x AS CC Ries A ee wes : ah ty neh fe ules ee Ss - ms - ON THE aeaen ‘ ‘ oN i nSONiAy JAN 2 6 1989 LIBRARIES BY WILLIAM H. EMORY, MAJOR FIRST CAVALRY, AND UNITED STATES COMMISSIONER. MOLUME. I. WASHINGTON: A. O. P. NICHOLSON, PRINTER. 1857, > eee 7 é Vv 7 ! 7 - > ; > d ~ . * PART it: q | E | | ’ | Nee " | : . “ani : | v te at} ; iki © oe . is j : - Ria g : . nn , = ts pa, GEOLOGICAL REPORTS OF DOCTOR C. C. PARRY AND ASSISTANT ARTHUR SCHOTT. NOTES BY W. H. EMORY. PALEONTOLOGY AND GEOLOGY OF THE BOUNDARY, JAMES HALL, OF ALBANY, NEW YORK. DESCRIPTION OF CRETACEOUS AND TERTIARY FOSSILS, BY TAS CONRAD, ESQ). . eRe. = . ’ ' . ‘ ‘ a? - * , ad ‘ ‘ ~ ts } ¥ he a CONTENTS.-PART II. CHAPTER I. GENERAL GEOLOGICAL FEATURES OF THE COUNTRY. General, physical, and geological features'of the country_....-..-....--..-----------.----~----<.-=-.--...- Springs and streams ---.------- Change in the scenery--------- Hacle: Springsi=-s--s-—e == 22S Corrallitos and Baranca -.------ Serr Amn ati em OAV CGI: RCO meee ate ete es ates oe eee ee ei cence ama Jaa ween niet aaieesicaeenciae ONS SA Te BERT ATO LONGO TAN hele ON U2 tel ete e at rer ein Siar Io So ne yr tener tate annie tee artes ewer svetcsuuses Ee are aL Oe TCR OT eae ene ore, ie i See ee ee Oe Re me ecee eee CS CCE eR eeu ew cn Ualence amare eee e ANT @UEL! TROUTCHE we cece Bo Se SESS Oo SS OSES ES BBS Er Se SSS DERE SEE Se DSBS Eee E ae Se Re ce Note by Major Emory --------- ANTALIS TTS OT MeN © Sse pc Seca ae te Oe SI OS a TI SE I SIRO ee ra CHAPTER Ii. SUBSTANCE OF THE SKETCH OF THE GEOLOGY OF THE LOWER RIO BRAVO DEL NORTE. From the Pecos downward, valle Sy SURau nea nOn: tWaAbeD ROS eee alee ae ee Bottom land, antedilivial dunes, upper metamorphic limestone-...-.-------------------------------------- How watered ; interspersed strata-....------ aan Pn, OR ea A eB a. J a ne TORR we Be aaa aS SIE Soe ORS ee oe ee a ea Parmicnicnman devo lean CLOsst asi sie esec ae oie ee se we me See eee eee aaa awe Sse hee eneS IBaRAl gest eG LcuniG a vicesiin Nexans). = memes tee ae ate ein me ie ee lta atte itn, DRIGIS tA) SUS eee aso os bee Bee eS en ee ee eee ne acs att SIVEES Teese) CUED ERs UIT EN ERTL CD LUM POG ee ot een ee per e cC ene ee ie ae ee n eee — Renee ae ne aaa BITE Ree DIG ovOhGienl in GSLOnG sacs asa eese mee oe ee ee as ees on a ee een a Blue clay ; green sand with fossil oysters and shells -------..--------.------------------------------------ SHWE eee ese otc cee eee Me Se Be eee Se a ee SE Se eee eee es TSS Maye ete oe See be ea a ee ee ee aT a eee Aine a orODd keene ets eee Cn 2 Se be Se ee ee ea ee ec. See eeeeetn me come IBAVElCRIntes UHCes OF tne COUN Ye = oa oee nese eae en ee a ele inne ee meme cea =~ 5-~<—sn=3 BISON ESE TeL Io eee ee ee ee ee ee eee a cw ada es aamece se soe em sitaciecesss ate heralds peer eee ae eee See ee ee Se eo OO sace cnn cuscodesascavasuassacct-ee She) Wore] -o soc 5 — ee Tee oe ee ae Seine cilew a mine acd ae aac cpa Sona iManame ate aena' a MR el ColL iva ane Geen = seen me eee ate Seine a cin ca nine oo eles oan smees smcesnan ction wee aa so eses seuaceeesenns Unieuteop eis s2 5 et See Dee an eee ee ee ee Alluvial development ........-.....----- ee ae See een a See cee eee e eens ese n see eee eaate General view of organic remains 29 30 31 32 33 33 33 34 35 36 37 37 39 39 40 41 41 43 43 44 45 47 VI CONTENTS. CHAPTER IIT. GEOLOGICAL FEATURES OF THE RIO GRANDE VALLEY, FROM EL PASO TO THE MOUTH OF THE PECOS RIVER. Page ower! limitejof thew) iPasosbasini=- -0-- <2 = sate Noce eee a ee aa aaieeae aaa mane anlar 5 49 Near Presidiovdel (Norte <2 = =< seeco = - en Seco ea sae a aw ae ate ere a a a ee a 50 Toy eee 50 CEO SSUES SO Se De Se ES EERE Soe SS See Sabise SA pes #3 Se RSet osssesse seen]es 52 Comanche tral so oocce ean ano sep esc- cen ee eceeeeee ee ee een ese Sa ae ae ee aes 54 Gatron tof San'Carlos.-< 2-2 cosa — eee a eons ee eeeelninie ane = ee i pee ee eee ee 54 Nalbsrot Sam Carl op Sx Ses a te ms Sp teem me ae nm Scat ah ue a 55 Chisossmountains' 252. 232203200 0c osteo le esnc ose aeee enka aelee eee seo aoe eee ee ee ee 56 SankCarlos valley o = acs ae mena soe cane eh ese eae eae eee eee ee eee es 57 Wado Plecha 2-2-2252 52 2s c22c2i2s 2222222352255. Sees ccc sense sce mee ae eee tle Sane pe ee 58 G@aiion of ‘San Vicente. 2.-5-s25. 22-25-52 on ieee cn eh odeke cane Socceein nen eee ee ee ee ae ee 58 @afion Carmel! 222-5 sooo son ser sie an ee ae een aoe ea beeen eee eee ee ee 59 Reak' -*“Picotera.-osctsesce> secs see cce se eee ae ee ee oe eae ea mae ne nie ea oe ee ee a ee ee 60 Lagoon formation inthe upland plains#2252 52 ss22>sq= Sacco esos sen eee nee ae ee eae cea eee 60 Santa ‘Rosaand! route'to Hagle Pass soos. 222 5 sssssse2 s22 5 cee ee se ee a ee ee 61 CHAPTER IV. GEOLOGICAL OBSERVATIONS ON THE COUNTRY ALONG THE BOUNDARY LINE LYING BETWEEN THE 111TH DEG.ER OF LONGITUDE AND THE RIO COLORADO. Geopraphicalisituations=="--e=scce oa 4escineaacecsie mam aenae ae cone ee eeeeeesseeeee (oiawieieiamte sa sfdeneaeses 62 General fe eolo pce tr crc ture ee te ee te ee ee 62 WD glitasyea ea rn a ra et ee me em ls wl ee 63 . Hypsometrical features of the mountain system-.--..