aR EAE Toten arta ates eyentr ees LEST f5eike eies + ® cae erate SALE Beate THE FIELD MUSEUM LIBRARY Class BXC : Uda he ca Cee: AUTO aM ne Nong fit alent \ Nuh AH orsth i Y TENTH ANNUAL REPORT OF THE UNITED STATES GEOLOGICAL AND GEOGRAPHICAL SURVEY OF THE THI rOR LES, EMBRACING COLORABO AND PARTS OF ADJACENT TERRITORIES, BEING A REPORT OF PROGRESS OF THE EXPLORATION FOR THE YEAR 1876. BY F. V. HAYDEN, UNITED STATES GHOLOGIST. e117 CONDUCTED UNDER THE AUTHORITY OF THE SECRETARY OF THE INTERIOR, WASHINGTON: GOVERNMENT PRINTING OFFICE. 1878. te pPorenli rae } iy TABLE OF CONTENTS. INTRODUCTION. REPORT OF DR. F. V. HAYDEN: Wetter tombe se cketdnyenmecicer sr ce een ie te oa ane oi esate eee aie PART IL—GEOLOGY. REPORT OF C. A. WHITE, M. D.: hettemofstransmnibtales eee coerce kon: ce een nies tenes comes wee sce Report on the geology of a portion of Northwestera Colorado: Chapterplealonbroduchione sere cso neces ee cites aren tose ice eneee © sl Chapters Suntacebteavuress-emiaeianseenca eect oer ece teens cee: Mo unatarim Suraasisewarsiierne eeicisisle cies circ Sele rasiaiee ese eee cele 'e ele scree Sci IDRMIDD GS .co655 scedog sos osu adocsenod cooSod bagson KeS6 os anaSaoouUOBE Barksyan dypasingyenreseimemssics oe steele tee civics oe ie nics aeclew ace cee Chapter III. Classification, description, and discussion of the groups of SIDI GS Sco b pote aa AOR SS CoD OAS CINE SEITE STE ena a elena nes seater BF PheySilomanysy Shem see ote = ey telat tae er ef-s) arial ERS an at Carboniferousisystemiewcys-pcstenyore naan) Mean Watery ears toe MherMeSOZOIC AGO scoters cielsicioyaiisemeteo eats isk Melee ek Geemiawied Gaps Triassic period ........- PSRs RAMP A Sah Sad i wr cpte eR mn, ive: Jurassic? Periodic Haye = se)s\e: avwieislet she eine siale wei= eke octet woeR ee os The Cretaceous period....-.-.-..---.. Snare Seer eae eee tes she spost- Cretaceous periods anaes sei ee ae eee se see recone Hbevhertiany: periodeyee acse ook cmoreinsicleejesierais ems Coase eeace hates EDS SOCnS ae eae ses Scich Ce CO HCC o MSA eIASEG BER See ChapterlVesDisplacementsaeea ene eee eee 5 eee eee Uplittsvandiapthrustsiseen cee sc sce cee cetera eae ae er eoe, vente: JES IGE] CS bem Geo SOOO Boer eA OAORABACH Soo Sere sea aaNet ie cia Meee rete Concludingsremarkss: feces a ees oe eee ema t enias Se Se eee cscs Chapter Viaesurtace sc eologyii.= toro 2s cece eee ee te kos = wee ic oe Relation of the valleys to geological structure and displacements of SUID co bos0 60606 00000 665055 0Db500 06000 bODaGu b600 Sega B406 baed REFORT oo M. aranos, S.N. D. , GECLOGIST OF THE WHITE RIVER DIVISION : Wetterrorsorams mc Gal tert rie rcer raise cea siatsiecicjetemlste(s sie. sia alee) «, atouelapaiaiee ates aie Repert on the geology of the White Bee District : [MBE CNOWKON Sorin SASAS5 cnag osha saceeuenooaS o665 ROUBSse Gratereteesleismasiators ate (CIA DUBE Maco BaGotoBooUoU Do sede HeCa eee PNA Poa ce) als cdc ae 5 DP) Pan al Ge a5) ays sy tataisias ste miaye see .s sisieisaaisisveccieinls aabeae eeiehsiace Sens Mopognrap hy ere =iney ecole crorenisiaie nats acre aeiayemon ciate sels we cleiathac siemens WYGRIGIGNGOI 5 oda oa beh Saeed Mbae BAe Doras Subd BEC Crone aos ED Ress Aen Chapter II. General geology eS releynicis CVS ale usre Te ener aR eae sels elamataclens Strationaphivyaeseacescee cea ceecsce FO Ee Al AES a ee a ea ee tel a era: TAS peewtepeerstetse se clete ce elena atic coe. Ae uretebecioeies HO Satay yee = eee terete rete re ee are rom arate alee wie Mecca) wrbyara ala ae penal PAMIGIOMbESLACTETS eyo ae csiers cicrels Sis croeeeicis = Soe wiarecr sak toca, Horse la eeyelawe IAM CIO Mtn lakes peers tyes rct terse cle scrctapeere ae Savana iam enciere irs peste eieie ea) OEDD reititefpereve ree atiarstore ere ca estate vet tolls aie oeis ecrciaice nei ora(isleie cieisvecs ersten yas oe Chapter III. Correlations of stratigraphy, lithological constitution of Strata and orocraphyessase eee eee cae eee ch ens Aes Crystalllimenacoreodteste ice cst se soe salon woe wane = Nedimrenbanys ROCKS eye eee see oo ee tees eis peisaye 2a) siaverete eva aeetsrarele Warts EWP LUV OREO lease a) asia iecveia cis a sueslers sacs caiciein a cele eieeeeree ais bw a coMociemne Specialifeabureswye es sh qeys1s sie cate cis \siomiasieds miperee winiomseiee ais’ s/=e teen's DSi ieee vereneeee poe epee Gane ss mensiate Aye rele cpeeretece aimee aie seo ietcjanee Sica Page. XIII Je) olle ony Tos Mea 1V TABLE OF CONTENTS. Rerort or F. M. Enpiicu.—Continued. Report on the geology of the White River District.—Continued. Chapter III. Correlations of stratigraphy, lithological constitution of strata and orography.—Continued. IBRVAONG o55cc0 soon edadeomoad cache 606 adaoGous SEC Oasalsono eaod NIGHT NWS 5658 odGood posede babe ndooed odcos pHacob Bed adocGe ace Sillutstilecso saopmecood pESoES eos Saas dees poccoe toad UabSoge6os asec IDENOMVEN Gace saad onde BoeScoodanboae 6G Disteieie is pe cece ness ce enee @anbomiterouse sscecs ee ca ee oe ee aie clears ale lets ntere) ool ene eer ieetererstets @retaceousic= ssa. e hese se aes ks Saves aaee See eer {25 Co ee post: CretacOus:s.-)-scee ses cee ene eine ace ie ae aa PPORWMALY etc d capone cae Sein ceiee cis = ema tiowere 8 lee ele sin ot See een Woleanic formations: jcc cecesced saceee «ccs Geese: scene Ce mie eee Metamorplosed nockstssseeeneseces- teeee eos oee Coes coe eee MOonUMenits) sass se anc os be teicis clare ecisieisisies owen eraeedetetae ieee eee Glaceatione-cescceree See ee seca ce eee eae Gee eee 2 fee WD Tifbiecosc ents Seen eee aste cad sew a ee oe ee tenet Sete eee SOM joss elie eo kesecene secs jacsoe teedes pense vaececs cee eee Metalliferousidepositshess cas -seie ccc lacion eee eioel sca eiennehe Seer Goldtand'silwers5-c.6 ccc oes soe does s Seesee oe ees. -e OEE Copper) zineyand™ leadees---.se sei oe Adis uses tee eee Coalhand ironioos2 ee Lec se se bk woes eeee cena Sees See eee MINERALOGICAL REPORT OF F. M. ENpDiIcuH, 8.N. D.: Hettenofstransmittal < scsc2 ace senses case baeee © Beeston eee Cataloeue of minerals found in Coloradoz. 25.4 -ee ose ee eee eee eos Systematic arrangement of Colorado minerals .-.--..--.-....--------- Reference to publications on minerals of Colorado ...........-2..----- Rerort oF A. C. PEALE, M. D., GEOLOGIST OF THE GRAND RIVER DISTRICT, 1876: Metteriof transmittal: -. osscd 2 acceso ties Gace coon oe coe a eee eee Geological report on the Grand River District : Chapter iGeneralintroduction(eos. 253s ces eee eee eee ene Chapter II. Area A—San Miguel and Dolores Rivers—Saucer Valley — Gypsum Valley—Basin Plateau—Paradox Valley—San Miguel Pla- UPEUUES Seco souopo cas Henn obisHan caeremeboresos EhetSierray Abajo mom the eastic se: sce. en 2c ace oetea shes 1°9 . Panorama from Abajo Peak looking north and west......--- 190 ; Fig. 1. A glimpse of the Dolores Caiion ..............--. 193 * 2 Fig. 2. Lone Cone from the southwest................-. ei . The San Juan Mountains from Lone Cone, looking east...... 194 REPORT or A. D. WILSON. (ABT, Ie) | Fig. 2. | J Fig. 3. \ Diagrams showing intersections of fore-sights in ; 984 Fig. 4. the primary triangulations...............--.. o Fig. 5. | (Fig. 6. J Sketch trom Stabiqnulas +. «yancesce 8 curso cs a 5 se one 298 Sketch piromys (ationpl eo. eg acc aN ays sa erase 12 be oie < 302 Eromicskerchrirom Station) ils ence. c8. sents Jae ee oe sence 304 C OULGUPRINAD are marae aes see inei moe onde ocuwaeloccmececes 306 REPORT OF G. R. BECHLER. XXII. Grand Hogback crossing the White River ..........-..----- 365 bite) Creat Yenparblatenn ose tee cc cr. cce sce ec eee ce cs te 369 MMewroncthe Yampa River sc. s-5 ccaceoccce.ssececeesiciec nce oe 37 Vamp ay FLverOanonenee sa aeee wee ene. ae MSN e vee ee aera tree 371 View of Ethy Park on Yampa River -.......--..+-.cc0se-+s- 372 Profile across Yampa Platéau 22.22.2226 s2.2..c2eee- coee - § Profile of Yampa Plateau, showing Fox Creek depression. 369 Profile from Lily Park to White River below Powell’s Park. IX PLATE XXIX. PLAT“ XXXYV. XXXVI. XXXVII. XXXVIIT. XXXIX. XL. XLI. XLII. XLHI. XLIV. XLY. XLVI. PLATE PLATE PLATE LXXVII. LXXVIII. LXXIX. XXVIII. XXX. XXXI. XXXII. XXXII. XXXIV. XLVIL. XLVI UIE Th LI. LIL Tah: LIV. LV. aval LVI. LVIIL. Ke Xe ye pane LXII. TIVE LXV. LXVI. LXVII. LXVIII. DG WO. DOwh OCT: ONT TRXLVE LXXV. LXXVI. LIST OF ILLUSTRATIONS. Facing page— Profile from White River to Yampa River ...........-.. } { Profile from White River to Yampa River ...-...---..... | 363 \ Profile from Yampa River across Williams Fork to ae (eGR ChiGglk sono cog ogc onases osSeeoBse6g6 600500 S00 bo SSa¢ General Pelerence Map alee l= eeta ale alnlealel= tam =e ae 378 REPORT OF WILLIAM H. HOLMES. Ite JA ene NES ono agesos CoBOdO eae6 DANSE dosea0 6559 HES 387 JON y@nsh SEN Vueil S550 sone 50m aaooodes CORDS DOSDOS 000550 Gaac 388 CEN GEION AO, IO WERVEOS Coocoo eons case poN8 C6cEen boeSsco cosoce 390 @aive-houses, Gz¢.h10) ManGOSs mene oe a) alee clei oe eee 391 Lehiela Aioniere 1K) MIAO So aposo enoooe dooaos Jocqeee Gon5 Socsac 392 Smiallrclilite towne sets ce ne ate elotetelole einictoneisiat a letelarene tetera 393 Mareerchiti-cowNes ee eeeee ose one een ae esas eee eee 394 Plans of Mancos cliff-houses...-.. ..--------.-----+ es00- een 399 Two-story cliff-house on the Rio Mancos.-......--.-----.---- 397 MecMlmoltow etesnssems cis <)> ces «el neo leicie = eho Sone eee aeeiee 398 Isis nen Symes) B68 Se oe seo soca cd sooo esos oss > 52-5 399 Ground-plan of ancient pueblo at Ojo Caliente............--. 401 Rock inseriptions jsese ce/st-eas ja esc cesses ce] eee 401 Rock inseriptions)2je<-- 25-1 Sao coaeete scree ok ose eee 402 FA CLEN bs POULOEY e-isisis a clei slate siecle eles etelaieele cis teiele el reenter 404 ANTM WOW, Saaoeg coogcuecee Hebe Huse BAB obogaabeGoC oS. =< 405 implements wweereee se eee elas aeare eee easier ene eee 407 REPORT OF WILLIAM H. JACKSON. JOG) Charalihy olbtit IIE 65556. c555b0 Senacocona os oh ana aaouee Gooc 424 Groundsplansy.2eio5 daac cme Sac iasec sce cieiseseae a issteis=e- oes cee 416 Wasa Melslicon: dat 2itae cc siclsitinel ao te okais eine eres eae een eee 418 De Chelly cave-town ........-... SooCuadonddu UaScod Geog Meso 422 psom| Creek towers esc sees Sears oe tiene emcees eleleeee 426 Montezuma ruin cece ce cts aie a cainayne oo eta eres Serene eee 428 Montezumairocks ise caoeeetiacty ne he sae ee eee eee 5 ts Caverhtouses seo os jaeeee rice eet ee Eee een Cee nee 430 Rueblos Pintado-angawejege.s2---.--.- si). eee 434 Pueblos Una Vida and Hungo Pavie ........-.......----.-- 436 ReubloyChettro: Kettles sea. cc. sees caters ese cece eee 438 Pueblovbonito.. is aebar soon eae ce bcc eee eee ee eee 440 Pueblos Del Arroyo and Nos. 8 and 9 ........---.-.----.-.-- 444 RueblocAltoc. 2 2h ae cece hoe deans Sion ae Cooma eee 446 Pueblopbenasca yb lancayeses ere eee eee eee eee ene 448 Maplot Chaco: Canon Qcr ease scence ene eee ae eee 448 SUGIE WAY «oie c on ete ines wale eevee waite eee ae ee a eee ae 448 Pottery, ancient painted fragments ...-...2..-. ..-.-.-- esse 450 Eottery, ancientjugs and) bowls=-----)-eceeese eee ee eee 450 Eottery, moquijugsiand ladlessee-) ssoceeeteccer cea cee oO Basketwork) andimares) oan. cence: eee seo ce eee 450 Pottery, small owlvand ducks 25550. .occe erence eee 450 Dacksiand’ pheasants: < so. \sscc Se ose eee a tae eso eee 450 Dargeowland ducks. - oss ce -scieece- soe oereniae cee 450 Ollavand bowls 5-8 eos eek wea nese eee: see ee eee 450 Restoration of the Puebla Bonito .40.+.. cose ee eee eens 450 Map of the Moqui Mesas, Arizona.............-..-.-.------ 450 Map showing the region occupied by the ancient ruins ....-. 450 REFORT ON CHACO CRANIUM, W. J. HOFFMAN. Ancient cliff-dweller’s\craninm . <1. -2.-eeeee eee eee eee 454 Ancient clitt-dwellers) cramum)-----eeeee eee ae see ere eee 456 REPORT OF W. J. HOFFMAN. C Pigs I Splint .tpeecesccceen onsen ceee estes Spsosncosodes 4G7 (sbigg2: Metapileiand metlatlies. 2 = 32 0-0ge see een eee Pictographionweekjim Arizonayes aas-ic5-e/-- co eee bossoae ATS CAGE TORIES) cin, 1d lew acloias ee ee eels ai eae RRR net ee 477 LIST OF ILLUSTRATIONS. Xi WOOD-CUTS IN TEXT. REpoRT OF A. 8. Packarpn, JR. Page Hig len Vellowgceranbernyewormeand pupasess «se 4562 son ees ce ee eelokes ole. alee 522 Fig. 2. The red-striped cranberry-worm ...........-----00- mip ay ea stern Saye 524 Hie nod CTA DERRY Ey NOM W OLN CMlAab@e Ces ato celia vale eu holes teks sc cek 524 Imig dle Ohenalnciay Calle Mivcs cao Canton bee asc OSE OBIS e eae Eh sapimy cy nmmn nia 525 igkcn Cranbenby WUC My Veevdlc mmc nsietani wines s- sec ecd Ses eenness Lob lel os 525 PATO. Oran Dernye ruc VVOPM ws sec is tarsaanae c <\elsesinee sa goeuo wees aeee oS 526 RNG Mi catctave\a: NG start aan er pay Se ctsislal ci)a)telc eiajarniate aie nya cies Sta niu el aiuinis aicicte eStats oe 527 saree Mon ohamMmmnsecOmimuisor seer isc eae saaciosecte + oi oe acco sedans cel sl cee.. 528 Pig. 9. Larva of Tremax Columba, natural size. ...-.. 2... coscss secece ccana- 531 ite a « aye “ yas ms ale RE Fi LETTER TO THE SECRETARY. OFFICE U.S. GEOLOGICAL AND GEOGRAPHICAL SURVEY OF THE TERRITORIES, Washington, January, 1878. Sim: I have the honor to transmit for publication the tenth annual report of the geological and geographical survey under my direction, embracing the completion of the work known as the survey of Colorado and portions of adjacent Territories. The systematic field investigation of the six rectangles which are included in what is called the Atlas of Colorado was commenced in the spring of 1873, and closed with the season of 1876. These six sheets embrace an area of rugged mountainous country of about 70,000 square miles. The field-work of the season of of 1876 was therefore entirely confined to the completion of the work in Colorado, and thus the area under investigation was located in the interior of the country, far remote from settlements, and among hostile bands of Ute Indians that attacked three of the parties the previous year. The point of departure the past season was Cheyenne, Wyo. Two of the parties, with all their outfit, were transported by railroad to Rawlins Springs, and proceeded thence southward. The other two were sent by railroad from Cheyenne southward, one party to Trinidad and the other to Cafion City. The primary triangulation party was placed in charge of A. D. Wil- son, and took the field from Trinidad, the southern terminus of the Denver and Rio Grande Railroad, August 18, making the first station on Fisher’s Peak. From this point the party marched by the valley of the Purgatoire, crossed the Sangre de Cristo range by way of Costiila Pass, followed the west base of the range northward as far as Fort Gar- land, making a station on Culebra Peak. About six miles north of Fort Garland is located one of the highest and most ragged mountain-peaks in the West, called Blanca Peak, the principal summit of the Sierra Blanca group. On the morning of August 28, the party, with a pack-mule to transport the large theod- olite, followed up a long spur which juts out to the south. They found no difficulty in riding to timber line, which is here about 12,000 feet above sea-level. At this point they were compelled to leave the ani- mals, and, distributing the instruments among the different members of the party, proceeded on foot up the loose, rocky slope to the first outstanding point, from which a view could be obtained of the main peak of the range. Although this first point is only 600 feet lower than the main summit, yet the most arduous portion of the task was to come. The main summit is about two miles north of the first point, in a straight line, and connected with it by a very sharp-toothed, zigzag ridge, over which it is most difficult to travel, on account of the very loose rocks TIL XIV REPORT UNITED STATES GEOLOGICAL SURVEY. and the constant fear of being precipitated down on either side several. hundred feet into the amphitheatres below. After some two hours of this difficalt climbing, they came to the base of the main point, which, though very steep, was soon ascended, and at 11 o’clock a. m. they found themselves on the very summit. From this point one of the most magnificent views in all Colorado was spread out before them. The greater portion of Colorado and New Mexico was embraced in this field of vision. This point is the highest in the Sierra Blanca group, and, so far as is known at the present time, is the highest in Colorado. The elevation of this point was determined by Mr. Wilson in the following manner: First, by a mean of eight barometric readings, taken synchro- nously with those at Fort Garland, which gave a difference between the two points of 6,466 feet; secondly, by fore and back angles of elevation and depression, which gave a difference of 6,468 feet. The elevation at the fort was determined by a series of barometric readings, which, when compared with the Signal Service barometer at Colorado Springs, gave it an elevation of 7,997 feet, making the Blanca Peak 14,464 feet above — sea-level. This peak may be regarded, therefore, as the highest, or at least next to the highest, yet known in the United States. A compari- son with some of the first-class peaks in Colorado will show the relative height: Feet Wncompahere Peak, above sea-level wx. 2c 0.5 ee ciccej eee sede wie Sele eee eee eee 14, 235 Blanca. Peaks above: sSea-leVels..-c..cos we snes eset ee ere renee cee eee eee 14, 464 Mount) Harvard: above sea-level. =: 2 .oae naccae selon ae eee ee Eeeeooerene 14, 384 Gray’s Peak, above sea-level ...-.....22.----20- een (aes NORE ne cence eee 14, 341 Mount lincoln above sea-level .. is. tc\sesoesccte soetle = see ee eee ree tears 14, 296 Mount) Wilson, above.sea-level 2. ..- 25: s..6 scc0) nies occclemicwlel= = celine ceiseenic 14, 280 Wong's Peak; above ‘sea-level « . 2at4 scpyek fs dacs oa iininisi wine aipaeidoe aire isis eee 14, 271 Pike’s Peak, above sea-level......-....-----sse-e- Shain pyeisrctete, Spel epePR nets cp ietereraters 14, 146 The foregoing table will afford some conception of the difficulty en- countered in determining the highest peak where there are so many that are nearly of the same elevation. About fifty peaks are found within the limits of Colorado that exceed 14,000 feet above the sea-level. From this point the party proceeded westward across the San Luis Valley and up the Rio Grande to its source, making two primary sta- tions on the way, one near the summit district and the other on the Rio Grande pyramid. From the head of the Rio Grande the party crossed the continental divide, striking the Animas Park, and thence proceeded by trail to Parrott City. After making a station on La Plata Peak, the party marched north- west across the broken mesa country west of the Dolores, making three stations on the route to complete a small piece of topography that had been omitted the previous year, on account of: the hostility of the Ute Indians. After making a primary station on the highest point of the Abajo Mountains, the party turned eastward to Lone Cone, where another station was made. Thence, crossing the Gunnison and Grand Rivers, LETTER OF THE GEOLOGIST. XV they proceeded to the great volcanic plateau at the head of White River, The final station was made between the White and Yampah Rivers, in. the northwestern corner of Colorado. During this brief season Mr. Wilson finished about one thousand square miles of topography, and made eleven primary geodetic stations, thus connecting together by a system of primary triangles the whole of ee and Western Colo- rado. In company with the triangulation party, Mr. Holmes made a hurried trip through Colorado, touching also portions of New Mexico and Utah. He was unable to pay much attention to detailed work, but had an ex- cellent opportunity of taking a general view of the two great plain-belts that lie, the one along the east, the other along the west base of the Rocky Mountains. For nearly two thousand miles travel he had con- stantly in view the Cretaceous and Tertiary formations, among which are involved some of the most interesting geological questions. He observed, among other things, the great persistency of the various groups of recks throughout the east, west, and north, and especially in the west; that from Northern New Mexico to Southwest Wyoming the various members of the Cretaceous lie in almost unbroken belts. Between the east and the west there is only one great incongruity. Along the east base of the mountains the Upper Cretaceous recks, in- cluding Nos. 4 and 5, are almost wanting, consisting at most of a few hundred feet of shales and laminated sandstones. Along the west base this group becomes a prominent and important topographical as well as geological feature. In the southwest, where it forms the ‘‘Mesa Verde” and the cap of the Dolores Plateau, it comprises upward of two thou- sand feet of coal-bearing strata, chiedy sandstone, while in the north it reaches a thickness of 3,500 feet, and forms the gigantic ‘“‘ hog-back ” of the Grand River Valley. While in the southwest he visited the Sierra Abajo, a small group of mountains, which lie in Eastern Utah, and found, as he had previously surmised, that the structure was identical with that of the four other isolated groups that lie in the same region. A mass of trachyte has been forced up through fissures in the sedimentary rocks, and now rests chiefly upon the sandstones and shales of the Lower Cretaceous. There is a considerable amount of arching of the sedimentary rocks, caused probably by the intrusion of wedge-like sheets of trachyte, while the broken edges of the beds are frequently, but abruptly, pressed up, as if by the upward or lateral pressure of the rising mass. He was able to make many additional observations on the geology of the San Juan region, and secured much valuable material for the coloring of the final map. He states that the northern limit of ancient cliff-builders in Colorado aud Eastern Utah is hardly above latitude 37° 45’. The Grand River division was directed by Henry Gannett, poate pher, with Dr. A. C. Peale as geologist. James Stevenson, executive officer of the survey, accompanied this division for the purpose of assist- XVI REPORT UNITED STATES GEOLOGICAL SURVEY. ing in the management of the Indians, who last year prevented the com- pletion of the work in their locality by their hostility. The work assigned this division consisted in part of a small area, con- taining about 1,000 square miles, lying south of the Sierra la Sal. The greater portion of the work of this division lay north of the Grand River, limited on the north by the parallel of 39° 30’, and included between the meridian of 108° and 109° 30’. This division took the field at Cation City, Colo., about the middle of August. The party traveled nearly west up the Arkansas River, over Marshall’s Pass and down the Tomichi and Gunnison Rivers to the Un- compabgre (Ute) Indian agency. Here they secured the services of sev- eral Indians as escort in the somewhat dangerous country which they were firstto survey. This area, lying south of Sierra la Sal, was worked without difficulty. It is a broken plateau country, and presents many extremely curious pieces of topography. Kleven days were occupied in this work. The Grand River, from the mouth of the Gunnison River to that of the Dolores, i. ¢e., for nearly 100 miles, fows along the southern edge of a broad valley, much of the way being in a low caiion, 100 to 200 feet deep. The course of the river is first northwest for 25 miles; then, turning abruptly, it flows southwest, and then south, for about 75 miles. This valley has an average width of 12 miles. It is limited on the north and west by the ‘‘ Roan or Book Cliffs,” and their foot-hills, which follow the general course of the river. These cliffs rise from the valley in a suc- cession of steps to a height of about 4,000 feet above it, or 8,000 to 8.500 feet above the sea. From its crest this plateau (for the Book Cliffs are but the southern escarpment of a plateau) slopes to the north-northeast at an angle of not more than five degrees. It extends from the Wahsatch Mountains on the west to the foot-hills of the Park range on the east, and presents everywhere the same characteristics. The Green River crosses it, flow- ipg in a direction exactly the reverse of the dip. It borders the Grand on the north for 100 miles, the crest forming the divide between the Grand and the White. On the south side of the crest are broken cliffs ; on the north side, the branches of the White cafion immediately. This leaves the divide in many places very narrow, in some cases not more than 30 to 40 feet wide, with a vertical descent on the south toward the Grand River, and an extremely steep earth-slope (35° in many cases) at the heads of the streams flowing north to the White River. This crest, though not over 8,500 feet in height, is the highest land for a long dis- tance in every Hasan. After leaving the Uncompahgre aeenee. the party followed Gunni- son’s Salt Lake road to the Grand and down that river to the mouth of the Dolores, in latitude 38° 50’, longitude 109°17’. At this point they turned northward, and went up to the crest of the Book plateau. They followed the crest to the eastward for upward of 100 miles, or to longi- - LETTER OF THE GEOLOGIST. XVII tude 108° 15’; then descended to the Grand and followed it up to longi- tude 107° 35’, and thence via the White River (Ute) Indian agency to Rawlins, where they arrived on October 23. The whole area worked is about 3,500 square miles, in surveying which about sixty stations were made. The geological work of this division, by Dr. Peale, connects directly with that done by him in 1874 and 1875. Sedimentary formations pre- vail in both districts visited during the past season. The country first examined lies between the San Miguel and Dolores Rivers, extending northward and northwestward from Lone Cone Mountain. The general character of this region is that of a plateau cut by deep gorges or caiions, some of which, especially toward the north, extend from the sandstones of the Dakota group to the top of the Red Beds. The depth of the cation, however, is no indication of its impor- tance as a stream-bed, for, excepting the main streams, it is dry the greater portion of the year. There are not great disturbances of the strata, what folds do occur being broad and comparatively gentle. The San Miguel River, on leaving the San Juan Mountains, flows toward the northwest, and, with its tributaries, cuts through the sand- stones of the Dakota group, exposing the variegated beds lying beneath, that have generally been referred to the Jurassic. About 25 or 30 miles north of Lone Cone, the river turns abruptly to the west and flows west and southwest for about 15 miles, when it again turns and flows gener- ally northwest, until it joins the Dolores. Between the San Miguel and Lone Cone the sandstones of the Dakota group, or No. 1 Cretaceous, are nearly horizontal, forming a plateau which, on approaching the mountains, has a cropping of Cretaceous shales. Beyond the bend, the San Miguel flows in a monociinal valley, in which the canon walls are of the same description as in the upper part of its course. As the mouth is approached, the Red Beds appear. Between this portion of the course of the San Miguel and the almost parallel course of the Dolores, which is in a similar monoclinal rift, there are two anticlinal and two synclinal valleys parallel to each other. They are all occupied by branches of the Dolores. Lower Cretaceous, Jurassic, and Triassic strata outcrop, and present some interesting geo- logical details, which will be fully considered in the report on the district. The Dolores River comes from a high plateau in a zigzag course, flowing sometimes with the strike, and sometimes with the dip of the strata. Its general course on the western line is about northwest, from which it turns to the northward and westward, finally changing to northwest again, to its junction with the Grand. It is in cafion the greater part of its course. In the region of country north of Grand River, the geological forma- tions extend uninterruptedly from the Red Beds exposed on Grand River to the white Tertiary cliffs forming the summit of the ‘Roan Mountains,” or Book Cliffs. The Grand is generally in a cation in the II G XVIII REPORT UNITED STATES GEOLOGICAL SURVEY. -Red Beds; on the north side the No. 1 Cretaceous sandstone forms a hogback, sloping toward the cliffs. Between the crest of this hogback and the cliffs there is a broad valley formed by the erosion of the soft Cretaceous shales which extend to the base of the cliffs, and in some places form their lower portion. The cliffs are composed mainly of Cretaceous beds, rising one above another in steps until an elevation of about 8,000 feet is reached. The summit is the edge of a plateau slop- ing to N. N. E. This plateau is cut by the drainage flowing into the White River from the south. These streams rarely cut through the Tertiary series. Coal of poor quality is found in the sandstones of the Dakota group, and also in the sandstones above the Middle Cretaceous beds.. Wher- ever noticed it was iu their seams, and of little economic importance. The White River division was directed by G. B. Chittenden, as topog- rapher, accompanied by IF’. M. Endlich, as geologist. The district assigned to this party as their field for exploration during the season of 1876, commenced on the eastward at longitude 107° 30’, joining on to the work previously done, and extended westward 30 miles into Utah Territory. Its southern boundary was N. latitude 39° 38’, while the White River formed the northern limit. In order to complete to the greatest possible advantage in the short time that could be al- lowed, it was determined to make the White River agency headquarters, and in two trips from there finish the work. About 3,800 square miles comprised the area surveyed. In working up the topography of this district the party spent 48 days of absolute field-work, made 41 main topographical stations and 16 auxil- iary ones, and traveled within the district about 1,000 miles. The party ascertained the courses of all the main trails, the location and quality of almost all the water, which is scanty throughout, and can map with con- siderable accuracy the topographical forms and all the water-courses. The area is almost entirely devoid of topographical “ points,” and the topographer is obliged to depend to a considerable degree on those far to the north and south for the triangulation. The country has hereto- fore been almost entirely unexplored, and was described by the nearest settlers as a broken cafon country, extremely dry. It was marked on the maps as a high, undulating plateau, with fresh-water lakes and timber. The party saw no lakes of more than 400 yards in diameter, and only two or three of these. The country is nearly all inhabitable, both winter and summer, and considerable portions of it valuable; and though three-quarters of it is within the Ute Indian reservation, the advantage of a more accurate knowledge of its character can readily be seen. While working in the low, broken country of southwestern Colorado, last year, Mr. Chittenden made use of a light, portable plane-table, and found it of great value. It appeared at that time that its value was greatest in that class of country, and that in a low, rolling district, with LETTER OF THE GEOLOGIST. XIX few prominent points, or ina high mountain country, it would probably be of little or no use. Altitudes were determined by the mercurial ba- rometer, with a base at the White River Indian agency, and checked by a continuous system of vertical angles. The altitude of the agency has been determined by a series of barometric observations extending over two years and a half, and referred to railroad levels, and can probably be depended on to within a few feet. The altitude of the agency being about 6,500 feet, and the altitudes in the district ranging from 5,000 to 8,000 feet, makes its location the best possible in height for a barometric survey of the region. It is the intention of the survey, during the coming year, to publish some tabulated results of the barometric work in Colorado, showing the system and its accuracy and reliability. This may be of use in future work, since the topography of the whole west must greatly depend on barometric determinations of altitude, and Colorado has furnished almost every possible phase of western topography. The longest dimension of the work lying east and west, and the White and Grand Rivers running in approximately parallel courses, the dis- trict stretched from the White River up over the divide between the Grand and White, and embraced the heads of the lateral drainage of the former river. The general topography is a gentle rise from the White River toward the south, and a sudder breaking off when the divide is reached into rugged and often impassable cliffs, known on the maps as the Roan or Book Mountains. The gentle plateau slope of the White River side is cut by almost numberless and often deep cations, and in many cases the surface of the country has been eroded away, leaving broken and most picturesque forms, the lower benches generally covered with cedars and pinons, and the upper rich in grass. There are four main streams draining into the White River within the limits of our work—a distance of something over 100 miles. The eastern- most is alarge running stream; the second, though tolerably good water may be found in pools in its bed, carries in the summer no running water for the greater part of its course; the third has for most of its length a trickling stream of the bitterest of alkali water, while the fourth and westernmost one is perfectly dry for some twenty-five miles from its mouth, and then forks, one branch containing pure, sweet water in pools, the other a running stream of bitter alkali. All of these streams have more or less good water at their heads. The party traveled nearly the whole length of all these water-courses, but found good trails only in the two middle ones. Trails, which traverse the whole district in every possible direction, keep mostly on the summits of the ridges and plateaus, and by taking care not to-cross the cafions, the country is very easily traveled through. The country is almost entirely destitute of timber, and has but little good water. Itis, however, abundantly supplied with grass, and, espe- xx REPORT UNITED STATES GEOLOGICAL SURVEY. cially in the winter season, must be well stocked with game. It seems well adapted to its present use as an Indian reservation, and is likely to remain for years to come more valuable for the Indians than it could be for settlement. In the far western portion, and outside the limits of the reservation, one large vein of asphaltum and several small veins were found, and also running springs of the same material, all of which, if once reached by railroads, will prove of great commercial value. These deposits have been spoken of before, but their location has not been accurately de- termined, The principal vein seen by this party is at present about one hundred miles from railroad communication, but less than half that dis- tance from white settlement, and is likely in the present rapid growth of that country to be within a few years made available. According to the report of F. M. Endlich, the geology of this district is very simple, though interesting. Inasmuch as but one divide of impor- tance occurred within the district, the work was somewhat simplified. This was formed by the Book Cliffs, between the drainages of the Grand — on the south and the White on the north. Both these rivers flow, a lit- tle south of west, into Green River, which they join in Utah. From the junction of the Grand and Green downward the river is called the Great Colorado. Orographically, the region surveyed is comparatively sim- ple. The Book Cliffs are the summit of a plateau about 8,000 feet above sea-level, continuing unbroken over to the Green River. Toward the south these cliffs fall off very steeply, forming deep cations that contain tributaries of the Grand River. On the north side, with the dip of the strata, the slope is more gentle, although, in consequence of erosion, numerous precipitous cliffs are found. Descending in that direction, the character of the country changes. Instead of an unbroken slope, we find that the plateau has been cut parallel by the White River drainage, and the long, characteristic mesas of that region testify to the action of erosion. Approaching the river, constantly descending with the slight dip of the strata, the bluffs become lower and lower. Though the creek- valleys are wide, and at certain seasons no doubt well watered, the veg- etation is that of an arid country. Dwarf pines, piflons, and sage-brush abound, to the aimost entire exclusion of other trees or grass. ‘Travel- ing down White River, this character is again found to change. A new series of bluffs, occasioned by heavy, superincumbent strata, gives rise to the formation of deep cafions. For forty-five miles the party followed the cation of the White, that, no doubt, is analogous to that of the Green, and probably closely resembles that of the Colorado in its detail features. Vertical walls inclose the narrow river-bottoms, and the slopes of the higher portions are ornamented by thousands of curiously-eroded rocks. ‘‘Monuments” of all kinds, and figures that can readily be compared to those of animated beings, enliven the scenery, which otherwise would be very monotonous; 2,000-3,000 feet may be stated as the height of the walls inclosing the White River. LETTER OF THE GEOLOGIST. XXI Geologically speaking, the district was one of singular uniformity. Traveling westward, the older formations reaching back as far as the Triassic, were found. This was followed by Cretaceous, which in turn was covered by Tertiary. About three-quarters of the region surveyed was found to contain beds belonging to this period. Owing to the lith- ological character of the strata, water was a rare luxury in this region, and men and animals were frequently dependent upon looking for springs. Farther west still the Green River group sets in, forming those numer- ous cations of which that of the White River is one. Having completed their work by October 14, the party marched eastward through Middle Park, and after twelve days of rain and snow reached Boulder City, Colo. The field-work of the Yampah division during the past season was principally confined to a district of Northeastern Colorado, lying between the Yampah and White Rivers, and between Green River and the sub- ordinate range of mountains that lies west of and parallel with the Park range. The area is embraced between parallels 39° 30’ and 40° 30’, and meridian 107° 30’ and 109° 30’. The party consisted of Mr. G. R. Bechler, topographer, directing, ac- companied by Dr. C. A. White, the well-known geologist. They pro- ceeded southward irom Rawlins Springs, a station on the Union Pacific Railroad, August 6, toward their field of labor. From Rawlins Springs to Suake River, a distance of eighty miles, table-lands form the chief feature of the topography, while from Snake River to the Yampah River the surface is more undulating and thickly covered with sage. Between the Yampah and White Rivers, a distance of fifty miles, the country is mountainous, and on the divide between the Yampah and White Rivers © the elevation is 8,000-9,000 feet. Mr. Bechler, after having formed the geodetic connection with the work of previous years, concluded to finish the more mountainous portion of the area assigned to him, which be- gan from a line of meridian with the White River agency, and extended westward to about 108° 10’. Here the party found water and grass in abundance, with one exception. The plateau country, however, was so destitute of water and so cut up with dry gorges or cailons, with scarcely any grass or timber of any kind, that traveling was rendered very diffi- cult. The party therefore made White River its base of supply for water and grass, making side trips into the barren hill-tops or plateaus in every direction. From the Ute agency, which is located approximately in latitude 38° 58’ and longitude 107° 48’, the White River takes an almost due west course for 15 or 18 miles, most of the way through an open valley, with here and there narrow gorges. About 50 miles from the agency the river opens into a broad, barren valley, with only here and there scanty patches of vegetation. Soon after the river enters a deep caiion, with vertical walls 2,000 feet or more in height, and continues to increase in depth until the river flows into the Colorado of the West. XXII REPORT UNITED STATES GEOLOGICAL SURVEY. The Yampah or Bear River deviates from a westerly course only for a few miles occasionally. Like White River, it flows through a plateau country, which rises gently from the river back for a distance of about eight miles. South of the river lie the Williams River Mountains, which have a gradual slope to the north. Williams Fork, flowing from a south- eastern direction, joins the Yampah River west of the junction. The Yampah traverses the country more or less in a caon, occasionally emerg- ing into an open, grassy valley, then enters a deep cation, cuts through the Yampah Mountains, when it joins with the Snake River. The place of junction resembles a fine park, surrounded on all sides with eroded terraces and plateau spurs that rise by steps to the divide on either side. This park is about eight miles in length from east to west. After leav- ing this park the river enters a huge fissure in the mountains, where it remains until, completing its zigzag course, it joins the Green River in longitude 109° 40’ and latitude 32°. After the junction with the Yam- pah, the Green River continues in a caiion for fourteen miles, where it passes through the picturesque palisades of Split Mountain into an open, broad valley, longitude 109° 15’, latitude 40° 28’, from which point it takes a southwest direction through the Wamsitta Valley, where it unites with the White River. Into both White and Yampah Rivers nu- merous branches extend from either side, forming deep cations the greater portion of their length. We may say, in brief, that the sides of the valleys expand and contract, at one time forming the beautiful grassy valleys which in olden times were celebrated as the favorite win- tering places for the trappers, or contracting so as to form narrow caiions or gorges with walls of varied height. The walls of Yampah Caton average 1,000 feet, while the mountains, receding back to the northward, attain an elevation of 4,200 feet, while the highest point of the plateau on the south side is 3,400 feet above the river-level. Of the plateaus between White and Yampah Rivers, Yampah _ pla- teau is the largest, and occupies an area of 400 square miles. The sur- face of the summit is undulating, and on the south side it presents a steep face, several hundred feet in height, covered with débris, render- ing it almost inaccessible. This plateau is covered with excellent grass, and gives origin to numerous springs, all of which dry up within a short distance of their source. As a whole, this district is very arid, barren, and almost destitute of tree vegetation. The total number of stations made by Mr. Bechler in the district as- signed to him was 40, and the entire area was about 3,000 square miles. Barometric observations were made whenever needed, and about 2,000 angles of elevation and depression, with fore and back sights, so that material for obtaining correct altitudes is abundant. The rocks of this district embrace all the sedimentary formations yet recognized by the investigators who have studied the region that lies LETTER OF THE GEOLOGIST. XXIII between the Park range and the Great Salt Lake, namely, from the Uinta quartzite (which underlies the Carboniferous) to the Brown’s Park group, or latest Tertiary, inclusive. Not only has the geographical dis- tribution of these formations been mapped, but all the displacements of the strata have been traced and delineated. The last-named investiga- tions bring out some interesting and important facts in relation to the orographic geology of the region, especially as regards the eastern ter- mination of the great Uinta uplift and the blending of its vanishing pri- mary and accessory displacements with those of the north and south range above mentioned. Much information was also obtained concern- ing the distribution of the local drift of that region, the extent and geo- logical date of outflow of trap, &c. The brackish-water beds at the base of the Tertiary series, containing the characteristic fossils, were discovered in the valley of the Yampah. They are thus shown to be exactly equivalent with those, now so well known, in the valley of Bitter Creek, Wyoming Territory. These last- named localities were also visited at the close of the season’s work, and from the strata of this horizon at Black Buttes station three new species of Unio were obtained, making six clearly distinct species in all that have been obtained, associated together in one stratum at that locality. They are all of either distinctively American types or closely related to species now living in American fresh waters. They represent by their affinities the following living species: Unio clavus, Lamarck ; U. securis, Lea; U. gibbosus, Barnes; U. metaneorus, Rafinesque; and U. complan- atus, Solander. They are associated in the same stratum with species of the genera Corbulo, Corbicula, Neritina, Viriparus, &c., and which stratum alternates with layers containing Ostrea and Anomia. The close affinity of these fossil Unios with species now living in the ‘ Mississippi River and its tributaries seems plainly suggestive of the fact that they represent the ancestry of the living ones. An interesting series of facts has also been collected, showing that some of the so-called American types of Unio were introduced in what is now the great Rocky Mountain region as early as the Jurassic period, and that their differen- tiation had become great and clearly defined as early as late Cretaceous and early Tertiary times. Other observations suggest the probable lines of geographical distribution during the late geological periods of their evolutional descent, by one or more of which they have probably reached the Mississippi River system and culmivated in the numerous and diverse forms that now exist there. The work of the season of 1876 shows very clearly the harmonious rela- tions of the various groups of strata over vast areas, that although there may be a thickening or a thinning out of beds at different points, they can all be correlated from the Missouri River to the Sierra Nevada ba- sin. The fact, also, that there is no physical or paleontological break in these groups over large areas from the Cretaceous to the Middle Tertiary is fully established. The transition from marine to brackish water forms XXIV REPORT UNITED STATES GEOLOGICAL SURVEY, of life commences at the close of the Cretaceous epoch, and, without any line of separation that can yet be detected, continues on upward until only purely fresh-water forms are to be found. Dr. White, an eminent paleontologist and geologist, says that the line must be drawn some- where between the Cretaceous and Tertiary epochs, but that it will be strictly arbitrary, as there is no well-marked physical break to the sum- mit of the Bridger group. If, however, a well defined nonconformity is found to exist it will be examined with great care and its proper value given, but up to the pres- ent time the views as stated above are sustained by the facts, so far as the investigations by this survey have extended. Excellent progress has been made in the report on the general geol- ogy ofthe country west of the 94th meridian. It is the intention of the survey to discuss the geology of the portions of the West which have been reported upon either by the parties under my charge or by others. It is believed that there is a remarkable unity in the geological structure of the entire area; that although formations of the same age have received a great variety of local names, they will be so correlated that a single sys- tem of classification will include them all. Asan illustration the pliocene lake basins which have received a variety of names, as Loup Fork, North Park, Uintad Group, Brown’s Park, Humboldt Group, may all be brought under one generic term and into one geological horizon. The Cretaceous divisious which are so well marked in the Northwest, and have already received suitable geographical names, can be extended to the Pacific Coast, and all the fragments be brought into one group or another. I had intended to publish several chapters on this subject in this report, but the pressure of other duties prevented their comple- tion in time. In order to show the unity more perfectly a map of the country west of the 94th meridian has been prepared, dividing the area into twenty- two rectangles, each of which on a scale of twelve miles to one inch will form a map of the size of the “‘ General Geological Map” in the “ Atlas of Colorado.” It is believed that in no other way can a systematic idea of the geology as well as the geography be obtained. The relation of the topographical surveys to the general system of public land surveys is important, and the economic resources have always been a leading feature in our plans. The following paragraphs from the letter of instructions of the Secretary of the Interior show the importance attached by the department to these features: In the prosecution of your surveys you will, when necessary, consult such public land surveys as have been made under this department, in the field of your work, for the purpose of connecting the established lines with your system of triangulation, and of accurately designating on your maps the position of mineral claims. You will deter- mine as far as possible the boundaries of Territories and Indian reservations, and mark the same by suitable monuments. You will also ascertain the position of all agricul- tural lands, and of such mineral lands as you may discover, by trigonometrical meas. urements, placing suitable monuments thereon for the guidance of the surveyors-gen- eral of the several districts which may be explored by you. LETTER OF THE GEOLOGIST. XXV It will be borne in mind that the ultimate design to be accomplished by these sur- veys is the preparation of suitable maps of the country surveyed for the use of the government and of the nation, which will wfford full information concerning the agri- cultural and mineral resources, and other important characteristics of the unexplored regions of our Territorial domain. To this end, a general plan for mapping the area of your survey should be followed. Such a plan was adopted by this department last year, and accompanied your instructions for that year. You will continue to conform to said plan, and will make such scientific observations, touching the geology, geo- graphy, mineralogy, and meteorology of the country surveyed by you, as may be neces- sary for the preparation of such maps. In addition thereto, you will obtain the neces- sary information for the preparation of charts, upon which shall be indicated the areas of grass, timber, and mineral lands, and such other portions of the country surveyed as may be susceptible of cultivation by means of irrigation; and will ascertain and report upon the best methods for accomplishing this result. The economic map in the “ Atlas of Colorado” presents an example of the minuteness of detail with which the economic features of a coun- try may be laid down on achart. This map, covering an area of over 100,000 square miles, shows with remarkable clearness, by means of colors, the agricultural and pastoral lands, the pine and other forests, the barren lands, and those above timber-line—all the valuable mineral deposits, as coal, silver, and gold. Anexcellent article on the economic resources of Colorado, by Mr. Gannett, is embodied in this report. In all the annual reports of the survey since 1867 more or less attention has been given to this subject. Before proceeding to a description of the triangulation in Colorado and its relations to the land surveys, it may be well to give a general description of the method of locating points by triangulation. In this method the only direct measurements made are those of one or more base lines; all other measurements are derived from those by the measurements of angles. For the measurement of a hbase line, a flat extent of country, of a suit- able length, is selected. The ground should be as nearly horizontal as possible, and the two ends, and, if possible, all points of the proposed base, should be intervisible. The length of the line should be measured with all the accuracy possible under the circumstances, as any error in this measurement is increased manifold in the subsequent triangula- tion. In the Coast Survey the lines are measured by metal bars, compensated for temperature, and the contact between the ends of the bars is made by a microscope. In this case the operation of measuring and remeas- uring a base five miles long occupies several weeks, and the error does not exceed a small fraction of an inch. In the work of this survey, which does not admit of the devotion of so much time and expense, these measurements have been made with a 100-foot steel tape. The measurements are, of course, corrected for temperature, slope, and error of tape, and are reduced to sea-level. The base measured, a distance of perhaps 5 or 6 miles, the next step is to “expand” it, that is, to obtain from this known distance of 5 or 6 miles XXVI REPORT UNITED STATES GEOLOGICAL SURVEY. the accurate length of a line 20, 30, or 40 miles in length, the mean dis- tance between stations of the triangulation. For this purpose, points are selected on the right and left of the base line, at such distances from it that the triangles formed by each of these points, and the two ends of the base, will be ‘‘ well conditioned”; that is, that the angles of the triangles will be as nearly equal as possible. Then all of the angles of each of these triangles are measured. Now, were these angles measured perfectly, the sum of the three of any triangle would be 180° plus the spherical excess. The amount of the discrepancy is an indication of the accuracy of the work. Now, in each of these triangles