This contained copper, lead, and iron, as accessory metals. Neither cadmium nor iridium could be detected. Bismuthite from Ward district, Colorado. Copper and iron were found in this ore, but none of the rarer metals. Uraninite from Leavenworth Gulch, Gilpin County, Colorado. This mineral is accompanied by iron and copper pyrites. Careful “Dr. J. L. LeConte, who examined specimens of this coal before, came to exactly the same couclusion. (See his report on the survey for the extension of the Union Pacific Railway, Eastern Division—now the Kansas Pacific Railroad—pages 38 and 39, and page 58 for the analyses.) ANALYSES OF MINERAL SPRINGS AND MINERALS. 637 search was made for rarer metals, especially for vanadium and molybdenum, but none were detected. Its composition is as follows: Wrau0so uranic Oxide... 0. .- 2. chs accesses tans cn «one e cama e ne mcincls cena 11.37 Sulphides of iron and copper .-..2.--.-----seee ese e reese erst erect ss ccee 45.81 Gangue, (quartz, by difference).......-------+--sr0ceseeerrt teres corer 42.82 100.00 ANALYSIS OF KAOLINITE. Analyses of kaolinite are important not only for a rational manufacture of China ware, but, also, in the application of this substance as a fire-proof material in metallurgical furnaces. The presence of iron or lime would render it useless for the latter purpose. Kaolinite from Gunnison, Utah. This clay is of a yellowish color and of uniform consistency. In con- sequence of its containing oxide of iron, it cannot be classified among the fire-proof clays. Its composition is: SAGO aso bo 20 deee Abd Pops SEAS pHbd old Un Gn Sr SOR One ia cc Maca in tog RET 46.79 JUWHMIND, aan boadeeoc soo BOPESn GosaOo Wns eS eC OT Sa Gnee Girly Oitmaa 34.00 Oniie@tinnn Yoacss Gsosddiabessssce codes! bas sou Deen oR Sone COR GO eeeeee 5.04 \WEKiS 2 aac DOO SHG HOOP Pre Socio o anc Olrrnt. Pes 6 Hi ate POC OO LOCO 14.07 99.90 Kaolinite from the Rio Francisco, Arizona. This mineral exists in this locality as the hanging of an extensive vein of cuprite ; the thickness of the vein is 8 feet. It is snow-white, and retains its whiteness perfectly on ignition. It does not show a trace of iron, and is free from grit. The small amount of lime it contains is of no significance, and therefore it may be considered a first-class fire-proof clay ; in fact, its composition is that of the best kaolinites known. Its composition is: SINE oa SUG ade se belcos a4 Shad Seto sae DER OOn Gms 5 fae OUCH aan 45.00 Alumina.......- |e ee i oo ee Be ees Gan apa on Serco eo 36.43 TUN a deensbice ACO FOR BRB Ab EGS Fost eudbsscone cine com pcniaeegs tarot iat 0.23 Movement oe ie oo 2s eet t= Soe eee sys ee ss 2 ele, Ree Abso Slight trace. Water ....-..--- Pee ios. elctaae Ba eee he cat re aoe SS Seer eran e nctoe 18.21 CHAPTER XXIII. THE ERUPTIVE ROCKS OF ARIZONA AND NEW MEXICO. Among the voleanic regions of the West, Arizona and New Mexico occupy conspicuous positions, not only with regard to the extent of country covered by volcanic material, but also in regard to the great variety of chemical composition, texture, and accessory constituents of these rocks. These volcanic masses present protrusions through the Cretaceous, as well as through the Triassic and Carboniferous beds, and occupy equally exten- sive tracts in the Azoic formations; a dike of basalt, 26 feet in width, and many hundred feet in length, protrudes from a mesa of Cretaceous age, about twelve miles southeast from the seat of the Moqui Pueblo in Eastern Arizona. Some forty miles south, hills of volcanic ashes cover the banks of the Colorado Chiguito, whence extends the basaltic formation southward over great areas, leaving exposed only little islands of the underlying Car- boniferous beds. The Cosnino Caves,* Flat Top Mountain, and Point Look- out constitute the most notable features in the volcanic region, representing parts of the easterly section of the Sierra San Francisco. The cation Diablo, heading in the southeast portion of aos region, is the dry bed of a former tributary of the Colorado Chiquito, and represents an erosion of 150 feet in depth, and of an average width of 40 to 50 feet, running partially