- Pee oso seca teense ce sence eso one nese eee 64 Spanishitoporraphicalexpresslonso- = == se a ne te et 65 SGT OGL TE EIB a6 See epoca SSeS SoC BE OO RESO Se Sn S OED nas abo soca sesercoosasSsSse sass ssconccoes 66 Yalley ‘of (Los! Nogales. -.\: -2--s-2-. 2.5 Scsccoscan ss t gone sees eaaneese este ceeeceee = —eeee wesesee sega 67 Sierras Janos and Atascosa -------------- te a 68 TherArizona, Mines=. - -/- ses 5-45 sec] sonines see cee sae se eens ern emcee eeec eee seen e shomenate 69 Sierra Escondidas.--ss6 225 sos ec coco ses es eee noes ene aeseucla ee een ae ee aoe eee eee eee eet 69 Sterrita deli Granizo' 22225-22522 2-- se eee Se ee ene Sees eee ee ee Bu Sectionalimiewsshowing iaiseries|or vOlcanicwprogucts- == 9-2 = sa =e eee ee eee 52 Sectional sketch ati Comanche! crossinpisoo-s- oo- 2a o- so aaae = seas eee Soe ac ene ee aeee se 54 Sectional view on a ravine leading towards Rio Bravo, near San Carlos ---...-.---------_----.-.---+--------- 54 Hallsof ARiosbravoy.near San (Carlos; so. nase sees esa ca acoso oS abeee Sonneries Seco ee 54 Outline view, of jthe:Chisos;smonntains =< cocoa ae eea woe on SS eee eee eee ee 56 Sectionaliaviewror whe! GreatsCanon, ear psa Carlos sae ae ee ate ee eee 57 Wiew of the-Presidioide’SaniVicenterand sierra|Carmel== sess =2=0 > see ae tee 59 Sectional view, ofsthesValley; dew os anvon sae ae alee ese ee re ea a 66 Walley (of os Nogales\ie -— noes ~ ean soaseaaso ace ecaan ee pose cee ee eens as eae ee ee 67 Section on the morthisiderofstihe Werroidel SonOr a= saree =a ar = re ale ee ee “69 Vertical sectionof theisierra devdavNariz- cos --- cee see eee ane ce seat see e see cee ne a eee 72 South side of the Sierra del Ajo, and part of Cienaga de Sonoyta_.....-....-.....---..----------- Ga eee 73 Pluto-voleanic peaks studding the Mal-pais east of Sierra Tulé.....---..---..-..---------.-.-_----------«---< 75 Sectioniof Lignite Bluff near San Diego ==: 2 Senseo s setae oe ete ate SR Re oe ee ee 85 Vertical section of an extinct crater in the tertiary formation, bordering the east slope of the California Cordilleras 92 View upon the eastern slope of the California Cordilleras from near Carrizo creek-.....--.-.------------------ 93 Valley of the Colorado of the west, and east slope of the Sierra Culaya.....--------------------------------- 99 21 steel plates of paleontology.(See—explanation of plates to Professor Hall’s report.) _.....---.-------------- 165 Nore.—I think it proper to state that Ido not concur with Mr. Schott in his conclusion on page 96, where he says: ‘‘From this we have the proof of a former immediate connexion in these latitudes between the two oceans of our globe.”’ In the original proof this conclusion was erased, but by some accident was afterwards inserted. Aen 1SE ID} ERRATA, On page 91, line 41, for ‘‘ nearly’’ read near. CHEAP EE Rall. GENERAL GEOLOGICAL FEATURES OF THE COUNTRY. Wasuineton, D. C., April 1, 1854. Colonel W. H. Emory, United States Commissioner : Str: In completion of the duties assigned me as botanist and geologist to the United States boundary commission, I present the following : I. GENERAL PHYSICAL AND GEOLOGICAL FEATURES OF THE COUNTRY. The general features of the Mexican Gulf Coast, in connexion with the United States and Mexican boundary line, present a marked contrast with those observed on the opposite Pacific coast. Thus, instead of the high cliffs, abrupt headlands, and general bold and rugged outline exhibited on the Californian coast, the Texan shore-line, throughout its whole extent, presents a uniform, low dead level. Generally, indeed, the main coast is shut in from the open sea by ranges of sand islands formed by the waves of silted sea sand and comminuted shells. Inside of this line of islands shallow bays spread themselves into the indented coast, and here the nume- rous rivers flowing from the interior meet the tide-water. The tide range is moreover small, and thus the alternating differences of level do not favor the formation of navigable estuaries by which the main land may be approached. These features, collectively, give to this coast an inaccessible character, and serve to render its navigation both difficult and dangerous. Its rivers are unapproachable, except by vessels of very light draught; while the inlets to its shallow bays, obstructed by variable sand-bars, present obstacles to navigation, sufficiently proved by the numerous wrecks that strew their beach. Proceeding inland from the line of sandy beach, a gentle slope spreads out in a uniform gradually rising plane, composed of dark rich loam, and covered with luxuriant pasturage. The scenery is rarely relieved of its blank outline by a clump of live oak trees surrounding a sunken morass. Farther on, at a variable distance of 10 to 20 miles, the surface of the ground shows gentle swells, still maintaining its fertile character, and displaying here and there groves of post oak and other timber. The river bottoms adjoining are occupied with a heavy timber growth, principally of elm, (ulmus erassifolia,) festooned with Spanish moss. The undergrowth comprises a complete maze of shrubbery, matted and tangled together by vines and creepers, and supporting a