there is given a side and the three angles, and a simple trigonometrical calculation gives the lengths of the other sides; these other sides, thus calculated, furnish bases for further triangles, each larger than those used before, and thus the enlargement goes on until the normal length of sides of triangles is reached. This completes the expan- sion, and thence the triangulation goes on by the simple measurement of angles, the sides of the triangles being kept as nearly as possible of the same length and the angles as nearly equal as possible. A second base is usually measured as a check on the first. From it an expansion is made, and the work connected with that from the first. To ascertain the direction or azimuth of these lines, it is necessary to know only the direction of any one of them, although practically the directions of several are measured, as checks on one another. The measurement consists in measuring the angle between the line and some slow-moving star, usually the pole star, whose distance from the north pole is known at the time. Now, this system of triangulation is consist- ent in itself, but its position on the earth’s surface is unknown. To de- termine this requires the aid of astronomy. Oneor more of the stations in this triangulation must be fixed by astronomical means, and the char- acter of the work is such as to warrant the employment of the best in- struments and the most refined methods for the determination of the latitude and longitude of this or these points. For the determination of the latitude, we use the zenith telescope, and the method of zenith dis- tances of stars. To describe this method would require more space and technical language than could be used here. Suffice it to say, that this method determines the Jatitude within a few tenths of a second, where a second is about 100 feet. . The longitude is determined by the comparison of the local time of the station with that of some point whose position is known. This com- parison is made by telegraph. The beats of the chronometer are trans- mitted back and forth by telegraph, and recorded side by side on paper, by an ingenious instrument known as the chronograph. The difference between the local times of the two stations is the differ- ence in longitude. This local time is determined at each station by ob- Serving the transits of stars, whose positions are known, with a transit instrument. These observations give the error of the chronometer and LETTER OF THE GEOLOGIST. XXVII hence the local time. By this method the longitude of a point can be determined within 30, 40, or 50 feet at the worst. Now, the latitude and longitude of a point being known, those of all other points also are determined, as their distances and directions from the first point are given by the triangulation, and the whole system is correctly placed on the earth’s surface. In the inception of the work in Colorado a base line was measured near Denver, mainly on the track of the Kansas Pacific Railroad. Two measurements were made of it, with a steel tape 100 feet long, under a tension of 16 pounds. The end of each 100 feet was marked by a knife- edge on the railroad track, or on a low stool. The profile of the line was leveled, and the temperature of the tape was constantly measured. The results of two measurements, corrected for temperature and slope, are respectively 31,861.304 and 31,863.102 feet, showing a discrepancy of about 1.8 feet, or about >=4,; of the length. It was, of course, cor- rected for error of tape, and reduced to sea-level. From this base, triangulation was extended and carried are the mountains. Then a second base was measured in San Luis Valley. The methods were the same, and the results better than in the case of the Denver base. Six days were occupied in its measurement and re- measurement. The corrected results are as follows: 28,522.74 and 28,522.558 feet, a difference of only 43; of a foot in 54 nflies. Connecting ine triangulation from those two bases with one another, the error was found to be only 94 inches to the mile. This error is the sum of the errors of the measurements of the bases and of the triangu- - lation as brought through nearly 200 miles. The angles were measured with theodolites whose circles were 8 inches in diameter, receding to 10” of are. All the stations were marked by monuments 5 to 10 feet in height. In the whole scheme of triangulation of Colorado, 143 complete tri- angles have been measured, with a mean error of closure of 13.3. The errors of measurement of the sides of the triangles will not exceed $ of a foot per mile, and the error of location of the primary stations is not greater than 25 feet. The area covered in Colorado is about 70,000 square miles. For the location of the work in latitude and longitude, it was deemed best, on account of the expense of instruments, &c., to ask the Coast Survey, which is completely fitted in this respect for the work, to determine the latitude and longitude of several points for us. This they very kindly consented to do, and established the position of points in Denver, Colorado Springs, and Trinidad, Colo., for us with the greatest accuracy. The next point is, how these locations are to be used for the inception of land surveys in isolated mountain valleys, and for the elimination of errors in the work of these surveys. We may premise that either case requires more knowledge of surveying XXVIII REPORT UNITED STATES GEOLOGICAL SURVEY. than usually falls to the lot of a deputy surveyor, and that they will not utilize these points unless required so to do by law. In the first of the above cases, we may Suppose a valley, surrounded by high, rugged mountains, over which it would be very expensive to run a line at all,and impossible to do it with any approach to accuracy. Suppose that a mountain peak on the edge of this valley has been ac- curately located and its latitude and longitude given. The latitude and longitude of the point in this valley which should be the nearest township corner to this peak can easily be deduced by calculation, whence the distance and direction of this supposed township corner from the peak can also be computed. All that remains to be done, then, is to find the point in the valley at the requisite distance and direction from the peak, and this point is the township corner, whence the survey may be carried on in the usual manner. Take, as an example, the valley of the Uncompahgre, in Western Colorado, a large, fertile valley, which will soon require to be surveyed. The nearest surveys are now, I understand, on the Gunnison, at the mouth of Cochetopa Creek. To carry a base line thence to the Uncompahgre Valley will require the chaining of about 50 miles over rugged mountain country. Instead of this, take Mount Sneffles, a peak in the San Juan Mountains overlooking this valley, as a Starting point. The township corner which will come near- est to this peak is, we will say, the 8th township, 7. ¢., 48 miles west of “the last one at the mouth of Cochetopa Creel, where the surveys now ex- tend. Knowing the latitude and longitude of the latter point, that of the supposed corner in the Uncompahgre Valley, being 48 miles farther west, can easily be computed, and knowing this, its distance and direction from Mount Sneffles can also easily be computed, and the line run from the summit of Sneffles to the required point. In the second case, that of using these points as checks on the accu- racy of the land surveys, I would recommend that the surveyors, when- ever, in running lines, they pass near a located point, be obliged to con- nect their lines with it by chaining. Then the astronomical position of the corner, as determined by their work, and by connection with the station of triangulation, should agree. If they do not, the most of the error 1S in the land surveys, and they should be corrected accordingly. This will not only vastly increase the accuracy of the work, but will prevent the manufacture of the notes in camp. Moreover, these geodetic stations, which are in all cases mountain peaks whereon the station is marked by an indestructible stone cairn, would furnish points of reference for all time, in case disputes should arise concerning boundaries, &c. Monuments are built on all the stations in the primary triangulation, and on those of the secondary triangulation, wherever material for their construction is available. They are built of stone, simply piled up in the form of a pyramid; are of a minimum height of 5 feet, thence up to 15 feet. LETTER OF THE GEOLOGIST. XXIX Where material is immediately at hand, as is usually the case, a mon- ument five to six feet high can be erected in half an hour by two men. Our experience has been that the erection of these monuments re- quires no additional force, and but a trifling amount of time, and hence need involve no extra expense whatever. On our final maps, those stations on which monuments have been erected will be appropriately marked, and their correct positions, in lati- tude and longitude, will be given. The public-land surveys, by use of these monuments, will be enabled to effect a great Saving in running base-lines and guide-meridians over difficult mountain country. Also, the large errors, which such lines are almost sure to involve, are avoided. A more detailed account of the publications of the survey and the office work will be given in the annual report for 1877, which will go to press in October. With the hope that this report wil! prove of value to the government and to science it is respectfully submitted. I have the honor to be your obedient servant, | \ F. V. HAYDEN, United States Geologist. To Hon. CARL SCHURZ, Secretary of the Interior. Fae ts teh ey aes ae 1G BeAr Fr. GEOLOGY. REPORT OF G. A. WHITE, M. D. LETTER OF TRANSMITTAL. WASHINGTON, D. C., November 1, 1877. Sir: I have the honor to transmit herewith my report on the geology of a portion of Northwestern Colorado, it being the district that was assigned to me for examination during the season of 1876. The amount of time I was enabled to give to the work during that season was comparatively short, and my movements in the field having been dependent on those of the topographical party, the results were necessarily incomplete; but having been able to devote a part of the season of 1877 to the same district, I have succeeded in working out its structural geology with a good degree of satisfaction. My method of prosecuting the work was, besides the ordinary exam- ination of the rocks and the surface of the region as I traversed it, to go upon the higher and more prominent points and make my field-notes and Sketches there. Besides visiting all the topographic stations in this way, I established many note stations of my own, also. Thus the whole dis- trict was examined in detail, and every feature of its geological structure was seen and traced by my own eyes; which the slight accumulation of soil or débris upon the surface and the sparseness of vegetation in that arid region rendered entirely practicable. On a subsequent page I have correlated the general section of the rocks of my own district with those prepared by Powell and King, respect- ively, for adjoining districts, as I understand them after a considerable personal examination of the geology of those districts. . This report is chiefly confined to the structural geology of the district, which is found to possess peculiar interest; but many interesting facts were also observed concerning its economic and surface geology, drift, trap-outflows, &c., which are recorded on following pages. Very respectfully, yours, C. A. WHITE. Dr. F. V. HAYDEN, In charge of the Geological and Geographical Survey of the Territories. REPORT ON THE GEOLOGY OF A PORTION OF NORTHWESTERN | COLORADO. CHAP Hl) i INTRODUCTION. The district upon which the following report is made, is included within the following boundaries: The eastern boundary is approxi- mately upon a straight line drawn from a point where the meridian of longitude 107° 50’ west from Greenwich crosses White River, to where the meridian of 107° 25’ crosses Yampa River. The northern boundary is the parallel of north latitude 40° 30'; the southern is the channel of White River, and the western the meridian of 109° 30’. The area thus inclosed’ contains about 2,400 square miles. The Yampa River has its course near, and its general direction approximately coin- cident with the northern boundary just mentioned ; bending and mean- dering on each side of it, so that, in general terms, the Yampa and White Rivers may be said to be respectively the northern and southern bound- aries of the district. The meridian which constitutes the western boundary is thirty minutes west of the joint boundary-line between Colorado and Utah. The eastern boundary is not a distinctly defined one, because this district adjoins the one which was surveyed by the late Mr. A. R. Marvine, and which was bounded on the west by no definite geographical features. It is, however, practically as above ‘stated. The Yampa and White Rivers are both tributaries of Green River, which is itself the principal tributary of the great Colorado River of the West. This district is thus shown to be upon the Pacifie-drainage slope of the continent, the great Rocky Mountain chain lying wholly to the east of it, but some of the western foot-hills of which rest upon its eastern border. Strictly speaking, this district is only in part a mountainous one, although it is by no means a plain-country in any considerable part. It lies between two separate and important mountain systems, namely those of the Uinta and the Park Ranges (the latter being a subordinate portion of the great Rocky Mountain Range), each of which, especially the former, occupies a portion of its area. The Uinta Mountains have an east and west, and the Park Mountains a north and south trend, or, in other words, their axes are approximately at right angles with each other. Theeastern end of the Uinta Range occupies a large portion of the northwestern part of the district, while the eastern portion of the district extends up to the western foot-hills of the Park Range. The district is an elevated one, aside from its mountains. The lowest level within its limits, which is the surface of Green River, is about 5,000 feet above the level of the sea, while the higher points of land, both those of the eastern and northwestern portions of the district, reach an altitude of more than 9,000 feet above the level of the sea. In con- sequence of this great elevation and of the dryness of the climate, vege- 5) 6 REPORT UNITED STATES GEOLOGICAL SURVEY. tation is scant and in large part dwarfed. This scantiness of vegeta- tion, and the rapid removal of the débris of disintegrated rock in time of rains and melting snows, and consequent flooding of the drainage- channels, leaves the surface, especially that of the hill and valley sides, so bare that the strata, for the rocks are all stratified, are as distinctly seen as the leaves of a book. The geologist, therefore, may go to the top of any of the mountains or higher hills and see the geological structure of the neighborhood spread out below him like a well-drawn picture; and even the geolog- ical structure of the more distant parts of the landscape may often be accurately determined from these elevated points of observation. These conditions of the surface give great advantage to the geologist ; not only insuring great accuracy in his work, but they also enable him to accomplish it with extraordinary rapidity. This explanation, besides setting forth an interesting fact, is also really dae to those who, not ‘personally acquainted with the peculiarities of that region, may com- pare the detailed reports that geologists have made upon various por- tions of it with the comparatively short time they are known to have been engaged upon the field-work. In no humid country, where the débris of disintegrated rock profusely and often deeply covers the underlying strata, can the details of geolog- ical structure be so accurately ascertained, even by years of careful search, as it may be done in a region like this, within a few days. CHAPTER ITI.. SURFACE FEATURES. / MOUNTAINS. Although the elevation, above the level of the sea, of the hills of the eastern portion of the district is quite as great as that of any other portion, the more prominently distinct mountain masses within its lim- its are located in the northwestern quarter, and consist of closely ad- jacent and inseparable portions of the Uinta system. The Yampa Pla- teau constitutes the principal one of these mountain masses, the others being appendages or prolougations from it, as itself is an appendage or accessory fold of the great Uinta Uplift, lying upon the southern side of the eastern end of that chain. Section Ridge and Split Mountain are western prolongations or spurs from Yampa Plateau, and Midland Ridge is a long accessory fold and eastern prolongation from the same, at least as a topographical featuce. The latter is not so high as the plateau except at its western end, but yet it forms a very conspicuous topographical feature of the region; its bright red strata making it also >a very conspicuous geological one. Beyond this group of subordinate mountain masses, to the northward and northwestward, lies the main fold of the Uinta system; and stretching to the westward ‘its great chain of peaks is seen, with their patches of perennial Snow glittering i in the midsummer sunlight. Junction and Yampa Mountains are remarkable, isolated mountains, each about 2,000 feet high above the surface of the lowland of the basin out of which they rise; but they both belong to the Uinta system and lie upon the vanishing extension of the flexure of the great Uinta Up- lift; which extension I have called the axial flexure. The first-named mountain lies some three or four miles east of the eastern end of the Uinta chain, and the latter, which must not be confounded with Yampa Plateau, lies some 15 or 16 miles still further eastward, in line with the great Uinta Axis. The structure and relations of all these mountains will be discussed in a subsequent chapter. Although the elevation of the eastern portion of the district is quite as great as that of the mountain masses of the northwestern portion, the rise to the eastward is so gradual, and the surface comparatively so little broken into separate mountains within the eastern borders of the district, that it is not, strictly speaking, mountainous there. Just be- yond its limits to the eastward there is a broad elevated district called the White River Plateau. This plateau has been largely formed as such by a great trap-outflow, the borders of which are now cut by ero- sion into deep gorges and ravines, among which White River and Wil- liams Fork of the Yampa have their rise. There are some other mountain masses in the more central portions of the district, left as such by the deepening of the drainage-valleys by erosion, that, although they are really important features, have been designated by distinctive names only so far as it was found necessary 7 8 REPORT UNITED STATES GEOLOGICAL SURVEY. to apply them as aids in descriptive geology. These are the Danforth * Hills, Gray Hills, Pinon Ridge, &e., the position of each of which is shown upon the accompanying map. DRAINAGE. The greater part of the drainage of this district is effected by both the White and Yampa Rivers, in approximately equal proportion, but a large part of the permanent water of both these rivers is derived from the mountain region that les beyond the district to the eastward. Green River cuts across the northwestern portion of the district, but as it traverses deep cations in the Uinta Mountains along a part of that portion of its course, it receives very little addition to its waters there at any time of the year except what reaches it by the Yampa. Below the canons, however, a few minor drainages reach Green River from the east side; and Ashley’s aud Brush Creeks empty into it from the west side. The water-shed which divides the drainage between the White and Yampa Livers consists of an irregular and somewhat tortuous line of hills, generally recognizable as a water-shed crest when seen from other elevations at a distance. The eastern part of this water-shed lies along the crest of the Danforth Hills, and is deflected so that it has there an almost due southeast and northwest trend, the eastern end of the dis- trict being almost wholly drained into the Yampa. The western portion of the water-shed, comprising the greater part of its length, has an ap- proximately due east and west course. Its western terminus is upon the western end of Yampa Plateau, a large, broad mountain mass, which, as already explained, lies adjoining and is accessory to the great Uinta Uplift. The course of the water-shed upon the plateau is in some places within four or five miles of the Yampa River, which in this part of its course runs in a deep, narrow caion. The relation of these drainage- lines and their water-sheds to the displacements of the strata in this re- gion will be discussed under appropriate heads upon subsequent pages. That portion of this district which lies between the two great moun- tain systems before named is more or less deeply cut by drainage-chan- nels, leaving between them many elevations that are quite worthy of the name of mountains. The region embracing this district Hes far within the limits of that great portion of the United States domain in which the annual rain-fall is insufficient for the purposes of agriculture. In consequence of this dryness of the climate, the drainage-valleys and ravines just referred to, which lead into the rivers, are with few excep- tions dry during a great part of the year. These drainage-channels, which for convenience of description are called ‘“‘ dry drainage-chan- nels,” all show marks of an abundant and strong flow of water and of great and rapid denudation of the surface that is drained by them dur- ing the wet season of the year. A stranger, not familiar with the meteor- ological conditions prevailing in tbis region, travelling through it in the summer, would be impressed with the belief that the country was formerly a well-watered one, a land of a multitude of flowing streams which, tor some cause not now apparent, had suddenly and permanently ‘ceased to flow, and that in consequence the land had recently changed to a dry and barren one. The present surface features of the district are almost wholly due to itwo principal causes, namely, elevation and consequent flexion and *So named in honor of Rev. E. H. Danforth, Indian agent at the White River agency. WHITE.) SURFACE FEATURES—PARKS AND BASINS. 9 other displacements of the strata; and both simultaneous and sub- sequent subaérial denudation of the strata thus elevated. The latter process has produced what may with propriety be called the drainage features of the region. These are really the most conspicuous features of all, for the elevated portions of the great flexures have been mostly removed by the erosion just referred to. A part of the drainage of this district, like a large part of that of the whole great region within which itis located, is antecedent.* That is, it was evidently established before the principal displacements, including the great flexures, were produced. This view of the subject implies that the flexures were produced very slowly, and that before the strata began to bend the streams were already established upon the surface, and traversed the future sites of the flexures at various angles; and furthermore, that the streams continued to retain their original positions by a constant erosion, equivalent in amount with the elevation that was in progress. Iam not unaware of the weighty objections that may be urged against this theory, but it seems to accord with the greatest number and most important of known facts. It is a most remarkable fact that during this elevation of the strata the streams seem to have been very little influenced in or changed from their courses by either the favorable or unfavorable conditions for erosion of the strata themselves; mountain masses of quartzite not forcing a divergence, nor the softest strata inducing a departure from their predetermined courses. So far as my observation has yet ex- tended, it is those channels only or mainly which have a greater or less flow of perennial water that are referable to the category of antecedent drainage. On the otber hand, the present location of the dry drainage- channels of the region, as well as the unequal depth and extent to which the erosion has reached in them and upon the surface they drain, is largely due to the difference in the lithological characteristics of the strata out of which the surface features have been carved, but modified and controlled by the displacements which the strata have been sub- jected to. In other words, this part of the drainage system is mainly subsequent to or consequent upon the great movements that have resulted in the present displacements of the strata. This “consequent” drainage, although consisting mainly of those numerous minor branches which are dry during a part of the year, has produced present physical features that are scarcely less conspicuous than those which have been produced by all other causes; for by its agency almost all the immense erosion and degradation which the region has suffered has been accom- plished, while the principal streams have served as vehicles for the trans- portation of the material thus removed from the surface. PARKS AND BASINS. The terms “park” and “basin,” as names of geographical features, have been variously and somewhat loosely used by different writers. Finding it necessary to use them in this report for purposes of descrip- into, I shall apply the term ‘‘ park” only to those expansions of the river- valleys that contain more or less broad spaces of comparatively level land, a part of which is susceptible of cultivation by irrigation, and * This explanation of the relation that the river-valleys of the great Rocky Mount- ain region generally hold to the displacements that the strata have suffered, by assum- jng that the displacements took place after the rivers were established, without mate- rial change in the course of the rivers, was first suggested by Dr. Hayden in the American Journal of Science and Arts for May, 1862, and afterward in his Report for 1872, page 85. The subject was afterward well elaborated by Professor Powell in his reports. 10 REPORT UNITED STATES GEOLOGICAL SURVEY. which are surrounded by such hills or high lands as usually border the valleys. The term “ basin” I shall use for similarly excavated or hollowed spaces in the general surface of the country through which no river or perennial stream flows by which its lands may be irrigated. The basin has been produced by the erosion of the dry drainage-channels, while the park has been excavated mainly through the agency of a perennial stream. Parks, then, being really portions of the valleys, will be de- seribed in that connection, but the basins of the district will be sepa- rately considered, mainly with reference to their relation to the struct- ural geology of the district. All the parks of this district are small, and their importance lies only in the facts that their relation to the struct- ural. geology is similar to that which the basins hold, and that they contain far the greater part of the tillable land of the region. Midland Basin.—This basin is comparatively small, but a separate de- scription of it is given because of the important relation it bears to the structural geology of its neighborhood. It lies near the middle of the district, and nearer to the southern than to the northern border. Its boundaries may be designated in general terms as follows: Pion Ridge borders it upon the east; the hogbacks of the Midland Flexure upon the south; the eastern end of the Midland Ridge, in part, on the west; and its northern boundary is indistinctly defined by the broad ridge which forms the water-shed between the Yampa and White Riv- ers, Separating Midland Basin from Lily’s Park, and is continuous with the western portion of the Danforth Hills. It occupies a part of the broad anticlinal axis of the flexure that has brought up the great mass of Triassic strata which constitutes Midland Ridge and also the Fox Hills, and Laramie strata that constitute Piton Ridge. The same flex- ure has, of course, brought up the sandy shales and clays of the Colorado Group, out of which the basin has been mostly excavated. Southwest- wardly this basin is continuous, with a broad dry valley extending far, but gradually narrowing, to the westward, which valley, like the basin, is mostly excavated out of the shales of the Colorado Group. The sur- face of the basin has considerable irregularity, but is free from hills of any considerable height. Its drainage all passes into White River through a gap in the hogbacks of Midland Flexure, just west of the east- ern end of Pinon Ridge. Coyote Basin.—Unlike the other basins of this district, Coyote Basin occupies a broad synclinal instead of an anticlinal; also, it is mostly excavated out of the bad-land strata of the Wasatch Group instead of out of the soft strata of the Colorado Group as the others are. With per- haps the exception of the Bridger and Uinta groups, the Wasatch and Colorado groups are constituted of softer material than any others in this region, although in a portion of the district the Wasatch Group is in part a firm sandstone. When the conditions were made favorable by the flex- ures that all the strata of the region have suffered, those of the two last- named groups have yielded more readily to erosion than those with which they are associated. Hence the basins have been excavated out of these yielding strata only. Coyote Basin is bounded easterly by the concave sweep formed by the Gray Hills and Citadel Plateau; on the north, in part by Citadel Plateau and in part by the broad ridge that forms the water-shed between the White and Yampa Rivers and separates Coyote Basin from Axial Basin; on the west by Pifion Ridge and the high land that connects it with the water-shed 1idge before referred to. On the south this basin is, in part, continuous with the valley of White River, with which it communicates and into which river it is drained. Its surface is an irregular, desolate bad-land area, traversed by numer- WHITE.] SURFACE FEATURES—PARKS AND BASINS. 11 ous drainage-channels, some of which are quite large; but even these are nearly or quite without water in summer. The syneclinal within which this basin lies is partially surrounded by the great bend of the Midland Flexure which is represented on the geological map, and is also described in a following portion of this report. Axial Basin.—This basin occupies a great anticlinal axis, which is the eastward prolongation of the vanishing axial flexure of the Uinta Mountain uplift. Itis solong and narrow that the term “ basin” does not apply to it with strict accuracy, but the use of such a term in this con- nection is not likely to be misunderstood. It extends from Junction Mountain nearly to the eastern border of the district, and is divided into two portions by Yampa Mountain, which is a sharp upthrust of Paleozoic rocks. Junction Mountain is a precisely similar upthrust of Paleozoic rocks, and it also occupies a similar position upon the Uinta axis, at the west end of the basin. Indeed it separates that portion of the basin which has been called Lily’s Park from the main portion, in the same manner as, but less completely than, Yampa Mountain has divided that basin into two parts further to the eastward. The boundaries of the eastern portion of the basin, that which lies east of Yampa Mountain, are more clearly definable than those of the western portion are, because they consist mostly of escarpment bluffs. — This eastern portion. of Axial Basin is bounded on the west by Yampa Mountain; on both the north and the south sides by escarpments of Fox Hills strata, and it ends eastwardly by a gradual rise of the whole land to the White River Plateau. The whole of this eastern portion of the basin was primarily eroded out of the shales of the Colorado Group, but for a distance of about four miles east of Yampa Mountain the sur- face is covered by the friable strata of the Uinta Group. Upon the top ofa hill about three miles east of the eastern border of this deposit of the Uinta Group rest some of the strata of the base of the Fox Hills Group, but with these exceptions all the surface of the basin is occupied by the shales of the Colorado Group, except where these are obscured by soil, débris, or scattered drift. The Yampa River passes through only the northwestern corner of this part of Axial Basin, but, viewing the region topographically, the most natural course for that river to run would seem to be through the whole length of the basin, instead of cutting, as it has done, through the elevated land that borders the basin on the north, and which is composed of the comparatively hard sandstones of the Fox Hills and Laramie groups. This eastern portion of the basin is drained by the upper branches of Milk Creek, and a few other drain- _age-channels, which are mostly dry during a part of the year. The boundaries of the western portion of Axial Basin are much less clearly definable than those of the eastern portion. In general terms it may be said to be bounded as follows: On the east by Yampa Moun- tain; on the south by the water-shed ridge between the Yampa and White Rivers; on the west by Junction Mountain, in part, and in part by Lily’s Park. It is continuous with Snake River Valley to the north- westward, and on the north it blends, by a gradual rise, with the high lands that lie between the valleys of the Snake and Yampa Rivers. The | western portion of the basin is, therefore, much wider than the eastern portion, and a very large part of it lies beyond the northern boundary of this district. The portion that lies within the district has, like the eastern portion, been primarily excavated out of the shales of the Col- orado Group, but its surface is now occupied in very large part by the friable strata of the Uinta Group, through which, here and there, the underlying Colorado shales appear. Resting upon the Uinta deposit 12 REPORT UNITED STATES GEOLOGICAL SURVEY. is the scattered drift so common in a large part of this region. It reaches considerable thickness upon the higher surface of the basin, and also constitutes a large proportion of the bulk of the water-shed ridge before referred to. Yampa River traverses this part of the basin from east to west, and it might, therefore, with some propriety, be designated as a large park. But its basin-like character constitutes a greater aud more conspicuous feature than any of the other similar excavations in the vicinity, especially as it occupies the lowest ground between the eastern end of the Uinta chain and the mountains that lie to the east- ward of this district. Other features of both portions of Axial Basin will be referred to in the description of the valley of Yampa River. fed Kock Basin.—This basin is located adjacent to the northwestern portion of Yampa Plateau, and near the confluence of Yampa River with the Green. Midland and Axial Basins have been eroded out of soft strata that rest upon comparatively gentle anticlinal axes; and Coyote Basin has been excavated by erosion out of other soft strata that rest in an equally gentle synclinal. But Red Rock Basin differs materially from those in the character and condition of its foundation, for it really consists of a very deep synclinal flexure of the hard strata ° of Carboniferous age, from which the somewhat softer, but comparatively firm Triassiev strata have been removed by denudation, except at the bottom of the flexure, which is the bottom of the basin, where Triassic Strata still remain. It is the southern side of this great synclinal that I have called the Yampa Flexure, and which synclinal-separates the main Uinta, from the Plateau Uplift. This great synclinal flexure reaches its maximum depth at the west end of Red Rock Basin, where it ends abruptly against a mountain mass that projects northwardly from Yampa Plateau, by a north and south fault of about 2,000 feet downthrow; the depth of the basin below the northern border of Yampa Plateau being also about 2,000 feet. From this fault, the basin proper extends east- ward five or six miles, when it becomes immediately narrower and grad- ually shallower, and thence extends eastward as a long narrow syncli- nal valley until it is lost among the hills at the eastern end of the Pla- teau Uplift. This valley and the deep basin with which it is continuous would seem to be a much more natural place for Yampa River to flow in than the one it has chosen, and which will be presently described, if it were not for the theory already explained that the streams are older than the flexures of the strata. The breadth of Red Rock Basin is about the same as its length. Its depth is so great that from the southern brim, the bottom looks: comparatively plain, but it is really traversed by deep gorges that are cut in the red Triassic strata there, between which. gorges the surface is rough and hilly. VALLEYS The descriptions immediately following are of the river—valleys as surface features. Their relations to the displacements of the strata over which the rivers flow will be discussed in a subsequent chapter. The parks being only portions of the valleys, the description of each of these will be included with that of the valley to which it belongs. WHITE RIVER VALLEY.—White River, which in summer is a rapid stream of clear, cold water, rises by numerous small branches among the gorges and ravines of White River Plateau, all of which have their conflu- ence with the main stream before it enters this district on its westward course. The bed of the river is almost everywhere strewn with drift- pebbles, and its banks are usually easy of approach, except where they WHITE.] SURFACE FEATURES—VALLEYS. ES are obstructed by athick growth of bushes. The valley varies in breadth, widening in some places to form the parks before mentioned, while in other places it is narrowed to a cation, especially where the Green River Group occupies both sides of the river. Agency Park.—Just above White River Indian agency the river cuts through the sandstone strata of the Dakota Group, which there dip to the northward and norhtwestward at a considerable angle. The dip, how- ever, Soon diminishes, so that for a space of several miles below the soft strata of the Colorado Group occupy the surface. Out of these strata Agency Park has been excavated, a portion of them still occupying its surface; the upper layers of the Dakota Group appearing within the park only at one locality, which is on the right bank of the river, near the middle of the park. This park is bounded on the north by a line of escarpment blufts of the Fox Hills Group; on the east and south by hills of Cretaceous strata that lie at the western ioot of the White River Plateau ; and on the west by the Grand Hogback, which is composed of the upturned strata of the Fox Hills and Laramie Groups and separates Agency, from Powell’s Park. Besides several dry drainage-channels that traverse Ageney Park to White River, there is one brook of perennial water. This rises in the hills to the eastward, and flows through the park two or three miles and empties into the river upon its right bank. Only a small proportion of the surface of any of the parks lies within reach of irrigating-water from the rivers that run through them, but, in consequence of the somewhat rapid fall of White River, a considerable area within the limits of Agency Park lies within reach of water that may be conducted in irrigating- ‘ditches. Besides the water that may be thus taken from the river for irrigating purposes, the brook before referred to may also be made to furnish a small but, under the circumstances, valuable addition. There are some broad level spaces within the limits of the park, the surfaces of which are at various heights, a hundred feet or more, above the level of the river, that cannot be reached by irrigating-water trom it, although they constitute a part of the park surface proper. These have somewhat the appearance of morainal benches, especially as they are usually more or less thickly strewn with drift-pebbles; but they are composed of the undisturbed strata out of which the park has been excavated. They doubtless represent periodical base-levels of erosion that were suecces- sively reached during the excavation of the valley, for they are of vari- ous heights above the level of the river and are common in all the broader portions of all the river-valleys of this region. Powells Park.—This park lies immediately west of Agency Park, with which it is connecied by a gap in the Grand Hogback, through which White River flows. Its name is given in commemoration of the fact that Professor J. W. Powell and his party spent a winter here during his early exploration of this region. It is excavated out of the bad-land strata of the Wasatch Group which flank the Grand Hogback, and pass by a monoclinal flexure beneath the hills which border it to the west- ward, and which are composed of Green River strata. This park is only four or five miles wide from east to west; but as it communicates with a long dry drainage-valley that extends to the northward, and also a simi- lar but smaller one that extends to the southward, its length north and south is great compared with its width, although its boundaries are some- what indefinite. The greater portion of the irrigable land of the park lies on the north side of the river, and consequently within the limits of this district. It is Hogback Valley that is continuous with that portion of Powell’s Park which lies within this district, the drainage of which 14 REPORT UNITED STATES GEOLOGICAL SURVEY. rises at the north side of Gray Hills and courses along the flank of the hogbacks of Midland Flexure and thence parallel with the Grand Hog- back to White River. This drainage carries a large amount of water in the wet season, but it becomes entirely dry in summer. Below Powell’s Park the bluffs of the Green River Group come near to White River almost all the way to its confluence with the Green, so that between Powell’s Park and the western side of Raven Park the greater portion of the width of the valley is upon the northern side of the river. Between Powell’s Park and Coyote Basin the valley has con- siderable width on the northern side, and at several places there are considerable areas of irrigable land. Raven Park.—A comparatively small uplift, which is separate from, but accessory to, the Uinta Uplifts, crosses the valley of White River at a point southward from Midland Ridge, where it has brought up to the surface the shales of the Colorado Group; and out of these shales Raven Park has been excavated. The park lies mainly upon the north side of the river; and since the Raven Park Uplift has a quaquaversal dip, the park is wholly surrounded by an escarpment of Fox Hills: strata. The park is a small one; the river traversing its southern por- tion, a comparatively large proportion of its surface may be reached by - water from irrigating-ditches leading from the river above its upper limit. Raven Park, like the others before described, and like many other portions of the valley, contains within its limits some of those broad benches or table-lands that have been before mentioned. They are above the reach of irrigating-waters and occupy a large portion of the surface of this park. Aside from the action of White River, the excavation of Raven Park has been mainly accomplished by an exten- ° sive dry drainage-creek that has its rise many miles to the northward, upon the slopes of Midland Ridge. For a distance of several miles below Raven Park the river valley is moderately narrow, but still there are some level bottom-lands on each side of the stream. Below this,’ almost all the way to the western border of the district, the river runs in an almost continuous, deep, narrow caiion, which it has excavated out of the strata of the Green ‘River Group. The walls of this cation are always steep and often perpendicular. In some places they are nearly a thousand feet in height above the river, and approach it so closely that it is always difficult, and for many miles impracticable to traverse it with a mule-train. : YAMPA RIVER VALLEY.—The Yampa has its origin by numerous mountain-brooks that rise among the granite gorges of the Park Range, and also among the Cretaceous rocks that flank that range on the west. Like White River, the Yampa is, in its upper portion, a clear, cold trout- stream, its bed being paved nearly all the way from its source to its mouth with smoothly-worn drift-pebbles. The Yampa has only’ two tributaries in this district, worthy of note, that carry perennial water. These are Williams Fork and Milk Creek, both of which will have fur- ther mention on subsequent pages. Yampa Valley, like that of White River, has its parks and narrower spaces of low lands, but it is most remarkable for its caflons; not so much because it has cafions along its course as because that river seems from a superficial or topographical view to run where nature had placed especial obstacles in its way, apparently giving no heed to the favorable opportunities it seems to have had for pursuing a peaceful and easy course. Between the eastern border of tbe district and the confluence of Wil- liams Fork, the valley of the Yampa is a moderately broad one, the WHITE. J SURFACE FEATURES—VALLEYS. 15 northern side, especially, sloping gently up to the high lands, while the southern side is formed by the steeper slope of the long high ridge that constitutes the water-shed between the Yampa and Williams Fork. The dip of the strata, which are those of the Laramie Group, is to the northward, and this portion of the valley is therefore a monoclinal one. The widening of the valley here is doubtless due to the softer condition of the strata of that group in this vicinity than those of the same form- ation have farther southward and westward in this district. Much of the bottom-land of this part of the valley is irrigable and the rapid fall of the stream renders its irrigation easily practicable. Near the confluence of Williams Fork, and for three or four miles below that point, the valley is narrowed by the encroachment of the bluffs, which are there composed of the strata of the Fox Hills and Lar- amie groups, those of the latter group being less soft there than they are farther up the valley, as before mentioned. In some places within these few miles of the narrowed valley, the sides are so steep as to give » it the character of a caton. This is particularly the case just above Canon Park, where the river makes avery abrupt bend among the hills. Canon Park.—This is a very small park, and is chiefly noticeable be- cause of its oceurrence in a portion of the valley that is otherwise very narrow, the sides of which are steep and rocky; and also because of its relation to the geological structure of the neighborhood. The occur- rence of this small park here is evidently due to the crossing of the river by a synclinal flexure or sag of the strata that has thrown the comparatively soft strata of the Laramie and Wasatch groups across the course of the valley, and out of these the park has been excavated, while the harder strata of the Fox Hills and lower portion of the Lar- amie Group form canon-walls, or high, steep valley-sides above and below. Between Cailon Park and the point where the river makes its exit through the bluffs into Axial Basin, which point is about six miles east of Yampa Mountain, the valley is tortuous and very narrow, being, in fact, a cation along the greater part of the distance. The sides of the valley in this part of its course are so steep and high that, except at a few favorable places, access to the river from the high lands by a mule- train is difficult cr impossible. This portion of the valley is excavated out of the strata of the Fox Hills and Laramie groups, those of the former group constituting, in great part, the south side, and those of the latter the north side of the valley. Westward from the point where the river makes its exit through the bluffs into Axial Basin, it pursues a meandering course through the ba- sin @ distance that in a straight line is about six miles to Yampa Moun- tain. Here, instead of passing into the western portion of Axial Basin through the comparatively low space at the north side of Yampa Moun- tain, it cuts through the northern portion of that mountain by a deep canon. After thus cutting through the mountain, the river meanders through the broad western portion of Axial Basin some 15 or 18 miles to Junction Mountain, through which it cuts its way by a still deeper and more precipitous caton than the one by which it passes through Yampa Mountain. These two mountains are, as before stated, isolated upthrusts of Paleozoic rocks through surrounding Cretaceous strata that lie exposed in the Axial Basin, and are located directly upon the line of the axis of the Uinta Mountain chain. In neither case is there any su- perficially apparent reason why the river should not have run around, instead of through the mountain, for the surface around the base of each of them has only a comparatively slight elevation above the sur- face of the river, amounting, indeed, to only a fraction of the height of 16 REPORT UNITED STATES GEOLOGICAL SURVEY. the caiion-walls. Moreover, the surrounding rocks are among. the soft- est that occur in the region, while those which form the mass of the mountains, and, conseqently, the canon-walls, are the hardest; and it is not probable that these relative conditions have materially changed since the canons were cut. There is a considerable amount of irrigable land in the immediate vicinity of the river, in Axial Basin, both above and below Yampa Mountain; but a very large part of the surface of even the lower por- tion of the basin is above the reach of irrigating-waters. Tily’s Park.—This park lies between Junction Mountain and the east- ern end of the Uinta Mountain chain, and is continuous with Axial Ba- sin around both the northern and southern sides of Junction Mount- ain. It is here that Snake River has its confluence with the Yampa, the former river passing between Junction Mountain and the east- ern end of the Uinta Uplift proper. After passing through Lily’s Park a distance of six or seven miles, and receiving the influx of Snake River, Yampa River cuts through a line of hogbacks composed of Tri- assic strata, and then almost immediately enters Yampa Cafion, pres- ently to be described. Lily’s Park embraces quite a large area of land that may be irrigated from both the Yampa and Snake Rivers. Al- though small, it is doubtless the finest body of irrigable land within the district. Yampa Cation.—If it were not for the existence of the much greater and grander cafions of the Green and Colorado Rivers, Yampa Cation would be worthy of renown for its great length and depth. This canon begins at the eastern end of the Uinta Uplitt and ends at Echo Park, where the Yampa has its confluence with Green River. The distance in a straight line from its eastern to its western end is about 25 miles, but its tortuous course makes its actual length much greater. Its general course is east and west and near the northern boundary-line of this dis- trict, but it passes to the north of that boundary-line a few miles be- fore it reaches Green River. Its course is along the southern side of the south flexure of the axial portion of the great Uinta Uplift, and approximately parallel with the synclinal flexure between the Plateau and Uinta Uplifts that I have ealled the Yampa Flexure. Along the greater part of its length the cafon-walls are nearly or quite perpen- dicular, and often more than a thousand feet in height above the sur- face of the river. As one stands upon the north side of Yampa Plateau, at the southern brink of Red Rock Basin, the bottom of which is about 2,000 feet be- neath him, looking northward over and beyond the basin, upon the broad mountain slope that forms its high northern side, he gets only occasional glimpses of the position of the cafon as it meanders through that great rugged surface. So sharply perpendicular are the walls of the canon on ‘either side that the observer from the point mentioned not only sees it imperfectly, even when itis at all visible, but even when he has clambered over the rugged cliffs that rise around the canon, he hardly realizes its presence in the neighborhood until he comes upon its verge and finds himself at a dizzy height above the rushing, roaring river ‘at its bottom—so high that the river looks like a brooklet, and its roaring is changed to a faint murmer before it reaches the ear. These are among the grander and more impressive scenes which this region affords, and once witnessed will never be forgotten. Williams Fork.—This stream, although a small one, is the principal tributary of the Yampa within this district. It rises among the ravines of the western side of White River Plateau and flows across the north- WHITE.) GREEN RIVER VALLEY. 17 ern corner of the district. Along this portion of its course it runs in a very narrow valley bordered by hills, the most of which are composed of strata of the Fox Hills Group. From the eastern border of the dis- trict to the confluence of a small branch that flows from near the eastern end of Axial Basin, its course is nearly parallel with and upon the north side of an anticlinal axis which produces upon its southern side a short, irregular line of hogbacks. From the confluence of the branch just mentioned to its own confluence with the Yampa, the course of Williams Fork is northward and through a deep narrow valley or cation. This portion of its valley has been carved out of the strata of the Fox Hills Group, the river running almost directly upon the axis of a comparatively short anticlinal spur that extends northward from the place of blending of the Uinta and Park Range flexures. Milk Oreek.