in basalt, partially in sandstone. The Sunset Gap Mesas, twenty miles west of Sunset Crossing, (the crossing of the Prescott road over the Colorado Chiquito,) represent two mesas of 400 to 500 feet in height, and a quarter of a mile in length, running from northwest to south- east; the road to Prescott passes through the gap between them. The mesas are covered with a layer of basalt 12 to 20 feet in thickness; the slopes are more or less covered with this material, but where a land-slide has taken place the true nature of these elevations is well exposed. They con- ~ For description, see page 629, in chapter on Mineral Waters, Inerustations, &c. : 638 ERUPTIVE ROCKS OF ARIZONA AND NEW MEXICO. 639 sist of a remnant of the former Triassic beds, namely: 300 feet red sand- stone, with silicified wood; 72 feet alternating layers of gypsum and clay ; 65 feet red sandstone; 7 feet of white sandstone. Another stance of this kind occurs at Cation Butte—a basaltic cone near the junction of Chevelon’s Fork with the Colorado Chiquito. Extensive masses of basalt cover the eastern portion of the Mogollon Mesa and the Cordillera del Gila in Arizona; leaving here and there the underlying Carboniferous beds freely exposed; for example, at Camp Apache and near the Triplet Mountains. ‘Chevelon’s Fork heads near the western rim of the extended basaltic formation on the Mogollon Mesa, a mesa composed chiefly of sandstone of Carboniferous age. The road from Camp Verde to Camp Apache strikes this basaltic formation some fifty miles west of north from Camp Apache. Volcanic tuff and conglomerate, lava and scoria, not unfrequently accompany the basalt. Some fifteen miles east of the Triplet Mountains, and two miles to their southward, tuff and conglom- erate become quite conspicuous. In the latter locality, the strata of tuff occupy a partially inclined position, and are overlaid by horizontal strata of the same material. In the former locality, the strata of tuff are super- posed by a more recent basaltic flow. That these volcanic outbursts have been frequent is therefore evident. Analogous protrusions through Carboniferous strata may be observed in the cation of -the Jemez Creek in New Mexico, some sixty miles west of Santa Fé The walls of this cation are 1,000 to 1,500 feet in height, and consist chiefly of sandstone beds of the Carboniferous period. Only in a few spots, however, is the underlying limestone, with the characteristic shells of Pro- ductus and Spirifer, exposed. These sandstone walls have been burst in many places by the protruding volcanic material, which, exposed in long vertical fissures, presents a most interesting feature in a geological point of view. Basalt and rhyolite compose the Peloncillo Mountain range in Southeast- ern Arizona; the lands bordering on the Rio Grande Valley in New Mexico are also in many places extensively covered with basalt. The five tributaries of the Rio Grande that originate in the Sierra Mimbres have worn channels for great distances through basalt, especially the Rio de las Animas, Rio de las Palomas, and Rio del Cuchilla Negra, while rhyolite prevails on the Rio Apa- 640 GEOLOGY. che and Rio Alamosa, the most southern and most northern of these five tribu- taries. The Sierra Mimbres is an extensive elevation, composed of rhyolite and basalt. On the Rio de las Animas and Rio de las Palomas, basalt appears in extended flows, in the form of mesas, through which frequently run steep and tortuous canons. Rhyolite underlies this formation, and farther toward the mountain-range appears in conspicuous pyramids, surrounded by basalt. In the cation of Rio de las Animas were found small bowlders of ande- site and aphanite, which would indicate the presence of these rocks in the neighboring mountains. In the cation of Rio de las Palomas, transitions of basalt into dolerite are distinctly recognized. Here olivine is rarely met with and sometimes not at all—a noticeable feature also of the basalts of Iceland. On the Rio del Cuchilla Negra, basalt appears in massive cones, the depressions being filled with tuff, which in some instances is from 20 to 25 feet thick, the strata