rank annual growth. At a distance of 50 to 80 miles from the coast, the ground-swells become more abrupt and form distinct ridges, between which are collected the drainage of the country. Along the course of the numerous streams there is an exposure of the geological substratum, consisting first of loose gravelly strata, which contain erratic pebbles of siliceous or calcareous character ; to this 1M 2 GEOLOGY. succeed occasional exposures of a coarse-grained sandstone, No. 1. Still farther inland we meet with a form of soft calcareous earthy rock outcropping along the sides of hills, and constituting the first outlayer of that extensive cretaceous formation which characterizes so large a scope of country throughout middle and northwestern Texas. From San Antonio, occupying the first step in the cretaceous series, at an elevation of 600 feet above the Gulf of Mexico, proceeding northerly on the line of the lower road to El Paso, we soon remark a rapid change in the general features of the country. The underlying lime- stone formation becomes more largely developed, and is less deeply covered with alluvial deposits. The rock stratum is frequently exposed in the beds of streams, which are everywhere thickly strewn with the’ water-worn pebbles of this formation. The streams here acquire an intermittent character, subject to sudden overflow and recession. Their course, when low, is marked by an irregular series of deep basin ponds connected together only by shallow brooks, cr even not at all above ground during dry seasons. As we proceed, mural exposures of limestone rock become more frequent, and the same for- mation is met with on summits of the higher table-land. The alluvial tracts along the course of the larger valleys acquire a more arid character of soil, and support a stunted timber growth, in which mezquite makes its appearance. Fossil, fresh water, and land shells are quite abun- dantly scattered over the lower depressions of these alluvial bottoms. At the crossing of the Rio Frio, near Fort Inge, occurs the first exposure of igneous rock. It is seen as an isolated knoll of dark-colored trap, showing at this place but slight disturbance of the adjacent cretaceous strata. This formation is thence observed to constitute a broken line, extending ina northwest course, and coming into view at several points along the road at variable distances of 5 to 10 miles, On approaching the line of the great table-land formation of Northwest Texas, we find near its base the sources of most of the minor streams of this region. These sources frequently exhibit magnificent basin springs, of which that at San Felipe is a noted example. We have here reached the main development of this extensive cretaceous formation, partially concealed from view towards the coast, as above noticed, by alluvial deposits, but here standing out in bold relief, variously exposed in extensive ridges, bounding, more or less closely, valleys Character of valley denudations in the cretaceous table-land formation. Upper portion of San Pedro river, Texas. of denudation, or else stretching in vast upland plateaus, thinly covered with soil, and support- ing a close even growth of upland grasses or scanty shrubs. GENERAL FEATURES. 3 The true character of this formation may be satisfactorily studied in the course of its principal streams, the Pecos and Devil’s river. As exposed along the course of these valleys, the view is bounded by steep mural cliffs, composed of limestone, disposed in nearly horizontal strata. This rock exhibits quite a variable texture, its weathered face showing an uniform gray or bluish tint, while its recent fracture has a much lighter color. Owing to its irregular texture, it frequently exhibits a cavernous structure, displaying in its various exposures all the grotesque features of ruined castles, forts, and dilapidated masonry ; examples of which may be seen by reference to numerous sketches. The river valleys either expand into more or less extensive alluvial basins, or are completely hemmed in by steep mural faces, forming chasms along their course, to which the Spanish term of cation is generally applied. Thus, in following out the course of valleys in this district, we have a series of basins connected by cations ; the relative extent of these distinct topographical features being dependent on the local character of the formation, or the varied influence of pre- vious denuding forces. The alluvial tracts partake to a great extent in the sterility of the plateaus with which they are connected, seldom showing evidence of fertility, and in a great measure destitute of timber growth. In the case of the Pecos river, which may be regarded as the main type of streams belonging to this table-land formation, we observe a contracted but constant body of water coursing through alluvial tracts, or clearing its way through rocky cations. In the former case, its tortuous course is marked out between deep banks of earth, so that its turbid waters are for the most part invisible till you come directly on its brink. The average width of the stream, during most of the year, is about 50 feet, and 8 feet in depth. Only