—This creek rises by several branches, some of them drain- ing the northern side of Danforth Hills, but the main one rises near the eastern border of the district. It is insignificant in size, but it de- rives importance in this dry region from the fact that it contains per- ennial water. It is also worthy of especial notice because, although so small a stream, it affords a good example of antecedent drainage. The principal branch just referred to flows northwestwardly through the eastern end of the eastern portion of Axial Basin, but instead of pur- suing its course westwardly down the basin to join the Yampa where that river enters it, the creek cuts through the bluffs that form the northern side of the basin and flows through a cation carved out of the sandstones of the Fox Hills Group and joins the Yampa where that - river is itself running in a similar canon. GREEN RIVER VALLEY.—Green River being the largest of those streams that unite to make up the great Colorado River of the West, is, properly speaking, the upper portion of that great river itself, and ought not to have received a separate name; but having received it, custom renders a change impracticable. It is into .Green River that the whole drainage of this district passes, either directly or indirectly; but the river itself traverses only the northwestern corner of the dis- trict, entering it at Island Park and leaving it about midway of the western boundary. This portion of the river’s course is quite tortuous, and it passes through one remarkable caiion, that of Split Mountain; but below this it passes through a broad open valley. Island Park lies in the sag or dipping synclinal between Split Moun- tain and the main fold of the Uinta Uplitt, and is thus bounded by high mountains on all except the western side. The park may be said to contain about ten square miles, but the amount of irrigable land within its limits is very much less; still, there is sufficient for the purposes of a small farming neighborhood, whenever it may be desired by settlers. The river here divides into several channels, and, quickly uniting, sev- eral small islands are formed, from which the park has received its name, and which add a feature of beauty to that small, secluded dis- trict. Split Mountain Cation —As Green River makes its exit from one of its great cafions through the Uinta Mountains immediately upon enter- ing Island Park, so it enters another great cafion, that of Split Moun- tain, immediately upon leaving the park. Split Mountain, as has already | been shown, is a large mountain spur from the western end of Yampa Plateau, and it has received this name because it is cleft entirely through, and from top to base, by the cafion. The walls of the canon are everywhere precipitous and in large part perpendicular, and are composed of Carboniferous limestones and sandstones. Its length is 2G. 18 REPORT UNITED STATES GEOLOGICAL SURVEY. upward of six miles, and the maximum height of its walls is nearly 3,000 feet. The view from the top of Split Mountain, upon the western verge of the caiion, is impressive in the extreme. The rushing river, more than half a mile beneath the observer’s feet, appears like a bab: bling brook; and, although securely poised, many minutes elapse before he can command his nerves to sufficient composure for a calm survey of - the terrible chasm. Immediately to the north of this point of obser- vation. lies the main range of Uinta Mountains, and to the east the broad Yampa Plateau. A broad expanse of lower lands stretches out to the southward and westward, upon the surface of which the struct- ural geology of the region is shown with all the distinctness of a well- drawn geological map, so slightly are the strata of the formations ob- secured by vegetation, soil, or débris, and so vivid are the various colors of the rocks which compose them. WONSITZ VALLEY.—The broad portion of the valley of Green River, which lies adjacent to this district, bas been called Wonsitz Valley by Professor Powell, Although, when viewed from the adjacent moun- tains, its surface appears to be only slightly elevated above the river, it is nevertheless true that comparatively little of its surface is within reach of irrigating-waters. The greater part of the surface that is thus irrigable lies upon the west side of the river and beyond the limits of this district; but still many valuable farms might be e-tablished within its limits and irrigated from Green Niver. ey i % CS. Geol,&. Geog, Survey. Plate I a Green fiver Wahsatch Laramie Hox Hills Colorado % i L As) Q N = oes o Dakota Jurasstc d Friassie ? Aira-t tas Upper Carboniferons Mddle ” | | Lower Ha I Carboniferons General Section in the Yampa District. CHAPTER III. CLASSIFICATION, DESCRIPTION, AND DISCUSSION OF THE GROUPS OF STRATA. The formations of this district present essentially an unbroken series from the Weber Quartzite, which lies immediately beneath the Carbon- iferous series, but is itself probably of older Paleozoic age, to the Uinta Group, which is the latest of the fresh-water Tertiary deposits of that region, inclusive. ‘ The accompanying illustration, Fig. —, is intended to represent in their order a general section of these groups of strata, as they are de- veloped or exposed in this district, to which area alone the thickness assigned to each is intended to apply. Following this illustration is a brief description of each of the groups represented by it, which is in- tended for more immediate reference in connection with the figure; but more detailed descriptions of the groups will appear where they are discussed on following pages. EXPLANATION OF THE SECTION. fig. I. No. 1. Uinta Group.—Fine and coarse-grained friable sandstones, with intermixed gravel in some places, forming a conglomerate ; distinctly or obscurely stratified ; the materials composing the strata in some places nearly or quite incoherent. General aspect gray or dull brownishred. Unconformable by sequence upon the other Tertiary, and several of the older groups in the district. Thickness about 1,200 feet. No. 2. Bridger Group.—Variegated ; reddish, grayish, greenish, and purple bad-land sandstones. Thickness exposed in this district only about 100 feet. No. 3. Green River Group.—Upper division consisting of irregularly-bedded sand- stones, often concretionary, with occasional laminated carbonaceous layers. Lower division consisting of laminated sandy shales or thin-bedded sandstones. Sometimes finely laminated shales which are more or less caicareous, and occasional dark carbona- ceous layers are interspersed. Maximum thickness of both divisions about 1,400 feet. No. 4. Wasatch Group.—Alternating soft and harder sandstones at top end base, be- tween which the greater part of the group is made up of soft variegated bad-land sand- stones. These bad-land sandstones are generally somewhat softer in the eastern than _in the western part of the district. Thickness aout 2,000 feet. No. 5. Laramie Group.—Sandstones ; thinly bedded, or in some places more heavily bedded, and forming hogbacks at many of the flexures of that formation in the district. Color sometimes reddish-ferruginous, and sometimes of the usual dirty yellowish or grayish hue; variegated in places by carbonaceous layers, and beds of coal. Tuick- ness about 3,500 feet, but in some places probably less. No. 6. Fox Hills Grovp.—Sandstones, heavily or thinly bedded; or sandy shales. Often weathering so soft at the base of the group as to obscure any line of demarca- tion between it and the next beneath. Thickness about 1,800 feet. No. 7. Colorado Group.—Dark-colored shales, clayey or sometimes quite sandy ; with occasional thin layers of sandstone. Thickness about 2,000 feet in the eastern part of the district and much less in the western part. No. 8. Dakota Group.—Yellowish or brownish rough sandstones above; irregularly bedded pebble conglomerate below; and between these there is usually a greater or less thickness of variegated sandstone. Thickness about 500 feet. No. 9. Jurassic.—Variegated, soft, bad-land sandstones with some strata of mere in- durated sandstone, and usually from 10 to 15 feet in thickness of shaly, sandy, and calcareous, fossiliferous rock near its base. Thickness about 600 feet. No. 10. Triassic? Yellowish, obliquely-laminated firm sandstones above; yellowish, soit sandstones below, and between them aseries of bright red or brownish red, more or less firm sandstones. Thickness about 2,000 feet. No. 11. Upper Carboniferous.—Irregularly bedded, light-yellowish sandstones with 19 20 REPORT UNITED STATES GEOLOGICAL SURVEY. occasional calcareous layers, the sandstone layers often containing masses and nodules of chert. Thickness about 600 feet. No. 12. Middle Carboniferous.—Compact, bluish fossiliferous limestone, heavily or thinly bedded, alternating in some places with strata that are sandy and ferruginous. Thickness about 1,000 feet. No. 13. Lower Carboniferous.—Massive layers of limestone alternating with those of sandstone and sandy limestone; all more or less ferruginous, generally presenting a reddish-brown aspect ; and all usually regularly bedded. Thickness about 1,500 feet. No. 14. Uinta sandstone.—Massive or thinly bedded, brick-red or more usually brown- ish-red sandstones; usually hard and often quartzitic. Thickness, exposed in this district, only about 400 feet ; but the group reaches a thickness of nearly or quite 15,000 feet in the Uinta Mountains only a few miles from this district. The districts surrounding the one here reported upon have, within the last few years, been geologically surveyed by different persons. That which adjoins it on the west has been reported upon by Professor Powell in his ** Geology of the Uinta Mountains.” A geological map of the dis- trict which adjoins this one upon the north has been prepared by Mr. Clarence King during the progress of the United States Geological Sur- vey of the Fortieth Parallel. Reports, to be published simultaneously with this, are in course of preparation by the other geologists of the United States Geological Survey of the Territories, on the other districts which adjoin this one. A few copies of Mr. King’s map have been dis- tributed to different persons and institutions in advance of a geological report which is no doubt intended to accompany it. An examination of this map shows that the author has, in the main, adopted the classifica- tion of the strata which he finds exposed in that district, which has long been in use by Dr. Hayden in his reports; but with certain modifica- tions in some cases. As no text yet accompanies Mr. King’s map, I am, in some cases, in doubt as to the intended limits of the respective groups of strata that are there named and represented by colors. Having, how- ever, made some personal examination of a large part of the region rep- resented by that map, I think I do not incorrectly represent its intent in the following table of general sections. A large proportion of the names of the different groups of strata which are used in this report are, by the custom of priority in such cases, adopted from Mr. King’s map, which is regarded as having been published in November, 1875. Mr. King’s name, “ Laramie Group,” although it is understood to embrace Strata that have previously received other names in different parts of the great Rocky Mountain region, is retained because of its more com- prehensive application as indicating a great period in geological history, which is epochally represented by the Fort Union, Judith River, Lig- nitic, and other series of beds. i Dr. Hayden’s name, ‘* Wasatch Group,” has, however, priority of pub- lication over Mr. King’s name, * Vermilion Creek Group,” and also over Professor Powell’s name, “ Bitter Creek Group,” and I therefore adopt the first-mentioned name. I adopt the name “ Weber Quartzite” of Mr. King for the great formation that Professor Powell has called the “ Uinta - Sandstone,” but not being in possession of Mr. King’s facts, Lam not yet prepared to adopt his reference of it to the Carboniferous age. Al- though the typical locality of the Lodore Group, which Professor Powell represents as existing at the base of the Carboniferous series and above the Uinta Quartzite, is near the northern border of the district here re- ported on, it does not occur within its limits. Professor Powell’s sec- tion alone, therefore, represents it in the table. Although Mr. King has not upon his map recognized the deposit called ‘¢ Brown’s Park Group” by Professor Powell as separate from the Green River Group, north of an east and west line that may be made to pass through the southern base of the great Uinta fold, a careful comparison WHITE.] GROUPS OF STRATA. rail of those deposits on both sides of the Uinta Mountains has left no doubt on my mind of theiridentity. I therefore adopt Mr. King’s name “ Uinta Group,” instead of Professor Powell’s name * Brown’s Park Group.” While adopting the name “ Colorado Group” of Mr. King, I, for pale- ontological reasons chiefly, so restrict its application as to include only what I understand to be equivalent with Nos. 2 and 3 of Meek and Hay- den’s original section, leaving the equivalent of No. 4 to be included with the strata of the Fox Hills Group, instead of with the Colorado Group, as Mr. King has done. The following table of general sections, as may be seen at a glance, is designed to show the correlation of the different groups named by the several authors, as I understand them. The first column represents the section that was many years ago prepared by Messrs. Meek and Hayden for the Mesozoic rocks of the Upper Missouri River region; the second embraces the names of the Tertiary and Post-Cretaceous Groups of Wyoming, Colorado, and Utah that have, from time to time, been proposed by Dr. Hayden; the third has been compiled from Mr. King’s map of the Green River Basin, that has already been referred to; the fourth is the classification proposed by Professor Powell in his Report on the Geology of the Uinta Mountains; and the fifth is the classification of the rocks of this district which I have adopted in this report. 22 REPORT UNITED STATES GEOLOGICAL SURVEY. Table of correlated general sections.* ee HAYDEN. KING. POWELL. _ WHITE. Pliocene. Uinta. Brown’s Paik. Uinta. Bridger. Bridger. Bridger. Bridger. =) E U. G@ Ri 5 : : . Green River. : 4 3 Green River. Green River. L. Green River. || teen River. dH Wasatch. Vermilion Creek. Bitter Creek Wasatch. | t Lignitic. Lignitic. i i Ignis ignitic Laramie. Pein Rncke: Laramie. RON Fox Hills. : No. 5. Fox Hills. Salt Wells. Fox Hills. Fort Pierre. No. 4. a eS es ae ee o) 3 Niobrara, g : © H No.3. Colorado. 3 oO 5 Sulphur Creek. Colorado. = Fort Benton. ; No. 2. Dakar Dakota. Henry’s Fork. Dakota. 5 . 4 : : a 4 ee Jurassic. Jurassic. Jurassic. Flaming Gorge. Jurassic. iS a © 2 3 = Triassic. Triassic ? Triassic. Triassic? Triassic ? S Permo-Carb. U. Aubrey. Upper Carb. i) : 5 L. Aubrey. Middle Carb. & = ‘3 Coal-Measures. a A : = Red Wall. Lower Carb. 5 S Lodore. g az Weber Quartzite. Weber Quake: Uinta sandstone “The right-hand narrow colamn is intended to indicate the higher groups of my own classification, while the corresponding left-hand one represents that of the other au- thors as I understand them. t See discussion of the name “ Post-Cretaceous,” on a subsequent page. WHITE.} .... SILURIAN SYSTEM. | 23 The columns of this table are arranged in the order of time of their publication, beginning at the left. The horizontal arrangement of the spaces within which the names of the groups of strata are placed is in- tended to represent their correlation; while the spaces themselves rep- resent simply approximate coordination, the relative breadth of each space having no reference to the relative thickness of each group. THE SILURIAN SYSTEM. No other strata than those of the Weber Quartzite in this district are referred to Silurian age; and, as has already been shown, this great formation has been only provisionally so referred. THE WEBER QUARTZITE. _ This formation is usually of a dull brick-red or reddish-brown color, and has a peculiar sombre aspect, especially as seen in the deep cafions that have been eroded through it in the Uinta Mountain region. The stratification is always distinct, the strata more or less regularly bedded; sometimes massive, sometimes in thin layers, and occasionally in the condition of sandy shales. Sometimes it is in the condition of a com- mon, but firm, sandstone, the grains being distinctly definable; but oftener the grains are socompacted by partial metamorphism as to give the rock the character of a true quartzite. In its common sandstone condition it is almost always harder than the sandstones of the Carbon- iferous and Mesozoic groups of that region usually are. So far as I am aware, no fossils of any kind have ever been discovered in any part of this great formation; and its true geological age is therefore un- known. Upon his map, before referred to, Mr. King assigns this group to the Carboniferous system. _ Dr. Hayden, several years ago, suggested the Silurian age of this great group, as did also Professor Marsh, who visited the region after- ward. With this judgment, I am disposed to agree; but as before in- timated, its geological age cannot be detinitely known without the aid of fossils. Professor Powell has suggested the Devonian age of the Weber Quartzite, in connection with his statement of the unconform- ity of the true Carboniferous strata upon it. With this statement as to its unconformity with the Carboniferous, I also agree; but accord- ing to my own observation the unconformity is usually so slight that it may easily be overlooked. Furthermore, at all observed places in this district, as well as within a large area outside of it, the strata of the Lower Carboniferous rest directly upon the Uinta sandstone, those of the Lodore Group being absent. The Lower Carboniferous strata are often so very like those of the Weber Quartzite in general aspect that a casual observer would be in danger of confounding one with the other, especially if the unconformity should be, as it generally is, slight or obscure. There are two or three localities, just where some deep dry-drainage cafions open into Red Rock Basin at the north side of Yampa Plateau | by cutting across the Yampa Flexure there, where some of the upper strata of the Weber Quartzite are probably exposed; but for reasons already stated I am not entirely satisfied on this point, and therefore refer those strata to the Lower Carboniferous. Strata of this group are well exposed in the walls of the cafion by which the Yampa passes through Junction Mountain, and they are also largely exposed in the southern half of Yampa Mountain, which lies some fifteen miles to the eastward of Junction Mountain. 24 REPORT UNITED STATES GEOLOGICAL SURVEY. CARBONIFEROUS SYSTEM. The peculiar characteristics of those groups of strata which are abun- dantly developed in the great Rocky Mountain region, and which have been, by all geologists who have examined them, referred to the Car- boniferous age, leave no doubt as to the correctness of that reference. It is, however, true that the three great divisions of the system, the Subcarboniferous, Carboniferous or Coal-Measures, and Permian, which are recognized in Europe and also, in part at least, in the interior region of North America, are not recognizable as such in the western portion of the continent, with the possible exception of the Subcarboniferous division, as distinct from the remainder. There seems indeed to be no good reason why we should expect to find this to be the case, because | the marking-off of a system of rocks into groups and formations, as well as the modifications of the then existing forms of life, the remains of which are now found to characterize those formations, was due to the then prevailing physical conditions, and their periodical changes, the former of which we have no reason to suppose could have been universal nor the latter simultaneous in different parts of the world. The coal- making condition, which was remarkably characteristic of the Carbon- iferous age in Europe and Eastern North America, seems not to have existed at all, or only in an exceedingly slight degree, in what is now the great Rocky Mountain region, during any part of this great geological age. During the whole of that age, the deposits there seem to have been wholly marine, and to have been largely formed in comparatively shallow waters. The Carboniferous strata of that western region are, it is true, marked off into groups, but they are not marked off in the same manner that they are in Hurope and Eastern North America; and there ought to be no strained effort made to require those of the latter regions to corre- spond with those of the former, for they are not separated from each other by similar faunal and floral differences. There seems to be very little reason to doubt that the whole of the Carboniferous age is repre- sented by the deposits referred to in Western North America, although the types of fossils they contain are seldom if ever of such a character as to warrant their distinctive reference to either the Subcarboniferous, Carboniferous, or Permian periods of the age. On the contrary, the types that are relied upon in Europe, and also others that are similarly relied upon in the eastern portion of North America, to prove the Sub- carboniferous age of the strata containing them, are here found intimately associated with an abundance of those forms that are equally charac- teristic of the Carboniferous or Coal-Measure period, and even with some of Permian type. Furthermore, the uppermost division of the Carboniferous strata in this far western region, which probably repre- sents in time the Permian Group of Europe, has not, to my knowl- edge, been found to contain a single faunal type that is in any proper - sense characteristic of the Permian period as distinct from the Middle or Coal-Measure period. Therefore, in this report at least, I shall make no attempt to refer any of the Carboniferous strata of this great region to either of the three divisions originally established for the system ; but I shall regard all the groups that have been named in the foregoing sections and elsewhere in this report as purely stratigraphical divisions, and probably inseparable from each other on paleontological grounds. This statement will explain why so little reference is had to paleonto- logical characteristics in the following account of the Carboniferous groups. Itis proper to mention, however, that from somewhat restricted WHITE. | CARBONIFEROUS SYSTEM. 25 exposures of strata at a very few points in Nevada, Colorado, and Idaho, collections of fossils have been made that are not only specifically different from those which are so widely distributed in the Carbon- iferous rocks of that great region, but they are in part specifically identical with some that are found only in the Subearboniferous strata of the States of the Mississippi Valley. The first of the following groups mentioned, however, is not to be here regarded as distinctively Subecarboniferous, although it may be so in fact, so far as anything is knowa to the contrary. THE LOWER CARBONIFEROUS GROUP. In some parts of the great Rocky Mountain region other observers have made out satisfactory lithological distinctions between the Lower and Middle Carboniferous Groups; but within the limits of this district the line of demarcation is so indefinite that I was not able to do more than make out a general separation of the two groups. I nowhere found any well-marked line of separation, and there being, as before stated, no sufficient paleontological distinction between the two groups, very few characteristics can be named as separating them from each other. The Lower Carboniferous Group in this district consists of a large pro- portion of compact limestone strata that are usually more or less fossil- iferous, alternating with layers of sandstone that are also usually some- what calcareous. In general aspect this formation is of an indefinite reddish-brown or ferruginous color, often like that of the Weber Quartz- ite. The strata of this group are well exposed along the northern border of the eastern half of the Yampa Plateau, and also in Junction Mountain, of which mountain it forms a large proportion. It is there scen resting upon the Weber Quartzite, and in turn underlying the Mid- dle Carboniferous. In Yampa Mountain, which is largely composed of the Weber Quartzite, the Lower Carboniterous is not satisfactorily sep- arable from the middle group. THE MIDDLE CARBONIFEROUS GROUP. In this district, as before stated, the Middle Carboniferous Group is separable from the Lower only in aspect, and by some general lithological characteristics. The greater proportion of the bluish-gray limestones. which it contains gives it a lighter aspect than that of the Lower, and distinguishes it also from the sandy strata of the overlying Upper Car- boniferous Group. It is more fossiliferous than either of the other two divisions of the Carboniferous system in this district; but in consequence of the compact and cherty character of the rock, the fossils are seldom well preserved. The limestones of this group, besides being cherty, are often unevenly bedded. As arule, they lack those marly and carbona- ceous or clayey layers of shale that so commonly separate the lime- stone layers of the equivalent of this group in the Mississippi Valley The Middle Carboniferous Group contains much the greater part of the region, and from which softer layers most of the fossils are there obtained. calcareous strata found in this district, the prevailing material being almost everywhere sandstone and sandy shales. THE UPPER CARBONIFEROUS GROUP. The Upper Carboniferous Groupis quite clearly distinguishable from the lower. In this district it is almost wholly composed of a light, yellowish- gray sandstone, often cherty, and containing only a few calcareous layers. 26 REPORT UNITED STATES GEOLOGICAL SURVEY. Usually, the sandstone is irregularly bedded, sometimes massive, and oblique stratification is quite common. Fossils are rare in this group, but a few have been found in its upper strata, and those yet known are not such as to distinguish it clearly from the other two Carboniferous groups. It is this group that Mr. King has designated as Permo-Car- boniferous on his map. According to my observations, it is only its superior position in relation to the other groups that would suggest such a designation, because the Carboniferous groups below it contain fossils that are as closely allied with the Permian of Europe as any that have yet been discovered in the strata of this upper one. The strata of this group are exposed at the surface of much the greater part of the area that is occupied by those of Carboniferous age in this district. They cover nearly the whole surface of the western half of Yampa Plateau, and nearly all the rugged surface through which Yampa Cation is cut, along the southeast flank of the Uinta Uplift, be- sides a narrow area along the whole Jength of the Fox Creek Flexure. Narrow bands of its upturned strata are also exposed around the bases of Junction and Yampa Mountains. It will thus be seen that all the Carboniferous strata of this district have been brought to view only by the Plateau and Uinta Uplifts, and by the two sharp Upthrusts of June- tion and Yampa Mountains. The remarkable peculiarities of these uplifts and upthrusts will be explained in a subsequent chapter. THE MESOZOIC AGE. Strata of Mesozoic age cover a large part of the surface of this dis- trict, and apparently form an unbroken series, from the base of those Strata that have usually been referred to the Triassic period, to the up- permost Cretaceous strata, inclusive. The strata that I have, but with some doubt, referred to the Triassic period, are everywhere in this dis- trict and the surrounding region conformable upon those of undoubted Carboniferous age. Therefore there appears tobe no important physi- cal break in the series, as found in this district, from the base of the Carboniferous to the top of the Cretaceous,* notwithstanding the fact that the Lower Cretaceous of Europe seems not to be represented in this, if in any, part of North America. Comparatively few fossils were collected from any of the Mesozoic strata of this district during its geological examination, but the facility for observation, as before ex- plained, makes their identification unquestionable, even if no fossils at all were obtained from them. : TRIASSIC PERIOD. _ The strata, widely distributed over a large part of the western portion of North America, that have until lately been referred with little or no doubt to the Triassie period, have generally been simply so referred with- out a distinctive name as to groups or formations, but some geologists have subdivided the series and given distinctive names to thedivisions thus formed. They have been called by some simply the Red-Beds; but Professor Powell recognized three separate divisions of the group under the names, in the ascending order, of “‘ Shinarump,” “ Vermilion Cliff,” and ‘‘ White Cliff” groups. These three divisions are recognized among those strata in this district, but they are not thought to be there of sufficient importance to be regarded as separate groups, coordinate * See also remarks concerning ‘apparent unbroken continuity of deposition of Meso- zoic and Cenozoic strata on a subsquent page. wHits.] MESOZOIC AGE. 27 with the other groups that are treated of in this report. Until lately, also, these strata have been generally regarded as unfossiliferous, with the exception of the existence here and there of considerable quantities of silicified exogenous wood; and they were referred to the Triassic period mainly in consequence of their position between the recognized Carboniferous and Jurassic strata. Serious doubts of the real Triassic age of the strata in question have lately been raised because of the dis- covery of fossils in the lower portion of the group that seem to be not merely similar to some that are found in the group above the one iu question, and which ail persons agree in referring to the Jurassic period, but they are apparently specifically identical. Dr. Hayden, on page 11 of his Report on the Geology of Captain Ray- nolds’s Exploration of the Yellowstone and Mississippi Rivers, made in 1860 and published in 1869, states that he found unmistakable Jurassic fossils near the base of this group. In 1874, Mr. Edwin BE. Wowell collected for Professor Powel several species of invertebrate fossils from the lower portion of the division of this group in Southern Utah, some of which, at least, I regard as specifically identical with well known-species, until then found only in unquestionably Jurassic strata.* These facts seem to indicate, with comparatively little doubt, that all the Mesozoic strata of that portion of Western North America, below the Cretaceous, belong to one period only, and that the Jurassic. This opinion is, of course, based upon the invertebrate fossils before referred to alone, no ver- tebrates or plants having been found or examined by myself. If the specific identification of the invertebrate fossils before referred to should be fully verified, there is no sufficient evidence, so far as I am aware, of the existence of any Triassic strata, distinguishable as such by its invertebrate fossils, in any part of the great region east of the great Salt Lake Basin and south of the Union Pacific Railroad. This ques- tion, however, is of so important a character that notwithstanding the evidence in favor of adopting the view just indicated, I prefer to use the provisional classification already given in this chapter, until material shall have been collected fora more complete discussion of the question. It is especially desirable to collect as much material as possible for this discussion, because these strata and their equivalents are distributed over so large a portion of the North American continent, where their lithological characters are generally so uniform as to render the group recognizable at once from them alone. However, in view of the fact that the relative position of this great series of strata seems to justify its reference to the Triassic period, while all its yet known invertebrate fossils show an intimate relation with those of the accepted Jurassic strata, I shall adopt for present use the general or collective term, Jura-Trias, for these two earlier Mesozoic groups. As shown in the description accompanying the figure of the general section of the rocks of this district, the divisions of this group are all sandstones, the middle one being very conspicuous in consequence of its bright-red color. The lower division is sometimes so very much like the sandstone of the Upper Carboniferous group that it is difficult to deter- mine where the one ends and the other begins, but in this district the strata of the former are considerably softer than those of the latter. The exposures of the strata of the middle division are often gorgeous in appearance as seen in the distance, for they are often exposed in exten- sive escarpment faces. Remarkable and extensive exposures of these red strata are seen in the southern and eastern faces of the great Mid- *See Geology of the Uinta Mountains, pages 80 and 87. 28 REPORT UNITED STATES GEOLOGICAL SURVEY. land Ridge, extending, indeed, almost continuously from its eastern to its western end. Besides entering largely into the bulk of the great Midland Ridge, the strata of this whole group form an almost continuous line of hogbacks around the eastern end of both the Uinta and Plateau Uplifts, the whole length of Midland Ridge, and thence continuously around the western bases of both Section Ridge and Split Mountain. ‘They also oc- cupy the bottom of Red Rock Basin; and small isolated exposures of the strata are to be seen near the bases of both Junction and Yampa Mountains. The fact that the middle and upper divisions of this group are so of- ten exposed in the faces of hogback and other escarpments is doubtless due to the softer and more yielding character of the lower division, which, becoming disintegrated more rapidly than the others, allows the superimposed strata to fall down, leaving precipitous escarpment faces of the remaining rock. THE JURASSIC PERIOD. In this district, a group of strata of the Jurassic period is found every- where bordering the exposures that are doubtfully referred to the Triassic. They consist mainly of soft, greenish, grayish, reddish, and purple bad-land sandstones, with a few feet of sandy calcareous layers. near the base, which contain the fossils that are characteristic of the group. Being soft, the strata of this group are often obscured by the débris resulting from their own disintegration, while the associated strata, both above and below them, being harder, resist disintegration, and are often conspicuously exposed as hogbacks or other escarpments. Sometimes, however, they appear in the lower portion of the face of a hogback or escarpment, being protected there from furtber disintegra- ~ tion by a cap of the harder strata of the lowest group of the Cretaceous period. The thickness of the group in this district being only about 600 feet, and being usually exposed by flexures of the strata, it occupies only a small portion of the surface. Its exposures are, indeed, mostly confined to narrow bands that appear among the upturned groups of strata that flank the principal uplifts in the district. It will thus be seen that all the groups hitherto described, occur in the northwestern portion of the district alone, all having been upturned along the flanks of the Uinta and its accessory uplifts. The whole of this large portion of the district is therefore occupied by the rocks of older date than the Cretaceous period, largely by those of Carbonifer- ousage. This space is, however, bordered by rocks of the Cretaceous period, which, together with those of the Tertiary, occupy the remainder of the ‘district. THE CRETACEOUS PERIOD. The whole series of Cretaceous strata as they are known to geologists, in the great Rocky Mountain region, is represented in this district, as well as another series immediately above them, concerning the proper age of which, geologists are divided in opinion, and to which I have given the separate but provisional designation of Post-Cretaceous. Un- der this head those strata are discussed upon subsequent pages. The original grouping of the Cretaceous strata, as they are found de- veloped in the Upper Missouri River region, by Meek and Hayden, is shown in the table of correlated sections on page —. It is also there shown that late authors agree in modifying that original grouping for Wwuits. | MESOZOIC AGE. 29 the Cretaceous rocks of Wyoming, Colorado, and Utab, by uniting the equivalents of certain of those groups under one designation, while pre- serving essentially the main features of the original classification. There is comparatively little difficulty in recognizing among the Cretaceous strata of the regions mentioned, the principal features of the classifica- tion which was originally made by Meek and Hayden for those of the Up- per Missouri River region. That which | have followed consists mainly in reducing the number of groups by placing together those that have the nearest paleontological affinities. I have thus placed the equivalents of the Fort Benton and Niobrara groups together under the name of Col- orado Group; and thoseof the Fort Pierre and Fox Hills groups together - under the single name of Fox Hills Group, leaving, as all others have done, the Dakota, as everywhere, a singie, separate group. Such a, grouping of the Cretaceous strata is not only quite sufficient for all re- quired purposes within the region to which it is applied, but it is as natural as the original grouping is for the Upper Missouri River region. The modification I have adopted is, for this district at least, quite as natural, stratigraphically, as that proposed by Mr. King (who joins the equivalent of the Fort Pierre Group to that of the Niobrara and Fort Benton groups to make up the Colorado Group), but I find it more natural, paleontologically. All the groups of strata that are referred to the Cretaceous period in -this report are, within this district, not only strictly conformable with each other as regards their stratification, but I have never been able to fix upon 2 plane of demarcation between any of them with entire pre- cision. The aspect of the strata throughout the vertical range of all three of these groups, is that of greta sedimentation. The general characteristics by which the groups are separated from each other will be given under the head of each. \ THE DAKOTA GROUP. The strata of this group are exposed as a narrow band among the up- turned strata that flank the uplifts in the northwestern portion of this district, and also as a small but somewhat broader exposure, which is found to cap a portion of Midland Ridge, as is shown upon the geologi- cal map accompanying this report, and also upon one of the sheets of the great atlas of Colorado, soon to be published. A very small exposure is also to be seen near the southwestern flank of Yampa Mountain, and another small one, of somewhat greater ex- tent than the last, in Agency Park, near the right bank of White River. The latter exposure is brought up by a slight flexure that is apparently the vanishing northern end of the Elk Mountain Uplift, the main eleva- tion of which is far to the southward. The general lithological characteristics of this group are somewhat variable in different portions of the great Recky Mountain region, but this variability. is not such as to prevent its ready identification wherever it is sufficiently exposed, even in very widely-separated localities. In this district the group reaches an aggregate thickness of between 500 | and 600 feet, and consists of two divisions, which, in some places, are more clearly defined than in others. The lower portion, having a thick- ness of some 300 feet, consists of a dark-colored, coarse, silicious peb- ble-conglomerate, which is somewhat irregularly bedded and easily dis- integrated. The upper portion, having a thickness of from 150 to 200 feet, consists of a yellowish or brownish, rough, heavy-bedded sand- stone, between which and the conglomerate some variegated bad-land 30 REPORT UNITED STATES GEOLOGICAL SURVEY. sandstones usually exist. These bad-land sandstones are similarin color and general character to those of the Jurassic Group; and where the conglomerate member of the Dakota Group is not brought up to view with the upper portion, as is the case in Agency Park, the bad-land strata of this group may be easily mistaken for those of the Jurassic. This group seldom furnishes invertebrate fossil remains of any kind, especially in this district and the adjoining region; but very important floral and vertebrate remains have been obtained from it east of the Rocky Mountains. Its lithological characteristics, as well as its strati- graphical position in relation to the other groups, leave no doubt, how- | ever, of itsidentity. Professor Powell reports the existence of coal in the Dakota Group at some localities in Utah, but I observed no indications of its existence among the strata of the group in this district. THE COLORADO GROUP. As already shown, the limits of the Colorado Group are restricted in this report so as to intentionally embrace only the equivalents of the Fort Benton and Niobrara groups of the Upper Missouri River section, estab- lished by Meek and Hayden, and it is also understood to be equivalent with the Sulphur Creek Group of Professor Powell, as thus restricted. It is doubtless true that in some places the strata which are regarded as equivalent with those of the Fort Pierre Group of the Upper Missouri River section, accord more nearly in lithological characters with those beneath, than with those above them. Mr. Meek, who studied the paleon- tology of these groups so carefully, has shown in his works that while the paleontological affinities between the Fort Benton and Niobrara groups, and the Fort Pierre and Fox Hills groups, respectively, are very close they are comparatively very slight between the two former and two latter groups respectively. Although the grouping of the strata of all geological ages in the western part of North America has been largely done by the field geologist, mainly upon stratigraphical grounds, and much of it properly so done, no person will justly question the necessity of giving preference to paleontological evidence in the proper geological grouping of strata. It is for this reason that, while adopting the name “Colorado” for the group under discussion, as having priority over that of “Sulphur Creek,” I restrict its application to the strata that I understand to be the equivalent of the latter, and also the equivalent of both the Fort Benton and Niobrara groups, instead of including under the name thus adopted, the equivalent of the Fort Pierre Group also, as Mr. King has done. The Colorado Group is perhaps more persistent in the uniformity of its lithological characteristics over a great region than any of the other Cretaceous groups, with the possible exception of the Dakota Group. It consists largely of that indurated clayey material, more or less dis- tinctly laminated, which geologists generally, but somewhat loosely, de- nominate “shales”; but occasional layers of sandstone, usually soft, are sometimes met with. The strata of this, compared with those of the associated groups, are easily eroded. Consequently they seldom appear in escarpment exposures ; and the stratification of the group is very often much obscured by its own débris. The lower portion of the group is more clayey, less sandy, and darker colored than the upper, but both being disintegrated and eroded with almost equal facility, a distinct line of separation between the two portions is seldom or never observ- able. The comparative ease with which the strata of this group are disin- Wate. | eae MESOZOIC AGE. gern Jl tegrated and eroded has produced a marked effect upon the topography of the region in which they exist. Where the strata are considerably flexed, the space occupied by those of this group is a hollow or valley between lines of hogbacks which are composed of the harder strata that belong above and beneath this group. But where the flexure is more gentle, and especially upon a broad anticlinal axis, the strata of this group are often so eroded as to form a basin or park, such as have been described in Chapter II. Near the base of the Colorado Group there is almost always to be found a bed of dark, fissile shales, containing the remains of teliost fishes. This bed not only occurs at all’ places in this district where the base of the Colorado Group is exposed, but it is equally characteristic of the lower part of the group in the adjoining districts. Overlying the bed of shales containing the remains of teliost fishes, there is often to be found a bed of coal. The only place in this district that I observed this bed of coal is a couple of miles south of the west end of Lily’s Park, and south- ward from Junction Mountain. -It is there tbree or four feet in thickness. In this district the strata of the Colorado Group occupy the surface of Agency and Raven Parks; of Midland Basin; of, at least the eastern half of, Axial Basin, and also a considerable space bordering the mountain uplifts of the northwestern portion of the district, THE FOX HILLS GROUP. In accordance with the modified classification of the Cretaceous strata adopted in this report, the Fox Hills Group includes not only the strata that are understood to be exactly equivalent with those of that group, as it was originally defined by Meek and Hayden, in the Upper Missouri River region, but also those that are equivalent with the Fort Pierre Group, as it was originally defined in that region. As already stated, Mr. King does not on his geological map include with the Fox Hills Group those strata that, he, as well as all other geologists, regards as equivalent with the Fort Pierre Group; but he includes the latter in the Colorado Group, together with the equivalents of the Niobrara and Fort Benton Groups. In the eastern portion of this district, and also to a less extent in other portions, the strata that I regard as probably equivalent with the Fort Pierre Group are more readily eroded and dis- integrated than are those which overlie them, and constitute there the upper portion of the Fox Hills Group. In this respect they more nearly resemble in general aspect the strata of the group beneath than those above them; but for paleontological reasons, as before stated, I include the equivalent strata of the Fort Pierre with those of the Fox Hills Group, designating the whole by the latter name alone, rather than place it with the Colorado Group, as Mr. King has done, appar- ently on lithological grounds. The fossils obtained from the equivalents of the Fort Pierre and Fox Hills Groups are not only so similar as to ally them closely with each other, but many of the species range through the whole series of strata that are understood to represent both of these groups. It is probable that some of the fossils of the Colorado Group range up through the remainder of the Cretaceous series; but, so far as the fossils of that group are now known, they seem to be so generally restricted to its: own limits as to give it quite definite paleontological characteristics, and to leave the Fox Hills Group quite as clearly characterized. In the western portion of this district the lithological difference be- tween the upper and lower portions of the Fox Hills Group is not so 32 REPORT UNITED STATES GEOLOGICAL SURVEY. clearly shown as it is in the eastern portion, but yet the lowest portion of this group is everywhere of such a character lithologically as to be not clearly separable from the upper part of the Colorado Group. In a general way, the lower division of the Fox Hills Group, which is about 800 feet in thickness, may be defined as a series of thin-bedded sandstones and sandy shales, which are often so easily disintegrated as to become covered with débris resulting from their own disintegration. In some places, therefore, the strata of this lower division seldom pre- sent escarpment faces; but in other places, especially in the western portion of the district, it contains one or two massive strata of firm sand- stone, near the top of the division, that form prominent features in all the exposures there of this portion of the group. The principal one of these massive strata is from 30 to 50 feet, thick, and is especially con- spicuous in escarpments, of which it forms the cap. Where this great massive stratum exists, those below it gradually pass into the soft strata of the Colorado Group, and the strata above it are also soft, and are in turn capped by another massive stratum; and upon these comes the remainder of the upper division. This description applies particularly to the strata in the vicinity of Raven Park. Upon the lower division rest about 1,000 feet more or less of regu- larly-bedded ordinary sandstones which constitute the upper division, and which form hogbacks wherever the strata are considerably flexed, and present bold escarpments under other conditions of flexion and erosion. These last-named characteristics of the group are particularly observable in and around Agency Park and the eastern portion of Axial Basin. Several carbonaceous horizons were observed in different parts of the district among the strata of this group, including both the upper and lower divisions, but comparatively little coal was discovered. Near the base of the group, however, a bed of coal, probably of workable thick- ness and quality, is to be found in some places. The strata of this group occupy quite a large part of the surface of the district, and the upper strata enter into the composition of a large part of the various hogbacks and escarpments within its limits. They are exposed in the north and west borders of Agency Park, in all the borders of Raven Park, and in both the north and south as well as the east borders of the eastern portion of Axial Basin. They occupy that portion of the surface between Yampa River and Williams Fork which lies adjacent to the latter stream, constitute a large part of Pilon Ridge, and are upturned to view in the Midland Flexure trom one end of the district to the other. THE POST-CRETACEOUS PERIOD. Resting conformably upon the Fox Hills Group there is another series .of strata which differs materially from any of the preceding groups in the character of its invertebrate fossils, although the sedimentation which produced it appears to have been continuous and unbroken from those groups into and throughout the series under discussion. The thickness of this series of strata is greater than that of any of the Cre- taceous groups proper that preceded it, reaching a maximum thickness ip the district here reported upon of at least 3,500 feet. A few hundred feet, constituting the upper portion of this series in the valley of Bitter Creek, Wyoming, has been, by Professor Powell* and myself, separated *See Geology of the Uinta Mountains, and Article XXV, Vol. III, Bull. U. S. Geol. Surv. Ter. WHITE, ] LARAMIE GROUP. 