of the latter dipping 5° to 18° south and southwest, and overflown by more recent basaltic masses. The Rio Alamosa is formed by the union of two creeks, which originate in warm springs. This union takes place about 40 yards above the entrance of the stream into the Canada Alamosa. November 9, the temperature of these creeks was respect- ively 80° F. and 67°.5 F. just above their junction. The stream formed by the mingling of these waters was 70°.5 F. It follows, therefore, that the latter carries 1.4 more water than-the former. The cation through which this stream flows is of moderate width. The walls are from 50 to 100 feet in height, and are particularly interesting on account of the variety of volcanic material of which they are composed. The juxtaposition of these rocks is such as not to permit a definite conclusion as to their relative ages. The red rhyolites are followed by white, these by propylite, and farther down the river, near the settlement Alamosa, by dark-gray rhyolite, and then trachyte. The propylite of this cafiion consists of a fine-grained greenish paste, composed of a mixture of hormblende and feldspar. In the paste are imbedded large crystals of orthoclase and hornblende, with little sani- dine; there is no magnetic titaniferous iron present. Next to basalt, rhyolite occupies a very conspicuous position in the volcanic regions of Arizona and New Mexico. It constitutes the greater part of the Sierra Caliuroin Southern Arizona. The summits of this range are ca ERUPTIVE ROCKS OF ARIZONA AND NEW MEXICO. 641 8,400 feet above the level of the sea; with the exception of a trifling quan- tity of oak, no timber is met with. Deposits of white tuff, 30 feet in thick- ness, are exposed on the foot of the northern slopes. This tuff incloses fragments of basalt and rhyolite, and consists here and there of what resem- bles most nearly metamorphosed zeolites; the crystalline form is partially retained, but the substance is changed, and has assumed a clayey character. While the lower and middle portion of these mountains is rhyolite, the summits of several of them are capped with basalt. On the western slopes of the northern foot-hills dykes of trachyte are quite conspicuous; the mat- rix is of a’ brownish-violet color. A great thickness of conglomerate rests upon the rhyolite on the western side of this mountain-range, sloping off to the Rio San Pedro. A system of deep cations has been formed in these deposits, which dip in various directions, and occupy only exceptionally their original horizontal positions. On the Gila River, above the mouth of Rio Francisco, rhyolite is accompanied by basalt, pumice, obsidian, and pitch- stone. The far extending beds of conglomerate are here often covered by opal and quartzites ; the opal, chiefly milk-opal, frequently incloses fragments of basalt. Chalcedony appears in basalt as well as in rhyolite in this region. The western foot-hills of the Burro Mountains, in New Mexico, are also composed of rhyolite. Here the rock exhibits a close relation to the granite which it overlies, inasmuch as it incloses semi-fused fragments of the latter. Moreover, we can trace quite distinctly the effects of various degrees of heat upon masses of feldspar, which have, in some instances, assumed a glassy appearance; extensive veins of quartz also penetrate this rhyolite. From this, it would appear that we here have a granite with partial transformation into a rhyolite. In many instances, the volcanic outbursts may consist of molten or semi-molten gneiss, primitive clay-slate, mica-schist, hornblende- schist, or granite, that came into contact with the forward pushing liquid interior of the earth, and whose great variety in texture and accessory con- stituents may be traced back to the varieties of these primitive rocks. On the other hand, accessory constituents may be taken up during the act of protrusion. Several examples were observed to confirm this view. On the Rio Francisco, seven miles above its mouth, masses of rhyolite occur that contain through the whole particles of kaolin-of the size of a small pea. 41ws 642 GEOLOGY. It is not reasonable to belive