limited portions of the adjoining valley are subject to that degree of overflow, such as constitutes what is commonly understood as bottom-land. Owing to the steep and crumbling nature of the banks, travellers often experience no small difficulty in watering their animals ; the water itself, though highly charged with reddish sediment, is not unpalatable. In its passage through cafions, this stream, like the Rio Grande, cleaves its way between steep walls of rock ; its course during low water being occasionally set off by lines of sandy or pebbly beach, and forming frequent rapids. All the small intermittent streams of this region are copiously bedded with rounded pebbles, derived from the adjoining limestone formation. The view from the summit elevations presents not an unbroken table-land, but rather a series of terraces, exhibiting occasionally truncated peaks, and showing a general increasing elevation westward. The mean level is, moreover, marked by depressed valleys, containing dry pebbly beds of streams, and frequently expanding into wide basins. The descent to these valleys is generally abrupt, and is the chief obstacle in the construction of roads, which, with this excep- tion, are marked out with ease, and are unexcelled for purposes of wagon transportation. The supply of water over these arid tracts, except in a season of rain, is confined to a few isolated springs, occupying the lower level of some of these depressed valleys, or occasionally bursting out from the base of high rocky ledges. These springs, though generally affording a copious and constant flow of water, are not sufficient to give origin to river tributaries, their issue being quickly absorbed in the lower course of their arid beds. In several of these springs 4 GEOLOGY. the temperature is as high as 70° Fahrenheit. Between these watering places occur what are termed by travellers ‘‘ dry stretches,’ being in some instances 50 miles in extent. In all our observations thus far, little disturbance is noticeable in the position of the strata. To ordinary view they appear strictly horizontal; the indications of the barometer and the changes of the climate prove, however, a gradually increasing elevation. The height, as indi- cated at the Leon spring, the most western point of the continuous table-land at which cretaceous fossils were collected, is 2,807 feet. This shows a rise of 1,800 feet from the lowest series of this formation, (the mouth of Devil’s river,) and 2,200 feet above San Antcnio, giving an average rise of 7 feet to the mile. Quite constantly in the distance, to the south and west, rugged mountain ranges are visible, evidently of igneous character, and connected with extensive disturbance of adjacent cretaceous rocks. It is through these, as we shall hereafter see, that the Rio Grande forces its way, pre- senting a series of chasms and deep cleft cations of a most stupendous character. The first indication of a change in the general features of scenery, as sketched above, on the line of the usually travelled road to El Paso, is encountered in the range of the ‘‘ Sierra Diavolo,”’ or Limpia mountains. This range may be regarded as the southern continuation of the great dividing ridge between the Pecos and the upper Rio Grande, including the Sacramento mount- ains to the north, the Guadaloupe and Limpia mountains, with their continuation south, to form the Sierra Rica of Mexico; through the latter portion of this range the Rio Grande forces its way a short distance below and east of Presidio del Norte. This range is characterized, at all the separate points observed, by the presence of igneous rocks, varying considerably in structure and lithological character, as noted by Professor Hall in rock specimens Nos. 12, 13, 14, 15. The elevation attained by this range, on the line of the El Paso road, is from 5,000 to 7,000 feet above the sea, On entering this range from the east, we pass quite abruptly from the horizontal limestone strata to the igneous exposures. The passage of this range is accomplished by a series of rather steep and rough ascents, fol- lowing up the course of the Limpia valley. The main pass, known as the ‘‘ Wild Rose JE exhibits gigantic walls of rock, towering up on either hand to the height of 1,000 feet or more above the valley below. The summit divide is composed of a coarsely-grained granitic rock, formed principally of feld- spar, and varying in color, in the different exposures, from dark brown to a dull whitish. In descending the more gradual western slope of this range, the rock exposures assume the char- acter of a close porphyritic trap, of a reddish color. As we leave the main range, passing to the west, we encounter extensive ridges of stratified limestone rock, associated more or less closely with interrupted igneous exposures, and showing a general dip to the southwest, or away from the Limpia mountains. The inclination, however, shows, in many places, a variable direc- tion and intensity, depending on local causes connected with adjoining igneous exposures. A degree of metamorphism is also exhibited in rock exposures, having a gneissoid structure and traversed by quartz veins. From the specimens collected, imperfectly characterized by fossils, Prof. Hall concludes that these stratified rocks belong to the carboniferous period. Between these irregular mountain ranges and spurs, which in this section of country meet GENERAL FEATURES. 