33 from the greater, lower portion of the series, and placed with the Wasatch Group above it. This was done because of an unconformity of the two portions in that district, and an entire conformity of that upper portion . with the strata of the Wasatch Group above it, although the affinities of the fossils of that upper portion are with those that are found be- neath, rather than with those of the Wasatch Group above. After a careful examination of the extensive exposures of this series of strata, as well as those of the Wasatch Group above it in this district, I have failed to discover any unconformity, such as exists in the valley of Bit- ter Creek. Therefore, the greatest unconformity that is now known to exist among any of the strata from the base ot the Cretaceous to the top of what I here designate as the Post-Cretaceous, is found among the strata of the latter group, and not atits top. In this district and the region immediately adjoining it, whatever catastrophalor secular changes may have meanwhile taken place elsewhere, or even extending within its limits, sedimentation was evidently continuous and unbroken, not only through this series itself, but also into and through the whole Wasatch Group also. The fact that this series passes insensibly into the Fox Hills Group below, and into the Wasatch Group above, renders it difficult to fix upon - a stratigraphical plane of demarcation, either for its base or summit. I have therefore decided to regard this group as essentially a brackish- water one, referring all strata below, that contain any marine Cretaceous invertebrate forms, to the Fox Hills Group, beginning this series with those strata that contain brackish- and fresh-water forms, and ending it above with those strata in which the brackish-water forms finally cease. Thus defined, the whole series seems to form one natural paleontologi- cal group, as well as to be a sufficiently distinct stratigraphical one, for which I have adopted the name of Laramie Group of King. My reasons for separating this group from the Cretaceous series, _where it has been placed by Cope, King, and Powell, and for giving it the provisional designation of Post-Cretaceous, have been discussed by me in Article XXIV, Vol. II, No. 3, Bulletin of the United States Geo- logical and Geographical Survey of the Territoiies, but they may be briefly repeated bere. The flora of this group is understood to be wholly of Tertiary types, according to Professor Lesquereux. None of its in- vertebrate fossils are of distinctive Cretaceous types, although fossils of similar types are known to occur in Cretaceous as weil as Tertiary strata. So far, then, as the flora and invertebrate fauna are concerned, there is nothing to indicate the Cretaceous age of the group. In fact, Inverte- brate Paleontology is utterly silent upon the subject. On the contrary Professor Cope finds reptilian remains, even in the uppermost strata of the group, that he regards as of Cretaceous type. I believe that, upon the evidence of invertebrate paleontology, the Fox Hills Group is later than the latest Cretacecus strata of Europe; and I therefore regard the Laramie Group as occupying transitional ground between the well- marked Cretaceous and Tertiary groups, but this opinion is only tenta- tively held until further facts are obtained. THE LARAMIE GROUP. The relations of the Laramie Group to those immediately above and below it in the geological series, as well as its general characteristics, have been pointed out in the last paragraphs, and it now remains to speak of its characteristics as they are shown in this district and those adjoining it. The Laramie Group, in a large part of Southern Wyoming and the 3G 34 REPORT UNITED STATES GEOLOGICAL SURVEY. adjacent parts of Colorado and Utah, consists mainly of the ordinary indurated sandstones that so largely enter into the composition of the Cretaceous groups of that region, together with somewhat frequent beds of carbonaceous shales, and several beds of coal of greater or less im- portance. This description has also a good general application to the group, as it is developed in this district; but in the eastern part it con- sists very largely of a series of reddish- colored, usually thin-bedded sandstones, together with someshaly and carbonaceous beds. These pecu- liarities, however, gradually merge into the more common characteris- tics of the group to the westward. Besides many more or less distinet carbonaceous horizons, the group contains several beds of coal within this district. One of the best is near its base, and another near its top, with others between, that may, perhaps, be found to be of workable thickness. The strata of the Laramie Group occupy a large space between the eastern portion of Axial Basin on the one side, and Agency Park and Hogback Valley on the other. It is brought to view along the whole length of both the Midland and Raven Ridge flexures, besides occupy- ing considerable spaces to the northeastward and northwestward of Raven Park. It also occupies the larger part of the space between Williams Fork and Yampa River, within the district, as well as the. most of that portion of it which lies north of the Yampa and between the mouth of Williams Fork and Yampa Mountain. For the more pre- cise limits of the surface occupied by the strata of the group within the limits of this district see the geological map accompanying this report, and also that of the large atlas of Colorado, published by the Survey. So far as known tome,-the strata of all the Cretaceous groups of Western North America, beneath the horizon of the Laramie Group, are of marine origin, except a few local deposits in different portions of the series, which contain brackish- and fresh-water invertebrate forms. On the contrary, no exclusively marine invertebrate forms are known to - have been obtained from the strata of the Laramie Group, as I have defined its limits in this report. The species of Inoceramus that have heretofore been reported from the lower strata of this group, I am now satisfied should be referred to the Fox Hills Group, the error of refer- ence having been made in consequence of the absence of a distinct stratigraphical plane of demarcation between the groups. The com- parative abundance of remains of land-plants in all the strata of the Laramie Group also indicates its separation from the open-sea deposits. THE TERTIARY PERIOD. In the great region that is now drained by the Green River there are three well-marked groups of strata, all conformable with each other, that come in their order above the Laramie Group, and which all agree in referring to the Tertiary period. These are the Wasatch, Green River, and Bridger ‘Groups, named in the ascending order. As already mentioned on a previous page, all the groups of the Cre- taceous period, as they are developed in the great Rocky Mountain region, so far as I have been able to observe, or to obtain information of them, are strictly conformable upon each other. I have also shown that the Post- Cretaceous Group is strictly conformable upon the uppermost of the Cretaceous groups, although some unconformity is known to exist among the strata within the limits of the Post-Cretaceous Group - (the Laramie Group), to the northward of this district. 1 have been equally unable to discover any unconformity between the strata of the WHITE. | TERTIARY PERIOD. 35 Laramie Group, which I have designated as Post-Cretaceous, and those of the Wasatch Group, the earliest of the Tertiary groups proper. Neither havel been able to discover any definite, stratigraphical plane of demarcation bewteen the two groups. THE WASATCH GROUP. In his annual report for 1870, Dr. Hayden proposed the name “ Wa- satch Group” for a series of strata that are extensively developed in Southern Wyoming and adjacent parts of Utah and Colorado. Iregard the series of strata to which Mr. King has given the name “ Vermilion Creek Group,” and Professor Powell, that of ‘ Bitter Creek Group,” as geologically equivalent with the Wasatch Group of Dr. Hayden, and I theretore use that name in this report, in accordance with the recognized rule in such cases. The Wasatch Group is the lowest of a series of three fresh-water Ter- tiary groups, all of which are intimately connected, not only by an evi- dent continuity of sedimentation throughout, but also by the passage of a-portion of the molluscan species from one group up into the next above. Not only were these three groups, aggregating more than a mile in thickness, evidently produced by uninterrupted sedimentation, but it seems equally evident that it was likewise uninterrupted between the Laramie and Wasatch epochs, although there was then a change from brackish to fresh waters, and a consequent change of all the species of invertebrates then inhabiting those waters. The Wasatch Group in this district consists very largely of soft, varie- gated bad-land sandstones that reach a thickness of about 1,500 feet, together with from 100 to 300 feet of the ordinary indurated sand- stones, alternating with bad-land material at the base, and a similar amount of similar material at top, the estimated aggregate thick- ness being about 2,000 feet.. The lithological characteristics vary some- what in different parts of the district, the middle portion sometimes losing its distinctive bad-land character, and the sandstones becoming more indurated, but they seldom become very hard. The exposures of the Wasatch Group in this district are mostly con- _ fined to that portion of the surface occupied by the principal flexures of strata, the surfaces of Coyote Basin and Powell’s Park being the broad- est spaces occupied by those strata. They are upturned by the Midland, Grand Hogback, and Raven Ridge flexures, and are exposed in the valley of White River along a great part of the whole distance from . Powell’s Park to a point afew miles below Raven Park. Being com: posed of easily eroded maierials, the strata of this group seldom pro- duce any conspicuous features of the surface, except the valleys and basins that are eroded out of them, such as Powell’s Park, Coyote Basin, Hogback Valley, and a part of White River Valley. Very few fossils were obtained from the strata of the Wasatch Group in this district. Specimens of the genera Viviparus, Goniobasis, and Unio were obtained from strata near the top of the group in Raven Ridge, near thesouthwestern border of Raven Park. The same genera, and doubtless the same species, were found in a similar horizon in the valley of White River opposite Pinon Ridge, where also fragments of Physa pleromatis White, were obtained. THE GREEN RIVER GROUP. Resting immediately and conformably upon the Wasatch are the strata of the Green River Group. Although intimately connected with the former by continuous sedimentation and specific identity of mollus- 36 REPORT UNITED STATES GEOLOGICAL SURVEY. can species, they differ considerably from those of that group in general aspect, and in composition also. The group is, lithologically, at least, separable into two divisions, but they are not regarded as severally of co-ordinate value wita the other recognized Tertiary groups. The lower division consists mainly of silicious and sandy shales, and laminated and thin-bedded sandstones, with, in some places, especially in the western part of this district, frequent layers of hard, dark-colored car- bonaceous shales. In some places the strata are also quite calcareous, occasional layers being nearly pure, compact, finely-laminated limestone. Others of the calcareous layers are sometimes odlitic in texture. The general aspect of the strata as seen exposed at a distance is light gray. The upper division consists mainly of sandstones that are coarser, as weil as less thinly and distinctly bedded, than those of the lower divis- ion. In some parts it is shaly, and in others carbonaceous. Much of its sandstone is ferruginous in aspect, instead of having the gray tint that the lower division has. Sometimes certain beds of its sandstones are earthy and easily disintegrated, often leaving, weathered out of the mass, spherical concretions of hard sandstone that vary in size from a fraction of an inch to two or three feet in diameter. Other beds some- times present butiress-like masses in the brow of bluffs, which form . conspicuous and somewhat remarkable features in the landscape. Such features are very characteristic of this division in the bluffs of Green River in the vicinity of Green River City, Wyo., and, to a less extent, they also appear in the bluffs which border the cafon and valley of White River, in the southwest portion of this district. ‘The invertebrate fossils which this group affords are similar to those that are found in the fresh-water portion of the Wasatch Group, some of the species being identical, and indicate a purely fresh-water condition throughout. They are almost wholly molluscan, and belong to the branehiferous genera Unio, Viviparus, and Goniobasis, beside several genera of pulmonate gasteropods, including both the limnophile and geophile divisions. The Green River Group has become somewhat noted for the fossil fishes that have been discovered in its strata in Wyo- ming, and, like the Wasatch Group, it has at various localities also fur- nished considerable collections of fossil vertebrates and plants. In this district, the Green River Group is well and characteristically developed, the lower division reaching a thickness of about nine hun- dred teet and the upper division about five hundred feet. The large hill-masses that lie between Hogback Valley and Powell’s Park are composed of it, as are also those that form the bluffs of the south side ot the valley of White River, from Powell’s Park to the western bound- ary of the district, except that portion of them which forms the south- ern border of Raven Park. It also occupies a considerable space ad- jacent to White River, between Raven Park and the western boundary of the district, and also a narrower space along the southwestern side of Raven Ridge. The strata of the lower division cf the Green River Group differ con- siderably in lithological characters in different parts of this district. In the hills that lie between Hogback Valley and Powell’s Park they are more largely composed of ordinary sandstones than is usual in this group, some of which constitute thick, heavy-bedded strata. In the southwestern part of the district the strata of this division are more | finely Jaminated, and contain much more calcareous and carbonaceous material than elsewhere. The principal flexures and other displacements of the strata of this WHITE. ] TERTIARY PERIOD. 37 region doubtless took place after the deposition of the Green River Group, but in the district here reported on the strata of the whole group are, aS a rule, nearly horizontal, or vary only a few degrees trom the horizon. This is evidently due to the fact that they have been eroded from the spaces that are now occupied by the more abrupt flexures, which they doubtless once covered, but are now found to occupy only or mainly the comparatively undisturbed spaces on the dropped side of the flexures. THE BRIDGER GROUP. This is one of the more important of the groups among those that, in western North America, are referred to the Tertiary period, especially as regards the vertebrate remains that have been obtained from its strata. It is most fully and characteristically developed in the region known as the Green River Basin, north of the Uinta Mountains, only the south- eastern portion of the formation, so far as it is now known, extending within the limits of this district. In its typical localities it is found resting conformably upon the Green River Group, into which it passes without a distinct plane of demarkation among the strata. Its molluscan fossil remains correspond closely with those of the Green River Group, some of the species being common to both, all indicating a purely fresh condition of the waters in which the strata of both groups were de- posited. At the typical local.ties the group is composed in great part of soft, variegated, bad-land sandstones, a peculiar greenish color often predominating over the others, which are reddish, purple, bluish, and gray. Limestone strata, marly and clayey beds, and cherty layers are ~ not uncommon, and grits and gravelly layers sometimes occur. Strata of the Bridger Group are found to occupy only a comparatively minute portion of the surface in this district, the only locality at which they appear being in the valley of Red Bluff Wash, between Raven Ridge and White River, in the southwestern part of the district, where these strata rest upon those of the upper division of the Green River Group, and are covered in turn by those of the UintaGroup. The strata of the Bridger Group exposed there reach only about one hundred feet in thickness, and probably represent those near the base of the forma- tion. The only fossils obtained from these strata were a few fragments of chelonian and mammalian bones. THE UINTA GROUP. Resting directly, but by unconformity of sequence, upon all the Ter- tiary and Cretaceous groups in the region surrounding the eastern end of the Uinta Mountain Range, is another Tertiary group that has received the name of “ Uinta Group” from Mr. King, and “ Brown’s Park Group” from Professor Powell. It is possible that this group was deposited continuously, at least in part, with the Bridger Group, but at the places where the junction between the two groups has been-seen in this region, - there is an evident unconformity, both by displacement and erosion. The group consists of fine and coarse sandstones, with frequent layers of gravel, and occasionally both cherty and calcareous layers occur., The sandstones are sometimes firm and regularly bedded, and some: times soft and partaking of the character of bad-land material. The color varies from gray to dull reddish-brown, the former prevailing north of the Uinta Mountains and the latter south of them. The only invertebrate fossils that are known to have been discovered in the strata of this group are some specimens of a Physa, very like a recent species. Therefore, invertebrate paleontology has furnished no 38 REPORT UNITED STATES GEOLOGICAL SURVEY. evidence of its assumed Tertiary age and lacustrine conditions of its deposition. Its fresh-water origin, however, seems unquestionable, be- cause of its intra-continental position, its limited extent, and the fact that none but fresh-water deposits are known in this part of the conti- nent that are of later date than the close of the Laramie period. While the known unconformity of this group upon the other Tertiary groups, as well as upon the still older rocks, might, in the absence of other facts, be suggestive of its post-Tertiary age, the following facts seem to show that it cannot be of later date than Pliocene Tertiary, to which epoch Dr. Hayden, upon the occasion of his first visié to that region, referred it. In many places the strata still remain in a nearly horizontal position, but in others they have been considerably displaced, as, fur example, by being flexed up against the flanks of the Uinta Mountains, and also in a similar manner against the Dry Mountains, northeastward from: Brown’s Park. This shows that, although much movement of displacement took place before the deposition of the Brown’s Park strata, as shown by their unconformity with those of the older groups, a considerable amount of movement, even of mountain elevation, has taken place since their deposition. Besides this, a large proportion of the immense denudation which tbe strata of that region have suffered is known to have taken place since the deposition and .~ partial displacement of the Brown’s Park Group, because these strata are involved with the others in that denudation. Furthermore, a re- markably extensive outHow of basaltic trap, covering a large region which lies mainly to the eastward, but which formerly extended much within the limits of this district, took place after the deposition of the Uinta Group, and also after it had suffered displacement and erosion to some extent at least. This is known to be the case, because the trap is found resting upon the unevenly eroded surface of a portion of the Uinta Group at Fortification Butte. That portion occupies a higher level than does the principal portion of the group, at least within this district; and the trap rests unconformably upon the Laramie and Cre- taceous strata in the immediate vicinity, as well as upon the Uinta Strata, in such a manner as to show that little, if any, movement has taken place since the trap outflow. The denudation of the rocks of that region has been so great since the trap outflow that the latter rock has been removed from a large part of the surface it once occupied, leaving only here and there mere shreds of the once massive and extensive sheet upon the higher hills. Water-worn fragments of this trap, together with those of other rocks, enter into the composition of the scattered drift of that region. This drift was probably contemporaneous with the great northern gla- cial drift, and is found not only in the valleys of that region, but also scattered upon the hills many hundred feet higher than the streams. These facts seem to be sufficient to prove that the Uinta Group cannot be of later date than Pliccene Tertiary, while its relations to the other Tertiary groups seem to show that it cannot be referred to an earlier epoch than the Miocene. But further evidence on this point is needed. This group occupies that expansion of Green River Valley which is known as Brown’s Park. From there it extends eastward and around the eastern end of the Uinta Upliit, except a few miles interruption of its continuity tliere, and thence extends westward alorg the southern base of the Uinta Mountains a large part of the length of the range. It extends northward from the eastern portion of the Uinta Mountains as far as Dry Mountains and Godiva Ridge. Remaining patches of it show that the formation formerly extended eastward as far as the foot- wnitn. | ERUPTIVE ROCKS. 39 hills of the Park Range. The relation which this group has to similar groups in different parts of that great western region remains for future investigation to determine. Its relation to those immediately associated with it isa matter of great interest, which will be much enhanced by any paleontological testimony that its strata may yet furnish. In this district the Uinta Group occupies nearly the whole surface of the western portion of Axial Basin, comparatively small areas immedi- ately east and immediately north of Yampa Mountain, and a consider- able portion of the space between Junction Mountain and the eastern end of the Uinta Upiift, all of which spaces are in unbroken continuity. It also occupies quite a large space in the western part of the district, which is bordered, in a general way, by Raven Ridge, Red Bluff Wash, and the western boundary-line of the district, beyond which it is con- tinued far to the westward. Throughout the whole of this last-men- tioned space the strata of the group have that dull rusty-red aspect and partial bad-land character before mentioned, while to the eastward of the Uinta Range the general aspect of the group is gray. ERUPTIVE ROCKS. Besides the stratified rocks of this district, which have already been described, a few of igneous origin are found in the eastern portion These are remaining portions of a most remarkable outflow of dark colored vesicular bassaltic trap, which, after the close of the Tertiary period, took place in the region bordering upon the eastern portion of this dis- trict, extending also to the northward and southward. Much the larger part of this great outflow has evidently been removed by erosion so that only shreds of it remain where it once occupied the surface as a contin- uous sheet. Broken masses of this rock are scattered profusely upon nearly all the higher hills in the northeastern portion of the district, but upon only one point within its borders was it seen to occupy its original undisturbed position. Just beyond the border of the district to the eastward, however, especially upon the White River Plateau, it yet abundantly overspreads the stratified rocks upon which it was deposited at the time of the outflow. This trap-outflow is known to have taken place after the deposition of the Uinta Group because the trap is found to rest upon the latter at Fortification Butte, some six miles north of the northeast corner of this district. It is known to be of older date _ than the drift of that region, and also older than other Quaternary changes that have taken place there, because it, together with other rocks, has suffered such extensive erosion since its deposition, and because the drift-pebbles are in part composed of the trap. Other outflows of similar rock have occurred at other localities in the Park Range, some of which were probably contemporaneous with this one, and it is probable also that this one was produced from more than one vent. The only vents I was able to observe, however, was one in the form of a dike, some eighteen miles north of the northeast corner of this district, and another at “Chimney Rock” in Egeria Park, in the mountains east of the district. This dike consists of a vertical wallabout twenty feet wide and three or four miles long. The rock of the dikes is . similar to that of the outspread trap, but is much less vesicular. Indeed, it was not often that any vesicles could be detected by the unassisted eye in the rock of the first-named dike, and these were flattened in the ver- tical plane of the dike itself. It seems to have been only in the hori- zontal portion of the outflow, where the pressure was at its minimum, that the vesicular character of the rock became most marked; and in some of the layers, for it sometimes has an indistinct appearanee of stratification, the vesicular character is wanting. CHA Paik gy. DISPLACEMENTS. This district possesses unusual geological interest, because it is the ground upon which displacements of the strata belonging to two differ- ent orographic systems, those of the Uinta and Park Range Mountains, meet and blend together. The district is so small, however, that it does not embrace within its limits a very considerable portion of either of these mountain systems. Some of the minor flexures, or the vanishing ends of more important ones, of the Park Range system, reach within the eastern border of the district ;- but the greater part of the displace- ments which the strata of the district have suffered belong to the Uinta system. The relation of these displacements to the Park Range system are not clearly perceivable until they are traced beyond the eastern and southern limits of the district here especially reported on; therefore ~ the accompanying map is made to embrace considerable additional space beyond both its eastern and southern borders. The labors of the other geologists of the survey have made known the orographic character- istics of that portion of the Park Range that lies to the eastward and southeastwuard of this district; while those of Mr. King and Professor Powell have made us acquainted with the structure of the Uinta Range. The main displacements of these two systems being thus known, their relation to and connection with each other and with accessory flexures within this district may be easily traced upon the accompanying geolog- ical map. The general plan of structure of the Uinta Uplift has been shown by Mr. King and Professor Powell to consist essentially of one great flexure of uplift, the axis of which is approximately east and west. The last- named geologist has shown that this great Axial Uplift of the Uinta Mountain system is distinctively characterized by an abrupt flexure of the Sirata, which is in some places a true fault, on each side of the great fold, and that between the two abrupt side bendings the antielinal bend- ing of the strata is comparatively slight. This peculiar form of folding of the flexures seems to be generic, so to speak, to the Uinta system, since it is tound to characterize certain of the principai accessory flexures as well as the Yampa and Junction Mountain upthrusts, as will be ex- plained in connection with their description on following pages. The Uinta system ends, as a mountain-range, upon and about mid- length of the northern border of this district; but the Axial Flexure, abruptly and very greatly diminished in scope, continues eastward from the end of the mountain-range through the strata of the eastern portion of the district and blends with certain flexures of the Park Range, as will be explained on following pages. The accessory or subordinate flexures or uplifts pertaining to the Uinta system, that lie within this district, are of a peculiar and interesting character. The larger ones lie approximately parallel with and closely adjacent to the Axial Uplift, and constitute an integral portion of the eastern end of the mountain- range; but the outlying smaller flexures are not only separate from the first named, but also from each other. The smaller ones diminish in 40 WHITE. ] DISPLACEMENTS. Al scope with their distance from the main axis, and diverge or sweep around to the southeastward as they stretch away from the Uinta Mount- ains. Although there is a greater or less degree of divergence of these subordinate axes of flexure, they have neither a common origin nor a common radial center in either of the two mountain systems; but the position of some of them, at least, shows equally intimate relations with both. There are within this district three of these subordinate flex- ures or uplifts which have intimate relations with the Uinta system, and that have received distinctive names, besides two peculiar isolated mountain upthrusts, all of which will be described separately on fol- lowing pages. These arethe Plateau, Midland, and Raven Park Uplifts, and Junction and Yampa Mountain upthrusts, all of which are shown in their relative positions in the sections at the bottom of the geological map accompanying this report. UPLIFTS AND UPTHRUSTS.* The Axial Uplift—This term is applied to the main flexure of the Uinta system. The general course of the axis of this flexure through the northern portion of this district is eastward, with a broad curve, the concavity of which is to the southward. Its course is plainly indicated on the geological map by the outcrops of the formations that border both the eastern and western portions of Axial Basin. Upon reaching the eastern borders of this district the Axial Flexure bends quite abruptly to the southward, and is lost among the hills that lie to the eastward of Agency Park, which are a part of the foot-hills of the Park Range of mountains. A short branch of the Axial Flexure sep- arates from the main portion at the eastern border of the district, aud turns abruptly in a direction a little west of northward, passing uear Caton Park, and blends with the general uplift of strata as they rise toward the foot-hills of the Park Range, north of Yampa River. Judging from the phenomena now presented by the eastern end of the Axia] Uplift, it seems probable that at least the portion of it which lies within and adjacent to this district was at first a simple, approx- imately uniform, upward flexure; and that while a part of it remained as originally flexed, those portions that now form the mountains were more or less sharply uplifted from the remainder, the added displacement amounting to thousands of feet. We find that the axis of the main Uinta uplift is prolonged eastward from the eastern end of that mount- ain range as a comparatively slight flexure of Cretaceous strata, which blends with those of the Park Range foot-hills, as before described, and that the mountains of the Uinta system are composed of those strata only that have been thus sharply uplifted, although the latter have suf- ferred immense erosion since their elevation. Possibly they would have suffered still greater erosion if it were not that the uplift has brought up _ the comparatively hard Carboniferous strata, and those of the still harder Weber quartzite, so high that they now constitute the visible portion of the whole mountain range. The amount of displacement embraced *TIn using the terms “uplift” and “ upthrust,” I do not thereby intend to express any opinion as to the actual direction of movement in the displacement of the strata, whether upward or downward. The terms, especially the first, will be readily under- stood, and it seems more convenient for the reader and investigator to regard, at least tentatively, the lower, which is the larger mass, as the fixed one; and the higher, which are relatively the smaller masses, as those that have been uplifted. The term “upthrust,” so faras Iam aware, has not been used before. Its applicability will plainly appear in the following descriptions of the displacements of Junction and Yampa Mountains. 42 REPORT UNITED STATES GEOLOGICAL SURVEY. by this separate elevation of the Palezoic rocks above the adjacent Cretaceous strata which now cover the less uplifted part of the Axial Flexure reached from 7,000 to 8,000 feet, and the displacement was accomplished partly by faulting this immense thickness of strata and partly by very abrupt flexure. The eastern end of the mountain portion of the Axial Uplift termi- nates by a broad, sweeping, or partiversal* dip of the strata, which dip is abrupt, much like that of the sides of the uplift. That part of the terminal mountain mass of the main range which lies within and. upon the northern boundary of this district consists of Carboniferous strata, and is flanked at its base by the upturned edges of the Jura-Trias, Da- kota, and Colorado groups successively. The strata of the Colorado Group, however, quickly become horizontal, or nearly so, and occupy the low ground around the mountain; but they are there partly obscured by the strata of the Uinta Group. A very large part of the mass of the Uinta Mountain Range consists of the Weber quartzite, which great formation is probably about fifteen thousand feet thick. All the visible portion of the Axial Uplift, however, that lies within this district, con- sists of Carboniferous strata alone, except the Weber quartzite, which is exposed in Junction and Yampa Mountains, presently to be described; and is also, perhaps, very slightly exposed at the point where Signal Shot Creek Cation opens into the eastern portion of Red Rock Basin. Junction Mountain Upthrust.—As regards their structure and origin, Junction and Yampa Mountains are most remarkable isolated moantain masses, both having essentially the same structure, and doubtless a simultaneous origin. Both are situated upon the axis of the Axial Flexure, eastward of and separate from the main mountain masses of the Uinta chain and from each other, and where that flexure is compara- tively slight. Junction Mountain is situated three or four miles east of the terminal mountain mass of the Uinta chain, between which two mountains Snake River flows to its confluence with the Yampa. Although this mountain is so near the other mountains of the Uinta system, and is so evidently a part of that system, it is, nevertheless, entirely isolated in its struc- ture and elevation as well as by its position. It consists of a separate and distinct upthrust of the Carboniferous and Weber quartzite strata through those of Mesozoic and Cenozoic age, which have remained almost undisturbed in the immediate neighborhood by that separate and remarkable displacement. The manner of this displacement, which I have called an upthrust, may be illustrated by the action of a large punch, worked by machinery, for perforating heavy iron plates, so clearly defined does the separation appear to be between tbe uplifted and the surrounding strata. The illustration will doubtless be more ac- curate if we imagine the punch and die to have become so worn by use that the iron plate is torn in places and nowhere clearly cut in the process of punching. This mountain upthrust is oval in form, the long diameter being nearly twelve miles and the short one about four miles. The strata about midway of both sides are nearly or quite vertical, while the dip at the northern and southern ends, although steep, is much less than at the sides. The direction of the long diameter is northwestward and southeast- *All anticlinal axes must necessarily dip more or less in some portion of their ex- tent; but in this region there are many examples of very short and rapidly-dipping anticlinals around the vanishing end of which the strata dip by asweep of the greater or less part of a circle. I apply the term “ partiversal” to such a dip, and use it in a sense similar to that in which “ quaquaversal” is used for a dip in all directions. WHITE.] DISPLACEMENTS. 43 ward, and neither this diameter nor the short one coincide with the di- rection of the axis of the main uplift. Its independence of the great axis, however, is not without some analogy in that of the Plateau Up- lift and the Yampa Mountain Upthrust, for the main axis of the Uinta system makes a broad bend to the northward opposite Yampa Plateau, which the axis of the Plateau Uplift does not coincide with; and it is the short axis of the Yampa Mountain Upthrust, and not the long one, that coincides approximately with the general direction of the main Uinta axis. These diverse positions of the axes of the accessory uplifts aod upthrusts in relation to the main axis, as well as the separateness of each of these displacements, seem to be in keeping with the assumed superaddition to the primary Axial Uplift, as has been before sug- gested. The amount of the relative upward displacement of the strata that now constitute Junction Mountain is easily computed from the known thickness of the intervening groups in that region. For example, the top of the Weber -quartzite, as seen in the canon which Yampa River has cut through Junction Mountain, has been raised to a height that is about equal to that of the top of the Colorado Group, as it now exists in immediate proximity, or the plane that its top would now occupy there if it had not been removed by erosion. Theretore, the sum of the thick- ness of the whole of the Carboniferous, the Jura-Trias, and the Dakota and Colorado groups is equal to the entire upward displacement of the strata that now constitute Junction Mountain, because all these groups of strata intervene between the top of the Uinta sandstone and the top of the Colorado group. The amount of tais displacement is, therefore, not less than 8,000 feet, as will be seen by referring to the thickness that I have assigned to those groups in Chapter Ili. Such an extraor- dinary displacement as this, and the no less extraordinarily small limit within which it has been confined, seems to justify the use of the term ‘‘upthrust,” as distinguishing it from ordinary uplifts. The illustration of the manner of this upthrust that has been used, by comparing it to the action of a dull punch upon a plate of iron, so that the sides of the hole would be somewhat torn in places instead of being everywhere cleanly cut, is appropriate, from the fact that at three or four places upon the borders of the upthrust, and near or at the base of the mountain, there are portions of Triassic strata that have been separated in the upward moveinent, but have been dragged up and thrown over backward, or otherwise tilted, and, as it were, caught in the jaws of the fault. The position of some of these dragged portions is shown upon the geological map. i The illustration of the action of a dull punch that has just been used, is still further applicable to the broadly-rounded surfaces of the uplifted Strata, producing a gentle quaquaversal dip from the center to near the borders of the upthrust, where the dip becomes suddenly greater, or a fault. The outline of the upthrust, as before remarked, is oval, and the faulting seems to have taken place only, or mainly, at the sides... At the ends, the strata appear not to be faulted, but only strongly flexed. Yampa Mountain Upthrust.—The general description that has been given of Junction Mountain, as to its origin and structure, will apply in almost every particular to Yampa Mountain. The amount of displace- ment which its strata have suffered in relation to those that immediately surround the upthrust, is a little greater than that of Junction Mount- ain, although the size of the Yampa Mountain Upthrust is a little smaller than the other, and its position is somewhat remote from the other mountain uplifts of the Uinta Range. This mountain upthrust lies 44. REPORT UNITED STATES GEOLOGICAL SURVEY. about sixteen miles eastward from that of Junction Mountain, with its long diameter upon and directly across the low, eastward extension of the Arial Flexure of the Uinta Range. Its long diameter has a direction a few degrees west of southward, and, therefore, it does not correspond with the axes of any of the other uplifts of the Uinta system. Upon casual view it might be expected that the long diameters of both these upthrusts would be found to correspond with the axis of the Uinta Range, or at least that they would correspond with each other, since the two mountains are so similar, and both occur on the samé axial flexure. On the contrary, iflines drawn through the long diameter of each of the upthrusts were produced southward, they would meet at an angle of about 50°. The relative position of the long diameters of these upthrusts is in keeping with the curvature of the Axial Flexure upon which they are located, as it sweeps around from the Uinta to join the Park Range system; and their transverse instead of longitudinal position upon that flexure is probably due to simultaneous impingement of force that was exerted from both the adjacent mountain systems while the upthrusts were in progress as superadditions upon the original flexure. ‘The strata of the Colorado Group which surround Junction Mountain are much obscured by the overlying drift and the soft strata of the Uinta Group. The strata of the Colorado Group also closely surround Yampa Mountain, and are also largely obscured by the same deposits as in the other case. The escarpments of the Fox Hills and Laramie groups that border both sides of the long Axial Basin reach within the immediate vicinity of Yampa Mountain; but the strata of the escarpment upon the south- ern side, while they partake of the general axial flexure, do not seem te have been especially flexed or otherwise disturbed by the extraordinary movement of this upthrust except at its immediate borders. Those on the northern side, however, are found to have been abruptly flexed to the northward by the less abrupt elevation of the strata composing the northern portion of the upthrust. The character of these two upthrusts is partially illustrated in the long section at the bottom of the geological map accompanying this report, and still further by the longitudinal section of Yampa Mourtain upon the same sheet. The Piateau Uplift.—The long, broad mountain mass which has been designated as Yampa Plateau upon the accompanying and other maps, is not strictly parallel with the axis of the adjacent portion of the main uplift of the Uinta Range, yet it is, in an important sense, a parallel and accessory flexure. It is not, properly speaking, divergent from the inain axis of the range, but by its northern side it lies closely adjacent to, really parallel with, a corresponding portion of the southern side of the main uplift, with which it in part coalesces; and yet the Plateau Uplift is quite independent in its termination at both ends, as well as nearly or quite so by a separate synelinal flexure. Ina mere topograph- ical sense, Midland Uplift also constitutes a part of Yampa Plateau, but for geological purposes that uplift must be separately considered. In some degree Plateau Uplift is an epitome of the great Axial Uplift, for it also consists of the full series of Carboniferous strata together with a central mass of the Weber quartzite. Its manner of uplift is also similar, for it rises by an abrupt flexure of the strata upon either side, the flexure of the strata between being comparatively slight. This character, as well as the relations of the Plateau Uplift toits associated displacements, is shown in one of the sections at the bottom of the ac- companying map. The flattening of the flexure between its two ab- ruptly-bent sides gives the uplift its plateau-like character, which, how- WHITE. } DISPLACEMENTS. AD5 ‘ever, is preserved in only a part of it, the remainder being narrowed by the erosion of Fox Creek Valley, and in part modified by the spur- like termination of both ends, The width of Plateau Uplift varies from about five, to ten miles; and its extreme length as a mountain elevation is about forty-five miles. It is widest at its western end, where it terminates by two great spurs or _ mountain ridges, namely, Split Mountain and Section Ridge, each of which has a westward-dipping anticlinal axis, and consequently a parti- versal* dip of its strata. At its eastern end, however, it terminates by only one dipping anticlinal, with its abrupt partiversal dip, the sweep of which is broader than that of the two western ones. The eastern end of the Plateau Uplift extends so far eastward as to blend with the terminal mountain mass of the axial portion of the Uinta Range. The intimate connection of the Plateau Uplift with that of the main Uinta axis will be understood by the statement that tke two are separated only by a sharp synclinal axis, which is in part a fault. The maximum amount of this displacement is fully 2,000 feet; but in some places, nevertheless, the mountain masses of the two uplifts are blended to- gether topographically just as the Midland Uplift, presently to be de- scribed, is in part blended with the Plateau Uplift. The mass of the latter uplift is, however, in large part separated topographically from that of the Axial Uplift by the deep Red Rock Basin, described on a previous page, and by the eastward prolongation of that basin in the form of a mountain valley.. The two great spurs which project from the western end of Yampa Plateau, with their rapidly-dipping auti- clinal axes and tbe regular partiversal dip of their strata, are remark- able for their magnitude as well as for their inherent peculiarities. They are really great mountain masses, their summits being more than 3,000 feet above the neighboring portion of Green River, which traverses Split Mountain by a profound cailon, as has been described on a pre- vious page of this report. The Midland Uplift.—The amount of displacement which took place in the elevation of this uplift is nearly 5,000 feet from the strata of the Colorado Group which flank it immediately to the southward, and which remain there comparatively undisturbed; and yet this displacement is about 3,000 feet less than that of Plateau Uplift,-with which Midland Uplift lies parallel and in close contact. The influence of the latter up- lift extended still farther eastward; but it is only the mountain portion that is specially discussed under this head. This portion constitutes the topographical feature I have called Midland Ridge, as well as a part of Yampa Plateau, with which itiscontinuous. The strata exposed to view by the Midland Uplift are almost wholly those of the Jura-Trias groups. Those strata that have been definitely referred to the Jurassic period, as well as those of the Dakota Group, flank the uplift all along its southern border; and upon the highest portion of the Ridge there is also a Small area that is capped by these strata. The red beds of the Jura-Trias have been much exposed by erosion in a. very large part of the Ridge, their bright colors and great elevation above the surround- ing country making very conspicuous and striking features of the land- scape. The mountain portion of Midland Uplift, the eastern part of which I have called Midland Ridge, does not extend so far eastward as the mountain masses of the plateau and great axial uplifts do; but as a flexure, Midland Uplift extends much farther eastward. Its’ axis also makes a bend to the southward in the course of its eastward exten- sion, somewhat like that of the eastward extension of the Axial Uplift; | * See foot-note on page 42. 46 REPORT UNITED STATES GEOLOGICAL SURVEY. and, passing through the southern end of Pifion Ridge, it crosses White River and quickly disappears by a partiversal dip of the strata of the Laramie and Wasatch groups. The extent of the displacement of this eastern portion of Midland Uplift is much less than that of the western portion, and has brought to view no strata beneath those of the ~ Cretaceous groups. Midland Uplift consists essentially of a monoclinal flexure, with the rise upon the northern side. The flexure is quite as distinctly monocli- nal in the less displaced eastern portion as it is in the western part, where the northern side of this uplift is in contact with the southern side of Plateau Uplift. The facts observed seem to warrant the conelusion that all the flexures of the strata which pertain to the Uinta svstem within and adjacent to this district were simultaneous in their origin, and that the movement of elevation of these folds proceeded simultaneously up to a certain stage and then halted in their common upward movement. Also that the specia] elevation of the mountain masses, which occupy either the whole or the principal part of each of the original folds, then took place as sharply-defined superadditions to their initial elevation, which culminated in the Uinta Mountain system. It is also evident (assuming for purposes of description the actual uplift of these folds) that certain of the specially-elevated accessory uplifts halted in their — upward movement, while that of the adjacent larger or principal ones continued. This view is supported by the fact that all along the flex- ure which divides Midland Uplift from that of Yampa Plateau the strata of the former are sharply flexed up against the latter, presenting the appearance of having been dragged by the superadded upward movement of the Pateau uplift. Midland Uplift terminates at its western end by narrowing rapidly to’ a point against the southern side of Section Ridge, so that the Creta- ceous strata, which are flexed up against its own south side, are con- tinued in like manner without interruption or material change in dip along the south side of Section Ridge and around its western end, as will be further explained under the head of flexures. Raven Park Uplift.—The middle of this uplift is some eight or ten miles south of the southern border of Midland Uplift. It is thus not only iso- lated from all those that have been before considered, but its elevation has involved a much less amount of displacement of the strata of the region than that of any of the others, the lowest strata that have been brought to the surface upon its axis being those of the Colorado Group. In this respect it resembles the less elevated eastern portion of both the Axial and Midland Uplifts, but it is free from any superadded uplift or upthrust, such as has taken place upon those primary uplifts. By this characteristic, as well as by its local separation and slight relative ele- vation, it is distinet from the Uinta Mountain masses, but it is never- theless an outlying fold belonging to that system of uplifts. Raven Park Uplift is a very short one, not more than twenty-five or thirty miles long, its eastern and western extent being scarcely so great as that of Midland Uplift, from which Raven Park Uplift lies immediately southward. Its longer axis, however, is not parallel with that of those portions of the three uplifts that lie directly north of this uplift, but its direction is northwestward and southeastward; inthis respect conforming in general direction with the southerly sweep of the eastern end of both Axial and Midland Uplifts. The significance of this change in the direc- tion of these axes from that of the general trend of the Uinta Chain is doubtless to be sought in the fact of their approaching relation to the uplifts and flexures of the Park Rangesystem. The flexureof thesoutbern \ WHITE. ] DISPLACEMENTS. at side of this uplift, which I have called the Raven Ridge Flexure, is much more abrupt than that of the northern side. This is also a peculiarity of the eastern prolongation of the Midland Uplift, the southern flexure of which is a part of the Great Midland Flexure, and also of the western portion of the Danforth Hills Uplift, presently to bedeseribed. In short, it is a common peculiarity of the flexures that are embraced within the sweep of the eastward extension of the Axial Uplift, as it extends from the Unita system to join with the Park Range system; but it is not a peculiarity of the Axial Uplift itself, which has a nearly uniform curva- ture or flexure from side to side. The significance of the greater abrupt- ness of the dip upon the southern side of these secondary uplifts is, no doubt, to be sought in the forces which have acted laterally as well as vertically in the elevation of the two great ranges of mountains, at least within the angle formed between the two within this district. The dip of the strata is in all directions from the middle of Raven Park, but it varies much in degree in different directions. It is very slight to the northward and westward, not reaching so much as 10 de- grees, while in the Raven Ridge Flexure, at the south side of Raven Park, the dip is as much as 60 degrees, from which point it diminishes both eastward and westward, until the uplift, as such, finally disappears. The Danforth Hills Uplift.—Eastward from the eastern end of the Plateau and Midland uplitts, and between them and the displacements that are more properly referable to the Park Range system, there is a broad, irregular synclinal, which is occupied by the strata of the Wa- satch and Green River groups, of Tertiary age.. The depth and impor- tance of this synclinal is shown in one of the sections at the bottom of the accompanying geological map. Its importance still further appears by the fact that the difference of displacement between the top of the Green River strata which rest upon it and that of the Carboniferous strata that are exposed in the uplifts and upthrusts that have been de- scribed, the latter of which are less than half a dozen miles from its borders, is more than 10,000 feet. This great synclinal is partly sur- rounded by an outcrop of the strata of the Fox Hills and Laramie groups, which are upturned by the Midland Flexure as it traverses by a tortuous course almost the entire length of the district. Adjoining the northern side of this broad synelinal is the Danforth Hills Uplift, which, although a comparatively slight one, derives peculiar interest from the fact that it is so intimately connected with the displacements of both the neighboring mountain systems that it cannot be exclu- sively referred to either. The displacement of strata involved in this uplift upon its northern, or rather northeastern, side is comparatively slight, because they connect by a very gentle synclinal with those that have been still more elevated by the Axial Uplift, and the general rise of all the strata of the district toward the foot-hills of the Park Range. The displacement at the southern side of this uplift, however, is very great, the drop of the Midland Flexure there being not only very ab- rupt, but it amounts to wore than 3,000 feet. The Danforth Hills Uplift is bounded on its southeastern side by the Midland Flexure, its other boundary being a gentle synclinal that ex- tends eastward from the point of junction of the Midland Flexure with that of the Great Hogback, in Hogback Valley, and sweeps around, but within, the entire eastern end of the Dantorth Hills, and thence north- westward along their northern slope, fading out in the vicinity of Yampa Mountain, where the uplift as a separate displacement also disappears. Sundry uplijts.