that this is the result of a metamorphosis of feldspathic particles formerly contained in the rock. Further, this is evident, that previous to the outburst this kaolin was not contained in the liquid interior of the earth. The most plausible explanation of this is that: the liquid rhyolitic mass, on bursting through the earth’s crust, had to pen- etrate beds of clay, which, being thereby shattered into fragments, mingled with the volcanic material and was ejected with it. An analogous case is the occurrence of carbonate of lime in basalt. No chemist will admit that the former was contained in the basalt before its ejec- tion, since the lime would have been combined with the silicic acid of the molten mass and carbonic acid liberated. Neither is there any foundation for the hypothesis that this carbonate of lime was deposited by infiltration of cal- careous waters; to a close observer this appears quite an impossibility. At places where the occurrence was observed, (Sierra del Gila, Rio San Carlos, Camp Apache, )its presence could be traced without any difficulty to the strata of limestone that had to be burst by the protruding voleanie material. The limestone broken into fragments by the concussion and heat of the molten mass fell in small particles upon and became entangled by it. The heat, how- ever, liberated a part of the carbonic acid of these limestone particles, and formed a bubble that could not escape, the mass assuming a thicker consist- ency after its ejection. The pressure prevented the total decomposition of the limestone particles, but the heat imparted to them a crystalline structure ; hence the calcite in the amygdaloid spaces of basalt. A piece of such basalt, two hundred grains in weight, was pulverized, and five grammes taken for a de- termination of the carbonate of lime, of which there was found 21.47 per cent. Another interesting point is the occasional occurrence of black dendritic ramifications in the amygdaloid spaces of basalt. On the northern slope of the Peloncillo Mountains they were found especially well developed. Anal- ysis proved them to consist of peroxide of manganese; also a substance that would be decomposed by the enormous heat of fused basalt. It was most probably formed during the cooling state of the ejected mass from the prot- oxide of manganese contained originally in the mass. The amygdaloid spaces in which this formation had taken place must have contained oxygen, otherwise the formation of the peroxide would be unintelligible. | ERUPTIVE ROCKS OF ARIZONA AND NEW MEXICO. 643 The Carboniferous limestone frequently forms islands in the volcanic formations. Some interesting cases of this kind were observed between the southwestern foot-hills of the Sierra Mimbres, in New Mexico. On the headwaters of the Rio Apache there is one of these, of over a mile in length, surrounded by rhyolite; its most western portion adjoins a dike of pyrolusite. The strata of the limestone dip 45° to 50° east. Ata distance of six to seven miles to the southward, in gulches, sandstone is exposed, underlying the rhyolite; the strata dip 35° to 37° east. The Sierra Madalena and Sierra San Mateo, in New Mexico, are also for the greater part composed of rhyolite, as well as the plateau, fifty miles west of Santa Fé, (Baca’s grant.) In this latter locality this rock is accom- panied by great thicknesses of pumice; also by obsidian, that in sonfe in- stances is full of spharulite. . On the southwestern slope of this volcanic plateau, toward the town of Jemez, there is an interesting occurrence of labradorite porphyry ; large erystalsof labradorite, with a magnificent blue iridescence, are imbedded ina gray, apparently quite uniform, matrix. Pitch stone also occurs in this vicinity. The voleanic tuffs have but seldom been the subject of close investiga- tion; I therefore subjected a tuff of a peculiar character to analysis. On the plain extending from Fort Bowie to the Peloncillo Mountains, about four miles south of Whitlock’s Cienega, are found stratified deposits of a yellowish, soft, porous material, in thickness from 12 to 13 feet, and in extent about one-sixth of a mile. The mass easily crumbled to powder between the fingers, had no similarity at all to clay, and the presence of very fine grit could be distinctly recognized. On digestion with strong acids, a complete decomposition was effected. Alumina, lime, magnesia, oxide of iron, and alkalies were dissolved, while silicic acid was separated, and remained with the fine grit, which proved to be plain silica. . Quantitative analysis gave the following results at 100° C.: Silica .