5 the eye in every direction, the intervening surface spreads out into wide basin plains of an allu- vial character. These basins receive and absorb the scanty streams of the adjoining mountains. Rarely indeed, except in the highest mountain recesses, is running water visible, the occasion- ally copious rains furnishing only a temporary current along the course of the numerous stream- beds. The water thus accumulated in rocky basins or marshy lagoons, affords the only supply for travellers, over these arid wastes. During the dry season these plains spread out their dreary tracts, unrelieved by a single feature of fertility, occupied by innutricious grasses or a scattered growth of dry shrubbery, among which the repulsive form of the ‘‘ Spanish bayonet’’ (Yuca) is a conspicuous feature. Owing to their exposed and elevated position, these plains are subject to great extremes of temperature. They are mostly shut off from the Rio Grande by a variable mountain range, composed of the carboniferous limestone, variously associated with igneous rocks. The passage to the valley is accomplished by following down the natural cleft made by some rain stream. ‘These passes exhibit fine sectional views of the tilted lime- stone strata, exposed in various conditions of disturbance, in some places inclined at an angle of 80° to the west, and at other points exhibiting evidences of igneous action in metamorphic changes. Eagle Springs. We have thus reached, on the line of the ordinary wagon-road, the upper valley of the Rio Grande, the external features of which, as more directly connected with the line of boundary, will claim a more detailed notice. At first, however, a more rapid sketch must suffice, while continuing to notice the general features of scenery and geological structure presented on the route westward to the lower valley of the Rio Gila. As we pass from the rocky caiion, by which we enter on the Rio Grande valley, we first come upon a gravelly plain, generally presenting a smooth and more or less uniform surface, sloping 6 GEOLOGY. gently toward the main bed of the valley. This plain, in receiving the drainage from the ad- joining mountain ranges, is variously cut up by deeply-trenched arroyos, and terminates on the alluvial tracts below in gravelly bluffs of variable height. This table-land is encountered wherever the course of the Rio Grande is not hemmed in by precipitous rocky cliffs, and is seen forming a belt of variable width on both sides of the river, extending to the base of the adjoining mouatains. In all these situations it presents very uni- form features. An obvious analogy will be at once perceived between the latter formation and the wide- spreading upland alluvial plains, before noticed ; in fact, a direct continuous connexion between them may be often traced. They evidently belong to the same general formation, representing basins filled up with alluvial and diluvial depositions, concealing, it may be, older tertiary strata below. The pebbles contained in this formation can readily be traced to their original sources in the adjoining mountains, being of larger size and more angular near the base of the mountains, and smaller and more rounded at a greater distance. The earthy medium is generally a coarse sand or fine marl, argillaceous matter being less frequent. Occasionally the exposed bluffs show de- posits of gypsum, which in some localities forms extensive beds. The most usual form of this material is in confused crystalline and fibrous masses, imbedded in loose marl. At other places a calcareous chalklike deposition is met with, occupying usually the upper stratum of the table- land. A general saline character, pertaining to this formation, is also evidenced in the growth of saline plants or direct salt efflorescence in the lower depressions of valleys. SECTION OF EARTHY TABLE-LAND FORMING THE BLUFFS OF THE RIO BRAVO ABOVE EL PASO, CORRESPONDING WITH THAT FORMING THE “JORNADA DEL MUERTO,” TO THE NORTH. 180" Bari at ge Aya Lees \ : Peay, © eons 2 NS eT l MSH | \ | ‘i ‘ | \ Se pee ee no Sun He \ A. Highly calcareous marl, chalklike, with occasional pebbles. B. Brownish gray sand, with nodules of clay. C. Yellow ferruginous marl. D. Debris of drifted sand and washed clay. As seen from any high mountain elevation, this table-land sweeps with all the exactness of a sheet of water, encircling as with a shore-line the bases of distant mountains, frequently com- pletely insulating peaks and ridges, and everywhere masking the true connexion of the various formations. The progress of subsequent drainage is also plainly seen in the various terraced elevations THE VALLEY OF EL PASO. v( which this table-land assumes. It may further be observed, briefly, that this is the formation _that stamps the character of sterility on so large a scope of country forming those desert tracts known as “‘ Jornadas,’’ of which the ‘‘ Jornada