—Besides the uplifts that have been specially described on preceding pages, certain portions of others reach within the boun- 48 REPORT UNITED STATES GEOLOGICAL SURVEY. daries of this district. Among these is the northern extremity of the Great Elk Mountain Uplift, the principal part of which has been so ably described and illustrated by Mr. W. H. Holmes in his report for 1874. Although the principal mass of that uplift is more than a hundred miles distant to the southward, its northern vanishing end is in the bluffs that form the northern border of Agency Park, where it is separated from the southeastern end of the Danforth Hills Uplift ouly by the gentie synclinal that has been before mentioned as a part of the boundary of the latter uplift. The connection of Elk Mountain Uplift will be further referred to under the head of ‘“ Flexures.” Two or three very faint uplifts, or undulations of the strata, cross Green River from the southeastern part of this district. These are doubtless the result of the same force that elevated the Uinta Mountain system, as it diminished in intensity with the distance from the great axis. Besides the uplifts the boundaries of which may be defined, there is a general uprising of all the strata, to the eastward, against the western flank of the Park Range system. It is upon this broad, gently-inclined plane of strata that a portion of the minor uplifts already described are defined. Hven the eastern termination of the great Axial Uplift of the Uinta system extends upon this elevated inclined plane of strata which has been lifted as a part of the Park Range system. FLEXURES. An uplifting, of course, always implies the flexing of the strata up- ‘lifted; but in this district the conditions of displacement and subsequent erosion of thestrata have been such as to make it desirable to give separate names and descriptions tocertain flexures. For example, the principal up- lifts that pertain to the Uinta system, namely, the mountain portion of the great Axial Up‘ift, including the two upthrusts, and the Plateau Uplift, do not, like some others, consist of a nearly unitorm convex flexure, but of two more or less abrupt lateral flexures, one at each side, with a com- paratively slight convexity between them. Others, and this applies to all others in this district except the eastern extension of Axial Uplift, which consists of a gentle, uniform, upward flexure, have one side very much more abruptly flexed than the other. This difference is so great in some cases as to give almost a true monoclinal character to the flexure of the whole uplift. In all cases of this kind in this district the steeper dip is on the southern, southwestern, or western side of the uplift, ac- cording to its position ; or, in other words, upon the inner side of the great curve which those displacements form as they reach from one mountain system toward the other. It is these steeper flexures to which I have given distinctive names, and which are briefly described in the following paragraphs. The Grand Hogback Flexure.—The Fox Hills strata, that flank the west side of Elk Mountain, Mr. Holmes has shown, extends northward as a continuous hogback, which he has called the Grand Hogback, a hundred miles or more, it being the same one that crosses White River and sepa- rates Agency, from Powell’s park. The flexure by which that great line of hogbacks has been produced I have ealled the Grand Hogback Flexure. It belongs, of course, to the Park Range system; but, after crossing White River Valley, which it does in an almost due north and south line, it becomes continuous with the great Midland Flexure, which extends in a tortuous course through this district and blends with the principal Uinta displacements. The latter flexure is, then, as much an integral part of the Uinta system as the former is of the Park Range system. — WHITE. ] FLEXURES. 49 Although the Great Hogback and Midland flexures are practically one and the same, their separate lines of hogbacks approach each other at an obtuse angle about eight miles north of White River, at the east side of Hogback Valley. Here the continuity of the two great flexures is unbroken, but at the point of meeting of the upturned strata of the hog- back lines there branches off the shallow synclinal axis which sweeps around the southeastern end of the Danforth Hills Uplift, and thence extends along its southern side. The Grand Hogback Flexure is nearly a true monoclinal one. The strata that lie to the eastward of it dip gently to the westward from the foot-hills of the Park Range to the flexure proper, where they have a maximum dip of nearly or quite 75 degrees, and then immediately stretch out nearly horizontally. The strata originally involved in this flexure, as they now appear at the surface, are those of the Colorado Group to the Green Group, inclusive, the maximum dip now appearing in the comparatively soft strata of the Wasatch Group. Subsequent erosion has so far removed portions of these strata that only those of the Green River and Wasatch groups now occupy. the surface west of the line of maximum flexure. ‘Those of the former group, that now remain, are nearly horizontal, and have evidently been little if any affected by that great flexure, although it is so near their present escarpments. The Midland Flexwre.-—This flexure is, in some respects, the most in- teresting displacement of strata within the limits of this district, espe- cially as regards its great length and unbroken continuity from one mountain system to the other. It is continuous with, and in fact a part of the Great Hogback Flexure, which, as before shown, is so intimately connected with the Elk Mountain Uplift. From the point of its nominal connection with that flexure in Hogback Valley, Midland Flexure ex- tends in a tortuous course through the whole remaining length of the dis- trict to the flank of the principal uplift of the Uinta Range, with the lateral flexure of which it blends and becomes continuous far beyond the western boundary of this district. The course of Midland Flexure is northwestward about twenty miles up Hogback Valley; thence due west nearly ten miles; thence almost directly south nearly fifteen miles to the southerr end of Pinon Ridge, around which it bends abruptly ; thence in a straight direction, 15° north of west, about fifty miles. At a point about midway of the latter distance it coalesces with the flexure of the south side of Midland Uplift, with which it is in fact a part, all the way westward from the southern end of Pifion Ridge. From the flank of Midland Uplift, Midland Flexure is continuous to and along the south flank of Section Ridge, where it blends with and becomes a part of the Fox Creek Flexure; thence around the western end of Section Ridge, into the retreating angle formed by the dipping synclinal between Section Ridge and Split Mountain. From here it sweeps around the end. of Split Mountain as it did around that of Section Ridge, and into a simi- lar but much broader retreating angle or notch,.at the apex of which is. Island Park; thence by an abrupt bend to the westward, along the flank of the main uplift of the Uinta Range, and far beyond tie limits of this district. It is thus shown that this remarkable flexure, regard- ing both the Great Hogback and Midland flexures as really one, can be: traced continuously from the west flank of Elk Mountain Uplift to the: south flank of the main Uinta Uplift, a distance of more than two hun- dred miles. Throughout the greater part of this distance a large propor: tion of the strata that are involved in this flexure are exposed in long lines of hogbacks, which constitute more or less conspicuous topograph- ical features. The dip of the strata, in all the long reaches of this flex- 4G 50 REPORT UNITED STATES GEOLOGICAL SURVEY. ure, is away from the axes of the two mountain-ranges, respectively, which the flexure connects; for its position there is upon the distal side of each of the uplifts which it successively flanks. In all these places the dip is very abrupt, but it is much less in all the partiversal sweeps around the end of the dipping anticlinals and in the sag of the dipping synelinals than elsewhere. The continuity of the narrow outerop of the Strata of the Dakota and Jurassic groups around the end of the mount- ain portion of Axial, Plateau and Midland uplifts would, at first sight, appear to indicate a separate flexure there; but this apparently continu- ous outcrop belongs in fact to the three different displacements just named, and portions of it are continuous respectively with the Yampa, Fox Creek, and Midland flexures. The character of the latter flexure, as well as the strata involved in it at various points, is shown in the sections at the bottom of the accompanying geological map. The Fox Creek Flexure.—From the point where this flexure blends with Midland Flexure at the south side of Section Ridge, it passes east- ward in a gently sinuous direction, forming the dividing displacement between Midland and Plateau uplifts. Then, sweeping around the east- ern end of the latter uplift, it ends against the Yampa Flexure, which in turn sweeps around the eastern end of the terminal mountain-mass of the Great Axial Uplift. Fox Creek Flexure is a very abrupt one, the maximum dip being nearly vertical, and it embraces a maximum displacement of abont 3,000 feet. The strata involved in it, which appear at the surface, are those of the Jura-Trias and Carboniferous. Its general character is shown in the sections at the bottom of the accompanying geological map. A marked peculiarity of the flexure is the apparent dragging of its strata against the side of the Plateau Uplift, which has before been mentioned. The Yampa Flexure.—From its sweep around the terminal mountain- mass of the Axial Uplift this flexure extends westward, and constitutes the dividing displacement between the Plateau and Axial uplifts. Its general direction is approximately parallel with that of the Midland Flexure, except that toward its western end it bends away to the north- westward. It ends abruptly, at least in part, against a great north and south fault at the-western end of Red Rock Basin, the western wall of which fault also constitutes the end of the basin. The flexures that have been herein described are all nearly true monoclinal flexures, at least in their more abrupt and characteristic portions. But Yampa Flexure is different in this respect, since it forms an abrupt synclinal with the almost immediate rise of the strata which form the southern side of the great Uinta Uplift. This flexure itself has a nearly true monoclinal character, similar to that of the Fox Creek Flexure at the other side of the Plateau Uplift. Contrary to the general rule, however, in the case of the secondary uplifts, Plateau Uplift has its strata sharply flexed upon both sides, instead of one only, the distal side. In this respect Plateau Uplift possesses a peculiarity that has been shown to characterize the main uplift of the Uinta Mountain system as well as some of its accessory uplifts. Within the southern border of Red Rock Basin, and some five or six miles from its western end, Yampa flexure divides into two branches, both of which are monoclinal, the northernmost or lower one having 400 or 500 feet greater displacement than the other. The aggregate dis- placement of strata at the western end of the flexure is not far from 3,000 feet, which amount gradually lessens to the eastward, where also the synclinal becomes narrower and shallower. Circumstances did not permit a careful examination of the mountain-mass at the western end WHITE.] FLEXURES. 51 of Red Rock Basin; but indications were observed that at least the upper or southern branch of the flexure just referred to passes through the mass to the northwestward. The Raven Ridge Flexure.—This flexure forms the southern and steeper side of Raven Park Uplift. It has already been mentioned as having a dip of about 60° opposite the middle of Raven Park, which dip rapidly diminishes as the Uplift fades out both eastward and westward. Oppo- site Raven Park the strata of the Fox Hills, Laramie and Wasatch groups are involved, the former constituting that part of Raven Ridge and the latter passing under the nearly horizontal strata of the Green River Group, by a monoclinal flexure. Although the flexure itself dimin- ishes very rapidly to the northwestward, Raven Ridge itself is con- tinued much farther in that direction, where it is successively made up of the strata of the Fox Hills, Laramie, Wasatch, and Green River groups; those of the first two groups leaving the ridge successively as they spread out to the northeastward of the ridge. CONCLUDING REMARKS. The facts observed in, and in the neighborhood of, this district show conclusively that, although the Uinta and Park ranges of mountains have their axes at right angles, and are also separated by a consider- able space of country, the two mountain systems are intimately con- nected by continuous and interplicated displacements. These facts, to- gether with the further one that there are no displacements between the two systems that can in any way be regarded as breaking their connec- tion, seem to suggest the approximately simultaneous elevation of both systems. This idea is further strengthened by the fact that a mountain axis may be traced, at least indistinctly, from the main range of the Recky Mountains, northwestwardly through the Park Range, describing a curve, which, if produced, would point in the direction of the axis of the Uinta Range. It has already been suggested that the various movements of dis- placement in the Uinta system were not uniform in their rate of prog- ress, and only in part simultaneous. It should, therefore, not be ex- pected that the details of elevation of the two systems were all simultane- ous with each other. It is nevertheless probable that the whole Rocky Mountain system, including the Park Range, as we find it developed in Colorado, and the Uinta system, have had essentially 2. common phys- ical history ; although each system presents some characteristics pecu- liarly its own, or at least different from the other. CHAPTER V. SURFACE GEOLOGY. RELATION OF THE VALLEYS TO GEOLOGICAL STRUCTURE AND DIS- PLACEMENTS OF STRATA. Except in such rare instances as that of astream having its course upon or near a synclinal axis, nothing is more evident than that, as a rule, all streams have been the instrument by which their own valleys were exca- vated; and, even in the doubtful cases referred to, it is probable that an examination of other portions of the same valley would show a confirm- ation of, rather than an exception to, the general rule. This proposition accepted, leaves other questions of a remarkable character, which are unexplainable upon any except geological grounds. For example, in the Rocky Mountain region we not only often see a river traversing an ele- vated district, cutting its course by a deep canon in the underlying rock, while the land-surface is much lower not many miles distant than that which the canon traverses, but we have examples of rivers cutting directly through a mountain uplift, and at right angles with its axis. Furthermore, cases of this kind occur in which the mountain uplift is not only a high one, composed of much harder rock than that of any of the surrounding strata, but the softness of the latter and the slight elevation of the surface they occupy seem to offer an especially favorable opportu- nity for the river to pursue its course around, rather than through, the mountain uplift. In fact, nothing is more apparent in the Rocky Mount- ain region than that the courses of the rivers are independent of the flex- ures which the strata have suffered over which they flow, and that their courses are also independent of the present character of the surface. The only explanation Iam able to give for this condition of things, or the one presenting the fewest objections, is, that the streams were established where the conditions of the surface then favored the course which they pursued, and before the strata were flexed to any considera- ble extent; that all the important displacements of strata, including the mountain uplifts, have taken place since the streams began to excavate their valleys. Therefore the movements of these displace- ments must necessarily have been exceedingly slow; never more rapid than was the deepening of the channels of the rivers by the ordinary erosive action of their flowing waters, or, if so, the elevation was not enough to produce a permanent damming of their waters, or a material deflection of the course of the stream. When the streams were first established, they must, of course, have found their way to the sea over the then less elevated portions of the surface ; but during the ages that have since passed, the continent has continued its elevation ; the strata have been variously displaced, in some cases producing great mountain ' flexures. Added to all this, the subaérial denudation has been so great that doubtless no trace of the surface upon which the rivers were orig- inally formed now remains. Indeed, it is known that, although the channels of at least some of the rivers of the Rocky Mountain region occupy a somewhat greater actual height above the level of the sea 52 WHITE. | : SURFACE GEOLOGY—VALLEYS. 53 than they did when they were first established, they have cut their way through many thousand feet in thickness of strata which were originally beneath their beds, and which have been brought up from below against the wearing action of the constantly-flowing stream. Not only have the valleys been thus carved out by the flow of the perennial streams, but their minor or tributary drainage-chanuels ; mostly those having only a periodical flow of water, have carried away from the surface such an immense bulk of material, that great moun- tain masses now remain in many places that are only shreds of the for- mations that were once spread continuously over the region. This tributary drainage has preduced what are now the most conspicuous topographical features of the great Rocky Mountain region, in the course of which the channels have been much influenced in their direc- tion and position by the varying conditions of the strata with which they have been brought in contact. ‘Therefore the drainage of this latter kind has been called consequent drainage, while that of the per- manent streams has been designated as antecedent drainage. The larger streams have of course had their tributaries from the beginning, but it is hardly likely that the identity of any, except those which con- tain perennial water, have been fully preserved; while not only the identity, but the exact position of nearly or quite all the streams that contain perennial water have remained unchanged from the beginning. This district, together with that which adjoins it on the north, affords some remarkable examples of antecedent drainage in connection with great and abrupt displacements of the strata that are crossed by the drainage-channels. Green River.—The cutting of Green River through the Uinta Mount- ain chain is probably one of the most extraordinary examples of this kind to be found on the continent, but as this has been fully described by Professor Powell in his report on the geology of the Uinta Mount- ains, and as only a small proportion of the wonderful cafions of that river exist within the limits of this district, a full description of even those of the Uinta Mountains will be omitted in this report. The portion which lies within the limits of this district is most impressive and remarkable, cutting, as it does, through Split Mountain from its base to its summit. This mountain is a sharply-folded spur, which projects westward from the body of Yampa Piateau, the summit of which is 3,000 feet above the river; and is composed, like the principal part of the plateau, of hard limestones and sandstones of Carboniferous age. The strata sur- rounding Split Mountain to the westward are comparatively soft, and the surface there has comparatively slight elevation. Viewing the re- gion topographically, the most natural course for the river to have pur- sued from and below Island Park would seem to be by way of a tribu- tary drainage, and the main channel of Brush Creek, around the western end of the mountain, instead of cutting entirely through it, as it does, Splitting it through its highest portion. Below Split Mountain the relation of the river to the underlying strata is not especially re- markable. Yampa River.—Although the cafions of the Yampa are not so deep as many of those of the Green and Colorado Rivers are, its valley is remarkable for the extraordinary displacements of strata through which they have been excavated. From the eastern boundary of the district, nearly to Yampa Mountain, the river runs in a monoclinal valley; that is, the general course of the river is to the westward, and the general dip of the strata out of which the valley has been excavated is to the northward. Moreover, the bendings of the river coincide in some degree 54 REPORT UNITED STATES GEOLOGICAL SURVEY. with the flexed borders of the outcrop of the different groups of strata in the neighborhood of the river. Concerning this portion of the valley, upward of forty miles in length, there is nothing especially remarkable in the relation of the river to the displacements of the strata over which it flows; but in the lower portion of its valley the case is very different. The isolated position of Yampa Mountain in the comparatively low land of Axial Basin, and its character as a sharply-defined upthrust of Paleozic rocks through those of Mesozoic age, has been already explained. Yampa River, after entering Axial Basin, which it does four or five miles eastward from Yampa Mountain, instead of bending around the mount- ain in the lower ground at its base, cuts, by a narrow canon, through the northern portion of the mountain. The walls of this cafion are not only several hundred feet higher than the low ground at the base of the mountain, but the strata through which it has been cut are composed of hard limestone, while those underlying the low ground are of soft sand- stones and clayey shales. Below Yampa Mountain, the river runs for a distance of fifteen or six- teen miles, to Junction Mountain, along the low grounds of the western portion of Axial Basin, and approximately upon the main axis of the Uinta Mountain Uplift. Reaching Junction Mountain, which is another isolated mountain upthrust almost identical in character and surround- ings with Yampa Mountain, the river cuts through it in the same manner as through the latter mountain, but by a deeper and longer canon. The length of this canon through Junction Mountain is about three-quarters of a mile in a straight line, from which its course varies a little, and its greatest depth is about 1,200 feet, the walls being almost perpendicular. As in the case of Yampa Mountain, the strata of the low grounds that sur- round Junction Mountain are soft and easily eroded; while the cafion is cut through not only the hard limestone and other strata of Car- boniferous age, but also through several hundred feet in thickness of the still harder Weber quartzite beneath them. After leaving Junction Mountain, Yampa River flows across Lily’s Park directly to the eastern end of the high range of paleozoic rocks that have been brought up by the Uinta Mountain Uplift. It then flows more than 30 miles through a tortuous and continuous caiion which it has cut in the carboniferous strata which form that portion of the southern side of the main fold of the great Uinta Uplift, and empties into Green River where itself is passing through a deep cation in the Uinta Mountains. Thewalls of the Yampa Canon are almost every where nearly perpendicular, varying in height above the stream from 1,000 to 1,500 feet. Along a great part of its course Yampa Cafion lies approxi- mately parallel with a valley that lies in the synclinal flexure between the main fold of the Uinta Uplift and the accessory one of the Yampa pla- teau. Red Rock Basin constitutes the western end of this synclinal valley, the bottom of which is 1,600 or 1,800 feet lower than the brink of that portion of the cation which lies opposite to it. Viewing this region, according to its present topography and the sus- ceptibility to erosion of the rocks that occupy the surface, the most natural course for Yampa River to have pursued to form a junction with the Green would seem to be around the north side of Yampa Mountain, thence past the southern end of Junction Mountain through Midland Basin, and thence down the dry valley that lies along the southern side of Midland and Section Ridges to the valley of Green River. On the contrary Yawipa River traverses the most mountainous and difficult por- tion of the district after having cut through, instead of around, two isolated mountains composed of hard and compact strata. WHITE. | SURFACE GEOLOGY—DRIFT. 55 White River.—In no part of that portion of its course which lies ad- jacent to this district, does White River Valley afford so striking an example of antecedent drainage as the valley of the Yampa does. Nevertheless, the course of White River is sufficiently independent of the displacements of the strata over which it flows to show that it should be properly placed in the same category in this respect, with the Yampa and Green Rivers. Upon leaving Agency Park, White River cuts through Grand Hog- back, which crosses the valley at right angles; and from there west- ward to the southern end of Pifton Ridge, a distance of between 25 and 30 miles, it runs in large part upon the yielding strata of the Wasatch Group, and in part upon the lower strata of the Green River Group. It then runs for a few miles among the strata of the Fox Hills and Lara- mie groups, where they are upturned by the Midland Flexure. It then returns to the Wasatch Group again, upon which it runs nearly to Raven Park, where it crosses in both the descending and ascending order, the Laramie, Fox Hills, and Colorado groups. After passing the Raven Ridge Flexure at the western side of Raven Park, the river again flows five or six miles upon the strata of the Wasatch Group, and then enters a canon which it has carved out of the strata of the Green River Group, nearly all the way to its confluence with Green River. This cafion is from 600 to 1,000 feet deep, from the adjacent upland surface; and although it is narrow, its sides are not usually so precipitous as those of Yampa Canon are. Throughout a large part of the course of White River, there is appar- ently no special condition of the underlying strata that might be sup- posed to have governed its direction so far as lateral deflection is con- cerned; but its direction seems to have been just as little influenced by the abrupt flexures the strata, have suffered over which it flows near Pinon Ridge and at Raven Park. Milk Oreek.—The upper branches of Milk Creek flow in such a man- ner and have such relations to the underlying strata as any kind of drainage, either antecedent or consequent, might have. But from the point at the north side of Axial Basin, where these branches coalesce, the creek, instead of continuing down the low land of the open basin, as one might expect it to have done, turns abruptly northward through 2 calon, or very narrow valley, three miles long and 800 feet maximum depth, which it has carved out of the strata of the Fox Hills Group, and joins the Yampa which there runs in a similar canon. No other theory than that of antecedent drainage. seems at all ade- quate to explain the extraordinary course of such a creek. It is, how- ever, most remarkable that a creek so small as this could have such a history—a history that dates back to a time before the great mountains near by were made, and before the grand lineaments which the conti- nent now bears were carved. SCATTERED DRIFT. No considerable portion of the surface of the region adjoining the Rocky and Uinta Mountains is free from well-worn scattered drift- pebbles. These pebbles are composed of various kinds of rock, but they are largely quartzites of various colors, and are usually as smoothly rounded as any that are now washed upon a storm-beaten sea-shore. To one who is familiar with the great northern glacial drift, these pebbles suggest the same or a similar history ; and when we attempt to trace their origin by comparing their lithological composition with that 56 REPORT UNITED STATES GEOLOGICAL SURVEY. of the rocks én situ in that region, it is evident that the original ledges from which they have been separated are those of the axes of the neighboring mountains. Therefore it is equally evident that they have been distributed in radiating lines from those axes; especially so since in every case yet observed, the differences in the lithological composition of the drift-pebbles at different localities adjacent to the mountain range exactly correspond to the changes of lithological characters of the rocks comprising different portions of the mountain axis. That these drift- pebbles were distributed by glacial action seems, in view of the accepted theories in relation to the great northern drilt, to be a natural inference upon casual examination; especially as this mountain drift is distributed upon the surfaces of the higher foot-hills of the mountain ranges, as well as in the valleys between them, and upon the lower lands at a greater distance. The true origin and distribution of this drift, however, involves the consideration of several questions, for the discussion of which the phenomena observable within the limits of this district do not furnish sufficient material. Therefore the consideration of the subject in this report will be mainly confined to the description, and an account of the distribution of the drift within this district. Before doing this, however, it is proper to refer briefly to some correlated phenomena. The drift-pebbles, as before mentioned, are as smoothly rounded as any: that are now washed upon the sea-coast; and it seems difficult to understand how this could have been done under any condition of trans- portation alone. Indeed, it seems impossible that these pebbles could have been so completely rounded in any manner except by attrition in a large body of water where the waves could have great power; and this view is strengthened by the fact that the pebbles are distributed over so broad an area. Whatever their origin as such may have been, it is cer- tain that the pebbles have been radiately dispersed from the mountain - axes. The character of the rocks composing the axial portions of the Uinta and Park Range uplifts respectively, is so different that it is quite easy to refer any collection of pebbles that may be found in the vicinity of both ranges to the one from which they were really derived, and also to recognize any mixture of pebbles as such that have been derived from both ranges. For example, it is easy to recognize the drift-pebbles of the eastern portion of this district as having been derived from rocks of those mountains of the Park Range which lie to the eastward; and just as easy to recognize those that are found in the western. part of the dis- trict as having been derived from the strata of Uinta Mountain uplifts. Upon the middle portion of the district, however, the drift of both eastern and western origin; or, in other words, that of the Park Range, and of the eastern end of the Uinta, Mountains, is found to be mixed. The former is mostly quartzites, with admixtures of basalt and granite, while the latter are mostly made up of fragments of carboniferous lime- stone and Weber quartzite, which latter rock is often, but not always, quartzitic. This Uinta drift contains no trap and no granite, for none .of those rocks occur in the eastern portion of the Unita Mountains. Granite, however, is abundant in the Park Range, and very extensive masses of the basalt exist just beyond the eastern borders of the dis- trict. The pebbles of eastern drift which have found their way in abundance into the beds of the White and Yampa rivers, have been ‘carried down by the current to points further westward in the valleys than any they have reached upon the uplands, -and further than any points to which drift from the Uinta Mountains has been transported eastward. WHITE.] SURFACE GEOLOGY—DRIFT, 57 It is upon the upland borders of Axial Basin, between Yampa and Junction Mountains, from 400 to 800 feet above the level of Yampa River, and so high that it could never have been reached by its waters, that we find the mixture of eastern and western drift-pebbles. No west- ern drift-pebbles have been found east of Yampa Mountain, and no peb- bles of eastern origin have been found west of Junction Mountain, ex- cept that which the currents of the rivers have transported as before mentioned. Junction and Yampa Mountains seem to have stood respectively as barriers, or, at least, as obstacles in the way of the transportation of the drift-pebbles in the direction of radiating lines from the two mount- ain ranges. For example, in that portion of the valley of the Yampa which lies north of an east and west line through the north base of Yampa Mountain, I found eastern drift-pebbles plentiful, with only a very slight admixture of those of western origin, and even this small proportion is not certainly known to be of more western origin than Yampa Mountain, because it may have been derived from that mountain itself, which has the same lithological composition that the eastern por- tion of the Uinta Range has. Furthermore, I found very few eastern drift-pebbles upon the surface immediately west of Yampa Mountain, and also very little western drift upon the surface immediately east of Junction Mountain. Western drift- pebbles, however, exist in great abundance upon all the surface east of the Uinta Uplift and south of an east and west line through the south base of Junction Mountain, and also extending nearly as far eastward as Yampa Mountain. All these facts are at least suggestive of the glacial distribution of this drift from both mountain-ranges, but it is proper to say that no glacial strie, either upon the pebbles or upon the rocks @ situ, were observed in this district, althouzh it is not certain that they do not exist there. Also, that the character of the underlying rocks of all that region is seldom such as to have preserved the strie if they had ever been made upon them. As to the origin of the pebbles, as such, of which the drift is so largely composed, the phenomena observable in this district afford no satisfactory information; but their origin as | pebbles was probably anterior to, and the result of, other causes than that which produced their distribution. As to the time when this distribution took place, some important data were obtained. The unconformity of the Uinta group upon all the other Tertiary groups, as well as upon those of older date, has been mentioned, which shows that group to be of much later Tertiary age than the Bridger Group. The great outflow of basaltic trap that has been before mentioned, is known to have taken place long after the deposition of the Uinta Group, because the trap is found resting upon a considerably eroded surface of that group at Fortification Butte, five or six miles north of the northeast corner of this district. A large percentage of the pebbles of the eastern drift of this district consists of fragments of this trap, which fact proves both the origin of the pebbles and the distribution of the drift to have been subsequent to the trap outflow. Nevertheless, this drift is known to be of great age, because there is much evidence that extensive erosion has taken place since its distribution; but still there is evidence that the great general features of the region as they now exist were produced by erosion before the distribution of the drift. So far as my observation has extended, there appears to be no reason why we may not regard the distribution of this drift of the Park range and Uinta Mountains as contemporaneous with that of the great northern glacial dritt. CAP a Bika VA, MATERIAL RESOURCES. With the exception of coal, no mineral substances of practical value were discovered in this district, and it is not thought probable that any others of importance exist within its limits.* The material resources of the district, therefore, both present and prospective, are confined to vegetable productions alone, if we except coal, stone, and clays. One of the series of maps composing the atlas of Colorado that has been prepared by the United States Geological Survey is colored in such a manner as to show by area-the natural productions and capabilities of the State. By this map it will be seen that a very large part of the sur- face is classed as grass-lands, and that only a small fraction of the whole surface is designated as tillable. Bearing in mind also that a large part - of the surface which is there classed as aspen-lands, as well as some portions of the cedar and piion lands, also affords good grazing, it will appear that pastoral interests are destined to exceed all others in the region of which this district forms a part, while in other districts mining interests will doubtless overshadow all others. Tillable Lands.—As this district is far within the limits of that portion of the national domain upon which the annual rain-fall is insufficient for the purposes of agriculture, the only tillable land within the district is that which it is practicable to irrigate. Such lands are of course found only along the valleys the streams of which produce a considerable flow of perennial water. No attempt was made to ascertain the precise area of irrigable lands in this district, but the map before referred to will show it to be comparatively small. Small as it is, it is quite suffi- cient for the needs of a considerable pastoral population along the val- leys of White and Yampa Rivers; and the grass-lands of this district are not too distant from the irrigable lands to be available for pastoral purposes from the homes that may be located in the valleys. The parks that have been described in Chapter II contain the largest bodies of irrigable land within the aistrict, but at many other points along the valleys of all the perennial streams farms of more or less importance may be made. The amount of irrigable land in any valley of course depends not only upon its being within reach of water from the adjacent stream by its fall, but it also depends upon the amount of water the stream carries during the part of the year that the crops need irrigating. The valley of a stream may therefore contain more tillable land within reach of its waters than those waters are sufficient to irrigate properly, but this is seldom the case with the larger streams. There is probably no portion of either White or Yampa River valleys within the limits of this district that is accessible to the river water which it is in any case insufficient to irrigate if judiciously applied. Under the head of ‘‘ Water,” in a follow- ing paragraph, the gauging of those two streams may be found. The elevation of this district above the level of the sea limits the va- * This statement may be regarded as a reply to the oft- repeated question, “Is gold or other precious metals likely to be discovered in that region ?” 58 WHITE. ] MATERIAL RESOURCES—WATER. 59 riety of farm-products that may be grown there successfully, but trials already made there show that wheat, barley, oats, rye, pease, beans, po- tatoes, and many of the common garden vegetables may be cultivated successfully. The tillable lands along the valley of Green River have less elevation above the level of the sea than those of any other portion of the district, and it is probable that maize, as well as some kinds of fruit trees, might be grown there with success. The soil of the irrigable lands is almost without exception very fertile, and needs only proper irrigation and cultivation to make them very productive. Water.—A dweller in a well-watered country is hardly able to realize the paramount value of the water that falls upon the land in copious and timely showers, and that traverses every valley in the form of rivu- lets andstreams. Jtisthe want of the copious supplies of water that bless the eastern part of the national domain that renders so large a propor- tion of the western part either a desert waste or untillable land. For this reason water is classed among the material resources of the dis- trict, and all its permanent streams and rivulets are especially noticed in this report, although some of them are so small that they would be deemed unworthy of notice in more favored regions. Except among the Danforth Hills and other hills in the eastern part of the district, and also at the bases of Plateau and Midland Uplifts in the western part, no springs are found, and they are not numerous in the parts designated. Therefore supplies of water must be obtained prin- cipally from the Green, Yampa, and White Rivers, and their very few tributaries that contain perennial water, and which have already been described in Chapter II. The water of these streams is sufficiently | pure and good, and the fall is almost everywhere so great in the Yampa and White Rivers that abundant water-power may be obtained, as well as an abundance of water for irrigating purposes. As a general indication of the amount of water carried by White and Yampa Rivers, I here insert a record of the gauging of each. Yampa River was gauged at a point four miles east of Yampa Mountain, and White River six miles below White River Indian Agency. The method adopted was to measure a line of 200 feet along the bank of the river, and note the time taken by a float to run from the upper to the lower end of the line; then to measure the depth at certain points opposite, together with the width of the stream. Gauging of Yampa River, August 5, 1877. Width from brink to brink -.....222. 2.2.22 - 2. eee cone cone een 175 feet. Runnin ghime) of floateesse ssc. ases = ese cee ce eek See eee cee 1 minute 57 seconds. Depth at north, quarter of the distance across..-.-.--.---.------ 2 feet. Mepthvatcemterimsse se eiese Sees aseas Secs dein dace eyemieiice Serserae cc 2 feet 5 inches. Depth at south, quarter of the distance across..--.....-...-. ---- 2 feet 9 inches. The bottom has, at the place of measurement, quite a uniform curve from brink to brink, so that a greater number of measurements of depth were deemed unnecessary. Gauging of White River, August 11, 1877. Widthifrom brink tobrinkseeotces. tk cece sae elec sees cece cels ct we 120 feet. Running ime Ob Moabes meres sees soa eeec bees ese ectas cee 31 seconds. Depth at south, one-eighth distance across..............------------ 1 foot 9 inches. Depth at south, one-quarter distance across.........--.------------- 1 foot: Depth at center .----.. Bee bocecesseee-cee I foot)/9 inches 60 REPORT UNITED STATES GEOLOGICAL SURVEY. The time of gauging of these streams was toward the close of the sea- son when irrigation of crops is necessary. Earlier in the season, when more water is needed for that purpose, the streams always carry a greater quantity. If future interests should ever make it desirable to have artesian wells in that region, they may, no doubt, be successfully made in sev- eral places; as, for example, in Coyote Basin, the valley between Mid- land Ridge and the Raven Park Uplift, in the valley of Red Bluff Wash, &e. The conditions of the strata of the district upon which this opinion is based are shown in the sections at the bottom of the geological map accompanying this report. Grazing lands.—Although irrigation is necessary for all cultivated crops in that region of which this district forms a part, very nutritious grasses grow naturally both in the valleys and upon the uplands, those of the latter being more nutritious than those of the former. The grass upon the uplands is thinly scattered, but the extent of surface upon which it grows isso great that it will furnish an abundance of food for all the grazing animals that may be required by the limited population which the irrigable lands of the valleys are capable of supporting. Fuel and building material—Al]though there are no forests, properly speaking, in this district, there is, upon the hills and mountains, a seat- tered and generally stunted growth of cedar, pifion, and aspen trees, which is quite sufficient in amount to meet all requirements fer fuel, fences, and such small, rude buildings as may be required for farm pur- poses. LHasily dressed sandstone is almost everywhere abundant, from which substantial buildings may be constructed. Besides the wood fuel, which will doubtless be quite sufficient for all the ordinary wants of the greatest population which the district will ever support, there are several localities where coal may be obtained in com- parative abundance. Among the best exposures of coal that were ob- served during the progress of the survey are those of two principal beds, one of which is found in and near Caiion Park, and another in the Dan- forth Hills, northwestward from White River Indian agency. Both of these beds occur among the strata of the Laramie Group, one being near the base and the other near the top of the series. Comparatively little search will doubtless fully reveal these and other beds of coal in those places, from which supplies may be obtained with comparatively little labor. The bed that occurs in the Danforth Hills is also seen ex- posed in the valley sides of Yampa River below Cafion Park. This bed doubtless represents one of those at the well-known mines at Rock Springs Station, on the Union Pacific Railroad, Wyoming. The bed that occurs in the upper strata of the Laramie Group, and which is exposed in Cafon Park, doubtless represents one of those beds which were formerly worked at Point of Rocks and Black Buttes stations, on the railroad just named. A bed of coalin the lower strata of the Colorado Group, near the south side of Lily’s Park, has already been mentioned on a previous page, but it seems somewhat doubtful whetherit will provetobe agoodone. Although the Laramie Group contains so much coal in the eastern part of the district, there seems to be comparatively little among the strata of that group in the western part. In the region of which this district forms a part, the Fox Hills Group is known to contain some coal, but within the limits of this district no good bed of coal was discovered among the strata of that group. REPORT OF F. M. ENDLICH, S. N. D., GEOLOGIST OF THE WHITE RIVER DIVISION. LETTER OF TRANSMITTAL. WASHINGTON, D. C., April 9, 1877. Sir: I have the honor herewith to submit my report for 1876 as geol- ogist of the White River division. In accordance with instructions re- ceived, we left Cheyenne, Wyo., August 14, 1876, and started for the field August 16 from Rawlins, Wyo. After a march of one hundred and eighty-five miles, we arrived at the White River Indian agency, where we commenced operations. October 12 we returned to that place, hav- ing completed the geological and topographical survey of the area assigned to us. During that time we obtained sufficient data for the purposes of preparing geological and topographical maps of a section of country comprising over 3,800 square miles. The subjoined report is divided into three chapters and a conclusion. Of these the first treats of the physical character of the country exam- ined, the second of its structural and geognostic features, and the third contains a short discussion upon the intimate connection between litho- logical constitution of rocks, stratigraphy, and special orographic feat- ures. In the “conclusion,” the various geological formations I encoun- tered in Colorado are briefly reviewed. A comparative table of forma- tions throughout the State has been added. I wish leave to express my sincere thanks to Mr. G. B. Chittenden, topographer directing, and to Mr. H. N. Dickerson, jr., meteorological observer, for their uniform kindness and co-operation during the field- season. To Mr. W. H. Holmes I am indebted for the preparation of illustrations. It gives me pleasure here to acknowledge the courtesy and material aid extended to us by Mr. Danforth, agent at the White River Indian agency, and Mrs. Danforth. To them we owe, in a great measure, the friendly footing upon which we were at once placed with the Utes, be- sides many favors that are most heartily appreciated by those accus- tomed to camp life and camp fare. Hoping that this report may meet your requirements, I am, sir, very respectfully, your obedient servant FREDERIC M. ENDLICH. Dr. F. V. HAYDEN, Geologist-in-charge U. S. Geological and Geographical Survey of the Territories. Gt REPORT ON THE GEOLOGY OF THE WHITE RIVER DISTRICT. INTRODUCTION. During 1876 the geological survey of Colorado was completed by the four field-parties sent out for that purpose. A short season only could be devoted to the work, but it proved to be of sufficient length to finish all that had been assigned to each individual party. On August 16 the division to which I was attached as geologist left Rawlins for the White River Indian agency, in order to survey a strip of country west and southwest from that point. To us had been assigned the region lying west of the agency, bordered on the north by the White River, on the west by longitude 109° 30’ west, on the south by north Latitude 40°, and joining on the east with the district of the late Mr. Marvine (1873) along a line of about longitude 107° 45’ west. The area enclosed within these limits comprises about 3,800 square miles. In order to expedite the work as much as possible, it was decided to estab- lish White River agency as a supply-post for provisions, and complete the survey in two trips from that point. This plan was carried out, and proved to save time in travelling. August 27 we left the agency, starting southward, and, after finish- ing the area we had expected to, we returned by a different route to our starting point September 9. Leaving it again September 11, we sur- veyed the remaining portion of the district. Our last station was made October 11. On the day following we left the Indian agency and marched eastward by way of Middle Park, crossing the continental divide over Boulder Pass. Snow and cold weather impeded rapid pro- gress somewhat, but on October 22 we reached Boulder City, from where we proceeded to Washington. In treating of the district completed during that time I have con- cluded to divide the discussion into two parts. The first treats of the physical character of the region, the second of the structural. Uniform _ in every respect, that section of country furnishes but very little of interest either to the geologist or paleontologist. It is not a pleasant region to travel through, owing to its arid character, and to the fact that much of the water which may be found, is little less than a satura- ted solution of carbonates and sulphates of the various alkalies. For Sanitary purposes it would answer admirably well, but this peculiar feature is not particularly acceptable to any one who may be dependent upon the water he meets with for his beverage and his cooking. In the subjoined pages special mention will be made of the most alka- line creeks and springs, and the origin of the alkalies in solution will be discussed. 63 CO ah ae aide o ee ead te a ii 2 lie PEER ¢ J : Cy oom, Ah «an mY ace See ree oe ae We: Pete katy dT. sa Fane ON} frie : oN a es ee A a 98 ft , femme iy dateh ; ramets er nt uti + acne fe art ise (ote Pasay eh i SAGs ssc ae et be sis a ‘iat ‘a2 oh ; if 19 we i (sh ath iy dias me sig, Party eae Lid Se a a es Bank nh teen aa CHAPTERL DRAINAGE. A.—WHITE RIVER DRAINAGE. 4 Four large streams flow into the White, heading on the Roan Moun- tains or Book Cliffs, and following a course of about south to north. Of these the first one (going from east to west) enters the White about 50 miles below the agency buildings. It is called Pi-ce-ance by the In- dians, and we have retained the name. This stream has a leugth of 45 miles, and carries water during the entire year. Most of its tribu- taries are dry, except early in spring and during a portion of the rainy season. Douglas’s Creek, named after the head-chief of the White- River Utes, isthe next stream of good size; it flows into White River, about 60 miles below the agency, having a general course west of north. Shorter than this is Evacuation Creek, which joins the White 25 miles below Douglas’s. The courses of the two last named are very nearly parallel. Starting with two main forks, which join at Station 32, is Two Water Creek; while its east fork, Bitterwater Fork, con- tains very unpalatable alkali water; the west one, Sweetwater Fork, is fresh. Below the junction we found no water whatever. Both of the last-named streams enter the White beyond the western border of Col- orado, in Utah, 100 miles below the agency. Besides these more important streams, there are several smaller ones worthy of mention. Between the agency and Pi-ce-ance is Cattle Creek, 4 miles below the former. It heads near Station 2, and after but a short run joins the White. Anether creek is found between Pt-ce-ance and Douglas’s, draining the low bluff country between the mouths of. the two larger streams. Asphalt Wash is a dry creek east of Two Water; it is but short, cutting deeply, however, into the sandstones and shales of the region. Near the heads of all these streams we found more or less abundant springs; many of them were flowing but feebly, during the time of our explorations (the dry season), and a short distance only. In the morn- ing, not unfrequently, the water was more plentiful, and camp could be made at a point from which any flowing water would be removed for some distance by evening. Evaporation during the day decreased the emitted quantity, which received a fresh supply during the night, by the cessation of this evaporation, and by the precipitation of moisture as. a copious dew. As has been observed in many arid regions through- out the world, so here, too, certain strata of rocks were more abundantly supplied with moisture than others. It was imsuch strata, or imme- diately below them, that springs had to be looked for. At almost every locality where the lithological character of strata shows only sandstone and shale, we will find the same occurrence. Requisite, of course, are conditions favorable to the emission of water retained by such “ water-strata.” B.—GRAND RIVER DRAINAGE. A small portion only of the drainage belonging to this river falls with- in the limits of our district, south of the agency. The divide between _ DG 65 66 REPORT UNITED STATES GEOLOGICAL SURVEY. White and Grand is but 12 miles distant, and there several creeks in our district reach the Grand without leaving it. Among them Rifle Creek is the most prominent. This heads near station 4, and flows in a gen- eral southwestern course until it enters the Grand. Roan, Salt, and Bit- ter Creeks merely reach our district with their head-water drainage, and, following a course east of south, join the Grand at varying inter- vals of space. These southern streams carry more water, 1. ¢., water for a greater distance in miles, than the northward-flowing tributaries of the White. While treating of the stratigraphy of the entire region this will be discussed. Summarizing the approximate lengths of water-courses contained in our district, and heading within its limits, we arrive at a result which shows that the length of the main streams is a comparatively large one, as compared with the area. Did all the streams contain water through- out the entire distances of their courses the region would be amply sup- plied with moisture. As it is, however, it is dry. WHITE RIVER DRAINAGE. Miles Length of White River within district ......