--. 2-2. 02-22. eee ee eee eee eee ee eect eee SECA e So aee Rae aaigete 64.61 644 GEOLOGY. PAMO ss os ees on Se ST eS Me afore Be ea Fe ee ae eee eee 3.01 Marnesit. <2 <2. - 2% s-=0 se eneheeeae ee ee etd oe TT Bak / 1.36 Sod ach asec ee dn curtdne aie tae eee ee eee aoe ate pie Eo EEA Ree Vale bn oem ee 3.19 POEASSA BIBS Me ar he DADS OOre DAS eras: DOmGHORO RomeNor REO Cog 7.75 Magnesia..... ---- ----- SERS He eens oaieeb es eecle mele tat ates eee 4.68 Die CRAP ST Polite Mapa e ceo Rice SE BBE Se Med mom tnononi. cy Mest rated ts es ams Birra Me ICE ee et el eee pee dice seael nmsainy = ani § : Protoxide of manganese ..-.-...---2+- +--+ eee eee eee ee rere eee ee Traces Sodae------ === SRSA Ee AOBEE Seat aA et DSL | DS CODE COEUR DSO PRm aes 1.03 TORSEE) oie osed erence Good te eC OEOG COodOdEe CoD CISD CROs Onno Do aeseonee 1-22 lirGlifgpets eh epee Meso Sood isd oe SS Adee odors Seen Geet cog Dopo rOISORra: Traces. Phosphoric acid.....-...-+----- 2-222 coset cece cette cerns see eee tee Traces. 98.90 BASALT FROM CANON BUTTE, ARIZONA. This locality lies about one hundred and fifty miles to the west of north from the Peloncillo Mountains, and a hundred miles north from Camp Apache. It isa conspicuous basaltic cone, and adjoining it is a small island of Triassic beds covered by the basalt. A number of cations, the walls of which consist of cross-bedded sandstone, head near the base of the butte ; hence the name “Cation Butte.” Cobalt, nickel, and titanium were found in the basalt, but in too little amount for a quantitative determination. The analysis yielded— PSillict wAA tee Ago aed Se a Tala a eS Ree arene efapelnl ie eimiataits (elwin's)<) s'=! See See eer ast ee een SNR e Traces. Mitanic' acid ~ << 22s 5 nancase bse eee tee ee Po eee ee eee ee eee Traces. Oh Bee err Aro ss SE ys eS ny hs ie ots sss sche 11.66 IMBPES A= = aon ee eae ee Ra ee ET Ie et eg St ten ay Daly ye ee oi 2.20 Potassa - - (by differences) ies = sare. ee eo eee er 4.84 Soda.. -.- 100.00 RHYOLITE FROM THE PELONCILLO MOUNTAINS, ARIZONA. This rock was of a light-violet color, with small crystals of sanidine and biotite distributed sparingly through its mass. On the weathered sur- face were observed minute specks, which proved to be malachite. Traces of cobalt were also found, and at a glance it would appear that the violet color of certain rhyolites was due to the presence of this element. Although no free quartz is visible in the rock, the quantity of silica would classify it among the rhyolites. Its composition is: Silica 2 <¢25 0: -0cebhushartotat sounnsehbe cheats ot hse Seen enn eae ee Alumina: <4 =c2s0 25.22.2505 2ee tec ee cen soe cases she 2 22.5c2 2oesoaeeeee 10.44 Oxide. of cobalt: -o. oes Se ane sae aise ses ee ele Se eee Traces. Oxidelon coppel. a...) sa es a ee eee Traces. Perexide Of Ion occ bes no eee ooo es - Ree ee eee eee ee eee eae 5.25 MGIUIMD | = So esdd be cato Deel ov clas Weald ca ee eo bap ane Peete ee 0.56 1 GPT RNA aS AO BA A Be eins ones amas OSiad 5,8 aaedwis tse sb ae Spectra = 0.53 Potassa. fcc 224 ek So ces ee oe eee ee ee ee 5.01 Sods 6.2 --> a atte nigtoars ers Dade ice 5 at eT Sepa eae eer Se ae 4.94 d Brit 1)t: ees eee eae Oe ea ey foe wees tenn bee ee cues eee wnat even een nes Traces. 98.47 TRACHYTE FROM THE SIERRA CALIURO, SOUTHERN ARIZONA. This mountain-range is about fifteen miles in length and four miles in width, and is composed of rhyolite, trachyte, and basalt. The paste of the trachyte is of a brownish-violet color, and incloses numerous crystals of bio- tite and orthoclase, which are, however, of small size. It has the following composition : Silica ./2520 2 2 Coe ee ee eee 2 2 oR en ee 66.57 ATuming 4323 es eee fee ee Pveicn's a's Ce ae es eee ad 12,26 Oxide of cobalt... .2 cao5.