del Muerto’’ is a noted example. It is to this character of country, moreover, properly belongs the Spanish term ‘‘Zlano Hstacado,’’ or Staked Plain, a term which has been less appropriately applied by travellers to the cretaceous table- lands of Texas, before noticed. The proper alluvial tracts of the Rio Grande, as here met with on our route, exhibit a belt of variable width, from a mere narrow strip to several miles in breadth. Its lower portions are marked by frequent sloughs and old river beds. The body of the soil is sandy, but acquires a somewhat compact texture from the deposition of river slime, and is further enriched by the decaying vegetation that luxuriates on its moist bottoms. The desert table-land is constantly encroaching on this alluvial belt, in the washing of its numerous stream beds, or the finest sand wafted by the winds. The roads occupying the river bottom are usually heavy, and whenever practicable are gladly exchanged by the traveller for the compact table-land. The river itself presents tew features of attraction. Its turbid waters sweep along during the flood season, in June and July, a swollen tide, spreading its enriching sediment through the various sloughs and lagoons that line its course, often cutting off all approach by land to the main channel. During low water, which includes the greater part of the year, the river con- tracts its dimensions, running in a very variable channel, over sandy shoals, interrupted by numerous islands and exposed sand-bars. Occasionally, in very dry seasons, it ceases to run altogether, and stands in stagnant pools. The portion of the river bottoin at present under cultivation in connexion with the El Paso settlements includes a large basin lying south of the El Paso mountains. In this is comprised the large alluvial tract known as ‘‘ 7'he Island,’’ which is 30 miles in length by 2 to 5 in breadth. This island lies on the American side of the main channel, being separated from the adjoining land by an old river bed, which, except in very low water, still carries a variable stream. The bifurcation of these two arms of the river at the head of the island is taken advantage of to direct a stream of irrigating water through the centre of this tract of land, extending nearly its whole length, and furnishing from its main trunk side branches to supply the cultivated fields. Thus in usual seasons a sufficient supply of water is obtained to meet the wants of ordinary cultivation. At times, however, low water in the main channel is a certain precursor of drought; while at other times an unwonted abundance exposes to the danger of floods. On the main banks of the river, including the Mexican town of El Paso, and Franklin, on the American side, these inconveniences are measurably obviated by drawing the irrigating supply from a higher source. This is accomplished by the construction of an artificial dam, located some two miles above these respective towns, thus allowing the construction of water- gates and waste-weirs to regulate the supply of water according to need. Hitherto we have observed the Rio Grande in its character of a variable stream, bordered by alluvial bottoms frequently of considerable width and extent ; these again everywhere limited by gravelly table-land, sloping upward to the bases of distant mountains. A short distance above El Paso a new feature presents itself, and we have the mountains themselves encroaching directly on the bed of the river, which here passes in a contracted channel between rocky walls. 8 GEOLOGY, The rock exposures on the river bank exhibit disturbed strata of limestone, characterized by frequent fossils as belonging to the Cretaceous period. A greater or less metamorphism of this or a more ancient sedimentary rock is also exhibited, while on either side of the river tower up to a height of 500 to 1,000 feet rugged igneous rocks, having a granitic texture, and character- ized by Professor Hall as ‘‘ feldspathic or granitic lava.’”’ (No. 40.) View of the Initial Point, on Rio Bravo. On the Mexican side, the various formations, stratified and igneous, are blended and intermixed in great confusion, the connexion between the various formations being obscured by the irregular exposure of igneous products, the greater or less degree of metamorphism of adjoining sedi- mentary rocks, and the presence of extensive diluvial deposits. The general surface is thus rendered extremely rugged and broken, the traversed roads being obliged to make a considera- ble detour from the course of the river. On the American side is conspicuous a high mountain range, nearly parallel to the river, at a variable distance of from & to 10 miles, and observing a regular north and south course. This range is seen to be composed of stratified limestone, dipping very uniformly at an angle of 45° W.S.W., or toward the river ; in the face of this dip rest the various igneous outbursts, asso- ciated with the disturbed cretaceous beds. This limestone is determined by Professor Hall to belong to the carboniferous series, being a northern continuation of that before noticed at Eagle Springs. The remarkable character of the