--. ..---. -.-- --- 020 see02 oe nce - 120 Wattle: Cree ke 2a pa cert Se eee eee ane een i tay cre ce ae eee LAS py pepe Ac tan sere 15 IPECe-ance Creek sceise ee eee eels sisiene'= seperate eae the ere cide se ee 45 IDYoeIeRYS OR e 5 a5 ocean Caos eneededsse G4 ses cacn So Sace soce sooeds sec 35 | Bvacuation Creekiscee eee meses fcc isiets vce oc since Wrap yeminle ine eie siatelal 5 ctalstelene arene eee 30 Asphalt Wash...-.....-.---------- eo HS aad micio tA en ras Sense oie nettle 2 18 TO bal ie ere eee ee esate aa. x esbrer eke eis ime) Sra eee ete reve ya ty lt aie cab cteta ucpene nae 263 Bitterwater Fork....-....- Up ees ape see Dees tA DEAL ee BR eS OO iis) ciecic a) ONS) eg DR xe OVA WU VFL od GM Oh Geen Ei sage lek AAR ES SP A es ee 18 Siweet water Horlas epee Solas cea Nie orceien rereraieraye reve) a ns -taye renege mmistenata 19 Wickerson’s' Creeley ssaske sas kook cdl oe els seis tle se Se ee Ea ce ea ee ster mie LS FTO tage ee ae tea ice ss ae oan) Sy ale ics me rwre nice susis aleneioiste eters ay etsatat Gatere sins en aioe 354 GRAND RIVER DRAINAGE. . INamel ess’ Greeks e wet eee ea wie: wie bbe cree Meets Bree Natale ore erayenay etcrerenrets 92 Wile: Creek: {ANN Ha Ns ee a Re racers ae ele aioe elope recente Sere eye 17 Roan Creek.-.---- Beng Sen SAS CH AREER ee ss Prod Se Bana adNHoSanG cGooKS 32 CSE UR Oo eve) .quseae ee Dh oh) Se ee eee ene nN rR er em ANG acide clea Q7 IBibbeT water Ore kere seats piste ee o oie dA 5 ais Skans, S Sy eta e me layey a maT Tee tore ee erate 30 ADYSISCEy mann On eVe bce As Ae TS 5 a eal rake oe eS Eh en Ss 32 Boy res Fecteau LY SG ae ene er ES) Se AL AES ian oa ao 160 Along nearly all of these main tributaries of the two rivers we found Indian trails, greatly facilitating travel, and frequently leading to springs which could scarcely have been found without their guidance. It is improbable that much travel should ever occur in that region, but for casual travellers the trails will prove to be of invaluable service. TOPOGRAPHY. e The larger portion of the district is, viewed as a whole, simply an ex- tensive plateau, which slopes to the north. Topographically it is a con- tinuation of the Grand Mesa south of the Grand River. As generally is the case, so here, too, the geological formations prove to exhibit cer- tain types of orographic features. We find in the eastern portion of the district that the mesozoic group is represented, and that there the country is more irregularly broken than farther west. A long line of heavy hogbacks stretches in a general direction a little east of south from the White to the Grand. At several places streams cut through this hogback, flowing westward. On its eastern face it is steep, generally ENDLICH.] ‘ TOPOGRAPHY. 67 almost inaccessible, but the western slope is more gentle. This hog. back ridge 52 miles in length, is about 1,400 feet above the valley east of it, presenting, as it does, good points for topographical and geologi- cal stations. East of the valley the hills rise to considerable elevation, for that section of country, so that Stations 3 and 6 are located at alti- tudes, respectively, of 9,904 feet and 8,533 feet. Cattle Creek flows north- ward through an almost straight, grassy valley into the White; a type of valley that is generally formed, of greater or less extent, wherever Colorado shales are overlying Dakota sandstones. A low divide con- nects this with Rifle Valley. Travelling down this latter we reach the Grand. At that locality this river flows in a broad valley, hugging the rising region on the south side. Low bluffs of variegated marls are found north of it, forming a transition between the steep hogback ridge and the valley proper. Looking off westward we see the nearly straight line of the Book Cliff. Rising to a relative elevation of 3,000 feet they present a bold escarpment to the south, one that is broken by passes at a few places only. The regular stratification and the admirable carving of the precipitous southern slope give this plateau-edge a characteristic appearance. At many places the strata composing it have yielded to eroding agents, and great masses have fallen down, producing vertical -walls. Their light color and well-defined stratification make them ap- pear as successive shelves; hence the name which has long since been given to this elevated plateau. Immediately west of the hogback the geological formation of the plateau and the latter itself commence. Ascending a gradual slope to its summit, the divide between White and Grand, we obtain a view of the entire structure. Forming a crest which trends about east to west, the Book Cliffs retain a very constant absolute elevation of their highest points, which, however, vary but slightly from the general altitude of the ridge. On average, this may be stated as being 8,700 feet above sea-level. An Indian trail runs along the entire length of the crest, as this is by far the most convenient place for travelling. A number of springs are found on either side of the divide, not far from its summit. Riding down any of the northward-flowing streams, we observe that their headwaters are generally contained in steep, narrow gulches, which cut down deeply into the tertiary strata. Upon reaching a lower level, however, the valleys widen, are very flat, and not unfrequently show evidence of having at one time contained lakes of considerable extent. ' These latter have disappeared in consequence of an enormous deposition of diluvial and alluvial drift. Inflowing waters have carried with them large quantities of sand and silt. Into the lakes where the rapid pro- gress of the stream was checked, this “‘removed” material: has been deposited; thereby the level of the lake-beds has gradually been raised and the water flowed off. We now have, instead of bodies of water, an equivalent of alluvial and in part diluvial soil. Through this the present streams and creeks cut deep, narrow gorges. Ire- quently it is necessary to travel for some distance before a point can be found where these gorges may be crossed by animals. During the rainy season and early in the spring, water coming from the more elevated portions of the pleateau transports large masses of the comparatively light material, and renders the streams and White River very muddy. On either side the flat valleys are inclosed by more or less steep bluffs, showing, generally, the exposed strata on their faces. Between the streams the space is occupied by long, narrow, mesa-like ridges. Hast and west these show steep slopes, are connected on the south with the erest of the Book Cliffs, and northward slope very gently toward the 68 REPORT UNITED STATES GEOLOGICAL SURVEY. White. On average, this slope may be said to be less than 200 feet to the mile. Short grass covers many of the ridges along their flat tops, while the sides are grown over in part by juniper and pifion. This gen- eral character holds good as far west as Evacuation Creek. Near the junction of that with the White it changes, however. A heavy series of superincumbent sandstones has produced a change here. Marching down the creek, we remain for a long distance in an unbroken cafion, the walls of which are about 600 to 800 feet high. Four miles above its entrance into the river the trail leaves the creek, and, ascending to the summit of the long ridge west of it, strikes across toward a sharp south- erly bend of the White. From there downward the river flows in a narrow ecajnon.- Walls, averaging 1,000 feet in height, enclose it on either side, presenting almost vertical faces. A dark-brown to yellow- brown sandstone, regularly bedded, composes them. Erosion has here produced numerous fantastic figures that a lively imagination can en- dow with life, and readily compare with animate beings. On the isolated hills and knolls south of the cafion, which former owe their existence to remnants of this sandstone, ‘‘ monuments” of all kinds can be found. Cleavage-planes in the sandstone strata have produced innumerable pic- turesque forms, and erosion, both by water and sand, has been the artist who shaped the original block. For about thirty miles this cafion continues. The bed of the river is — narrow, covered with shrubs and brush, which greatly impede the progress of man and animal, Dry washes coming from the north are cut deeply into the yielding sedimentary beds. Throughout the district, west of the Great Hogback, the topographical features of the region are remark- ably uniform. ‘‘ Like cause produces like effect” finds another applica- tion here. We find but very subordinate changes in the lithological constitution of the sedimentary beds, and in accordance therewith we notice that the general features observed undergo but slight changes. As a rule, it may be stated that the shales and marls, whenever suffi- ciently compact, have produced steep, inaccessible cliffs, while the sand- stones and sandy shales form more gentle slopes. Sandstones, mostly, can be found as the capping of Jow bluffs, which they have protected from erosive influences, thus giving rise to their formation. Many detail features, due partly to erosion, partly to vertical cleavage of the strata, were noticed, and will be referred to at the proper place. Inasmuch as certain geological formations comprise similar or identical strata (lithologically speaking) within circumscribed areas, occurreuces of such a nature may, locally, be regarded as characteristic of well-de- fined geological groups. Viewing the subject from this standpoint, the “monuments” and other minor orographic features become of import- ance to the geologist exploring. In the subsequent pages space will be devoted to a short discussion of the influence that stratigraphy and the lithological character of strata have upon the orograpby in general, and upon that observed in Colo- rado in particular. ‘To the field- geologist, who is required to accomplish his work with as much accuracy as possible i in a very short time, hints furnished by exterior physical appearance are of the greatest value. Colorado, perhaps more. than many other regions, furnishes excellent material fur a consideration of this subject, and at the end of the report on that State a brief treatise thereupon may justly find its place. VEGETATION. - Each special region of the country has its own more or less charac- teristic shrubs and trees. In the low valleys and along the plateau-like e ENDLICH.] VEGETATION. 69 ridges we fiud sage brush (Artemisia Ludoviciana) covering the ground. Greasewood (Sarcobatus vermiculutus), growing most luxuriantly in the dry valleys, is interspersed throughout. In the moist valleys willows (Salix nigra) occur in dense masses ,often very effectually blocking the passage of a pack-train. Small trees, bearing the buffalo berry (Shepardia argentea) and service-berry bushes (Amelanchier alnifulia) are found together with them. These latter may serve as a hypsometric guide, occurring in that latitude rarely above 7,000 feet elevation. Another tree that may be utilized in the same way is the quaking-asp (Populus tremuloides). It was noticed that this tree, as is the case with all Salice, is mostly found near moist places, and it is frequently, there- fore, regarded as indicating the presence of water. In this we were often mistaken, however, but found that where it grew in dry (tempo- rarily so) places, it invariably selected the northern or northwestern slope of a valley or cahon. Two circumstances combine to render these expo- sures more favorable to the reception and retention of moisture, the prevailing vapid winds and the absence of sunshine during a considera- ble portion of the day. Quaking-asp sets in at an elevation of about 7,500 feet above sea-Jevel. In the larger river-valley groves of cotton- wood (Populus balsamifera) afford excellent camping places. They grow to considerable height, and the bottom of the groves is generally free from underbrush. All the low bluffs and ridges are covered with pifion (Pinus edulis) and juniper (Juniperus communis). The former bears small nuts in its cones, which are collected by the Indians, and serve as food, either raw or roasted. Neither of these two trees grows to any consid- erable height, but remains small, with strong, brittle limbs... At about the same elevation yellow pine (Pinus ponderosa) occurs in our district, though sparingly. Higher the white pine (Abies Engelmanni) is found, mostly only in some of the gulches and ravines leading down from the summit of the Book Cliffs. Very little tall timber occurs in the district, owing, no doubt, to the comparatively small supply of water. During the time occupied by our work in that region we had very little rain, and in all probability the season was, in that respect, not an exceptional one. Snow during the winter, beginning early and lasting long, supplies in a great measure the moisture for a large portion of the area, which during the summer receives noue except that from dew and occasional rain. It seems improbable that any section of that region should ever be settled, excepting the broad valieys along White River. There, by means of irrigation, fair crops may be raised, that will repay the labor bestowed upon them. Mr. Danforth, Indian agent at the White River Agency, has made some very successful attempts at raising wheat, oats, potatoes, and other vegetables. By demonstrating to his Ute Indians the benefits derived from a comparatively small amount of labor, he has induced a number of them to follow his example. They have ob- _ tained very satisfactory results, and were, at the time of our visit, well pleased with the experiment. On the ridges leading to the summit of the plateau and along the watered valleys there is good grazing, and those portions would answer well as a sammer-range. Before the com- pletion of the transcontinental railroad a wagon-road was projected and partly completed, following down the White and from the Green River westward, extending to California. It is known as Berthoud’s wagon- road. The building of the railroad, however, made an overland wagon- route superfluous, and the werk was dropped. Game seems to be abun- dant in the higher portions of the district, but is very shy. CHAPTER II. GENERAL GEOLOGY. In the district examined during 1876 the variety of geological forma- tions is very limited. It may be well to state that on the east side con- nection is made with the work of the late Mr. Marvine, which he accom- plished during 1874, and on the south with Dr. Peale, 1876; on the west I nearly join with Major Powell, and on the north my northern border was the southern one of Professor White. Fortunately for the peace and happiness of the formations involved, these latter are at all points very characteristic, so that no misapprehensions exist regarding their age. “On the east we find the oldest group, that of the ‘‘Red Beds.” They are sufficiently well developed, and, as usual, narked in so decided a manner that no mistake regarding their identity could occur, in spite of an entire absence of fossils. To a certain extent they have been dis- turbed by local plications and faults, although their general trend is in conformity with that of overlying younger beds. In cafons they appear, rarely reaching to the summits of any of the more elevated points, although farther east they no doubt can be found higher up. Superin- cumbent upon them are the Jurassic and Cretaceous beds. The latter formation is represented by three groups, the Dakota, Colorado, and Fox Hills groups. Of these the first forms prominent hills south and southwest of the agency, showing a considerable thickness. Its distri- bution is one following an approximate north to south line, parallel to the strike of the strata. Upon this series of sandstones, that retain their well-known characteristics, are deposited the Colorado shales. As usual, these have afforded an opportunity for the formation of deep, narrow valleys, bordered on the east by the Dakota beds and on the west by the Fox Hills group. Owing to their peculiarly ‘‘tough” nature, the shales do not permit the water to sink down to any considerable depth, but as soon as the superficial strata are sufficiently saturated the water is forced to flow off, thus producing, in these valleys, streams that are not dry even during the hottest season of the year. At some points the Colorado shales form the base of the long hogback ridge running from the White to the Grand. Above them Fox Hills beds close the Cretaceous. Their vertical development is but inconsiderable as com- pared to that of Southern Colorado. Throughout the entire formation fossils are rare, save the most common species. This is to be regretted all the more in the upper members of the Fox Hills, as a liberal supply of characteristic fossils would greatly facilitate the accurate definition of the boundary-line between the Cretaceous and the succeeding Post- Cretaceous. Of the Tertiary formation two groups are represented, the Wasatch and Green River. They follow each other in the regular succession, and are perfectly conformable with each other, as well as with the under- lying formations. Although paleontological evidence in these groups is sadly wanting, it has still been possible, from correlation partly, 70 ENDLICH.] STRATIGRAPHY. T1 to determine their geological position. The first group appears but subordinately in the district, but the Green River covers a very large area. It composes the entire mass of the Book Cliffs, and extends northward beyond White River. shales. 9 Ss Park Range...........|..006 Fe ee Blue limestones are pre-'| 300 BS dominating. Arenaceous | to o|8 shales. 400 |S || Pleasant Park ........ Terebratula, Spirife- | Cherty blue and gray lime- | 114 5 R rind. stones. 3 =| 130 PALAEOZOIC. DEVONIAN. SILURIAN. = A iS) S FI 3 Ay a iS) & a a = a PRIMORDIAL PERIOD. REPORT UNITED STATES GEOLOGICAL SURVEY. Synopsis of the geological formations found in Cuolorado—Continued. Locality. Fossils. Lime Creek Rhynchonella, Spiri- Jer, Crinoids. South of Mount O30 ...| Productus subacu- leatus, Orthoceras, Athyris, Betlero- phon, Euompha- lus, Rhynchonella Endlich. Massive blue Character of strata. Massive blue limestones..... limestones, with sandstones and shales near top. Thickness of strata in feet. EHuomphalus. partly magnesian. S$ || North of Mount Ouray.|....-....-.---.--.---- Light gray and blue lime- | 299 3 stones. S North of Arkansas | Heterocrinus, Ortho- | Dark gray quartzitic lime- | 150 L River. ceras. stones. , || Trout Creek. ..---...-- Lingulepis, Obolus, | Red calcareous sandstones | 100 S Orthis desmopleu- and pink limestones. to iS ra, Huomphalus. 150 & || Along the border of |.......---..--.------- Hard gray limestones,quartz-| 180 oy Front Range, be- itic in part. = tween Colorado 5 Springs and canon. SS ||] Clin) pete ss s6o5ksensp Bucanella nana..---. Red shaly limestone.....-.-.| 70 3 Williams’ Cafion ...... Ophileta complanata.| Reddish arenaceous lime- |.....- iS) stones. PAversge bhickness ofstrabaeeeaassb ere sce sane eer aee eee ee eee 160 bh ORES soscedsascallesaads sosonocaasnosbace Whitesandstone and quartz- | 250 ite. IPPYEIE) JRYOP. cosccs aon] anoobeoadesonoep os0005 White quartzites........... 300 to & 400 = || Four-mile Creek.......|...-..-------e-------- Red and pinksandstonesand | 160 |. & quartzites. = MroutiCneokeessewrer ce | tecciccies cccicecc emcees Yellow and pink sandstones 80 S || North of Mount Ouray.|.-...-.-.-.----.------ White and pink quartzites -.| 200 rs || Near Canyon City ...-|...-.---.--.-.-.-.---. Variegated micaceous and |....-. 2 calcareous sandstones Ryn Glen eiiy rl ese seem iat ememtetetetsteteieiemnele ieee Red sandstones and quattz- 40 ites. ENDLICH.] GEOLOGICAL FORMATIONS OF COLORADO. 131 THICKNESSES OF FORMATIONS AT CERTAIN LOCALITIES. Locality. Groups. | Thickness. White River and Grand .-..---.--- ®haaain ERGGP on Le age aes Ue A 5300 Animas River ..-..--.-----2------ ; AV AING RIO) Oy Beaconnaoononuedooeedodeon 2200 to 2600 BVViet AS ALC I hee Woomera ana Semmene siya esiseecie scalar rind a dees secre saree ee eater Post-Cretaceous. 2700 Golders ae ee ee ara eae caiarataincve sina ssc eielaraicetates ie Sieleteieslafevere eisleistatajeietereisie 3200 Cretaceous. Mesa Verde ......--.-----------=- PROKOP ET si yee eee ecte ate Saha tate ac Repertoire meeetens 3500 to 4800 Wolornd ones eases eae ec asine seeleererae claret cleteverete , IDRIROUR A Sse ooo sooeobCnEBadocReaborececHmooacas PAMIMAS RVD ace soe eee THO x celal Sie eeeeee tice ho anlotels eerste crelee ies setererers 3400 ; Goloradoe esa se eae usec oe ew serase seers ; ; : Dakota .-.....------- aQoodscousnssaess sagesoese White River: -2- 2.22.5 scccese==-=- 1Qti>- <8 s BUD eco Se ee S OSC n A Ee EE en rCnbE ee a aoD acon 3600 Color adore oceeineeismie we coiaeiae eneyeecisleiats ; : ieee DalkOtiay cece aclsea = owle encima am ee nal =1~ =) lel=l=i== Region of Rio Piedra .......-..--. § TORS Ad ST ie CPE NRE RR er Se UN ats 3600 to 5000 Colorado... l Dakota ...- Bear Cafion..... soda Gaeereeaa oss ei Sta ee psa o sean ee 750 } WolOrad One eee eb a se ces ce aatae eee ecto JORGE, Bap Kodbodsoo bboboe boboce basecacoudobeaadE Hagle River ...-.....---------.--- 960 Pleasant, Pare se yee ert eae yess oe NS ld Ns ce ee id Say 460 MOAT CATH OT co cee re ea eae ercie Oe ciate Scifi a oie Gane elon ore Mian a orelare ersea' ale 870 Saint Vrain’s| Creeke sect nee ene erste cc ee bat ee Seen coeineeoe tes 450 Unaweep Cafion ........-.----.--- Trias 600 Eagle River .---- EBB Sa0 SoS COO | eee SR II Ne aie alta alta erate oie hha a eel 1000 Canyon Citys: 52ers ne = siriccleicicieincSisnic/Si cs er iesise teres aye Soi 1200 IEE ENA A BEA Soceno oe sacoe conadod| | Tete eT Ses OB SCO 007 DECOOR ESR CCOGOO SO COCHOO SR COCOCAaG 1500 Glen Hy ries secje Sac se eee a ae at ies ee ne eee Sin See ci sislaisisicinic sierra a 1100 Little Lhompsonesess eee sess leae ee eee ee ee eae ee Pa ee gee 750 e f Permian. le River. cccca. eee eae CLMMAM . 22-2 - 22. ene cece eee wee = nee ne Q wagle River ; Permo-carboniferous a Carboniferous. Upper Carboniferous ...-...------------------- Head of Salt Creek............-.. j atid Carboniferous see neeeee eee ee eee eee neeees 5500 Lower Poeniionius Be Bre eye tithe opel ste aj Spate rami aharetS : nm Upper Carboniferous ... Animas Region..-......-..------- S Middle Carboniferous. 3100 Lower Carboulteyous ea Upper Carboniferous .....--.-----.-------- : Park Range ....--.-.------------- } Mid Carbonitero ust eee een 4300 to 4900 Lower Carvontiorous SECC OIC OCORAC DOS ACOE a U E ILCLOUS 22 es ee aeeee ee eeies rae al Mic Mountains peseeeeeeeneecera: } wide GaRGatrarous NALS ere ere Ne a Re tae 0 4500 to 5000 Lower Carboniferous .-.--..-----....---------- ,) : Devonian. Time: Creek ie Se seeep etc ee ese eee ae oN a a uaa Ie ck Ds 1200 to 1500 : Silurian. Hnglo River’... 2 ee § Galeeroug 0200 TI 770 Potsdam BB eR HOS CIRCE OB oEEES aAccceSodasooonae Hour ile! @recks asses ss seeeeeeeee § calcitetons SoH opU OER ouoHoE scomas utgane seHconet 360 otsdam ...- North of Mount Ouray ........--- ; Caleetous soe 400 OLS Al se etica cence eles Gon Byrio .---2e.-ecne-sensseeen Tec ce MEd eat 110 Adding the thickness of all the sedimentary formations occurring in Colorado, we arrive at the maximum result, giving a thickness of 24,500 feet. MINERALOGICAL REPORT OF F. M. ENDLICH, S. N. D. LETTER OF TRANSMITTAL. WASHINGTON, D. C., January 2, 1878. Siz: I have the honor herewith to transmit the “ Catalogue of Min- erals found in Colorado.” It has been made as complete as possible, up to date. A plan differing from that previously followed has been adopted. So tar as practicable, analyses of Colorado minerals have been given. They will aid examination and show the interest taken by specialists in the minerals from this State. All available material has been utilized in the preparation of the catalogue. A systematic enumeration of the Colorado mineral species and references to the publications thereon have been added. I desire here to thank those gentlemen to whom I am indebted for verbal and written information. Hoping that the subjoined pages may meet your requirements, I am, very respectfully, your obedient servant, FREDERIC M. ENDLICH. Dr. F. V. HAYDEN, Geologist in-charge United States Geological and Geographical Survey of the Territories. 133 CATALOGUE OF MINERALS FOUND IN COLORADO. By F. M. EnDuIcg, 8. N. D. The continuous development of mineral resources of Colorado is pro- ductive of a more complete knowledge, not only of their distribution, but of their specific character. In 1873, I published my first catalogue of minerals of that Territory. An enlarged list was printed in the United States Geological Report for 1875. Now, the survey of Colorado is completed, many additions of species new to the State and of new localities for known ones have been obtained. With a view, therefore, of presenting, as complete as possible, a catalogue of Colorado minerals I have undertaken its preparation a third time. In so doing, I have availed myself of all accessible material. Publications and private communications by the following gentlemen have furnished very material aid in the completion of the work: Dr. F. V. Hayden, United States Geologist; Capt. E. L. Berthoud, Golden, Colo.; Prof. J. D. Dana, New Haven, Conn.; Prof. P. Frazer, E. M., Philadelphia; Prof. F. A. Genth, University of Pennsylvania, Philadelphia; E. Goldsmith, Philadelphia ; J. D. Hague, BH. M., Survey of the Fortieth Parallel; Prof. N. P. Hill, Black Hawk, Colo.; W. H. Holmes, United States Geological Survey ; Dr. G. A. Koenig, Philadelphia; Dr. O. Loew, Survey West of the One Hundredth Meridian; Prof. J. EK. Mallett, jr., Canyon City, Colo.; W. McCree, EB. M., Del Norte, Colo.; Dr. A. C. Peale, United States Geolog- ical Survey; Mr. Richard Pearce, Black Hawk, Colo.; Mr. Peters, E. M., Fairplay, Colo.; R. J. Raymond, United States Mining and Mineral Commissioner; Prof. J. F. L. Schirmer, Denver, Colo.; A. von Schulz, ii. M., Black Hawk, Colo.; Prof. B. Silliman, New Haven, Conn.; J. Alden Smith, State Geologist, Boulder City, Col. An arrangement has been followed differing somewhat from that adopted in previouscatalogues. So far as was possible, only well-accepted mineral species have been enumerated, without according specific posi- tions to the varieties. The most popular names for certain species have been inserted, and references have been made leading to the name accepted by mineralogists. It is intended that every available analysis of Colorado minerals shouldbe given. Necessarily many that have been made and might prove valuable cannot be obtained. So far as possible this intention has been carried out. Analyses of ores or metal-assays are not given, as they would be of no mineralogical value, however inter- esting to the miner and smelter. A systematic enumeration of the species occurring has been given at the end of the catalogue. It is arranged in accordance with Dana’s sys- tem of mineralogy. In addition thereto, reference is made to publica- tious bearing upon the mineralogy of the State of Colorado. Undoubtedly the most interesting mineral occurrence in Colorado is that of the tellurides. Gold, silver, lead, iron, mercury, and oxygen are combined with the tellurium, forming compounds that have either been considered heretofore as among the rarest, or were totally unknown to science. At no place have tellurides occurred in such large quantities and in such admirable form. As ores they are greatly sought after on account of the high percentages of gold and silver they contain. Another 135 136 REPORT UNITED STATES GEOLOGICAL SURVEY. rare occurrence is that of the pitchblende. It is to be regretted that the mine is not worked at present, and has not been for several years. Thus much that might be learned as to its distribution in the vein is lost. - Among those minerals classed as “ores,” the argentiferous species are prominent in Colorado. Compounds of sulphur, antimony, tellurium, bismuth, arsenic, and other metals and metalloids with silver, are found in varying ratio. Galenite may be regarded as invariably silver-bearing. I have made wore than a hundred assays of western galenites and have never failed to find the precious metal. It remains to be said that the per- centage is highly variable, and that, as arule, it is small unless argentite be present in the mineral. This is not unfrequently the case. It may be noticed that many very coarse-grained galenites show, upon break- ing, dark gray, or black, dull, cleavage-planes. This is, in many in- stances, produced by a very thin coating of argentite. It is not to be supposed that the number of minerals occurring at any particular locality could be fully ascertained by members of the survey while examining the region. During the regular field-work only such mineral localities will be obtained that happen to be found more or less accidentally. It may be hoped, therefore, that in future years more knowledge will be gained regarding the non-metalliferous minerals. Oo these the enumeration at the present time is rather meagre. Thus far but comparatively few epigene minerals have been found in Colorado, considering the large number of mines worked. With increas- ing depth of the mines, and time, no doubt the mineralogist will event- ually be rewarded, and will find many a secondary mineral-product that now he looks for in vain. Upon undisturbed dumps a few such species have been collected. Should further discoveries, or more complete examination of the min- eral regions already known warrant it, I propose to prepare another edition of the catalogue whenever such preparation may seem advisable. ACTINOLITE.—In radiated form, of light-green and bluish green color, on Mount Ouray ; on Buffalo and Sopris Peaks; crystallized at Bergen’s Ranch, Jefferson County; on Boulder Peak. AGATE.—See QUARTZ. ALABANDITE.—At Quartzville. ALABASTER.—See GYPSUM. ALBITH.—Quartz Hill, Central City ; Gold Hill, Boulder County. ALMANDITE.—See GARNET. ALLOPHANITE.—Franklin Mine, in Gilson Gulch; Fowler and Wells’s Branch, Sugar-Loaf district. ALTatrE.—Red Cloud and Cold Spring Mines, Gold Hill. It occurs in various mines of the Sunshine district; minute crystals were obtained from the Red Cloud. Analyses, published by Genth,* show the follow- ing result. The specimen was from the Red Cloud Mine: (1) (2) Per cent. Per cent. Quartz) tio cick cee eee ses eke) OL TD 0. 32 Gol ees ora yarlerere nimi crea oce 0.19 0. 16 Silvie esa hes ears eke UTS 0. 62 0.76 Copper se eee eee eo -- 0.06 0. 06 Mendig scab Lewes eeeewaa eas 60. 22 60. 53 ANI G spe Saat) 20 Sra Paes Behl ecaicis V2 0.15 0. 04 1 Be oy Ra I A i 0. 48 0.33 Tela SS ae ee Sane ee ey Re 37.99 37. 51 99. 90 99. 74 * Proc. Am. Phil. Soc., Philadelphia. Vol. XIV., p. 226, 1876. ENDLICH.] CATALOGUE OF COLORADO MINERALS. 137 Atum.—Mount Vernon. ALUMINITE.—Monunt Vernon. AMALGAMITE.—Occurring in connection with coloradoite in the Key- stone Mine, Boulder County. AMBER.—(One specimen found near the head of Cherry Creek. This may, however, be one of the numerous resins occurring in the lignitic coal. They resemble amber, but differ in composition. See WIEEL- ERITE.) AMETHYST.—See QUARTZ. AMIANTHITE.—North Boulder Creek. AMPHIBOLITE.—Occurs at numerous localities in the dikes traversing granite. Small acicular crystals can be obtained from the porphyritic and sanidinitic trachytes. Good crystals arerare. Found on Buffalo Peaks; Montgomery; Head of Ohio Creek in voleanic breccia; on the Gunnison in trachytes. ANALCITE.—In minute crystals in basalt, near Uncompahgre Peak. ANDESITE.— Minute crystals in the trachytes near Black Mountain. ANGLESITE —Freeland Mine, on Trail Creek. In crystals at the Horse- shoe lead mine, in South Park. Clifton lode, at Central City. Pros- pector lode, in Arastra Gulch, near Silverton. ANHYDRITE.—On Elk Creek. Crystallized at the salt-works in South Park. ANTHOPHYLLITE.—N orth Boulder Creek. ANTHRACITE.—Anthracite Creek ; ““O Be Joyful” Creek; in the Elk Mountains; in Uncompahgre Cafion. ‘This anthracitic coal is of Lower and Upper Cretaceous age. Partly its greater age, partly other causes, have given to it the anthracitic character. Nearly all of it was originally simply bituminous coal. Dr. Peale, with reference thereto, says:* “The eruption of the trachyte found bear the coal first mentioned, probably so heated it as to deprive it of the bitu- minous matter.” An analysis made by Dr. Peale of coal from An- thracite Creek furnished the following result : AWG? GLA Cbs AS SHES Noes Se ESP pn ersers pias = Sie tye) 1. 60 HMixedkCaTbomtsces soceoowes .sese esas. 88. 20 Volatile combustible matter........----..--- 3. 40 UNS Nyce 2 te rh BPS Serpe tiaras eS el 6. 80. An average taken from seven analyses of Elk Mountain anthracite furnishes : A\WVEIIGIE SS oCe Cle eS = aes ue Bese SIA OL TST UXCCUCARVOM Eee ee Soe wale ar boe sewer ss 77. 360 Volatile combustible matter ...........----. 13. 620 ATS nes arpa tirm ee tnepee tc a eRe LN EAU Me None Olea 6. 291 SOSCIIG PANINI Goad acou cooonoseUdobosaT 1,740 ANTIMONY.—Gold Hill; found there in minute crystals. ANTRIMOLITE.—See MESOLITE. . APATITE.—At Fairplay. APOPHYLLITE.—Hunt’s Peak. Reported from some of the basalts near San Luis Valley. ARAGONITE.—Occurring in the form usually termed flos ferri, very beautifully in Marshal’s Tunnel, Georgetown, Golden. Table Moun- tain. In the trachytes near Del Norte; on the Rio Grande, above Fir Creek; at Idaho Springs. * Rep. U. S. Geol. Surv., 1874, p. 176. 138 REPORT UNITED STATES GEOLOGICAL SURVEY. ARFVEDSONITE.—Occurs in quartz in El Paso County. An analysis furnished Dr. G. A. Koenig the following result :* Per cent. PO pe sig SOC CEO GCE Eee EO Pe her embatr gmt ss 49. 83 Dien eess sce ee Ss Hees Se caseee «ese be sec Meetesee 1. 43 LG) Ose ahaa Soe eae een Saeed Sobers ce eee 0.75 AIO) Mennepmatcls ee oR CEU ded ce ode ee ee euler trace le HO see ee Neos eos wae cee Ree aae eee emcee 15. 83 A CIO acinate ns sis B tic Skim, c Se cies. cise einleraye oie eee eee 17. 95 Mimi @ ese te Soe e.c ie! Gaus sdinete aeeaeere me sae eres 1.75 Nag O a on Tn Eh Ree ne da 8.33 ROWER ces otic cisne s cetig neice spn amie eeeaeecesererecy, Baa Mao: 2o os. se csaceccee ceet eceee eeomeeae are 0.41 TGpaNOMy ooo So5néaocs cose coed cheo ocoseo sn SeoS 0.21 97.97 ARGENTITE.—Colorado Central Mine, Terrible, and other mines near Georgetown; in the No-Name, Caribou, and others at Caribou; in some of the silver lodes near Nevada; in the Senator lode of the Hardscrabble district ; in many of the lodes of the San Juan mining region associated with fahlerz and pyrargyrite. At the Silver Star, Moose, and other mines near Fairplay. Usually it is found in small, irregular particles or seams, rarely crystallized. Decomposition re- sults in the formation of native silver. ARSENOPYRITE.—Crystallized and massive in the Bobtail and Gunnell mines. Intimately associated with pyrite and chalcopyrite there. Generally auriferous. Together with silver and copper at the Park lode, Bergens ranch. Occurs also in the Priest Mine near Fairplay. With franklinite on Rio Dolores, Nevada district, Gilpin County. ASBESTOS.—Occurs in small quantities, partly radiated, near Caribou. ASPHALT.—Found inthe White Riverregion. It occurs in veins, is very compact and brittle. Occurs in springs near the summit of the Book Cliffs; Canyon City. (Loew.) Several of the petroleoid products of Colorado have been termed asphalt. ASTROPHYLLITE.—Occurs in quartz on Cheyenne Mountain. Imbedded in quartz in E] Paso County. An analysis furnished Dr. G. A. Koe- nig the following result :* Per cent. STO a) Bo ete is se Se ia Ree ee ee eee ro aa 34. 68 "EL Og tete seats coors eae erent enae sree eae ye ere Oe eee 13. 58 Zit Og oI Ma, ae nee Ra eee ee 2. 50 Fe, O3 PORE yr eM rae ei SRM de eure Beal (OH \0) Ai 51 Og seth eh ee Sr es eee area aia ohee ms ereeree rs 0. 70 WE Oe. ose ee emee Bee eee Sanne ee ee oe eee 26. 10 1 G0 @ msn te ee 8 eT a A he a 3. 48 5.) oo ok So ee ee ee eics Gee eee eae 5. O1 Nae On oe et ine ee cece eee 2°51 Mag Ovid. 1: Eee, ee feel Grete 0. 30 CaO less ue a aes ars Resa cokers 0. 42 Ta Oz 6090006000000 DOD oOo DHOO SoGDe5 4006060 S906 0. 80 Hg O) wwe sos we made cee ese De aOe ae eee DEE 3. 54 99. 91 ATACAMITE.—On Kendall Mountain in some of the argentiferous lodes near Howardsville. AVENTURINE FELDSPAR.—See ORTHOCLASE. AVENTURINE QUARTZ.—See QUARTZ. * Proc. Ac. Nat. Sci. Phil., Part i, 1877, p. 9. ENDLICH.] CATALOGUE OF COLORADO MINERALS. 139 AZURITE.—In the No-Name, together with malachite, the result of de- composition of fahlerz, Caribou; in the Rosita mines in Hardscrab- ble district; in the mines around Fairplay and Idaho; on Trail Creek ; Crater Mountain; in the mines of the Elk Mountain district, Mala- chite lode, Bear Creek, Gendhemas lode, Tucker’s Gulch. Generally the azurite is regarded as “ blossom-rock” by the miners. If result- ing from the decomposition of fahlerz it usually indicates silver-bear- ing ore. No ecrysta!s of any size were observed, the largest scarcely measuring 0.5 millimeter. Small, very brilliant crystals were found on Kendall Mountain, near Howardsville. BARITE.—In clear, yellow, tabular crystals in the Tenth Legion Mine, at Empire; colorless crystals in the Terrible, at Georgetown; near Canyon City, transparent crystals are found in the arenaceous shales of that region. Crystals occur in the limestones near Fairplay ; on the Apishpa River, crystals with fine terminations are found. Barite oceurs also in Gilson Gulch, Georgetown; Montezuma; white, red, and brown in Clear Creek Cafion; on station 17 of 1873, and on sta- tion 46 of 1873. At the Rosita mines. - BASANITE.—See QUARTZ. BERYL.—On Bear Creek, Tiffany’s Ranch; Stone Dam, Jefferson County. BIoTitE.—On Buffalo Peak and station 64 of 1873. Several of the trachytes, more particularly the porphyritic, contain small crystals of biotite. It is also found in some of the basalt. When decomposed it becomes splendent brown, otherwise it is very dark green, brown, or black. BisMUTH.—French Gulch. BISMUTHINITE.—In the Las Animas Mine, pseudomorphous. Dr. O. Loew* mentions copper and iron as occurring in the bismuthinite of the Ward district. Occurs in the Pittsburgh Mine, Clear Creek County. BIsMUTITE.—From the Las Animas Mine, incrusting the preceding min- eral. BITUMINOUS CoOAL.—See COAL. BorniITr.—Found on Rio Dolores; San Juan region; at Copperville, near Canon City. BovURNONITE.—Terrible Mine, near Georgetown, in small crystals. BRvUcITE.—On James Creek. CALAMINE.—Park County. CALAVERITE.—Associated with other tellurides in the Red Cloud. Good crystals have been obtained from Sunshine district. Found in the Keystone and Mountain Lion Mine, Boulder County. Genth pub- lishes an analysis of calaverite,t and obtains the following result: Per cent. AN ie fee ee te aracy Snare ahs uliimcins BRIS sels ciate 38. 73 IAS Oona een eR a ay alee aay nc a te bie aijelaieisbie arsiieie 3. 05 BENGE Sec a On A Rare ee = 57. 32 NEO eres sshd Sale deta cae eas 0. 05 Ble Y Oye eee ee aera taccisi ow bens welarapeeeisinns 0. 30 AS Oso NOM SEC re seeeacc alslsa/cisclcccinalcecicee 0. 55 100. 00 CALCITE.—In small erystals, scalenohedra, at the Monte Cristo Mine, Central; Mount Vernon; Bergen’s ranch ; rhombohedral crystals on Cheyenne Mountain; in the limestones of South Park; in the car- boniferous limestones near the Arkansas River, lining cavities; sca- * Explorations and Surveys West of the 100th Meridian, vol. ili, p. 636. _ t Zeitschr. fiir Kryst. uod Min., P. Groth, vol. ii, No. 1, p. 6, 1877. 140 REPORT UNITED STATES GEOLOGICAL SURVEY. lenohedra in the Elk Mountain district ; “fpeneed in Trout Creek Park; on Frying-pan Creek. Brown, rose. colored, yellow, and white on Table Mountain at Golden ; scalenohedra and combinations of rhom- bohedra in quartz geodes near Ouray. Marble.—Marble occurs at several localities in Colorado. North of the Gunnison near Taylor River Park is perhaps the most ex- tensive deposit. CALEDONITE.—Freeland Mine, Trail Creek. CAOLINITE.—Camp near Mount Princeton. The white, chalk-like bluffs on Chalk Creek near Mount Princeton owe their appearance to the presence of caolinite. There it is the product of decomposed oligo- clase. CARNALLITE.—Salt-works, South Park. CARNELIAN.—See QUARTZ. CERARGYRITE.—Gilpin County lode, Black Hawk. Small compact quantities in the Wade Hampton Mine, Argentine, Caribou. Small specimens were obtained from the Red Cloud Mine, Gold Hill. At the Rosita mines. Reported from Upper Animas region. CERUSSITE.—J. P. Whitney Mine; in very small crystals, Central; No- Name, Caribou; Caribou mine; Silver Hills mines and Rosita mines, in the Hardscrabble district. Freeland Mine, Trail Creek. In the Horseshoe Mine it occurs earthy, and is found throughout the mines of Elk Mountain district. Cation City. Found also in the Prospector lode, Arastra Gulch, near Silverton. CHABAZITE.—Golden, ’Colo., Table Mountain. In basaltic geodes near Uncompahgre Peak. CHALCANTHITE.—On Clear Creek, below Black Hawk, in a deposit, and on several dumps near Central, in this case an epigene species of chalcopyrite. CHALCEDONY.—See QUARTZ. CHALCOCITE.—Bergen district, near Idaho City. Liberty lode, Bear Creek, Canon City. At the Rosita mines. CHALCOPYRITE.—Malachite and Pocahontas lodes, Bear Creek. 0.17. - 0. 19 Cai@ < coseicwcbe cote worsoseSeereseeeee 0. 48 0. 26. MROt alesse ere eine Gere stele tslatore velelbemiave mieiaielseisiDiene -99.01 99.82 MAGNESITE.—In small quantities in the Running lode at Black Hawk. MAGNETIC IRoN.—Bear Creek, Ralston Creek, Grape Creek. MAGNETITE. —In loose nodules on C-unnell and Procer Hills, at Central; in small octahedric crystals in the gneissic rock on station 1. Occur: ring in the granites of various localities, Silver Hills, White House, Capitol ; in the dolerite rocks generally. At Idaho and Caribou. — Oc- curs near Golden. Octahedral crystals on Quartz Hill, near Central. On Grape Creek, near Cation City, is an extensive deposit of magne- tite, which is mined as iron ore. MAGNOLITE.—F rom the Keystone Mine. It occurs, according to Genth,* in capilloid and acicular crystals. It is the result of decomposition of coloradoite, and has the formula Hg, TeQ,. MALACHITE.—Is found as the result of decomposition of fahlerz and other minerals at the Dallas, Leavenworth, and other mines near Central; at the No-Name, Caribou, Seven- Thirty, Fourth of July, and others; at Caribou; at some of the Georgetown mines; at the Hardscrabble mines, on Mount Princeton, and other localities ; at Crater Mountain, jin the mines of Fair Play and Elk Mouptain district. Malachite lode, Bear Creek, Gendhemas lode, Tucker’s Gulch, Oro City, Cafion City, Pollock, Montezuma. Allen’s copper mine, head of San Luis Valley. MARCASITE E.—Philipps Mine, Fair Play. MELACONITE.—Occurring at the Gunnell, ‘Briggs, Leavitt, Leaven- worth, and other mines near Central; at the Unknown Mine, i in Mont- gomery, Tucker’s Gulch, Jefferson County, Colorado. Pollock, Mos- ~ quito. MELANTERITE.—On the dumps of the Wood, Dallas, and Kansas mines, _and others, near Central; in the Sweet Home Mine. MeErcury.—Native; associated with mercury-telluride in the Sunshine district, Boulder Gounty. MursitrrE.—Black Prince lode, Lump Gulch. MESOLITE.—Golden, Colo., South Table Mountain. MISPICKEL.—See ARSENOPYRITE. i Minrum.—Freeland Mine, Trail Creek, Georgetown, Central City. Dutchman lode, San Juan district. METEORIC IRoN.—See IRON. MOLYBDENITE.—Leavitt mine, at Central; occurring in thread- like veins in Silver Hills, near Fair Play, Boulder County. Douglass ‘Tunnell, Georgetown; Alice Cary lode, San Juan district. MOLYBDITE. —Alice Carey lode, San Juan district. MuscovitTE.—In good crystals on Mount Ouray, and in the coarse- ‘grained granite near Cafion City; throughout the granite and partly in the schist rocks. Fine crystals from Topaz Buttes. NAGYAGITE.—Gold Hill. This mineral is rare, and its identity is scarcely fully established. *Zeitschr. fir Kryst. und Min., P.‘Groth, vol. II, No. 1, 1877. i ae oe es ee ENDLICH.] CATALOGUE OF COLORADO MINERALS. 147 NATROLITE.—Golden, Colo. Table Mountain. In cavities in the Basalt near Uncompahgre Peak. OBSIDIAN.—Porphyritic, in a dike, at station 27 of 1873; Buffalo Peak, Arkansas Valley, and Union Park. Under the trachyte, on Gunni- son River (porphyritic and spherulitic). A heavy vein of porphyritic obsidian occurs near the Rio Grande Pyramid, and continues from there southward in the trachytic beds.’ Nodules occur in the lower members of the trachytic series. A dike of obsidian, light-gray, clear sets across the Colorado Central lode near Georgetown. North of Saguache Creek with concexrtric structure. OLIGOCLASE.—Occurs in many of the granites and in the volcanic rocks of Colorado. Good erystals are rare. OLIVINE.—Transparent, green in the basalts of San Luis Valley. Onyx.—See QUARTZ. OPAL.—Aguas Calientes, Gilson Gulch; Idaho Springs, here the Opal occurs in narrow seams in the granite ; mostly it is brownish; milk- white at Colorado Springs. Semi-opal.— Found together with the Chalcedonies at the Los Pidos agency. North of Saguache Creek in trachyte. Wood opal.—On Cherry Creek, near Florissant, Soath Park. Hyalite—In the trachytes, near the Los Pilos agency. At the Hot Sulphur Springs, Middle Park. Basalt of North Mam. Sometimes occurring in very fine specimens in the trachorheites of the Uncompahgre groups. ORTHOCLASE.—Occurs in very fine, though small crystals, on Bobtail and Gregory Hills at Central. Crystals there are either simple or Carlsbad twins. It is found in very large pieces in some of the coarse-grained granites. Near Mount Ouray this is particularly the case. Large tablets of flesh-colored orthoclase can there be found. Crystals of large size, simple and twins, occur in the porphyritic dikes at Gold Hill, Boulder County, at the head of Chalk Creek, interlaminated with oligoclase in the porphyritic protoginyte. Crystallized in Jefferson County; greenish in South Park, west of Pike’s Peak; reddish on Hlk Creek; brown and gray at various localities near Central City. Beautiful, green crystals of orthoclase are found on Bear Creek, near Pike’s Peak, associated with smoky quartz. An analysis by Dr. Oscar Loew* of this orthoclase furnishes the following result: (1) (2) Sultcievacideeesc sie cise asec cues wines 63.1 PMI any NG), 4 Sere A REN Re BORER eee a 19. 94. 19.78 Protoxide of iron...-....---0..c-ce5 0. 89 1.51 OBIE a cies eco eae St Es eR Be REN 3. 15 2.11 IROLASSAES EPs ees ciaisisie sisi ones ee mere 8. 84 12. 57 ION GTO 5S Sol SSSR ee ee a pans trace 0. 66 Macitesideen concen ceo eke we woes trace 0. 13 99. 83 99, 88 ' The coloring of this orthoclase, therefore, is due toa small percentage of protoxide of iron. Dr. G. A. Koenigt regards the coloring-matter of this green orthoclase as dependent upon a ferric compound, probably an “ organic salt.” OZOCERITE ?—From head Cherry Creek. *Aun. Rep. Expl. and Surv. West 100th Mer, App. L. L., 1875, p. 111. tProc. Ac. Nat. Sci., Phil., Part II, 1876, p.1 5D. 148 REPORT UNITED STATES GEOLOGICAL SURVEY. PARGASITE.—Small particles in quartz. In a dike north of Centre- ville. PEGMATITE.—At_ several localities in the vicinity of Georgetown. Bear Creek and Gold Hill, in Boulder County. Mount Ouray. PETROLEUM.—From the oil-wells in Oil Creek Catiion, to the east of Canyon City. Smoky Creek, 10 miles south of Golden. PETZITE.—In the gold mines of Gold Hill, occurring in narrow seams and veins. This mineral occurs also in the other telluride districts. Reported from Lake district. An anlaysis published by Genth* fur- nishes the subjoined result : Per cent. Quartz »..20,. sas Beencicteeclacein ecco dine 0. 62 Goldicce.ce: Desa eS a ole tai a 24.10 SiILVerccee se eee eres Bee Bae eee Bee 40.73 Copper: hee sae eee Sees Sanieic cise eget trace Bisminth5. oe See Seen ean oe eres 0. 41 BASEN 0 ames ety mS ya reteed, oO UG ee 0. 26 ZANG ice cers Sere ee ee One ie eee Ss cede ORO: TRON Seca ee ee eee ic sae Soe wee oee 0.78 Tellurium sg. eee eee ee heats Sean 33. 49 100. 44 PHLOGOPITE.—Mount Princeton; probably a number of the small, splen- dent brown erystals in granites are phlogopite. PICKERINGITE.—This mineral was found by Dr. John Le Conte near Monument Park. It is crystallized in thin needles. An analysis fur- nished BE. Goldsmith the following result :t Per cent. Si, Og icieie Ea eee pe ae eR ea k F 38. 69 oe Og aah tN PE ile aR oe tee ca Se 11.90 FO ar Roe eee ete man ear ette Crate dor ere paiva. Ss cei aterais 4.89 (Ks O Nag O) oo ne Scdo S600 Snod O50H DeD0 500005 0. 68 TOUS Wee ae eh Get Gers ty I so ies le male ee core er en eS 1. 90 By: dit: Ho'OS: See ee eet bee ee Oates 41.94 100. 00 PITCHBLENDE.—See URANINITE. PLUMBOGUMMITE.—On lead and copper minerals of the Dallas lode near Black Hawk. POLYBASITE.—In tabular crystals at the Terrible mine, near George- town, Clear Creek County. PRASE. —See QUARTZ. PREHNITE.—} air Play, in some of the mines. PROUSTITE.—Occurring in the Brown lode, intermixed with galenite. PSEUDOMALACHITE.—Little Platte River, south of Fair Play. PsILOMELANE.—Seaton Mine, Idaho; occurs in small quantities. PYRARGYRITE.—In the Colorado Central, Terrible, International, Cold Stream mines, at Georgetown, associated with galenite, fahlerz, ands sphalerite. Inthe Brown lode with galenite; Argentine, Georgetown ; in many of the Georgetown silver mines ; in the mines near Fair Play ; in the mines of the San Juan district. Fine crystals occur in the Wheel of Fortune lode, Mount Sneffels district, San Juan. PYRITE.— Pyrite is one of the most widely-distributed minerals of the State. It is found in all the mines of Gilpin County. It occurs in the Empire mining district, in the Gold Hill mines; in the Trinidad gold mining district; in the Summit district; in the San Juan and Lake districts; in Summit district; in the mining districts of South * Proc. Am. Phil. Soc., Phil., Vol. XIV, p. 227, 1876. t Proc. Am. Nat. Sci., Phil., Part III, 1876, p. 333. ENDLICH.] CATALOGUE OF COLORADO MINERALS. 149 and North Parks. Mostly it is auriferous and associated with chalco- pyrite. J’ound both massive and crystallized. Massivein the Leavitt, Briggs, Kansas, Bobtail, and other mines near Central. Large bodies of it occur in the Mammoth, Gunnell, Grand Army, and other lodes near Central. Cubes in combination with the pentagonal dodecahe- dron are found in the Winnebago, Mack, Dallas, Kansas, Grand Army, Gunnell, and other minesat Central. Crystallized and massive in the mines of Silver Hills, Buckskin, Idaho; in the Tenth Legion mine at Empire; in the Elk Mountain district. Cubes are found in the Gran- ite of the Mount Princeton group, on Eagle River in the mines of Summit district. Cubes of four to five inches edge in the Phillips mine. Cubes and octahedra, simple and in combination in the San Juan district. _Pentagonal dodecahedra in the Bobtail and Briggs at Central. Octahedra at the head of the Uncompahgre. Octahedra on Anthracite Creek. j Radiated pyrite (possibly Markasite)—Smoky Hill River; Purgatory, Apishpa Creek. PYROLUSITE.—Massive at Buckskin and in Silver Hills. Eureka Gulch near Howardsville, San Juan. PYROMORPHITE.—Freeland lode, Trail Creek. PYROXENE.—Near Fair Play. In a number of locates in younger volcanic and metamorphic rocks. Crystals in the basalts of Southern San Luis Valley. PYRRHOTITE.—Malachite lode, Jefferson County. Nevada district, Gilpin County. QUARTZ.—Occurs massive in some of the very coarse-grained granites. Many of the quartz-veins are almost or totally devoid of ore, in which case the quartz is generally milk-white and pure. Crystals, very pretty quartz crystals, small; occur on Quartz Hill near Central. The Bobtail, Gunnell, Briggs, and other mines near Central furnish good, small crystals. In the Rosita lodes and in some of the mines of Georgetown. On East River; in the mines of the Elk mountain district; Iowa Gulch; Sopris Peak; head of Anthracite Creek. Good crystals with many combinations of the pyramidal faces are found on Topaz Butte. Dihexahedral crystals occur in the por- phyry of the Sangre de Cristo range and in the rhyolite near Uncom- pahgre Peak. At Spanish Peaks. Smoky quartz —The locality on Bear Creek near Pike’s Peak has become well known on account of its smoky quartz crystals associated with green orthoclase. Large crystals, reaching over a foot in length, are there found, in cavities of the granite. Crystals are also found on Elk Creek and on the Upper Platte. Rosy quartz.— Occurs at many localities in Colorado, in the granites. Good specimens can be obtained from the head of Roaring Fork. Found, also, near Clear Creek, and on Bear Creek. Ameth, yst-—Small erystals at Nevada and neighboring localities ; on Rock Creek; Clear Creek County; on the summit of the range east of the Animas. Agate.—Fine specimens, lined with amethyst, on the summit of the range east of the Animas. Cloudy, of white and gray color, in the lower trachytic formations of the Uncompahgre group; in various forms, cloudy, banded, laminated, and variegated, at the Los Pinos agency. In South Park, in the drift; in the Lower Arkansas Valley; on the Frying Pan; throu ehout Middle Park; on the Lower Gunnison and adjacent regions. Moss-agate.-—Below the Uncompahgre, near Grand River. 150 REPORT UNITED STATES GEOLOGICAL SURVEY. Chalcedony.—Chalk Hills, eight miles south of Cheyenne Mountain ; at the Los Pinos agency; on the bluffs near Wagon-Wheel Gap; along the Upper Rio Grande Valley ; in Middle and South Parks; Buffalo Park; Fair Play; Frying Pan; Front Creek; Gunnison River. Found frequently in drift accumulations. Flint.—Occurs together with chalcedony. Found very frequently in the lower members of the trachytic series. Aventurine quartz.—On Elk Creek. Chrysopase.—Rare in Middle Park. Carnelian.—Middle and South Parks; Los Pinos agency. Onyx.—Middle Park. Sardonyx.—Middle Park. Basanite.—East of the salt-works in South Parl, It is found, to- gether with flint, in some of the trachytes. Prase.—Middle Park. Jasper.—Green and red, station 33 of 1873. Yellow, red, brown, ' and gray at the Los Pinos agency. Throughout Middle and South Parks; along the Gunnison, Dakota group, Arkansas, Grand, White, Animas, and other rivers in the drift. Occurs also in some of the trachytes, mostly red, brown, and green. The best locality for this horizon is at the junction of Lost Trail Creek and the Rio Grande. Siliceous sinter.—South Park. QUICKSILVER.—See MERCURY. RHODOCHROSITE.