<< 00g cna 6 one wen a a a ee Tae 0.02 Oxide of nickel’ .. =. coke ont nc amon aicate meh = op ene ee js Re ee eee Traces. Peroxide of iron ..< 1. soho Bondad Go eBEe sans obS otecbatn 12ce0 booooD DOE OTE DOOD OCS Onan oor 1.34 Macnesia..---.--..--..- He boo otocced concd So soternUpe Sob oeopcEEareneac ance Trace. oe s (byaditierence) i ssa - 1s eaters tata aral no herot=re Siesta eo eee 11.40 650 GEOLOGY. PROPYLITE FROM SEVIER PLATEAU, UTAH. This is a erypto-erystalline rock of a greenish color, in which small erys- tals of hornblende and sanidine are recognized. Small particles of magnetic iron are also present. Although this rock differs somewhat from the genu- ine propylite, it is more related to this volcanic rock than to either trachyte or rhyolite. The chemical analysis also shows less silica and more lime than in both these latter rocks. No traces of manganese, cobalt, or nickel could be discovered. It consists of— SiC 63 =< aso eae hing a Ge AS bel Roe ee ee ae a eee oe a eee 62.86 ALOMM as 506, wp. 20's cg hac p sicle noe ate eee cid ceils ie a Sere a ee ee 14.49 Proto-sesquioxide OF ion 423 = sce cc ete ene ce tee eae oe oe ee 7.98 DMG: ee -Amis S2see Sse Sk SSE Ce ee ee ee oe 6.90 Marnesiae 55 =. a2 7 setae oo 3 eee ote ee ee ee 0.71 Soda..... ep by difference) §\- 0-53 2hcpacij cas gage eae oe Oo eee ee Bie K y difference) 7.06 100.00 ANDESITE FROM GRASS VALLEY, UTAH. This rock represents a dense mass of a dull-black color, with here and there white amorphous spots. It includes sanidine sparingly ; cobalt, nickel, and titanium could not be detected. The analysis gave— IL II. Siies c+ foo Poach se ees ao oaas v eateeme Ghat, 5 eee ee. Bee 65.95 65.09 Alnmina) 261-5 3 a\ceSiehe gels du ob gabe eats ee eee eres ee 21 24.1 Oxide of; tron’ :.s-..4232-2.-£2.<.ch- 5 eee eee eee = 4 Lime. 3 S25 228 Bs oS oi eee eee 3.13 2.61 Magnesia e-6 352500. cpscote oe Seu SI ic} ce ‘ 0.57 4,10 Soda..... ; by diff 8Q) ct3a 20) ok o.oo See ee ae ee ee ee : ’ Petessis a! K y difference) 9,12 5,45 ; 100.00 In column II is represented the composition of an andesite from the Chimborazo. The amount of silica in both is very nearly the same. BASALT FROM CALIFORNIA, (EL PASO MOUNTAIN.) It contained some olivine. Neither cobalt nor nickel were found. The analysis gave— ~)| (nn er rennmenrame Aye ME MOT ee es 62.90 ERUPTIVE ROCKS OF ARIZONA AND NEW MEXICO. 651 INI So oe COS a58 FEO Be ero resCe otc Se OS edOs OS GeO I5 tr oS SOU Ceor ES : 26.8 Oxide of iron. ...... .--.-/ 1-2-2. eee ce eee ete cette renee ere teens i Protoxide of manganese ....-. .--. +--+ 22 eee eee ee eee ee eens Trace. itor seas Ooo | BRBe Hop ean Cen Goleta co ener ene cm Toc aten Eats 7.39 Magnesia... - - 20-22. oon ne oe eine en ces mene seer neces Sone cece 1.01 Soda..... a (ihe GMT R)) aoe eeaoobes Heo snc Se soo ppp Scu Eee aweUEt nares cstc 1.83 Potassa - i ‘4 ) 100.00 A glance at the following table will suffice to show the great difference of composition existing among the basites as well as the acidites. The quantity of silica in the basalt of Canon Butte is far below that of the nor- mal basitic composition, while the basalt from California is unusually rich in it. With regard to the acidites, we find the rhyolite of Belmont, Nev., and of the Burro Mountains, New Mexico, nearly of the normal composi- tion, especially with regard to the amount of silica; while the rhyolite, from the Peloncillo Mountains, has 5.13 per cent. less silica. T. Sterry Hunt had already pointed out that no definite system could be based upon the distinction established by Bunsen, although the two great natural groups of volcanic rock are fixed between certain outlines. Between these the composition may vary considerably. Table for comparing the composition of basites and acidites. gee: e o.4 8 DS ° ag) : ag | 8, | 34 ba [SH 188 1 3 28 s2 | a0 F ae | es las : @ (exert OS ta g g |&é : ! g 5 S&S |a = as 3 Hes ae = “DB =nc} as a ust os g 5 53 o7, Constituents. z ofa oa ag 8 &< Sea|/fne6 ao 2 cae | de eG DEES See Ss B86 |o° §]/ e888] 28 = 3 o 3 a = P=} aj saa Bo 2oN 23 ~ 3s ps mBoN| S38 = 8 aoel| as laek| «2 44 of#|Sbs8| OF 6 234) 4A 2A 6 a6 Pod) Baa | 2 A (aa) [a2] [as] A a 2) 7) m cape a erares a icret ata arsie’ ole tern cletstata 48.47 51.50 40.91 62.90 76.67 66.57 7-54 76.84 76.23 Alumina... <0 sscetwecce cusses 18.60 -26 7 E E 2 : 30.16 : e358. 