—Sweet Home Mine, Park County, in very beautiful specimens; in the Diadem Mine. RHODONITE.—Eureka Gulch, near Howardsville; San Juan. RIPIDOLITE.—Trail Creek, Clear Creek County, Colorado. In the Little Giant lode, Arastra Gulch, and in the Crystal Lode, Silverton. ROScOLITE.—A greenish mineral, intimately associated with quartz, found at the Keystone and Mountain Lion Mines, in Boulder County. Genth publishes an analysis,* with the following result: Per cent. Ta Oa a Be ie ire Bia aR a SRS are ea) Sea 57. 15 TG Ogee sclcvsls ate Sie pete oe Se kee bine arajeit dette Fe 19. 94 VO ceghic cis saps cee eee ncinie wisars ers ose ayae 8. 44 VA ral @) 26S 2 SERA rc ee nae ee eet ae a eae ee Yao etal trace FeO) esos he oe a ee ee ee oes See ee 3. 51 IW Q) sasage sacode sbocos 065559 nob 500 HoaGSu0d 2. 87 SDE Ors eae ee Uy RR a es Whats Ly oy ale eyimavete trace IN cou Os 2 aya ae pe eerie ees ci eke es cta tla 0. 94 TRG CANES NEA kl occa ch a 8.11 EEO ME Seas 2 Re NS cere a te not determined “100. 96 RUTILE.—On the Ute pass, occurring in quartz. ‘SANIDITE.—Occurs throughout the trachorheites, sometimes in very handsome crystals. Wherever the trachytes have been reheated the sanidite is adularizing. SARDONYX.—See QUARTZ. SCHAPBACHITE.—Occurs near Georgetown. SCHEELITE.—Crystals are reported from some of the mines near Baker’s Park. SCHIRMERITE (Endlich).—Red Cloud and Cold Spring Mine, Gold Hill. Occurs also in the other telluride districts. A specimen from the Red Cloud furnished,} gold, 18.82; silver, 28.60 percent. (See PETZITE.) pes tee ee * Zeitschr. fiir Kryst. und Min. P. Groth, vol. ii, No. 1, p. 11, 1877. tRep. U.S. Geol. Surv., 1873, p. 354 ENDLICH.] ~ CATALOGUE OF COLORADO MINERALS. 151 SCHIRMERITE (Genth).—With tellurides at the Red Cloud Mine, Gold Hill. An analysis by Professor Genth furnished :* (1) (2) Percent. Per cent, Te DAS CbS CH ECD ORC O CEE AEA Mere 12. 69 12.76 Oreo ic cee sce Tar eee 22.82 24.75 Bi Se ees galas bee 46. 91 47, 27 EM er eetepaeicie) cininss es aeiatainiacisicen's Soe 0. 08 0.13 le ee iosaiae ac nicin wei alte aieinysic/eis xt eeiase 0. 03 0. 07 See C- SS CRED BOER CES eae pe aaa 14. 41 15. 02 96. 94 100. 00 SCUREIBERSITE.—In the Colorado meteorite. SELENITE.—See GYPSUM. ; SEMIOPAL.—See OPAL. : . SERPENTINE.—Small specimens of serpentine occur in the metamorphic rocks of Mosco Pass. - SIDERITE.—Crystallized in South Park, Gold Hill, Colo.; Veto lode, Gibson Gulch; Rob Roy lode, Central City. At the Rosita mines. SILVER.—Native, as wire-silver, at the Terrible, Georgetown; at the International, on Mount McClellan; as wire-silver in the No-Name and Caribou mines, at Caribou. In small nuggets and thin scales _ near Fair Play in Washington Gulch, Homestake lode; Sunshine; Gold Hill; Blue River, Montezama; Jones Mountain and Mount Sneffels, San Juan. SINTER: CALCAREOUS.—See TUFA. SINTER-SILIGEOUS.—See QUARTZ. SMITHSONITE.—Jones’s Mine on sphalerite, near Central, Running lode, _ Black Hawk. v SopAa.—Carbonate, from the Hot Springs. SODIUM-CHLORIDE.—See HALITE. SoDA-SULPHATE.—See GLAUBER-SALT. SPESSARTITE.—See GARNET. SPHALERITE.—Occurs in almost every mine; only few exceptions take place. In the lead-silver mines it is more abundant than in the gold mines. Itis found in the Winnebago, dark brown, Dallas, Gunnell, J. P. Whitney, Kansas, Wood, California, Running, Bobtail, Briggs (small quantities in these two), Monte Cristo, and numerous other mines in the vicinity of Central. The mines of Georgetown invari- ably contain it. The Caribou mines show at times large quantities of themineral. Mount Princeton: sphalerite, containing cadmium, found in several mines near Fair Play. Occurs in nearly all the mines of the San Juan region. Varies in color from greenish yellow to brown and black. Brilliant crystals are found in the Terrible lode at George- town. SPINEL.—Crystal Mine, Virginia Cafion. | . STAUROLITE.—Simple and twin crystals in the micaceous schists near ’ Mount Oso, Quartzite Mountains. STERNBERGITE (iron and silver sulphide).—Georgetown. (Loew.) STEPHANITE.—Colorado Central, Georgetown, Moose Mine, near Fair Play, Montezuma, and other localities. STIBNITE.—Terrible Mine, near Georgetown, Boulder County. STILBITE.—-Very fine:crystals in cavities of basalt, near Uncompahgre Peak. * Proc. Phi!. Soc. Phila., xiv, p. 230. 152 REPORT UNITED STATES GEOLOGICAL SURVEY. SULPHUR.—In small crystals on galenite from the Clifton Mine, near Central; found in Middle Park, Pagosa Springs. Sometimes found in narrow seams in galenite, the result of decomposition of the latter. SYLVANITE.—In the Red Cloud Mine, of Gold Hill, occurring in foliated masses and thread-like veins. In erystals and crystalline masses in the Sunshine district. According to Professor Silliman* the ratio of gold and silver for a specimen from the Red Cloud, is, gold 1.7 to silver 1.0. Professor Genth publishes an analysis of sylvanite ob- tained from the Red Cloud Mine,t showing the following composi- tion : Per cent. (QUE s coa6 Sonoma codons os5000 ca0509 00086 0. 32 Golds cleats see ee ee eee c ohoiciere 24, 83 Silver22 ceo Soeee ee erence cele sae 13. 05 Coppers tease ae ee ee ee eee eee eer eater er 0. 23 TANG seek ete Be ele See te ee aoa che lsicleicre 0.45 i Sift) see EA Pe aM menor aici to os a) ae aera 3. 28 Tellurium ies 2scs See aerec eee eee wi sisiociers 56. 31 Selemiim.2 sce 2s Sec ee ee a ee Micioce trace. SHH MUNG S sa dee ooeesa GeG4 a5546 poder dadaeo 1. 82 100. 29 TaLc.—In fine scales among the gangue-rock of the Bobtail and Kan- sas, near Central. In light pink scales in the Silver Hillsand Barton mines, Hardscrabble district. In Mosco Pass. TELLURITE.—A new species described by Dr. Genth.¢ It is the result of decomposition of tellurium and sellurides. Its formulais Te Q;. Found in the Keystone, Smuggler, and John Jay mines in small erystals. TELLURIUM, NATIVE.—At the Red Cloud Mine, of Gold Hill, in erys- talline masses, belonging to the hexagonalsystem. The largest speci- men known was obtained by Professor Schirmer from the Red Cloud Mine. It weighed about five pounds, and consisted in a mixture of quartz an@ tellurium. Upon examinations it was found to contain 90.85 per cent. of tellurium, small quantities of selenium, iron, and bismuth, and traces of gold and silver. Professor Silliman|| did not find any selenium. Genth publishes an analysis of tellurium from the Magnolia dis- trict, Boulder County. DERE ae CORE Graco DAO CCO COC OODDEOOEUESOn 0. 60 Nee et So ee io eis 0. 07 EO ee oe we oie ee REE icles a'eiais siovsiniain 96. 91 NG OR Sein teloseanicciae Gace: cadcueMdauemaauode 0. 49 BO ns Be eect e oe eee eee ails cceecoacee 0.78 Hg Ale O; Mg O K2 O, &...-.....- = 2-2-2 1.15 100. 00 TENNANTITE.—Crystals in Buckskin Gulch; Geneva district; Park County. Freeland Mine, Clear Creek County. TETRAHEDRITE.—Crystals in Buckskin Gulch. Fine crystals in the Clifton lode, Central City. Crystals in the Colorado Chieftain lode, San Juan district. Massive in a number of the San Juan silver- mines. * Rep. U.S. Geol. Surv., 1873, p. 690. tProc. Am. Phil. Soe., Philadelphia, vol. xiv, p. 288, 1876. { Zeitschr. fiir Kryst. und Min. P. Groth, vol. ii, No. 1, p. 7, 1877. § Compare Rep. U.S. Geol. Surv., 1873, p. 355. || Ibid., p. 685, and Am. Jour. Sci. xlii, p. 571. {| Zeitschr. fiir Kryst. und Min. P. Groth, vol. ii, No. 1, 1877. > ENDLICH.] CATALOGUE OF COLORADO MINERALS. 153 TORBERNITE.—(URANITE.) Found by Captain Berthoud on Lyden Creek.* Probably mostly decomposed. Found on Griffith Mountain, Clear Creek County. TOURMALINE.—In the quartz of Gunnell Hill, near Central; on Run- ning Hill, at Black Hawk; on Guy Hill, and at Nevada; in quartz north of the Arkansas River. Crystals with both terminations at Montgomery ; on Ralston Creek. All tourmaline of Colorado is either black or dark brown. TREMOLITE.—Smith’s Fork of the Gunnison River. TuFA.—Calcareous. On Currant Creek; Roaring Fork; Frying Pan. _ At the mineral springs of White Earth, Wagon-Wheel Gap, Pagosa, Animas, and in Uncompahgre Park. TURQUOISE.—Southern Colorado. (Doubtfui.) URACONITE.—Wood lode, Leavenworth Gulch, near Nevada. URANINITE.—Occurs in large quantities, massive in the Wood lode, Leavenworth Gulch, near Nevada. An analysis by Dr. O. Loew? fur- nishes the following result : Uranoso-uranic acid.....----...-...-.-.--.-- 11.37 Sulphides of iron and copper..--............- 45.81 Gangue (quartz by difference) ............... 42.82 URANOCHALCITE.—Wo0d lode, Leavenworth Gulch, near Nevada. VESUVIANITE.—In large crystals of simple combinations on Mount Italia. North of Arkansas River, in the granite. WAVELLITE.—South Table Mountain, at Golden. WHEELERITE.—Described by Dr. Oscar Loew.t This mineral, which is quoted from New Mexico, probably also occurs in the coal of Col- orado. It is a resin, related toamber. Its existence in each particu- lar instance, however, can only be determined by analysis, on account of its physical resemblance to other resins occurring in the same man- ner. The analysis of Wheelerite by Loew furnishes : (1) (2) Per cent. Per cent. @arbonieesenasces ceciessees cece seed 73. 07 72.87 iy dro Genesee Ga cic ce ascians ece ese 7. 95 7.88 Oy elena maine sicie(cseinie Scniniclclo sal 18. 98 19. 25 WILLEMITE.—Jones’s Mine, Central City. WOLFRAMITE.—Reported from Southern Colorado. W OLLASTONITE.—Occurs in small quantities in some of the limestones near Fair Play. ~WULFENITE.—Is found in Park County; at Gold Hill, Boulder County. XENOTIMITE.—Reported from Cheyenne Mountain. ZINCITE.—Jones’s Mine, Central City. ZIRCON.—Bear River; Middle Park. In small crystals. Crystals of zircon are found in the feldspar of Pike’s Peak. Dr. G. A. Koenig§ has furnished the following analysis: Per cent. Sil OR So55 SCO SOBER SOS Se epee ene ares eae 28.00 Mic Oe oie i teen FBS (Her On Zi Oona soins oclscice es cecseeaces | 00200 IETS, © espe sioiaich cine ae aio cinseis acerdic omnes ciate 3. 47 100. 40 * Proc. Ac. Nat. Sci. Phil., Part II, 1875, p. 363. t Rep. Expl. and Surv. West 100th Mer., vol. iii, p. 636. { Rep. Hal and Surv. West 100th Merid., vol. iii, p. 630, and Am. Jour. Sci., vol. xlii, p. 571. § Proc. Ac. Nat. Sci. Phil., Part II, 1876, p. 156. 154 REPORT UNITED STATES GEOLOGICAL SURVEY. Zircon has also been found in quartz in El] Paso County. An analy- sis furnished Dr. Koenig the.following result :* Per cent. Ra QE daisy 31 as ae ISR dA SE) TT ee aa An 29. '70 VSM Oar) eee ees Seer cies len ois 60.98 TSA On ae Cees se oocd Sec coe Goceaotacreos 9, 20 MoO hess ane coe eres toscccae 0.30 100. 18 ZINKENITE.—S weet Home Mine, small crystals. ZIPPEITE.—W 00d lode, Leavenworth Gulch, near Nevada. *Ibid., Part I, 1877, p. 9. expiicu.] SYSTEMATIC ARRANGEMENT OF COLORADO MINERALS. 155 SYSTEMATIC ARRANGEMENT OF COLORADO MIN- ERALS.* : I. NATIVE ELEMENTS. Gold (1). Lead (15). Silver (2). Antimony (18). Quicksilver (8). Bismuth (20). Amalgam (9). Tellurium (21). Copper (12). i Sulphur (22). Iron (13). Graphite (25). II. SULPHIDS, TELLURIDS, SELENIDS, ARSENIDS, ANTI- MONIDS, BISMUTHIDS. A. SIMPLE SULPHIDS, &c. Stibnite (29). Pyrrhotite (68). Bismuthinite (30). Greenockite (69.) Molybdenite (34). Schreibersite (74). Dyscrasite (35). Pyrite (75). Schapbachite (36 A). Chalcopyrite (78). Argentite (40). Chloanthite (83.) Galenite (44). Mareasite (90). Altaite (48). Leucopyrite (91). Boruite (49). Arsenopyrite (94). Alabandite (52). Sylvanite (98). Sphalerite (56). Calaverite. Hessite (58). Nagyagite (99). Chalcocite (61). Covellite (100). Sternbergite (63). B. DOUBLE SULPHIDS, &C. Zinkenite (106). Bournonite (119). Jamesonite (112). Schirmerite (112 A). Freieslebenite (114). Pyrargyrite (117). Proustite (118). Tetrahedrite (124). Tennantite (127). Stephanite (130). Polybasite (131). KEnargite (132). Ill. COMPOUNDS OF CHLORINE, BROMINE, IODINE. Halite (138). Cerargyrite (140). Embolite (141). Iodyrite (143). Carnallite (147). Atacamite (153). * The classification herein adopted is that given by Dana in his “ System of Miner- alogy.” The numbers placed in parentheses after the mineral-names, correspond to the numbers given by Dana. 156 REPORT UNITED STATES GEOLOGICAL SURVEY. IV. FLUORINE COMPOUNDS. Fluorite (159). (Chlorophanite). V. OXYGEN COMPOUNDS. A. OXYDS. 1. Oxyds of elements of series I. Cuprite (172). Zincite (176). Melaconite (178). Hematite (186). Iserite (181 A). Spinel (183). Magnetite (186). Goethite (204). Limonite (206). A. Anhydrous. Franklinite (188). a Chromite (189). Uraninite (190). Rutile (193). Minium (197). Pyrolusite (199). B. Hydrous. Brucite (210). Psilomelane (217). 2. Oxyds of elements of series II. Molybdite (224). 3. Oxyds of carbon-silicon group. Quartz (231). A. Hypersthene (235). Wollastonite (237). Pyroxene (238). Rhodonite (241). Anthophyllite (246). Amphibolite (247). Arfvedsonite (248). Beryl] (254). Chrysolite (259). Willemite (266.) Garnet (271). Zircon (272). Vesuvianite (273). Epidote (276). Chrysocolla (346). Calamine (361). Prehnite (363). | Opal (232). TERNARY OXYGEN COMPOUNDS. 1. SILICATES. A. Anhydrous. Phlogopite (288). Biotite (289). Astrophyllite (292). Muscovite (293). Lepidolite (294). Leucite (309). Labradorite (311). Andesite (312). Oligoclase (314). Albite (315). Orthoclase (316). Tourmaline (320). Staurolite (333). B. Hydrous. Apophyllite (370). Allophanite (374). ENDLICE. J SYSTEMATIC ARRANGEMENT OF COLORADO MINERALS. Zeolite section. Chabazite (386). Stilbite (392). Heulandite (394). Margarophyllite section. Tale (399). Caolinite (419). Serpentine (411). Ripidolite (450). 2. COLUMBATES. Natrolite (378). Mesolite (381). Analcite (383). Columbite (474.) 3. PHOSPHATES. : A. Anhydrous. « Xenotimite (490). | Pyromorphite (493). Apatite (492). B. Hydrous. Turquoise (563). Pseudomalachite (543). Torbernite (572). Wavellite (554). Plumbogummite (556). 4. TUNGSTATES AND MOLYBDATES. Wolframite (610). Wulfenite (617). Scheelite (614). 5. SULPHATES. A. Anhydrous. Caledonite (636). Glauberite (640). Lanarkite (641). Barite (630). Anhydrite (632). Aunglesite (633), B. Hydrous. Gypsum (654). Aluminite (688). Melanterite (664). Jarosite (691). Goslarite (666). Glockerite (696). Chalcanthite (669). -| Uranochalcite (706). Kalinite (674). Zippeite (708). Pickeringite (678). Uraconite (710). 6. CARBONATES. A. Anhydrous. Calcite (715). Rhodochrosite (722). Dolomite (716). Smithsonite (723). Magnesite (718). Aragonite (724). Mesitite (719). Cerussite (729). Siderite (721). 6 B. Hydrous. Trona (738). Azurite (752). Malachite (751). Bismutite (753). VI HYDROCARBON COMPOUNDS. Ozocerite ¢780). Asphaltum (830). Succinite (799). Mineral coal (831). 157 REFERENCE TO PUBLICATIONS ON MINERALS OF 3 COLORADO. 1869.—Report U. 8. Geological Survey, F. V. Hayden. Reprint 1867 to 1869, p. 201. ‘‘ Mines and Minerals of Colorado.” By Per- sifor Frazer, jr. . 1870.—‘ Catalogue of the Principal Minerals of Colorado.” Denver, Colo., 1870. By J. Alden Smith. 1873.—Report U. S. Geological Survey, F. V. Hayden. 1873. pp.: a, 267; b, 355; c, 353; d, 688. a. Catalogue of Minerals.” By Dr. A. C. Peale. 0. “Catalogue of the Minerals of Colorado Territory.” By F. M. Endlich. . ** Mineralogical Notes.” By F. M. Endlich. d. ‘The Telluride Ores of the Red Cloud and Cold Spring Mines, Gold Hills.” By B. Silliman. Neues Jahrbuch fiir Mineralogie. Leonhard und Geinitz. 1873. p- 477. ‘Ueber das Vorkommen. verschiedener Tellur Miner- ale in den vereinigten Staaten von Nordamerika.” By Dr. Burkart. ; 1874.—Report U. S. Geological Survey, F. V. Hayden. 1874. p. 178. ‘¢ Catalogue of Minerals noted in the area assigned to the sec- ond or middle division, United States Geological Survey, in 1874.” By Dr. A. C. Peale. Mining and Engineering Journal, August, 1874. “ Tellurium Ores of Colorado.” By F. M. Endlich. Proc. Am. Philos. Soe. of Philadelphia. Vol. xiv, p. 230. 1874. 1876. “On American Tellurium and Bismuth Minerals.” By F. A. Genth. American Journal of Science and Arts. New Haven. 1874. No. xlii, p. 571. “On Wheelerite.” By Dr. Oscar Loew. Lib. cit. No. xliii, p. 25. ‘Mineralogical Notes.” By B. Silli- man. en: 1875.—Report United States Geological Survey, F. V. Hayden. 1875. pp.: a,100; b, 226. a. Catalogueof Minerals.” By Dr. A.C. Peale. 0b. ‘Catalogue of the Minerals of Colorado.” By F. M. Endlich. Report on Explorations and Surveys west of the 100th Meridian. G. M. Wheeler. 1875. Vol. iii, p. 652. ‘Mineralogical Tables.” By Dr. Oscar Loew. Annual Report Explorations and Surveys west 100th Meridian. Appendix L L, p.111. “Orthoclase.” By Dr. Oscar Loew. 158 ENDLICH.] BIBLIOGRAPHY OF COLORADO MINERALS. 159 Proceedings Academy of Natural Sciences of Philadelphia. 1875. Part II, p. 363. “On the occurrence of uranium, silver, iron, &c., in the Tertiary formation of Colorado Territory.” By E. L. Berthoud. 1876.—Annual Report Explorations and Surveys west 100th Meridian. 1876. Appendix J J,p.136. “Listof Minerals.” By Dr.Oscar Loew. Proceedings Academy of Natural Sciences of Philadelphia. 1876. Part II,p.155. ‘Mineralogical Notes.” By Dr. G. A. Koenig. Inb. cit. 1876. Part III, p. 333. “ Pickeringite from Colorado.” By HK. Goldsmith. Proce. American Philosophical Society of Philadelphia. 1876. See 1874. 1877.—Proceedings Academy of Natural Sciences of Philadelphia. 1877. Part I,p.9. ‘On Astrophyllite, Arfvedsonite, and Zircon.” By Dr. G. A. Koenig. Zeitschrift fiir Krystallographie und Mineralogie. P. Groth. Leipzig. Vol. ii, No.1. “Ueber einige Tellur und Vand-min- eralien.” By F. A. Genth. REPORT OF A. C. PEALE, M. D., GEOLOGIST OF THE GRAND RIVER DIVISION, 1876. LETTER OF TRANSMITTAL. WASHINGTON, D. C., December 28, 1877. Sir: I have the honor herewith to hand you my report as geologist of the Grand River division for the season of 1876. The division was in the field just two months, of which thirty-two days were occupied in the work. During this time the area actually ex- amined so that its general geology can be mapped is about 4,000 square miles. The district assigned us consists of two widely separated areas, par- tially reported on in previous reports. Both are remote from settle- ments, and hence almost half the time the civision was in the field was necessarily occupied in marching to and from the areas. In the geological investigation of these detached areas (which in the ~ report are designated as areas A and B) difficulty was experienced from the limited amount of time, owing to the lateness of the season. Owing to this cause also another difficulty was met with, the lack of water. Both areas are desert-like, even at the best, and it is utterly impossible to study them in detail unless the work be undertaken in the spring and early summer, when the streams contain water. Fortunately, however, the geological structure was found to be com- paratively simple, as the sketches accompanying the report show. Had it been otherwise, the character of the country, and the rapidity with which we were obliged to travel over it would have precluded the pos- sibility of coloring the map. ‘In the report I have followed my usual plan, considering first the general features, and afterward the special geological facts relating to the district. The geological map and general sections for the Atlas of Colorado have been prepared. For the illustrations accompanying the report I am indebted to Mr. W. H. Holmes and Mr. F. D. Owen. The profiles of the sections are based on the topographical work of Mr. Henry Gannett, to whom also I am indebted for the accompanying maps. With great respect, I have the honor to remain your obedient servant, A. C. PEALE. Dr. F. V. HAYDEN, United States Geologist, in charge. 116 161 GEOLOGICAL REPORT ON THE GRAND RiVER DISTRICT. CH ASP Ry? i. GENERAL INTRODUCTION. The area assigned to the Grand River Division for 1876 was divided into two parts. First was a district of about 1,000 square miles south of the Sierra la Sal, between the Dolores and San Miguel Rivers, and extending south as far as the parallel of 38°. The larger portion of the area, consisting of about 3,000 square miles, lies north of Grand River, extending from the river as a southern line, northward to the parallel of 39° 30’, bounded on the east by the meridian of 105°, and on the west by 109° 30’. Sedimentary formations prevail in both districts. The area (area A) south of the Sierra la Sal is the portion not completed in 1575, on ac- count of the difficulty with the Indians, and it is the area first worked in 1876, nine days being devoted to it. A general view (Fig.1, Plate X), obtained from the summit of Lone Cone, shows it to be plateau-like in general, cut by deep gorges or cafions toward the east, and rendered somewhat irregular toward the west by several broad folds. Near Lone Cone Mountain the country is somewhat hilly, and in places mesa- like. Here the Cretaveous shales (Middle Cretaceous) are seen resting on the Dakota group, which in general forms the floor of the plateau. The streams cut through the Dakota group exposing the Jurassic shales, especially toward the north, and as we follow the streams we find them cutting deeper and deeper, until the Red Beds (Trias?) appear beneath the Jurassic. West of the San Miguel Plateau, beyond Naturita Creek, the Dakota sandstones rise in a fold, the axis of which is northwest and southeast. Toward the northwest this fold is marked by the Par- adox Valley, which appears to occupy its axis. Beyond Paradox Val- ley is the Basin Plateau. This is a gentle synclinal basin; for the strata on the west side of Paradox Valley dip gently to the southwest and, beyond the centre of the basin, rise again gently to the edge of the bluffs forming the eastern or northeastern wall of Gypsum Valley, which is similar to Paradox Valley. Between Gypsum Valley and the Dolores River is another synclinal basin, the sides of which dip south- west and northeast. At the northwestern end there is a dip to the southeast, which gives a saucer-like shape to the valley. From this fact we called it Saucer Valley. Around the northwestern end or rim of this valley the Dolores flows in a canon, emerging from it into Gyp- sum Valley. Southwest of the Dolores the country rises into the north- ern border of the Sage Plain. In working up this area we took the following routes: From the crossing of the 8:n Miguel we travelled northwestwardly along Naturita Creek, reachii the San Miguel again 163 164 REPORT UNITED STATES GEOLOGICAL SURVEY below the great bend, and just above the point where it turns again to the northwest. From this bend we crossed to the head of Paradox Valley, down which we followed a few miles; thence we travelled south- ward across the Basin Plateau, and a little southwest across Gypsum Valle, and Saucer Valley to the Dolores. Returning, we crossed the head of Gypsum Valley, and, skirting the country near the northern slopes of Lone Cone, turned north to the crossing of the San Miguel, having completed the circuit of the area. Four days’ travel from the Uncompahgre Indian agency, on the Un- compahgre River, brought us into our northern district (area B). The southern line of this area is Grand River, which, after it is joined by the Gunnison, curves around the northern end of the Uncompahgre Plateau, flowing at first northwest and afterward southwest. In this area the geological formations extend uninterruptedly from the Red Beds (‘Trias ?) exposed on the Grand, to the Tertiary strata outcropping at the summit of the ‘‘ Roan” or ‘ Book Cliffs.” Grand River is, for the most part, in a low cafion in the Red Beds. On the north side, the Dakota sandstones, with the underlying shales form low hogbacks, dipping away from the river toward the cliffs. Between the crest of the hogbacks and the foot of the cliffs is a broad valley, formed by the erosion of the soft shales of the Middle Cretaceous. These - shales extend to the base of the cliffs, and in some places form their lower portion. The cliffs rise in steps to the summit, which has an ele- vaticn of 8,900 to 9,000, rising about 4,000 feet above the level of Grand River. The summit of the cliffs is the southern edge of a plateau, slop- ing northward to White River (Dr. Endlich’s district). The strata in the cliffs are Tertiary sandstones and shales, through which the streams flowing to White River rarely cut deep enough to expose the Cretaceous. Our line of travel through this district was as follows: Crossing the Grand on the wagon-ford above the mouth of the Gun- nison, we ‘followed the road (which keeps on the north side of the river) nearly to the mouth of the Dolores. We then crossed the Grand River Valley to where Desert Creek emerges from the cliffs. From this point we followed the Indian trail, which leads up the western branch, to the summit of the cliffs. We then turned eastward on the trail, which fol- lows the crest of the divide between the Grand River and White River drainage, leaving it at the head of Roan Creek. ‘This latter stream was followed to the Grand, up which we travelled to Cactus Valley. With this our work ended, the northern portion having taken twenty- three days to complete. The area included is about 3,000 square miles, while area A included only about 1,000 square miles. From Cactus Valley we proceeded to Rawlins Springs, on the Union Pacific Railroad, via the White River Indian agency. We reached Rawlins on October 23, having been in the field just two months, nearly half the time being occupied in marching to and from and between our districts, on account of their remoteness from settle- ments. Shae ras Br re Bs f ae 3 t 2 ca i fie a oasupt finales ra airs rage ia iar Rie C4 ooo pion nari. . EAE SPCONIELENTN eG? ey Map of Area A, U. S. Geological Survey. 2 Plate No, VII. —— = Alluvium Upgiy ff Gy ty, Lower Dakota [ | SS QQ ; Vy Le YY yyy y er Carb, J.ower Carb, : ~NQ | = Ly WH WY GG AN RQ WS SN G WW AQGQS Z My MYM mo Ye tyyon Metamorphic | Granite ie} —— =, S—> =} hy 9 Trt GLP IA: ey titi, Yi. WHY EK ke Z LZZ ZELDA GAG 15 AM. PHOTO-LITHO. CO. N.Y. (OSBORNES PROCESS) om LCD. Oven. Del. OF * 8 a aie Fo) — Scale of Miles ——— So U.S. Geological Survey. Vit ML AGLE: fy $s VEGGIE A Z; GULL, 7 (| eee NS WVHA ZZ Y RQUTGZ WYYpsyliiyglerg VENI Wy GD. Wid WWE JIS VWs SSNS AMIN Ne | ZZ Ley. Uy DASA \30 Cpe == a) ALLE ————— (i165;00 8 1aae ri AM. PHOTO-LITHO. CO. N.Y. (QSBORNE'S PROCESS) CHAPTER II. AREA A—SAN MIGUEL AND DOLORES RIVERS—SAUCER VALLEY—GYPSUM VALLEY—BASIN PLATEAU—PARA- DOX VALLEY—SAN MIGUEL PLATEAU. Area A includes about 1,000 square miles, lying between the San Miguel and Dolores Rivers, and bounded on the south by the parallel of 38°. (See map, Bite) VIII.) DRAINAGE. The drainage of the area is by branches of the San Miguel and Dolores. The larger streams head in the Lone Cone group of mountains. The general direction is toward the northwest, and the changes in course are usually abrupt, many of the streams changing at right angles to their former courses. This gives a zigzag appearance to the drainage. The two general courses followed are northwest and northeast. RIO SAN MIGUEL. The Rio San Miguel was partially described in the Report for 1875, and little need be added here, except what is necessary to make the de- scription of the area complete. The river forms the eastern and a por- tion of the northern boundary of the area. Where the Indian trail from Muache Creek crosses the river, the cation is 800 feet in depth. The massive sandstones of the Upper Dakota group (Cretaceous) form the top of the cafion wall. The more shaly beds of the Lower Dakota group are exposed in places below, but are generally concealed by the débris, which is overgrown with pines and cedars. Whether there are any Jurassic layers outcropping it is impossible to say positively. Lower down on the river they undoubtedly occur. The river-bottom is very narrow, and in some places must disappear. There are cottonwoods (Populus bolsamifera) and the growth of shrubbery common along the Western streams. The river is rapid, flowing over a rocky bottom. From the crossing it keeps an almost northerly course to the mouth of Muache Creek, which comes in from the east. It then flows north- west for three or four miles, when it turns to westward, keeping this course for about seven miles. The next direction assumed is parallel to that of the streams rising in the crest of the Uncompahgre Plateau, viz., south- west. In this portion of its course the river emerges from its narrow caflon and flows through alluvial bottoms of considerable width—the walls on either side not being over 400 feet in height—composed of the Dakota sandstones, with cappings of the shales of the Middle Creta- ceous. About a mile and a half below the mouth of Naturita Creek the San Miguel turns to the northwest and flows in cation to its mouth. The callon at the head is 400 feet deep, and at the mouth 1,000 feet or more. 165 166 REPORT UNITED STATES GEOLOGICAL SURVEY. The rocks at first are the Dakota sandstones, which are rapidly cut through, Jura and Trias showing a short distance below Naturita Creek. Naturita Creek rises on the northern and northwestern slopes of Lone Cone. The various small streams unite to form two branches, which soon join, and the stream thus formed flows nearly due north for about eight miles , when it turns nearly west, gradually turning to a north- west course. The sources are in a beautiful park-like country underlaid with the Middle Cretaceous shales, which are soon cut through, exposing the Da- kota group, the sandstones of which form the cafion walls to the mouth. The cafion becomes shallower as we go down the stream. Southwest of Station 4 it is about 500 feet deep, and at the mouth only some 200 to 300 feet. There is a narrow valley bordering the stream in this lower portion of its course. There is running water in it, probably, throughout the entire year. Below the bend are two unimportans branches that rise in the low divide separating Naturita Creek from Basin Creek. The creek was named trom the abundance of the Spanish bayonet-plants (Yucca angustifolia), which the Indians call Natuwrita (the Spanish name). When we were in this region the plant was in fruit, and the Utes were gathering and drying it. Basin Creek joins the San Miguel a few miles below the bend below Naturita Creek. It rises in the rolling mesa country northwest of Lone Cone, and flows northwestward across the Basin Piateau to within six miles of its mouth, when it turns abruptly at right angles and flows northeast to the Miguel, cutting across an anticlinal fold and a synclinal depression, with a fault on the east side. In the Basin Plateau the stream keeps near the eastern side of a synclinal depression, which is occupied by the Cretaceous shales. In this part of its course the stream is dry during the summer. Near the head, pools of alkali-water were found in September. From the Basin Plateau it turns at right angles and plunges into a canon cutting across an anticlinal fold, in the centre of which the Red Beds (Trias?) are exposed. In this cation the stream has running water, which sinks again when it emerges into the synclinal valley east of the fold. On the east side of this synelinal depression of Cretaceous shales, there is a fault with the down-throw on the west. This fault will be described under the head of Paradox Valley. Basin Creek cuts across this fault, and joins the San Miguel a short distance beyond. Southwest of Basin Creek, the first creek of any importance is Disap- pointment Oreek. In midsummer, water is found in it only in holes. It joins the Dolores on the southwest side of Saucer Valley. RIO DOLORES. The reports for 1875 describe the upper and lower parts of the Dolores. There was left undescribed, however, a gap of unexplored country through which the Dolores flows. On ‘the eastern side of the Great Sage Plain the general course of the Dolores is a few degrees west of north. It zigzags somewhat, flowing sometimes with the dip of the rocks and at others with the strike. It isin deep cafion for the most part in the Red Beds. On both sides of the river the beds dip to the eastward or northeast, and are capped with Jurassic (?) shales and Dakota sandstones and shales. On the west the country rises to the Great Sage Plain, which stretches away to the westward and southwestward. This region was visited by Mr. Holmes, PEALE. ] AREA A—RIO DOLORES, ETC. 167 and will be described in his report. Below the mouth of Disappoint- ment Creek the river is flowing toward the northwest, but it soon curves toward the north and east around the northwestern rim of Saucer Val- led, and a short distance east of Island Mesa emerges into the lower part of Gypsum Valley. Island Mesa is capped with Dakota sandstones, a remnant of the strata forming most of the surface in Saucer Valley (see map of area A, Plate VIII). North of the Mesa the river is seen flowing toward the west. It however soon turns to the north, and farther on curves again to the eastward, to the western side of Paradox Valley. In the portion of its course just referred to, the Dolores is bordered by red sandstones and shales, a portion of which ought probably be referred to the Upper Carboniferous. The cafion walls on both sides are bluffy, the upper beds of the bluffs being of Jurassic and Lower Cretaceous rocks. The adjacent country is mesa-like, gashed by streams tributary to the main river. But few of these gashes or cafions carry water during the summer months. The Dolores cuts across Paradox Valley at right angles to its direc- tion, and immediately plunges into the canon that continues to its mouth. This portion of its course is described in the report for 1875. The folds across which the river cuts its way are those of Gypsum Valley and Paradox Valley. Its course was therefore probably outlined before the folding took place, and the cutting of the caton appears to have progressed gradually with the formation of the present folds. SAUCER VALLEY. At the lower end of the valley of Disappointment Creek is a saucer- like basin which gives name to the valley. Through the western rim of this basin Disappointment Creek cuts its way to join the Dolores. The latter is in a monoclinal valley in Jura- Trias and flows around the northern rim of the basin. The surface of Saucer Valley is composed mainly of Upper Dakota sandstones. In the centre are remnants of the Colorado shales which prevail so extensively farther up stream in the neighborhood of Lone Cone. Disappointment Creek cuts a deep gully in the soft.shales. In September we found water only in pools in this gully. The drainage from the rim bordering the Dolores unites in a stream that cuts across the western rim about three miles north of Disappointment Creek. Near the sources of these streams or gullies, where the dip is greatest, beds of Lower Dakota age are exposed. The eastern, or rather north- eastern rim (for the strike is northwest and southeast), is the south- western border of Gypsum Valley. GYPSUM VALLEY. Gypsum Valley is named from the prevalence of gypsum in it, espe- cially at its head. When first seen, the valley seemed to be a simple anticlinal, of which the centre had been eroded away. On the south- west is a hogback-like ridge 400 to 500 feet high. The Dakota sand- stone forms the summit and southwestern slope of this hogback, dip- ping about 15° to the southwest. Beneath this, and presenting the edges of the strata to the northeast, are the shales of the Lower Dakota group, which pass below into the Jurassic. The soft character of the strata has caused the valley to become filled with débris which conceals the greater portion of the underlying strata. 168 REPORT UNITED STATES GEOLOGICAL SURVEY. On the northeast side of the valley is another bluff, which faces the southwest. This also is capped with Dakota sandstones, which dip 10°-15° to the northeast. The angle soon decreases and the beds form the floor of the Basin Plateau. At Station 10 the sandstones are nearly 1,400 feet above the valley, and below them the Jurassic shales and Triassic red sandstones outerop. It is probable that a portion of the Upper Carboniferous also shows. Following the ridge to the northwest it is noticed that the dip toward the northeast becomes less, and the country is more mesa-like. At a point a little east of north from Island Mesa, at the westward bend of the Dolores, on the north side (see a in Fig. 1, Plate IX), there are evi- dences of an anticlinal fold, the axis of which is on a line with the edge of the bluffs on which Station 10 is located. At the station there is no fold. At several points on the opposite ridge, however, there are ob- secure evidences of a fold, but the beds in the centre of the valley have been completely eroded away. Northeast of Island Mesa the Jurassic rocks show the folding as indicated at b in the section. (Tig. 1, Plate IX.) Whether the lower part of the valley is a synclinal or not is diffi- cult to determine. I am inclined, however, to think not, but that the condition is folding and faulting, as represented in the section. The eastern fold dies out to the southeast, although the fault continues. This also dies out, or rather changes to a fold, for at the head of the valley the sandstones of the Dakota group are seen curving around to con- nect with those of the southwestern ridge. There is considerable ob- security here, resulting from the soft character of the strata, owing largely to the presence of gypsum. BASIN PLATEAU. From the northeastern edge of Gypsum Valley the Dakota sand- stones dip gently to the northeast, and become almost horizontal in the centre of Basin Plateau, and beyond rise in a low ridge through which Basin Creek cuts a deep cafion. The centre of Basin Plateau is floored with the lower portion of the Colorado Cretaceous, remnants of the strata that form mesas farther south. Toward the northwest the Da- kota sandstones form the surface, extending eastward to the southwest edge of Paradox Valley. The ridge through which Basin Creek cuts its way out of the plateau begins in the southeast as avery gentle fold. Its culmination appears to be at the cafion of Basin Creek. (See sections, plate No. [X.) The red beds are exposed in the centre. The western side of the anticlinal diminishes in inclination as we trace it toward the northwest, where it forms the wall of Paradox Valley. The eastern side of the fold, as we trace it, is. seen curving to the eastward, forming the rim of a dish-like depression. On the east side of this is a line of faulting which fades out into a fold to the southeast. The axis of this fold is parallel to that next west, but the fold is much gentler, and soon dies out in San Miguel Plateau. The sections in Plate No. IX will give a clearer idea of this folding. PARADOX VALLEY. About four miles above the mouth of the San Miguel River the Rio Dolores is seen cutting its way from a broad valley through a bluff wall some 1,600 feet in height. The valley is about three miles in width, and the river comes into it from a cafion on the west which is almost as deep as the one by which it makes its escape. This valley, which stretches ya ps EY: 7Za SEO GLS EI LL PEELE PIE Bz Beet tue San Miquel. 10,000 ft, + = eS DL oS ION NE g000 ft, ee LILI. RYN LL P PS. Ba D.Owen. Del. 4 AM. PHOTO-LITHO. CO. N.Y. (OSBORNE'S PROCESS.) Sak de rea hase Risen Na), i - ae ; fe eat wy, EEA i 5) a4 Cant CARE 3 Ba oid Paes R. esi * an ih ere ta vy Ay Sa U.S. Geological Survey. Plate Ix. Lsland _ WALLED Wiirn MELEE COAL EPIL. YY LLL S Saucer LZ LEE Pe: y§ Ue ID: ee Upper Dakota. fa Lower age | Great Sa Plain. ELIE WOEE: WAGE QPL BB § BETES: Zi, STZ =e gue: Paradox YS pvp , Dolores * ii i GEL. CBee: Lis TEE, LE, YIP Bip pap Lp Lyf il LIEB The, Gi 3 UM DE <7} LEE LE LEZ. 39 miles. Section on line A.B. of Map. Plate 8. Basin Plateau- Valley. st yy Uneopg Plat, i: MOGUL GLE YELL ate CG Tabegiache EZ = Bn Yi Yi LEE ip PLE BEG Uf GHEE: ye LLL dl LLL? an SD CRI” =| lt tse A, ASD Vartegdled Beds. Red —Beds, —ssw- TG.3. Rmitles Section on [ine Gypsum. es Basin Plateaw. WE Ve liarita Cr | aso ope 10,000 ft, Ltta San Miguel. Miguel Plateau. (TS Sey LLL PH LILI. LE) ZL LLL Section o 3% 1 2 of Map Plate 8. 8 10 Bb sl iH line FG. SS ne Scale 39 miles. F.2D. Owen. Del. AM. PHOTO-LITHO. CO. N.Y. (OSBORNES PROCESS.) “hh 8 nearer mk ae Biloaih wii re {Oe Ne neti | PEALE.] AREA A—PARADOX VALLEY, ETC. 169 to the northwest and southeast at right angles to the course of the river, has been named Paradox Valley. The beds on both sides of the valley present their basset edges toward the axis of the valley and dip gently away from it to the southwest and to the northeast. It would appear, therefore, to be a simple anticlinal axis with the centre removed. The erosion of the strata has greatly obscured the relations of the dif- ferent beds. The bluffs on the southwest are lower than those on the northeast, and show no beds lower than the Jurassic variegated shales, while the ‘opposite ones show a considerable thickness of the underlying red sandstones and shales that we have been accustomed to refer to the Trias. If, therefore, this valley be a simple anticlinal, it must occupy a position west of the axis. Iam inclined to believe that it—the fold—is not simple, but analogous to that of Gypsum Valley, 7. ¢., there is a fold with a fault to the eastward, along the foot of the bluffs on that side. Crossing to the southeast to the synclinal basin on Basin Creek, we tind evidences of faulting on a direct line with the bluffs. The fault of the west side of Sindbad’s Valley (see p. 63, Report U.S. Geol. Survey for 1875) is also on the same line. The prevailing formation in the valley is the Trias? covered in most places with drift. The latter increases toward the north. The bluffs on the northeast, as we go north, are in two steps, the upper being of Dakota sandstone, which slopes to the San Miguel River. The lower step has Jurassic shales cappin g the red sand- stone. North of the Dolores, the Red Beds prevail and Upper Carbonif- erous beds outcrop at the base of the cliffs. Owing to the limited time, this portion of the valley was not visited. SAN MIGUEL PLATEAU. The San Miguel Plateau calls simply for a mention here, as the re- ports for 1875 refer to it so frequently. We crossed it on the trail that leads from the Uncompahgre agency to the Navajo Indian country. The elevation of the plateau near the mountains is about 8,000 feet, and here pines are found. Near the mouth of the San Miguel! the ele- vation is about 6,000 feet, and the surface covered generally with sage- brush. All the streams ‘are in canons from 800 to 1,000 feet below the surface, with but little bottom-land. The Dakota sandstones form the surface. rock, but that higher beds once prevailed over the entire area is evident from the remnants of Colorado shales that are now found at several localities. The largest area of shales is found between the San Miguel River and Tabeguache Creek, occupying a synclinal depression. The areas of shales are indicated on the map (Plate VIII). CHAPTER 7111. AREA B—GRAND RIVER VALLEY—ROAN OR BOOK CLIFFS— LITTLE BOOK CLIFFS. As indicated in a previous chapter, Area B includes about 3,000 square miles. Of this, 1,100 represent Grand River Valley. The en- tire drainage of the area is tributary to Grand River, which forms the southern boundary. The northern boundary is the crest of the Roan or Book Cliffs. Almost all the area is a desert, and can be worked in detail only in the spring or early summer months. It was visited by us in the last week of September and the early part cof October, when the streams were dry. Salt Creek was the only one carrying water, and it was a trickling stream of strongly alkaline water. The region between the crest and the foot of the cliffs is also destitute of water except at a few places. To be worked in detail it will have to be visited in the spring; and the crest, along which an Indian trail takes its way, will © have to be the line from which it is worked. The cliffs are rugged and precipitous, and considerable time will have to be spent in finding good places to descend. Fortunately the geological structure is so simple that a good idea of the areas occupied by the various formations was obtained during our hasty trip aloug the crest, and no difficulty was ex- perienced in coloring the geological map. The formations represented are mainly Cretaceous and Tertiary, the outcrops of Jurassic and Tri- assic being limited to a narrow belt along the course of Grand River. GRAND RIVER VALLEY. Following the Uncompahgre River northward, we find the broad val- ley in which it is located extending northwestward along the Gunnison and becoming the Grand River Valley below the mouth of the Gunni- son. It keeps a northwesterly course as far as Salt Creek. It then curves around to the southwest, following the course of Grand River, which curves around the northern end of the Uncompahgre Plateau. Beyond Muddy Creek the valley extends westward toward Green River. The total length of the valley following the general course of the river is about 75 miles. Its width opposite the mouth of the Gunnison is 9 miles. On Salt Creek it is 15 miles, and on Muddy Creek about 20 miles. The valley is nearly flat, there being a slight slope from the foot of the cliffs toward the river, and a still smaller slope toward the cliffs from the edge of the low hogback ridge bordering the river. A line of sta- * tions was made on this ridge. The valley is for the most part a desert, covered with a sparse growth of stunted sage-brush, which grows in a stiff alkaline soil made from the débris that is washed from the Book Cliffs. Along Grand River in the bottcm-land there are groves of cot- tonwood. A portion of the valley between the Little Book Cliffs and Salt Creek may be reclaimed by irrigation from Grand River. Beyond Salt Creek the level is too high above that of the river, which is in cation, to be available for agricultural purposes by irrigation. West of Muddy Creek the country rises into the divide between Grand and Green Riv- ers. The streams flowing from the cliffs to Grand River have cut deep 170 PEALE. ] AREA B—GRAND RIVER VALLEY. 171 arroyas or gullies in the soft soil. Salt Creek was the only one that car- ried any water when we crossed them. Desert Creek had asmall stream at the edge of the valley close to the foot of the cliffs, but the water, which was alkaline, soon disappeared. The formation forming the floor of the valley is the Middle Cretaceous or Colorado group, the dip of the beds being away from the river. Between the mouth of the Gunnison and Station 4 a wide alkali flat ex- tends from the foot of the Little Book Cliffs to Grand River. The latter stream comes from a deep cation (named Hogback Caiion) cut through the Little Book Cliffs, and flows almost directly west across Grand River Valley nearly at right angles to its course. On the south side of the river, the shales of the Colorado group are seen dipping 2° or 3° in the bluff, which is about 200 feet high. Atter the Gunnison joins the Grand the latter takes the course fol- lowed by the former above its mouth, and hugs the lower or southern side of the valley. South of the river is a low. hogback ridge of Dakota sandstones, dipping toward the northeast. On these sandstones rest remnants of the shales. The Dakota group crosses to the north side southwest of Station 4, at the point where the wagon-road leaves the river, and soon rises into a ridge of about 300 feet, on which Station 5 was located. - Station 4 was on a remnant of a former level of the valley, a yellow- topped butte underlaid by black argillaceous shales (probably Creta- ceous No. 2). Station No. 5 was on ihe edge of the cafion of the Grand. The river is in the upper part of the Red Beds, above which is the following sec- tion: ° Base. Feet. 1. White sandstones with thin bands of limestone 80 Par Greenish isiileswees << 2-6 secs eee cece melee a8 pe et we ey WV Hite SAMOSUOMESH ee ce cs + eltja.c ie a4. -Telomegue wjf ec oie eae Beers cx lel dee 71 4, Variegated shales and marls reddish and ereenish.. ; .Aeeiee-.. a 70 5. Yellowish white sandstone, rather massive...... Shperacasébecs 88 309 The thicknesses were measured by angles, taken with the gradienter. Layers Nos. 4 and 5, and perhaps No. 3, belong to the Dakota group, while the remainder of the section is referable to the Jurassic, the de- crease in thickness from that in the southern area being probably due to the presence in this region of limestones. Station 6 was located on a mesa of Dakota sandstones. The dip here is not great, although it increases a little as we go north from the Station, and the sandstones disappear beneath the Colorado shales. Salt Creek flows into the Grand at the head of the bend. From this bend to Station 8 the river is in a narrow cafion cut in the Red Beds. These are seen on the south side of the river rising to the south in the Uncompahgre Plateau. Opposite Station 7 several buttes are seen which have cappings of Jurassic shales. On the north side of the river the Jurassic forms most of the surface, although there is one area be- tween Stations 7 and 8 where it has been removed. The following sec- tion was obtained here: Top. . Feet. 1. Massive sandstone, general paler light red, white on top....-... 150 2. Red laminated sandstones and shales... .......22---0 22+ sees: 100 3. Massive sandstone, deep red in places and light red in others... 200 = ; 172 REPORT UNITED STATES GEOLOGICAL SURVEY. On the south side of the river the upper layers appear to have been eroded away, not showing until the mesas, five or six miles south of the river, are reached. The cation of the Grand appears to be impassable, and the road makes a detour around it. It is thirty miles from where the road leaves the river, above Station 5, to the point where it touches it again, below Sta- tion 8. The gullies crossed in this distance are all dry, with the excep- tion of Salt Creek, the water of which is alkaline. Although dry, these gullies are deep, especially between Stations 7 and 8. The following is the section at Station 8: Top. 1. Massive yellowish sandstones with faint impressions of pees Ba 5 Se ER RARE 3, CAMS Bese Be TANS OF 3 200 feet. . White marls and reddish sandstones............--.- 3, Dark-colored hard sandstones, with a layer at the t eel containing modules of jasper see-5).-. -- = 2. 22a eee 4, Variegated marls..... Mes 3 6 iC RET See lo aco 6 360 feet. 5. Greenish marls and sandstones with thin bands of lime- | SONG, Aho WS WHR hie Seas eae tcs-o csdaeeeda adoccoassous \ 6. Massive red sandstones (top of Trias?)......... gs heise MING tet c's. Loves ilevateve CRMEREP ISI Cs sc -ccls cuocateretaneterelsiene neat 510 feet. -It is difficult here, as at the other localities, to draw the line between the base of the Dakota group and the top of the Jurassic. Between Station 7 and Station 8 is a kind of basin of Jurassic shales, the stations being located on two points or tongues of the Da- kota sandstone. North of the hogback ridge of Dakota sandstone the shales form low bluffs, and between these and the foot of the Book Cliffs the surface is diversified by buttes and mesas eroded from the shales. The Dakota sandstones dip toward the northwest 3°-5°. Bitter Water Creek joins the Grand below Station 8; and just below the mouth of the creek, the river enters a cafion in the Red Beds. This canon is 500 or 600 feet in depth at its head, and this probably increases as the river is followed. From the head of the cafion to the Horse-shoe Bend, the Red Beds outcrop on both sides of the river. Station 9 was located on a Jurassic- capped butte on the north, or rather west side of the river, for the Grand here is flowing but a few degrees west of south. On the east side its tributaries cut profound cafions in the Red Beds, and at their sources may even expose the underlying granitic rocks. At Horse-shoe Bend the valley becomes more open, and below the bend the river flows from the Red Beds into the Jurassic shales. Beiow the mouth of Granite Creek the Grand makes a right-angled bend and flows to the southwest, cutting across the hogback ridge into a syncli- nal basin of Cretaceous shales. The strike of the Dakota group is at right angles to the course of the river, and just above the mouth of the Rio Dolores we find the Grand again cutting across the Dakota group at right angles to its strike. The synclinal depression between the Dolores, Granite Creek, and Grand River is the result of two folds meeting, viz: that of the northern end of the Uncompahgre Plateau, and the fold that marks the western edge of the same plateau farther south. This latter fold, with its axis slightly changed (%. ¢., more to the west- ward), continues from the Grand to Green River. A line of hogbacks, capped with the Dakota sandstones, is seen stretching to the westward be PEALE. ] AREA B—GRAND RIVER VALLEY-—BOOK @LIFFS. Jurhoie 49 from the Grand at the mouth of Muddy Creek. South of this is the Dome Plateau, named from the domed shape of the country. From the foot of the hogbacks there is a gradual swell, covered for some distance with a portion of the Jurassic. This, however, soon dis- appears, and the upper part of the Trias (?) forms the surface, reaching to the edge of the cliffs overlooking the Valle Colorado of Grand River. A section of the beds in these clifts at station 12 was given in the Report for 1875, p. 83. ~In the western part of Grand River Valley there are three streams, Muddy, Alkali, and Desert Creeks, rising in the Book Cliffs. The names were given as an indication of the kind of country through which they flow. Muddy Creek rises in the cliffs outside of the district. Like the others in Grand River Valley, the course of this stream can be traced by the line of sage-brush along its gulley. In the cliffs it probably has running water, and near its mouth we saw several pools of alkaline water. Alkali Creek we found entirely destitute of water, and it is probably only in the spring that it is a running stream, The bed of Desert Creek contained a trickling stream at the entrance to the cliffs, but it soon dis- appeared in the clayey deposits of the valley. On the way across the valley to the exit of Desert Creek, we crossed a low mesa about half way from the Grand to the cliffs. This mesa, not a hundred feet high, is capped with a sandstone which had a dip of 1° or 2° toward the cliffs. Grand River Valley is a valley of erosion determined first, perhaps, by the fold resulting from the upheaval of the Uncompahgre Plateau. An immense amount of material must have been removed to form the trough that we now see extending along the Uncompahgre, Gunnison, and Grand Rivers to the Green. We leave the Grand just as it enters the great callon-country so characteristic of the great Colorado River of the West. As has already been stated, the valley is not adapted for agricultural purposes, and much less for grazing, unless there should be a change of climate. Traces of -a poor quality of coal are found at several places in the sandstones at the summit-of the hogbacks along the Grand, but it is of no economic importance. Gypsum is found in the Jurassic shales, and also in the Boloved Cretaceous, but as far as = Beet not in beds, nor as large deposits. ROAN OR BOOK CLIFFS. The cliffs that overlook the Grand River Valley are divided into two portions, the Roan or Book Cliffs, overlooking the western part, and the Little Book Cliffs, overlooking the eastern part, extending from Hog- back Cation of Grand River to Salt Creek. The name Roan is given on account of the color, and the name Book Cliffs from the resemblance of their edges to those of a bound book. The summit of the cliffs forms the southern edge of the Roan or Book Plateau, which extends north- ward, forming the district investigated by Dr. Endlich. In this direc. Lion the Streams flow in the direction of the dip of the rocks, and the country is not so rugged as that on the south. North of the bend of Grand River is the basin drained by Salt Creek, which has its sources about 16 or 18 miles north of the northern edge of Grand River Valley, while the other streams have a much shorter course in the cliffs. The _ edge of the cliffs is the divide between the drainage of Grand River and that which flows to White River. From Bitter-water Creek this divide has a nearly due east and west direction until the head of the first 174 REPORT UNITED STATES GEOLOGICAL SURVEY. branch of West Salt Creek is reached, when an abrupt turn to the’ northeast is made. At the head of West Salt Creek the course is some what winding between the branches of that creek and those of the White River streams. The plateau character so noticeable farther west: is lost here. The general direction of the divide is east and west to the head of Roan Creek. East of Roan Creek the plateau character again prevails, especially along Grand River, as shown in Fig. 2, Plate X (a sketch of the cliffs and plateau on the north side of the Grand from Roa — Creek to Cactus Valley, made by Mr. Holmes). Thedip of the strata here is to the northward. Between Salt Creek, Roan Creek, and the Littl Book Cliffs the country is considerably broken up. The drainage is generally to the east, and remnants of the plateau are left as long tongue- - like mesas between the branches of Roan Creek. The surface rocks on the plateaus everywhere throughout this region are the white shales of the Green River group of Tertiary. Between Desert Creek and Bitter-water Creek, the summit of the cliffs is about 12 miles from the edge of Green River Valley. The intervening country is very rugged. Spurs extend southward from the cliffs between the streams. These spurs are composed mainly of Wahsatch beds, which, toward the west, are composed of sandstones, generally white in color, but with layers of a pink color. : We reached the summit of the cliffs by following an old and rough Indian trail that led up Desert Creek. This part of the cliffs was out- side of the district, but it presented the only means of access to the pla- teau, which here is 3,787 feet above the valley. At the entrance of the creek to the valley there are low hogbacks, in which the beds dip about 6° toward the cliffs. The general dip appears to be a little east of narth, and this becomes more easterly as we follow the cliffs to the westward. The following section was made at the exit of Desert Creek, the thiek- ness being estimated : shales and sandstones .......