26.87 14.23 oe para ey 2° Oxide of iron ......5...6--05 *14.09 *17.36 5-99 5.25 1.02 3-08 Oxide of Copper ........sseeeleeec cece eeleceecereeeleeseneeeeeleeeecerereleseeserene eeeeeeeees “be E sdb ocacdaand bcoeesooes Oxide of manganese ........-|..-+-++++- Trace...| Trace...| Trace...|.....-.---|.-.e%se-0s Becasde|poodonacd bocea pace Oxide of cobalt .....-..+s.s0+Jeseeeeee an) ees c 5 : 4 0.0 ==} soaneconse| bespoassde 4 “S a8 RShaaoosts Oxide of nickel ...........---|..0--+--0- § g aa, eee Sat Titanic acid........cceeeeeeeeleeee cen eeefencecseces EERACC Er ME XAG cien| ine siatanicle self acs nin cic\e/ een eelnle:clnie n\e'«| ueleisisvieinvie|i'= = 581, 630, 632 Ojo Caliente -------++----+---7 277" 581, 624, 644 Pueblo .----- -----2 eee es errr 619, 621, 634 San Mateo. .------------ Sake Meeeoarsee 581 San Miguel .....----------+ +--+ 5-777" 5-1 San Pablo ...--.-----+ e-e-er reer eect? 581 San Pedro ....-----+------2- 0-797" 589, 590, 596 Santa Catalina..-. .--+-----++ --+--2 77+ 589, 628 Santa F6 ...--------+----- 580, 583, 608, 627, 632 Santo Espiritu. ....-----------+-+-+++--7- 581 Silver City ...--------579, 580, 596, 597, 632, 644 663 664 INDEX. Page. Page. Cities (towns and villages)—Continued. Groups of rocks—Continued. SESONG = c- 25 -Se aes soe inee tiene eee 581, 583 Phonouiio rook: soe eee eeeenlecens a) ee ao ee MierraAmarilla 222 .2.c2 recedes 626 Post-Tertiary 2s2-. 22. -ofecc ce cele ee 74 Andesite... .-- 2... 220. ons wane 644, 650 \ 7-1 Pee eee eee ee ees | 619, 634 AD thracite .-->-se—racrss-ne see sam 636 Rizton: 202 tech 9457-7 eee 618 Basalt - ... 587,588, 590, 593, 597, 625, 630, 634, 638, Saltsseieteslagaete sss: eee 573 639, 640, 641, 642, 644, 646, 647, 648, 650, 651 White Mountiin’ :2 3255235 5Jo-2cn55 se 573 Bismuthite 636 Calcite s=oisede ac adasasan eee eee 642 D. Chalcedony 641 Wesert Painted..22.-6222222222 020. seen OS Coallsesc-cis2sue “630, 631, 632, 633, 634, 535 District Springhill 2525. Sogo sl jose ee eee 636 Coals of New Mexico and Colorado - -..- 631 Whani= 222 to o2cncscaceccasnse neces 636 Copper octsaca-= 2525 casenee eee fsccewe 636, 645 Dolerite <352.222ssepsee sete eee 640, 646 i. Guneiss. 2... “Osc secen te ofa eeee 619, 624, 641, 644 FAINDAO IG cee ee) 2 eee ee Se Granite: --<2.2--52 2s-. 590; 598; G25j638; 030, C48 Ephedra antisyphilitiea ....-.......--....-. 611 Gypsum ....... Cate 589, 591, 597, 630, 634, 639 “eR RE ry bi G12 Horn blende-schist)=22ee. « s2206e eae = PNM O LOCKS sa-<2-52 02s c0as0o -osan Seas 638 Tron PRPs aaa TREO ie 8 TS ee 634, 5 AOU: .20023,t5.c025 2 boone eee ee 641, 642 F. LS) UC ea See ey ea fe ee meee 637 bavradorite eee clean ana nw nee 643 LO) EGU To Di ae Beer ee Eyre am “cite 587 Tava se ae ee er ..--629, 639 Chevelon’s ..-..-- 574, 585, 586, 587, 595, 597, 639 10 ea) Be reer ek SOE Le 636 Navajo, Somtliy..- 20.25 5-2--2--asee noel Melap ty tes= nee een(eeee ean eens * 645 ORB ATORG sae nldda cages neon anes) sa-s/ eee 579, 617 Mios-schisticoe eo ee eee 641 BAWIG oon diane t focecstatosas!<. sae 643 Obsidian 2.352353 o ees 643 rl eee reas 2 575, 576, 580, 581, 617 Dials. (ooo, ee ae 641 COMMING fo wane sass siege el oo sa = eee 617, 644 Propylite -<.2<......'..-.0.-.sas-%-2040)644, 650 Defiance (old) .....----..--------+---- 582 Protoriiesen. woos nc case cae eee ee ae Goodwin (old)-...--..---+--+--+-- 593, 598, 602 Quarigitess: Coc focce fo oowe acces .aeeasOuey GL Wingate ...--.-----+-2+2 ee-2-2 eee 582, 630 Resin (fossil) coe wees co oe oe 630, 631, 632 Fossils (animals) : Rhyolite... .. .582, 590, 593, 639, 640, 641, 644, 646, Promuchs sa. a0 ces cee e = eorin-=wade cae) One 648, 649, 651 G. Soliinen sy a= 2 cue doe oodes ee = ater ot 627, 628 Bilwant aes ~ © 574, 634, 636 Point Lookout ..----.---------- 589, 604, 638 (Oh egosanecica 573, 574, 578, 593, 597, 598, 599, 641 Taylor...--- ---- +--+ e-e2 eee eee eee eee 581 Grande or Rio Grande del Norte --..---- 574, 581 Wifee iis li owmeememecre Soeembaees 593, 610, 645 JOWOR ss ats ooo lees eeteaiweres 581,597, 644 Mountain Doz Cabezas.-.-.-.----- .--------- 592, 628 Mimbresj222. Sole Sscceosu rs eceeeee = 074 Flat Top -----.----- --------- . -588, 638 Pajarito ..50.. .-220-- 202+ pone eo eee oe - 625 VO it doen ae Sensace coaoUseese or 619 Gelas Palomas sseece eons o< = se a 573, 639, 640 Mountains Burro ..-.----- 578, 579, 580, 599, 630, 641, Pojoaque ..--2: --- 222-226 +222 eee eee 574 646, 649, 651 Puerco of the Eagt Sst oe 574, 581, 597, 632 G@aliurose. Sases aces =s 589, 590, 591, 644 Puerco of the West ....-.--------.----- 574 Ghinicahiuis.-- ------'------)------ 591 Sani@arlow!3-0-c-c-6 (ssacc orien = saa aaias 573, 642 Dragoon...--- .------------+---- 628 San Francisco.. ...--. 573, 578, 593, 598, 599, 636, Hardscrabble or Greenhorn ..---. 619 637, 641 Los Cerrillos... .----.---------- 634 SansPedroisseceaceoneseaess> as 574, 589, 597, 641 Peloncillo.....---- 591, 642, 643, 644, 647, Santa; B6.scoaccuewantee seas voles en tees OMa One 648, 651 Wesuque): 2-2. s-seceks25----5---~ 574, 581, 583 Pinos AltOs!.c- sce cee aee ce = on - 580 | River Mimbres .......-.---- ------ -- =-----579, 580 TO pena eeE SE DEESOCEe OL DO EEas 632, 634 IPHIGtOrs 2 son so rcss to feta es ee eS 593 Rocky ..---------- «----) ----+--- 623 San‘ Juan 222225252622: SeeeeSeocogeo 626 San Francisco. .587, 588, 597, 605, 629, 638 Santa Rita ..---.-. sods 7 2ets cee e0 S. Mripletiecs- + cas ~-0-------==="° 593, 639 Wheatstone ...---- Re ee 591, 597 | San Carlos reservation .-.----- ...--. ---=-- 593, 598 TATA TR Sate ee = OS ES 8 2k 627 | Settlement Alamosa. ..----.----- ----------- 640 Sierra Ca ltUrO = seo-s-saina eee elnnes eee oo 640, 648 N. dei Cuerno Verde..---.---.----------- 619 Navajo reservation. ...--------------------- 581 el Gilascocese sos sso=5 593, 599, 639, 642, 645 Madalena .......--.-.---------<----- 643 o. RAPE ten Gace Soe: OAD NS Ojo del Macho -..-..-.----------+----------- 644 Mojada csis-vsss ==5- ie a ee eee 619 de Tad: +... --------seecee-n----------- 627 Oe lataiecses ona ecto me w= mine 622 Ojos Cahentes ....---------------- 581, 613, 616, 644 San Mateo .----.----- Ee ON Ea ate 643 Ozone tests in New Mexico and Arizona -.-.. 601 daNanta Catarina .c<:-2-2<-s- 5-2-2 589, 590 P. Soapweed (Yucca baccata) ..---..---------- 609 S : i = Park Amimas\cccossc+-.0~- =< Sikieedntactosete ds 626 ante Home Mexico and AnZ0ne 250s oe Pass Wagonwheel Gap ---..--..------------ G22! rae Ripeen era? Mee CT ta of Abiquiu ---<-.,-----ss9-6 —=--,--5-= 624 Renin @onlenceajeeac a enieosseentce=ntassyresa0e9, 044 Nat Vad 617 HMomphreys -225-3-2s=< <== Se - 629 Cape Bae at eee eee 61 BUR Gaeta ks Ae eee GIR MDS io ae cae ae ae puis GU : é of Cafion City...-..-.-..----------- 617 Plants of medical and technical use-.-..-.-.. 607 Carlisl 621, 622 Plateaw Sevien<: .-25\- = 649 of the Rio San Francisco... ...... --.. 616 | Sunset Crossing ..--...--..----..----- 585, 628, 638 of, Banvisidrn 222. aoa nessa teas aE LO Shoshone «~~» os-sasresa-t erates 619 T. Solphinrs 7a ao pea se ee 591,592 | Tehua tribe...........----..----.---------- 583 Sulphur (South Fork of NavajoCreek) 620 Tite, Sodelascsae eon nee, OND ¥: of Wagonwheel Gap .....--..---..- 622, 623 | Valle Grande............- 581, 582, 595, 603, 604, 616 Whitlock’s Cienega. .--.....-.--.--- 643 | Valley Arivaypa . ........-..-2.0. e202 -e--ne 591 SWIC cats Janeen oan an Sate ole 630 Gili. «So sosncene oieeaneee 596, 598, 599, 647 States and Territories : Grass (Pia 5 ..o. «oo sesame = 52 650 Arizona -.... 571, 573, 588, 593, 597, 628, 630, 638, Pueblo Viejo...... Rae ee ee nee 593 644, 646 of the Rio Grande -.....-...---- 574, 578, 639 COENEN eee 649, 650, 651 San Mipuel -.----. .. - 5. oo ee 627 (DOME sing cen ne aol canna aa and ee 571, 581 MEXICO nc coms etoacetamnss cn ociseeeeeens 589 W: INGVHth See nein awe eaain enna smn aie 649 | Water of the Rio Grande.-.........--.- 575, 576, 578 4 ee) whe , . BS, ¥'¢ . 4 , aes sy see kates . ¢ ® 4 = wey. E "i 5; ) 5,9 * . » . : a ee xy * UNIVERSITY OF ILLINOIS-URBANA Q.557.3UN31W c001 NN