-..--...---. 4, 000 11. Greenish laminated shales and white sand- Green River stones and shales. Section. Base. Feet. Colorado .. 1. Colorado shales about....... beyeisteleror pee aysicas 200 Di SANS UOTIG pe rae i! di cii0'e < ia.cpa vars ai vies Hida Suave ie eialate (ae 75 3. Shales with lignite band ....... .-.......... 300 Al ‘Sands tome aie ois e's, - oheiej =< ihc abbeys ey eae 50 oxenEL MS) 2 Aa: Ales yc 50 Ns tei ler talai > o'sie es hare ee ee ana ee | 1G DS andstones see tis ws eces alow tien se eee 25 | 7. Shales with lignite band...... Be ae, 15 (48a) SandistOmes): pis sei. ss. iu). este epee en 25 Laramie?... 9. Massive sandstones with thin bands of shales. 600 ( 10. Heavy bands of white and yellowish sand- Wabhsatch ? . { stones with interlaminated red and reddish l Bed 1 represents only a portion of the Colorado group. The sandstones 2 and 4 form escarpments facing the valley, As No. 4is traced up the creek, it is seen to thin out as it sinks Into the hills beneath the upper beds. Instead of one band of sandstone there are several, and the line between 4 and 5 becomes very indefinite. This we find to be the case very frequently in this region. A band of Sand stone may be very persistent for a long distance, and then split into several layers and perhaps disappear. The line between the Laramie group and the Fox Hills is especially indistinct. The time at our dis posal did not permit of careful search for fossils. } My NL oan . suse ne Rte bel, AID cd Canty 1h ik, a, San Miguel Plateaw. _ 0.b,b. ,Naturtta Creek. i : J. 5. Geological Survey.. eee eee ddd, Pio Dolores. a aye, ox Fe FLL. Basin Plateaw. ACA Gypsum Valley. “hae ek "4 | VIEW OF THE SAN MIGUH | } | aI = Eee aie a a, «, a, West end of Cactus Valter. ce, White Mountain. d,d,d, Carton of Roan | Ahh, Norther< Spurs from Batllement Mesa. VIEW OF THE Rom “OR BOOK CLIFFS ON GRAND RIVER 6,,b, Valley of Grand River. e, e, e, Canon of Parachute Creek. ff, tf. ftoan LONER FIG 2- EEE aii ee iit, Island Mesa. kkk, ,Muache Creek 0 Sterra la Sal. PLATEAU FROM LONE CONE. | FIG, 1. ih, Sawcer Valley. mmm, Uncom pahgre Plateaw. 0. Grand | IGG. Wahsatch Variegated Bers. 4000.4 Colorade Shales, Cretaceous. VIEW OF THE LITTLE B - Tertiary. ; capped with Green Fiver Tertiar ¢, Laramie Post Cretaceous. poK CLIFFS £§ : : # a é a Sey EN } . : ) e eae = ——<$—<——— { AREA B—BOOK CLIFFS. 175 is marked No. 11 are undoubtedly the Green River group of “ary, as fossils were obtained from the beds farther east. The ‘veca them and the Wahsatch (No. 10 of the section) cannot be *\) Cvawn in the western part of the cliffs, as the variegated charac- ' \7ahsatch group noticed farther east is here almost lost. ‘on 19 the summit is 3,400 feet above the valley. Between » \9 and 21, the plateau character is well preserved. The streams »*). do not cafion very rapidly and the angle of dip in the strata 104°, Grass and sage-brush grow everywhere on the plateau. verlooking Grand River Valley are composed of sandstones ‘minated greenish shales with spurs projecting southward iD like faces on the west side, while the eastern slopes are more snd grassed over. »© head of the creek, flowing northwest from Station 21, a num- »altum springs were found. They are really in the district ) Dr. Endlich’s party, but as they were visited by us, I insert “o}ption: These springs are found in two cafions, marked a and o° area B (Plate XI). On the north side of canon a a space ot square is covered with the hardened asphaltum, and a line material leads to the crevice above, from which it came. ‘eit early on a cool morning and no flow was noticed. Near », however, the tar was soft. On the opposite side of the caton spot was noticed, and farther down the canon four or five more. um appeared to come from‘under a steel-gray sandstone, ‘ich is an oolitic limestone. In some places the latter ap- clude irregular masses of limestone. Cation 0 was tributary | on the east side contained an area of about 50 square feet on ‘i.e hardened asphaltum formed the surface. Several points were ‘bere it oozed from the side of the cafion, but the rocks were -exposed. It, however, is at about the same level as those in in Ganon. _saipbur springs were noted in connection with the asphaltum. first detected by their odor. The water flowing over the ied it with sulphur. An oily substance was noted on the { the water. The temperatures were 45° F. and 47° F., while at 55° F. The time was 9 a.m. The discovery of these « due to Mr. J. E. Mushback, of our party. Others of the _ the same region probably have similar springs, and Dr. sotes the occurrence of asphaltum farther north, which is prob- onneeted in some way with this locality. The subject will be dis- is report. Stations 21 and 23 the divide is narrow, in some places ely room enough for the trail. The cafions on both sides are | j6is often difficult to find a way of descent. An oolitic lime- uad all along the divide, and also fine green shales, that are ‘gillaceous. water Fork appears to occupy a slight synclinal depression + of Station 23. On the west side of the stream there is a dip « north, and on the east side the beds dip a few degrees north -ion lying between Stations 25 and 26 and the edge of Grand ailey was not visited, but simply seen from the stations. The er shales continue to form the surface-rocks on the highest )) the variegated Wahsatch beds showing in the canons. coaching Grand River Valley, we find the sandstones of the 176 REPORT UNITED STATES GEOLOGICAL SURVE: Laramie group appearing, and below them the shales and of the Fox Hills Cretaceous. We left the plateau at the head of Roan Creek, and fc.) > stream to Grand River. Where we descended, the cliffs ». 1,400 feet high. This is just east of Station 27. The strata © horizontal, and belong to the Green River group. A sho” down the stream we reached the Wahsatch beds, which c, outcrop along the creek almost to its mouth. The variegatc of these beds is very marked in this region. There are slight evidences of an anticlinal fold in the Wa in the bottom of the valley. In the cliffs the Green Rivi ‘pears to be horizontal, and there must therefore be either an © ability between the two groups or erosion has removed tha the Green River group which was affected by the fold. Ere: o obscured the beds in the valley that it is difficult to determi - conditions. That there was a fold I think is evident, and » © | hills bordering the creek on the upper part of its course, for: anticlinal, the creek occupying the axis of the fold. This fe determined the course of the creek. As we go down the str appears to die out. AS we approach Grand River a series of massive and lam ») °: stones appears beneath the Wahsatch group. South of W ain these sandstones form bluffs of 400 to 500 feet faein: They probably represent the upper part of the Laramie grou: ing up the river these sandstones soon disappear, and tl. Wahsatch beds also sink for a short distance, but soon rise continue almost horizontal. What dip there is appears 1 the north. The white and yellow beds of the Green Rive1 cliffs at the summit of the bluff, while the underlying soft beds weather in their characteristic slopes. This is well sh 2, Plate X (a sketch of the Roan Cliffs on Grand River, 1 Holmes}, Between Parachute Creek and Cactus Valley the Wahsate) be the characteristic weathering of Bad Lands into columns Along the river there are well-marked terraces cut in the so the south side these terraces are covered with bowlders o/ have been washed from the Battlement mesa. I did not n: the north side. The steepness of the cliffs on the north sid: deep gullies to be cut by the small branches of the Grant on the south side are more rounded, and the stream-beds mic |: depth. In Cactus Valley we found the variegated beds formin; facing the river, and low hogbacks inclining from the Gran’ Range. This, however, lies in Dr. Endlich’s district, | described by him. The only portion of the district rema.» «2 deseribed is the Little Book Cliffs, through which Grane |.» its hogback canon from the mouth of Plateau Creek to Gi) Valley. LITTLE BOOK CLIFFS. The Little Book Cliffs extend from Grand River north® °<')) 3: Hast Salt Creek, a distance of some thirty miles. Fig. gives a view of the cliffs as seen from the south side of the € +21 cliffs are about 1,800 feet in average height. Near the Grind || lowing is the section (point ¢ ? in Fig. 3, Plate X). The thi measured by angles taken with the gradienter from a ste’. south side of the Grand. Oe ee ns SY . Fiate XI. lon on = U. S. Geological Survey. ww WAY AG Ls g Yip YUY fA “yy Gy YY; VAS VEY, mA, I 7 ee WD HPS dey, aad Sy Il | Hal] — Legend — Zi] Green Fiver. ) WM Wahsaten. NN KV Laramie. Post-Cr ~ gar == vox Hills. - d Hip ut as Vea fi SA | Colorado. | SHOWING THE GEOLOGY OF [- é hee | E== 1 ower " ie ce = : [i elaccous. Cr AND THE BOOK CLIFF PEALE. AERA B—LITTLE BOOK CLIFFS. 1% Section. Base. eet. Upper part of 1. Black and yellow shales, with lime- S00 _ Colcrado Cretaceous. { SOMOS 2 ak he ee pees CMe wes reek a aes i ( 2. Yellow sandstone, forming an indis- ) tInctyescarpment 42) 221s 22) 5 3. Yellow shales and sandstones, with + 710 fox Hills Cretaceous. { a band of wom near the upper | Pathe Meee ss SA VRE aga entae AGH SS ATL OSU OMEN ne ci sue sors ee age eye aka, Forfa bel tel OYE IS ey ee ci Nala Ce Leen a 380 Laramie ? 6. Pinkish sandstones ..-...-.--..... NGG AMPA coo A 16 SSR Pc? ee I Naki ah i a 1, 890 These beds dip to the northeast at an angle of about 8°. As we trace layer No. 2 toward the northwest along the cliffs it becomes somewhat indistinet. The beds also, as seen from Station 4, appear to sink, and the Laramie sandstones undoubtedly form the escarpment at the sum- mit of the cliffs. Still farther along, the beds rise again. Kast of Station 4 and back of the first line of cliffs a second Lie. is voted, in which the beds are the variegated shales and sandstones of the Wahsatch Group. The sketch in Vig. 3, Plate X, is taken from too _ low a point to show this line of cliffs. As we approach Hast Salt Creek the Wahsatch beds come to the front, continuing westward from a low _ tange of hil!s which represent a portion of the Roan Cliffs. They do _ hot remain in front long, but retreat and form the base of a line of cliffs . _ which extend southwest from Station 28. The latter marks the angle of ou 4 bend, a line of cliffs extending southeast from the station. Station _ 30 is located on the same line. ‘These cliffs are capped with Green River ( Tertiary, and are about a thousand feet higher than the outer cliffs, _ irom which they are distant about six miles. _ The map of Area B will enable the reader to obtain a clearer idea of he extent of the cliffs and the areas occupied by the various formations epresented in them. There is room through all this region for much detailed work which he lateness of the season and small amount of time at our disposal orevented us from accomplishing. 124 CHAPTER IV. Pearce FORMATIONS OF THE GRAND RIVER DISTRICT. In this chapter I shall endeavor to present in as concise a manner as possible the various facts observed in regard to each formation. The following list represents those coming under observation during the season: Upper Carboniferous. Triassic ? Jurassic. ( Lower Dakota group } Upper Dakota group. Cretaceousacee.. fs. 6 5 2.e2 4 Colorado group. { Fox Hills group. Post-Cretaceous........... i : Wahsatch group. Tertiary .----.--.-.-----.. Green River group. b Post-Tertiary and recent. fh On the south side of Grand River (in Area B) there are a few isolated fy) exposures of granitic rock. These were not visited this season, but were referred to in the report for 1875 (p. 66). Neither Silurian nor Devonian a was recognized in either district. Area A is composed almost entirely of Cretaceous strata, while Area B is about equally divided between the Cretaceous and the Tertiary. Area A.—A reference to the accompanying map (Plate VIII) will show the areas in which rocks of the Upper Carboniferous formation are ex- posed. The line separating them from the Trias has been arbitrarily fixed, as the soft sandstones and gypsiferous shales are much like the beds forming the base of the Trias. This is what would naturally be expected when it is remembered that the deposition of the sediments in this region was probably continuous, and the materials entering into their compo- sition derived from the same sources. Both the localities (in Paradox Valley and in the Canon of the Dolores) noted on the map were seen from a distance, and therefore no details respecting them can be pre- sented. They are probably similar to the rocks of the same age showing farther north and west, which were described in the Report for 1875 ({p. 71). Area B.—The map of this area shows a small outcrop of Upper Car- boniferous on Grand River below the mouth of the Rio Dolores. It is unimportant, and was referred to in the Report for 1875. } UPPER CARBONIFEROUS. | JURA-TRIAS. The line separating the Triassic from the Jurassic is almost as obscure as that separating the Carboniferous from the Triassic. The line has 178 PEALE.] GEOLOGICAL FORMATIONS—JURA-TRIAS. 179 been drawn lithologically, the massive red sandstone being consid- ered the top of the Triassic. The confiicting evidence presented by the organic remains found in the Jurassic and Triassic beds of the West has been referred to in previous reports (1874 and 1875). Area A.—Hardly more than 60 square miles of the area are covered with the red sandstones of the Trias. A massive red sandstone, becom- ing lighter colored toward the top, cross stratified at many places, is the prevailing characteristic rock. Its thickness is from 500 to 1,000 feet. The beds become lanimated below, and gypsiferous, passing gradually into the Upper Carboniferous. The variegated sandstone shales that lie above, have been colored on the map to represent the Jurassic. The general character is the same as previously described—soft greenish and gray argillaceous and arenaceous shales and marls near the top, passing into the Lower Dakota sandstone, and dull, reddish laminated sandstones and shales at the base. The limestones that occur farther north near the base appear to be absent here. The area occupied is about 80 square miles. The Rio San Miguel has an outcrop of Jurassic at the bottom of its cafion walls almost its entire length. A few of its tributaries also cut deep enough to expose the Jura. The mesa northeast of Paradox Valley is capped with the reddish shales that lie at the base of the for- mation. This is also the case with the region included in the bend of the Dolores north of Island Mesa. The streams tributary to the Do- lores here cut into the Red Beds beneath. Ali about Island Mesa, Ju- rassic rocks are exposed, and the débris filling Gypsum Valley is from rocks of the same age. The structure of this region was described in Chapter II, and a study of the map and sections will make the descrip- tion more intelligible. Area B.—In Area B the Trias and Jura are found only along Grand River, the former principally on the south side, and the latter on the north. The lithological line separating them is much better defined than it isin Area A. The sandstones forming the upper part of the Red Beds are very massive, and the shaly beds just above contain thin layers of limestone. Below the massive sandstones come blood-red shales, fol- lowed by massive sandstones, generally of a deep-red color, although in many places the color fades to almost white. The thickness exposed is nearly 500 feet, which represents only a portion of the formation. In the Red and Variegated Beds the Grand cuts a caiion of varying height, but at no place does it exceed 1,000 feet. : The general section of the beds referred to the Jurassic is about as ollows: Base. | Feet. 1. White bands of sandstone with greenish marls and a few thin layers of cherty limestone at the base........-.-........--- 80 2. Variegated green and red sandstone shales and marls ...... 120 SOMO LEC SAMOS UOMO netomat era Riri ois opens caicscisareiaveye a/'s\g eunln aParehuies os } ¥ TO Galera esate gee loaner ilk ou Na cc. oS 200 The variegated character of the shales and marlsis much more marked at some localities than at others. At Station 10, near Horseshoe Bend of the Grand, they are rather brilliant in color, and gypsum seems to enter largely into their composition. From Alkali Creek to the Bend the Ju- rassic beds are seen as remnants capping isolated areas, and on tie Dome Plateau the lower portion of the same formation covers a consid- erable area south of the hogbacks that border the Grand River Vailey at this place. A reference to the map of Area B will give the best idea of the extent of the formation. 180 REPORT UNITED STATES GEOLOGICAL SURVEY. The line separating the Jurassic from the overlying Dakota is indef- inite. The discussion in regard to it will be found in the reports for 1875. CRETACEOUS. Area A.—Of the 1,000 square miles included in the area, about 850 are covered with rocks of Cretaceous age. Of this 850 square miles, about 70 have the Colorado group as the surface formation, the rest being mainly Dakota Group. The Dakota group for the most part is horizontal, and the conditions of the strata are very uniform. It forms the tops of the bluffs on all the cafons. It is a moderately compact, yellowish, silicious sandstone. Beneath are greenish shales and bands of sandstone. The latter have been referred to the Lower Dakota. The total thickness is about 600 or 100 feet, about 200 feet being referable to the upper Dakota. The massive sandstone at the top in most places appears to have formed a barrier to erosion, the overlying shales having been swept away. Remnants are stiil seen in Basin Plateau, and in the angle of the San Miguel opposite the mouth of Naturita Creek. Farther south, however, near the slopes of Lone Cone, the shales are more persistent, forming mesas extending northward. The eruption of the trachytic masses seems to have had some influence in protecting them in this locality. These remarks are merely intended to supplement the Re- port for 1875. Area B.—As already stated, the whole of Grand River Valley, and a considerable portion of the cliffs bordering it, are occupied by beds of Cretaceous age. Of this, the Colorado shales occupy over 1,000 square miles in the space between the cliffs and the hogbacks on Grand River. They are so eroded and covered by débris that ‘but little can be predi- cated of them. They form low bluffs back of the hogbacks. The total thickness of the group is about 1,500 feet. The beds consist of calea- reous and argillaceous shales with sandstone and limestone bands. The sandstone of the Dakota group here, as at so many other locali- ties, seems to have presented a decided resistance to erosion, and as a result we find it forming the summit of the hogbacks. It is somewhat difficult to determine the exact thickness of the Dakota group, as we do not know exactly what its lower limit is. We find the same difficulty in dividing the Dakota Cretaceous from the Jurassic that is always found where the deposition of sediments has been continuous from age to age. The following is the average section of the Dakota group in the hog- backs on Grand River: Top. Thickness in feet. 1. Massive yellow, siliceous sandstone, with faint impressions vat dicotyledonous stems, at some localities.-..-.. aes ae { 90-200 . Variegated marls, with bands of reddish sandstones. These . Gea ave the characteristic weathering of Bad Lands .... 3. Dark-colored sandstones, with bands of marls and shales. Near the base is a layer containing nodules in which there 50-100 AROMAS POMS) (2S oPhe este yeta|aials didiel eaeeahe alee Aare eraeaeee Ie cares Total thickness ..... TPE ee aD ae ea See Rg sah 140-300 The greatest thickness is noted as we go to the southwest, beyond the bend of the Grand. / PEALE.] GEOLOGICAL FORMATIONS—POST-CRETACEOUS. 181 Bed No. 3, and a portion of No. 2, I have called the Lower Dakota, the name suggested by Mr. Holmes. (Report 1875, p. 261; see also p. 88 of same report.) Above the Colorado shales, in the Book Cliffs, is a bed of sandstone that forms a well marked escarpment. This bed probably represents the base of the Fox Hills group. Above it are shales and sandstones as follows: Feet. ie Sandstonessamed shales! 20 hci. as sp bees ercriers 2. Sa cle eee > eos GOOD 2. Massive sandstones, with a few bands of shaly sandstones..... 600 I am inclined to consider a part, if not the whole, of layer No. 2 as belonging to the Laramie group; but, as already stated, the line between the two formations cannot be definitely drawn in the absence of fossils. ‘In the Little Book Cliffs the sandstones and shales referable to the Fox Hills group are about 1,000 feet in thickness. (See section p. 177, Chap. III.) Professor White had good exposures of the Fox Hills group farther north, and to his reports the reader is referred for details, especially those of a paleontological nature. At no point in the district did I ob- tain any fossils from its strata. POST-CRETACEOUS. Dr. Hayden first pointed out the transitional character of the sand- stones that lie between the marine beds of the Cretaceous and the fresh- water beds of the Tertiary.* The paleontological evidence has been conflicting, those studying the fossil flora differing from vertebrate paleontologists. As Dr. White has ably shown in his comparison of the Cenozoic and Mesozoic groups, the testimony of invertebrate paleon- tology but confirms the position of Dr. Hayden.} For these transitional beds Dr. White has proposed the name Post-Cretaceous. The beds of the Laramie group are the ones so designated. They consist mainly of sandstones. In Area A no beds of Post-Cretaceous age were noted; sol pass to Area B.—In the western part of this district there is no distinet litho- logical line separating the Laramie group from the Fox Hills below nor from the Wahsatch beds above. In passing up through the sand- stones, it is noticed that they have a tendency to separate into massive bands, between which reddish shales or laminated sandstones appear. As we ascend still higher, they pass insensibly into the shales of the Green River Group. On Grand River, near the mouth of Roan Creek, there are bluffs in which about 500 feet. of sandstones outcrop. These sandstones are probably the upper part of the Laramie group, the variegated beds just above representing the Wahsatch group. In the Grand Hogback Range, just east of Cactus Valley, the follow- _ing fossil plants were obtained, the identification being by Professor Lesquereux: Ficus auriculata, Lesqx. Ficus planicostata, Lesqx. Ficus planicostata var. Goldiana, Lesqx. Diospiros crassinervis, Lesqx. Salix ——? Cinnamomum, fragment. * Report U.S. Geol. Survey, 1870, pp. 165-166. tBulletin No. 3, vol. iii, pp. 624-629. 182 REPORT UNITED STATES GEOLOGICAL SURVEY. In a letter, Professor Lesquereux says ‘‘all” these leaves “are char- acteristic of the Lower Lignitic or of the Lower Hocene, and have been found at Point of Rocks, Black Butte, and Golden, especially, the most abundant fragment being of Ficus planicostata, and its variety Goldiana. These plants were obtained from a sandstone at the very top of the group which I have referred to, the Laramie group; and this bed may perhaps be referred in the future to the Wahsatch group. TERTIARY. The Tertiary strata cover larger proportionate areas in the northern district (Area B) than any other. The accompanying map (Plate’X1) will give the best idea of their extent. In Area A there are no beds referable to the Tertiary. The Tertiary strata capping the Book Cliffs extend northward into Dr. Endlich and Dr. White’s districts, dipping gently away from the edge of the cliffs. The Green River group forms the summit as an escarpment, in which the beds weather of a white color, from which the variegated beds beneath are distinctly separable in the eastern portion of the area. Toward the west, however, the distinction is not well marked, as the Wahsatch beds consist of harder sandstones and the variegated character is almost entirely lost. i The following table will show at a glance the differences at the different points. The third section was made in 1874, but is in the same neigh- borhood : 183 TABLE OF TERTIARY. GEOLOGICAL FORMATIONS PEALE. ] : *IOAINT PUBL U0 UHI yooAH NveyVI[q UO JOyZOIN) A[quqoad ore spoq 949 Ysnogye ‘sassauyorq? 9} ul Aourdososip oy} OZ qunodoe sdevty -Jod [JIM SIQT, ‘JojaMoIvq ploreUR UL WIA poInsvom Apred puv poyeMyse APIVd G1 SosseU HOI, OY} YOO nvoye[q uO ‘JOJUIIPLIS OY} TIM UdyZv sopsue Aq polASvoUT OIOA\ SOSSOUYOIG) 9} UlLJUNOP 71 AA 7V OpVUl UOTOS ON} UT (OE in IRS aR eS ae ey ee Be Oia ee ede 9u1098 -puaes oatssum Avis-YstMoljod puv ystppoy | 4100S 27 She SS Pectin’: SOU0ISPULS PO}LUIUIL] puL OAISseTY | ONO'E |°-~> Souojspues Avis pozVULUIT] puL AISSLTT "QUULDLDT. UU LD'T OUULDLO'T VR URS pee 1 gg se | ere eee ee a a SSOUOTGY [CIOL CEG Ee eee wel cae nee a Sieg 2k SSOTHOTGY TLIO, QOS CRN Sy saee soa eng aoe SSOU OY} TeIOT, OO DEI alee os | eee eee Sens ees Sieios denies §[TeUL Gt |) ooeesse ioe poeoljou ov OTOISpUTS JO Spueq osLq O47 YSIn{q pus ‘aesrs ‘youl “so[eys 0078 IVON ‘“snosievoyvo puv snosogyisdAs ov PULLS PUL S[IvUL oSuBIO pue ‘needs ‘Avid Speq osoyT, ‘So[vys omoyspuRs puL SpIVUr ‘pey ‘“ouo}spureg “sp[Ivul pue sou0}s (ueeis pu ‘mo]jeA ‘pol) poyesorliva ‘70g -pues snodsosisdAs Moret pue ‘pos ‘egg AL °YDIDSYDAL "D7 DSYDAL (a eee ie ee nents Sereys e038 5 - 8¢‘@ |———— -pUvS PUL OTOJSpULS YSIppol poyecimMey aes. j= OG uilnseepae sce sesinesielsie: So[CYs pur souoyspueg Jo spuvq Aq pozvavdoes sou0yspuLs oAIssEyL GG pert eo Sine ans aga aa aie a ase inin ees SoTeYs sno 00g ‘Et |--77° FOTOISPULS JO Spurgq WTA ‘soyeys sno -O0U][[ [suv YSIMseIs PUL S9MOISpUUS OAISSE, -90U][ISIV PUB SHOSIvOTRO PoJeINPUL OFIT AA i { *YDIDSYD AL (Kim) fh |lopB POPE SSS Sh ono Ur Coace Scmacesnaeooa so]eys fey) jpeoeeadedooeca scarey onenesehosaagss gyro | 009 & Y[sitoeis pure selojspues pivy pue jos oy} jo do} 049 9% guomdavose oy} sur | |[°-""""""""" SOLS SNOSOL]|[Io1v poyviUpUt 0002 (es So[BYS Ystuoeis puv sAvpo poyeaunpuy -UW110} SO[VYS PUL SOUO}SOUTTT ‘Spoq YSTAOT[O A JIA. PU sSoTLyS poxvaimel ystueel4y 007 | °120T “LOURT UIILD 007 | "3007 “MAURY UIOLD yoo | | wad Waa.) “FLBT ‘10019 . “LLAT “UPRATNOTL “LL8T ‘SUMO. * NVIzVIq TO THOM JUOMO]IV JO Opis [NOS OITA Je JOATY puvzy uo spo uwe0y yoog 10 uvoy oy} Jo wotjzod m199sO AA [reany puvsy ivou ‘gq vory] “OPVAOJOD ULIISINYZLOAT WL DIV.NS hiwYyiay fo Wos.mdwop 184 ‘REPORT UNITED STATES GEOLOGICAL SURVEY. WAHSATCH GROUP. In the western part of Area B the Wahsatch group cannot be definitely separated from the overlying Green River nor from the underlying Laramie. I therefore pass to the eastern portion of the district. A belt of Wahsatch beds extends from Grand River up Roan Creek a little above the bend, southeast of Station 27. The creek appears to occupy the axis of an anticlinal fold in the variegated beds. The out- crop becomes thicker as we descend until the entire thickness is exposed. At the top are laminated sandstones and greenish shales. These may be the lower portion of the Green River group. Below are the variegated greenish, yellow, and red marls and shales, separated by bands of lami- nated sandstone. The latter are not persistent, but often entirely fade out. On Grand River I counted five separate bands, which varied in thickness. At one place they were 50 to 75 feet thick, and a short dis- tance beyond only 5 or 10 feet. Some of these sandstones are pink, others yellow or greenish, in tint. In most places the variegated beds weather into the columns, spires, and other forms so characteristic of Bad Lands. These beds are the same that in 1874 were referred to the Green River group, in which was ineluded the Wahsatch group (Report 1874, p. 156). From the beds on Plateau Creek the following vertebrate remains were obtained: Crocodilus, Emys, Trionyx, Pappichthys. In the Cactus Valley, a low mesa extends southward from the Grand Hogback Range east of Rifle Creek. In the bluff, ou the east side of this mesa, the following fossil plants were found: RAhamnus, species new, Aralia gracilis. Of these Professor Lesquereux says: ‘‘ No. 5 (the num- ber of the specimens) has two species only, a new species of Khamnus like R. Goldianus, Lesqx. (Lower Lignite), but with a somewhat different nervation, more like species of the Lower Miocene of Europe. Aralia (Araliopsis) gracilis, Lesqx., is a very fine species, as yet represented by one specimen only trom Bridger Pass. Again he says: ‘“‘Specimens No. 5 are Upper Eocene?” Similar beds, holding the same stratigraphical relation to the Green River Group as these, outcrop in Dr. White’s dis- trict. He will discuss the question of their-age more at length in con- nection with the evidence furnished by paleontology. GREEN RIVER GROUP. The white shales mark the beds of the Green River group all along the Book Cliffs. They consist of indurated, argillaceous, calcareous, and arenaceous shales. When broken, they are generally dark-colored inside. Toward the west therearelayersot green and white fissile shales. At Station 20 the summit of the cliffs is a yellow sandstone, and all along the divide in this neighborhood there is an oolitic limestone that comes in near the summit. At the Cliff Spring the shales contain fossils in at least two different layers. The following is the general section : Top. Feet. 1. Sandstones, limestones, and shales ........----. ---.------- + 40 2. Argillaceous shales, dark colored, containing fossils No. 1.. 3. Thin white shales, probably calcareous and argillaceous.. - 133 4. Dark argillaceous shales, containing fossils No. 2.......--. 5. White arenaceous and argillaceous shales to base of cliff. The angle of dip is about 4°, and the inclination is a little east of north. The fossils from layer 2 are—- Planera Ungeri, Heer. Planera longifolia, Lesqx. XT. mules. 16 Plate. XI. a a lis om Map in Plate br Lines of SeciPlate XL nurs of the Boo | (@SBORNE'S PROCESS) -LITH®. CO. N. ¥. AM. PHOTO ae ZI Wire iow re , Ge apa Ah ele he meee Tate et “i U8. Geological Survey. Plate. XI. 8 < Sas ‘ S : iss 8 N + ibs = < £ 88 S Ss S ' ae = Cr. Pi-ce - ance AT. ZA ii i ——— = ; = = i Sees CA CACAC AACA CURT, TaD T ies i= — i— —=—I—T Ic iE if I = if We, 10 ic - L a res CLA CL LAS ZACTBCAZACACACAA INTE. CAURE, = IE = SESE Te Seal siete — a io : I Section, /. Northern Spurs of the Book Plateav. x 8 _ ~ s Ss SI 2 S & : ALAGAACZACEO e CNEL EAE: g AZZ AT 2) CLA CHL a= 2A2EZAC2AZ2ACZAE GZ2ACD CZAR ia a Cea Ge g SS 8 SS Se SS a a 3 ee SS ste SS SS SS [ T = aa eae BEE ETS p é Fe & & : 8 S 8 Qs % BS ws ts .e go g é S = Ss 2 Grand. Fiver Valley. 3 : 8 Section, 2. 5 8 3 S 2 < g S Ss IN) iS} & Q TELLER 2 CILLA TET (DESL DA et STEELE. a LEE ed : Ge aoe ; eon et —= om Z MALELES: Ose ee Ze Grand Fiver Valley. Uncompahgre Plateau. Section, 3. os 2 rs alt 5SSSs| jae TOUR, im ao Green River. Wasatch. Post taceous Sa Cretaceous. mee Variegated eae — JSurassie. Laramie ,— €re et ‘Daketa ¥.D.Owen DEA n 0 7 n xs ETT n a ~ = Lit OLS 2 SIA SS BAAD ALS OI Cs CALI CSS SA,SIR LL, Tt TX LIF SLL SLL eee ELE LOLA ELLA UE Ie CDE KON apo V STAVE Letver. White Water. Gunnison event Mek, — = ————— — = LEA Z Z CLA KLEL, APA: Yatnnsie MSNA CAri irre ba tet ee Sa Se Gunnison Valley. ZZ 4 : : ZA Red Beds, — Friassic. Opper C arbonigferoa 9. Granite . WELLE De NEEKEL stirs m LA Grand Mesa. — Remarks.— hor lines of Sections 2and 8, see Map tr Plate XI, Sectiary lis om a tine Just North of the Miup in Plate XT. Horizontal Scale. ru Vertical Seal miles. 8 12 20000 to 1 inehv. 16 AM. PHOTO-LITHO, CO. N. ¥. (OSBOANE’S PROCESS) i Pn i¥ * 13 Bakgtoneateny tedienl Sui iP Mey 5 tne AT ee pane NAh + i ety Ve RTE, : esi Bg ee wameieione ee cae ng PEALE.]} GEOLOGICAL FORMATIONS—GREEN RIVER TERTIARY. 185 Myrica latiloba, Heer. Fraxinus predicta, Heer. Myrica acuminata, Ung. Sapindus angustifolia, Lesqx. Myrica Copeana, Lesqx. Spicifer buds of Equisetum. From layer No. 4 the following were obtained : Planera longifolia. Spicifer buds of Hquisetum. At camp 37, near Station 27, the cliffs were again found to be fossil- iferous. The following is the section : Top. 1. Limestone, white and crystalline shales. 2. Greenish-gray sandstone with fossils No. 4. 3. Dark argillaceous shales with fossils No. 3. These fossils are about 10 feet below No. 1. 4, White shales to base of cliffs. Fossils No. 3 are the following : Myrica latiloba, Heer. Myrica acuminata, Ung. Sapindus CAIUS NIE Lesqx. Sapindus flex affinis, ids Stem of Hquwisetum. Crushed feathers? or hairs. Fossils No. 4 are— Myrica latiloba, Heer. Myrica acuminata, Ung. Sapindus angustifolia. Myrica undulata, Lesqx. For these identitications I am indebted to the kindness of Professor Lesquereux, to whom the specimens were submitted. Professor Les- quereux says: ‘“‘All the specimens represented from No.1 to No. 4 show evidently the same formation, that of the Green River group, or Mio- cene, as it is represented at Elko Station, Middle, and especially South Park, &c. Ihave specimens of most of the species indicated in your table from the localities here named, Florissant, Castello Ranch, &c. The small cones, spicifer buds of Hquisetum, are very fine and new.” The following is a general section of the Green River group in the cliffs east of Station 27. It does not include the entire thickness, as a portion of the upper beds has been removed by erosion. Section. Top. Feet. 1. Indurated argillaceous, arenaceous, and calcareous shales, ; with thin bands of limestone near the top. These shales weather white, but when broken are generally dark inside. | 2. Rusty colored sandstones with interlaminated shales ....... + 1,600 3. Thin greenish argillaceous shales, with bands of laminated | BE SAMMSCOMC panne et ae nie 6/eis, siacie are et choices Sic Sie ehela Cray cla) sls e. | 4, Rusty laminated sandstones..............---. -.--s5se0e2- ) This thickness was measured with an aneroid barometer. The section at White Mountain is given in the table on p. 183. It is in bed No. 1, of the section just given, that fossils Nos. 3 and 4 were obtained. REPORT OF WILLIAM H. HOLMES. LETTER OF TRANSMITTAL. OFFICE UNITED STATES GEOLOGICAL AND GEOGRAPHICAL SURVEY, Washington, February 1, 1878. Sir: I have the honor herewith to transmit my report on the geology of the small area examined by me during the season of 18/76. Very respectfully, your obedient servant, WM. H. HOLMES. Dr. F. V. HAYDEN, United States Geologist in charge. 1&7 =i heat , pe ROSES 3) Line met h i ne sate wan " a bite liao tne atalaede 2 Ara aSeremh ys Soe EpMael era An aM eae) — HAsO QRa WA ov seas “As: > i a LM Me a Ty) TT | f if ni Wil fniuua AM. PHOTO-LITHO. CO.M.¥ (OSBORNES PROCESS) a, South—Nast point—trachyte. b, Abajo Peak, primary station —trachyte. c,c, Hagbacks of Lower Cretaceous Sandstones. d, ad, 2, Cretaceous Shales. Montexuma Caron in Joreqrouna—Cret, Sandstope. THE SIKRRA ABAJO-FROM THE EAST. Plate Xi amt NN | : ON i <2 49 Zee Zi SH ee aa Gi t ABAJO-FR Ss 2 a olth —Hast pont —" ¢ Lower Creta REPORT ON THE GEOLOGY OF THE SIERRA ABAJO AND WEST SAN MIGUEL MOUNTAINS. By W. H. HOLMES. In the summer of 1876 I accompanied Mr. Wilson, director of the primary triangulation, to the Sierra Abajo or Low Mountains of South- east Utah. We approached them from the east, by way of the old Spanish trail, which led us around the south base of the La Plata Moun- tains and across the Great Sage Plain. It was not difficult to recognize the various features of the country west of the south bend of the Rio Dolores by the descriptions of Dr. Newberry, recently published. Leav- ing the Dolores at the-point touched by the trail, we passed up to the south over the bluffs of the Dakota sandstones, and found smooth, monotonous traveling over the almost unbroken plain. Considerable areas of the fossil-bearing shales of the Middle Cretaceous were observed in localities subject to the least amount of drainage, but the main floor of the plain is composed of the Dakota sandstones. Ten miles out we came upon a shallow wash in which was a spring. A small band of Utes was encamped here, and on the west bank of the ravine extensive ruins were noticed. This is probably the Surouara of Dr. Newberry. At night we made camp in a pretty little valley about midway between the Dolores and the Sierra Abajo. At this place a small spring issues from the lower slope of the Cretaceous bluff, and affords water enough for a small party. On the following day we left the tortuous trail, which seemed to be leading northward toward the Sierra la Sal, and rode directly westward. Atter some 40 miles travel we struck the caiion of the Montezuma near its head, and, crossing this, encamped in the evening close under the east slope of the Sierra Abajo. In traveling 85 miles we had not changed altitude more than 500 feet, and had not varied 200 feet above or bélow the geologic horizon that separates the Middle and Lower Cretaceous strata. The floor of the plain is everywhere of the Lower Cretaceous sandstones, which have generally a gentle southern dip. Small areas of the shales remain on the less eroded districts. In no case do the stream-courses penetrate to the Red Beds. At the point of crossing, the Montezuma Caton is only 150 feet in depth, and the walls are composed at the top of about 40 feet of massive, yellowish sandstones, beneath which are soft sandstones and shales, mostly covered with débris. - The altitude at the crossing is 6,200 feet above sea-level. From the caiion, which runs north and south, a gentle slope of 9 or 10 miles leads up to the base of the steeper faces of the mountains. Thesketch (Plate XIII,) taken from theeast bank of the Montezuma Cation, will give a good idea of the general appearance of the eastern face of the group. There is nothing striking in the outlines of the mountains, and there is a total absence of the bold forms and naked rock-masses that characterize the larger groups to the east. We encamped at the base of the principal eastern spur, where we were unfortunately detained for three days by a rain and snow storm. On the fourth day, the 19th of September, we succeeded in making 189 190 REPORT UNITED STATES GEOLOGICAL SURVEY. the ascent of the main summit. A steep ridge, with steep, smooth sides, projects 4 or 5 miles to the east from.the main crest, up which we were able to ride to the highest point. This point is only slightly higher than a number of other summits to the west and north, and is by no means a marked peak; it is simply the highest point of a long east and west ridge. Here Mr. Wilson made the desired primary tri- - angulation station. We were unable, however, to build a monument, as a foot or more of snow obscured the trachytic shingle that abounds near the summit. The latitude of our station was determined to be 37° 50’, the longitude 109° 27’. It is therefore about 23 miles west of the Colorado line, and 58 miles north of the line of Arizona. The view from the summit is one of more than ordinary interest, since within the circle of vision there is much that has never passed beneath the explorer’s eye. To the eastward the view is only interrupted by the La Plata and San Juan Mountains, 100 miles away. In the south are the Sierra Carriso, in the west the Henry Mountains, and to the north the Sierra La Sal, all in plain view, yet outlining a circle nearly 150 miles in diameter, and including an area of 20,000 square miles. This vast area lies beneath us a silent desert, a plateau land cut by innumerable waterless caflons, and dotted with a thousand fancifully carved and brilliantly colored rocks. To the south lies the broad valley of the Rio San Juan, the delicate thread of green that lines its bank being barely visible through the notches eut by the deep side cafions.. Beneath us on the west, yet many miles away, is the Rio Colorado, its general course scarcely trace- able through the labarynth of cliffs and cafions. These two streams join in Utah, about 100 miles to the southwest. The lower course of the San Juan can be followed by the eye until it passes the north base of Navajo Mountain, a massive dome-shaped butte that lies a little to the southeast of the junction. In the angle between these streams there is a high red table-land, the Bear’s Ears Plateau, which seems to be pretty nearly separated from the surrounding table-lands. It seems to extend to the San Juan on the south, and far out toward the Colorado on the west, while the deep drainage courses that extend north and south from the Sierra Abajo sever it from the Great Sage Plain. It is also severed from the Abajo by a low depression produced by the meet- ing of the northern and southern drainage along the west base of the Abajo group. As far as the eye can reach, the strata, excepting on the eastern border, are nearly horizontal, and there are only a few low buttes that rise above the general level of the plateau. Of these buttes the two known by the Mexicans as Orejos Oso, and two or three inferior ones a few miles further north are distinctly visible. From the interior of the plateau deep cafons open out to the San Juan on the south and the Colorado on the west, which show in their steep faces the brilliant colors of the lower Mesozoic formations. It is probable that the sur- face strata at least are of this age, but the Paleozoic rocks are doubt- less exposed in the cafions of the San Juan and Colorado, as well as in the deeper side canons. This triangular area comprises nearly 2,000 square miles, and is probably one of the most thoroughly barren districts ot the great Colorado basin. On the east the Bear’s Ears Plateau ends in a great monoclinal. fold, with the down-throw on the east. The Cretaceous floor of the Sage Plain extends westward to the line of this fold, and occupies about the same absolute horizon as the middle portion of the Triassic formations to the west. The throw of the fold would therefore be approximately 1,000 feet. Although the amount of displacement is so slight the fold is Sly ——<——— — = —— : : a WHA Se So ST Pa Ge B24) (TO ee = aime NED, alla w RAN = SSS SSS — LATTER WL eM a ee es ‘ 7 MW a é Fe Le = iN Wor \ oA a x Wy a YN Lg : Nifke wae Ne 1.2, North edge I Beurs Hars plateaw. e, e, Here. oie ott inh Peat (hea Pet ty re a bees Plate XIV. a z 2 a UN : jt = " ay x hp ¥ > HA ee eo, AE ZS - Bi Z Te Ki, Red Cli77s. L, Casa Colorado. mm. Great fold in Red Strata—JIuraTrias. n. Cold Spring Caufion. 0. Cahiow Pintiudo, 2,@, Western Group Abajo Mins trachyte. aa, North edge of Beurs Ears plated. e, e, Henry Mins, F% Probable line of Colorado Canon. 9, 9, Fed Clip. hh, Regior of brownish and gray sandstone and probably bad land. it, Red table lands IG Sterra La Sat. PP Escagment of the Lower GCretuceous Sandstones western b,5,.V Western . 7 Ph ee aR : _— . : 6.0, Northen», . a ule PANORAMA FROM ABAJO PEAK, LOOKING NORTH AND WEST. , 2 See edge wr the Sage Pla | Aw. PHOTG-LITHO: CO, N-¥:(OBBORNE’S PROCESS) 4 stelle weenbtr ence pee = marge HOLMES] ABAJO MOUNTAINS. 191 easily traced by a number of monoclinal valleys that follow its axis — from the base of the Abaio group to the San Juan. The ridges that separate these valleys have smooth, sloping faces to the east, and one of them, which presents a continuous line of white or pinkish faces, can be traced south to the San Juan, and far beyond into Arizona. Macomb and Epsom Creeks on the north, and the Rio de Chelly on the south, occupy the more prominent of these valleys. Beyond the San Juan, to the southwest, the wonderful forms of Monumental Valley can be seen; beyond this the outlines of a broad table-land can be made out, which extends eastward from Navajo Mountain. toward the Rio de Chelly, and southward toward the Moqui country, probably connecting there with the ‘‘ Great White Mesa.” West of our station, which is near the eastern border of the Abajo group, are a number of small partially isolated groups of mountains, which obscure portions of the plateau country beyond. The formations near the west base of the mountains are certainly of the Jura-Trias Red Beds; beyond these we have glimpses of the canoned region of the Rio Colorado, with its almost infinite series of red, gray, and whitish cliffs. Rising out of this broken plateau region are the Henry Mount- ains. Their outlines, as well as much of the detail of form, could be made out by aid of the field-glass. They appeared to resemble very closely the vorious groups of trachytic mountains that lie along the eastern border of the Colorado Plateau. The nearest peak of this group is distant about 70 miles from this station. The Sierra’ La Sal is a large group of mountains that lies directly north of the Abajo at a distance to the central peaks of some 44) miles. There are a number of finely-shaped summits, somewhat conical in shape, that fall off to the level of the surrounding plateau in long, steep slopes. This group stands quite alone, and is surrounded for the most part by red rocks, but a series of shelving-spurs on the east and west probably retain a capping of the Lower Cretaceous rocks. Between the Abajo and Sierra La Sal is a broad valley of rather ex- traordinary configuration. It is drained by the Caiion Colorado of Dr. Newberry, but from this point no particular caflon can be traced. We see only a broad, depressed area, which falls off in a succession of irregular cliffs from the western border of the Sage Plain to the Rio Colorado, over the whole surface of which are a multitude of masses of naked rock, white, red, and gray ridges, hillocks, and monuments smoothed and rounded by the winds and water, the whole being as monotonous, except for the occasional lines of cliffs, as a chopped sea. The eastern rim of this valley extends considerably to the east of a line drawn between the two groups of mountains, and in the middle part two or more cafioned valleys penetrate the plateau-face of the Sage Plain, and extend many miles eastward toward the Rio Dolores. A glance at the panorama will make the topographic features of this region clear. The Abajo group, as will be readily seen, lies on the western border of the Great Sage Plain. The western limit of the Lower Cretaceous formation is uniform with that of the plain; south of the Abajo it terminates against the eastern base of the Bear’s Ears Plateau, while north of the Abajo it breaks off in the high escarped cliffs that overlook the valley of Cafion Colorado. The dip of the strata of the plain is almost uniformly to the south and southeast, so that the drainage is turned back in those directions from the western and northern borders, leaving but little surface tributary to the Colorado and Dolores Rivers. The Sierra Abajo consist of a number of small groups of volcanic 192 REPORT UNITED STATES GEOLOGICAL SURVEY. summits. The trachyte of which they are formed seems to have reached its present place through a number of channels, although probably from the same nucleus. The masses now exposed were doubiless forced up through narrow crevices or apertures until the yielding formations of the Middle Cretaceous were reached, where the melted material spread out to the right and left in great masses and sheets. The shales are still found in all parts of the group, caught up in a manner identical with that observed inthe Lateand Carriso Mountains, and the lowsaddles between the various groups of summits are invariably of these shales. All along the east and south bases of the mountains the sandstones of the Dakota group are turned up at high angles. Near camp, at the base of the primary triangulation station, a double row of hogbacks composed of these sandstones skirt the flanks of the hills. They are somewhat metamorphosed and have a dip of 45°. The slopes above these outcrops are for the most part covered with grass and bushes or with loose slides of finely broken trachyte. In a number of places, however, there are outcrops of variegated shales and slates, and toward the sum- mits considerable masses of trachyte protrude. The tendency in all parts of the mountains is to weather into smooth, rounded forms, owing, perhaps, to the homogeneous and rather slightly compacted character of the trachyte. Itemarkable uniformity is notice- able in the height of the various summits, and some are nearly flat- topped. As their general height above the surrounding floor of the Da- kota sandstones represents so nearly the thickness of the Cretaceous shales, the idea is suggested that possibly the great mass of tracbyte did not penetrate the very massive sandstones of the Upper Cretaceous, which at that time must have covered the whole region. There are four principal groups of mountains which, together, cover an area of some 150 square miles. Their arrangement is such that the total extent is a little greater northwest and southeast, but the trend is not sufficiently marked to make a well-defined range. The southeastern section is the only one that comes within the limits of the Colorado sur- vey. This is the group usually seen from the east, and its character will be understood by reference to Plate XIII. Our station was made on the central summit. At the south end is a prominent point almost as high as our station, which presents a sharper summit and more abrupt faces than any other of the entire Sierra. The drainage of the north and east faces of this group belongs to West Montezuma Creek, while that of the south and west is appar- ently tributary to western branches of the same stream. The extreme head of the Montezuma seems to be northwest of our station, between the second and third groups of mountains. From this point it circles around to the northeast and south, passing near the north edge of the Sage Plain opposite the head of Cold Spring Cafion. The canon begins at a point near the east base of the mountains and rapidly deepens toward the San Juan. In the middle part it is upward of 1,000 feet in depth, and the red rocks of the Jura-Trias are exposed. Between the base of the mountains and the Montezuma Cafion there is a considerable area occupied by the Cretaceous shales. East of the caiion the shales only occur on the higher and more protected spots. Although the country which surrounds this group of mountains is desert-like in the extreme, there is a narrow belt about the flanks and lower slopes that abounds in vegetation. Considerable forests of pifion pines occur about the cafioned region to the east and south. Large groups of these trees are also scattered at intervals over the greater parts of the Sage Plain. Groves of large yellow pines skirt the imme- OS. Geological Survey. PlateXV Varalin| SS eat at 5 ‘ Wp 1 "m \ si ip seine : J aS ” A Glimpse into the Dolores Cafior. Fig. WN pe MO a \ Wo —