stratification is conspicuous at a great distance, its deep gullies presenting fine sectional views, and the different exposures of its sloping surface exhibit- ing variously curved lines, as the strata are thus brought to view by the action of the denuding forces. The highest summit of this range presents a sharp, jagged crest, such as might readily be MOUNTAINS NEAR EL PASO. 9 mistaken at a distant side view for an igneous formation, Connected with this upper crest, we also notice outweathering masses of siliceous rock, (No. 38;) these frequently assume grotesque forms and positions, representing various tower-shaped prominences. MOUNTAINS EAST OF RIO BRAVO SEEN FROM EL PASO. . Cretaceous rocks resting on granite, and diping at an angle of 10-15°. . Granite. Carboniferous limestone. . Porphyry peak. Drift. HOA D At another point this mountain range is interrupted in its usual stratified character by the presence of a porphyritic exposure, (specimen rock No. 41,) forming a dyke, passing through the entire ridge from east to west, and constituting the highest point in this range. This igneous mass is variously associated with the adjoining limestone strata, lying either above or below, without showing any local variation of the ordinary dip, or exhibiting meta- morphic changes at the point of junction. On its eastern aspect, this range exhibits a precipitous slope, revealing the thickness of the formation in the regular succession of the uplifted strata, as thus exposed, from summit to base; there is developed at several points a thickness of not less than 1,500 feet. No very marked change is observable in the character of the rock from above downwards, or any local evidence of a change of formation. We have, however, evidence from erratic fossils of the presence of a lower order of rocks, belonging to the Silurian period, in this vicinity. Such a formation has been assigned to a corresponding location west of El Paso, by Wislizenus, and there is little doubt but a careful examination along the lower line of these uplifted strata would bring to light this lower class of rocks. This range continues to the north, forming the Organ mountains, at which point these strati- fied rocks give place to various forms of igneous products, as indicated in rock specimens Nos. 42 to 46, inclusive. About seven miles north of El Paso, the mountains adjoining the river give place to the more usual character of gravelly table-land and alluvial bottoms, as noticed below. The table-land is here seen swelling to its broadest dimensions, encircling the distant mountains in every direction, and stretches northward to form the dreaded ‘Jornada del Muerto;’’ thence sweeping round the northern point of the Organ mountains, it constitutes the extensive desert tract be- tween the Rio Grande and the Sacramento mountains. ‘To the west the same formation is seen, variously interrupted by mountain ranges and isolated points of igneous rock, extending to the base of the Sierra Madre. In further continuation of our general sketch of external and geological features of country, 2M . 10 GEOLOGY. we now take up the line of march westward, leaving the valley of the Rio Grande at El Paso, to follow out the most southern line of emigrant travel to the lower valley of the Gila river. On leaving the alluvial basin, in which El] Paso is situated, we first ascend over a lower step in the gravelly table-land, sloping gradually upwards, and presenting all the characters of scenery before described. We pass mountain spurs on the right and left, composed of the lime- stone rock, similar in appearance to the range noticed on the American side of the river, and having the same general dip to the southwest, but at a smaller angle. Our route, following at first the regular Chihuahua road, passes nearly due south; in about 15 miles from the river we reach a second terraced elevation of the table-land, rising as a steep bluff 80 to 100 feet above the lower step over which we have been passing. The character of this higher deposit is here plainly exhibited in the face of the cliff, consisting of alternate layers of yellow ferruginous marl and coarse brown sand, capped with a thin layer of highly calcareous marl. From the summit of this second elevation stretches a wide table plain, variously indented by shallow valleys, and swelling toward the base of the mountain ranges. On approaching the line of mountains lying to the southeast, we pass over a spur of limestone rock, connected with this range, showing a dip of 15° to the northeast, a similar inclination being apparent in the principal range. The rock formation appears to be identical with that before noticed near El Paso, having a directly opposite dip, thus forming a synclinal axis, in the trough of which our route seems to have been marked out. Leaving this latter range to some distance on our left, we approach a long serrated ridge of mountains lying directly in our course; near the base of the southeastern extremity of these mountains, occurs the first permanent water since leaving the Rio Grande, about 32 miles distance. This locality is the ‘‘Samalayurca Spring.”’ A short distance beyond this, commences the singular formation known as the ‘‘ Medanos,’’ or Sand-hills. They here rise conspicuously to view from the plain below, presenting an exact appearance of the sandy dunes along a stormy seacoast. It is difficult, at first sight, to discon- nect this remarkable formation from such an obvious cause, and not to represent it as the sandy beach of the extensive lake in which the deposits were made, forming the wide expanse of table- land so often referred to. The present facts, however, do not warrant such an exclusive opinion; thus the separate grains of sand composing the sand-hills are seen under a lens to be angular, and not rounded, as would be the case in regular beach deposits ; they are also extremely light and penetrating, of which every traveller who has occasion to pass this locality in a dry, windy day will have ocular demonstration. In fact, the peculiar features of this formation are suffi- ciently explained in the topographical arrangement of the country, which presents an immense plain, stretching out in the direction of the prevalent northwest winds. In overlooking the surrounding country from the projecting point of the adjacent gneiss range, these sand-hills are seen to form a crescent, with its concavity toward the northwest, and rising highest where the accumulated deposit is most sheltered by rocky barriers, from the levelling influence of winds, other than those from the northwest. The spring which occurs in this locality near the base of these sand-hills occupies a natural depression of the general plain, Its issue spreads ina shallow pool surrounded by aquatic plants and shrubbery. The central spring source forms a deep hole, about two feet in diameter, bedded with quicksand, which is surges up intermittently at various points. The temperature of the water is 70° Fahrenheit. SAND HILLS ON THE CHIHUAHUA ROAD. ai On entering the sand-hills from the north, we first pass over a considerable swell of limestone rock, from the southern slope of which we pass at once into the hills of sand. Its surface, at first variously scattered with arid shrubbery, becomes as we proceed almost pure drifting sand, blown by the wind into varying ripple-marks, and assuming all the different shapes of drift and hollow imaginable. As the view of the surrounding country becomes shut out, there is presented an exact picture of the sandy dunes on an exposed seacoast, and it seems almost strange not to hear the roaring of the surf, or catch a view from the highest elevations of a wide ocean expanse. The greatest height of this formation is on the southern side, or in the convexity of the arch, which terminates with a somewhat abrupt face, merging into the shrubby plain below. Our route from this point leaves the Chihuahua road, passing more to the west, and thence skirting along the base of jagged mountains, forming a broken range to the south and south- west. The plain traversed is similar in character, and continuous with that on the opposite side of the sand-bills, having, however, an increased elevation. Our route, bearing 8.S.W., is interrupted by occasional spurs of limestone rock, proceeding from the adjoining mountains to the south. This character continues for some twenty miles, when we begin to notice an obvious change in the external features of the country. The frequent valleys leading from the broken mountain range on our left acquire a more fertile character, and, being removed from the incursions of drifting sand, support a richer growth of plants. Beyond this, the country spreads into wide basin plains, presenting tothe eye an uniformly smooth outline. The soil is composed of a stiff clay sediment, and is occupied exclusively with a growth of coarse grasses. In their lower depressions these extended plains frequently present a perfectly bare surface, destitute of all vegetation, the retentive soil either holding the product of recent rains in wide, shallow pools, or more often showing a surface cracked and blistered under the influence of an arid atmosphere. We find frequently scattered over its surface recent land shells, as indications of its lacustrine character. In certain localities these lower depressed flats are covered with a white saline efflorescence, resembling at a distance sheets of water, to the frequent disappointment of the thirsty traveller. The roads leading over these tracts are firm and excellent. The natural supplies of water are very inconstant, being in great measure dependent on rains. Our road hence, for a long distance, traverses a succession of these plains, of greater or less extent, alternating with short ridges, occasioned by the passage of an irregular mountain range. These ridges present along their line of elevation various depressions, at which the passage is generally accomplished by an easy gravelly slope. The exposed rocks are of carboniferous lime- stone, associated with various igneous products. This character of country continues till we reach the first flowing stream yet encountered on our march from the Rio Grande; this is the Rio Sta. Maria. As here exhibited, it shows a flowing brook of limpid water, from 10 to 20 feet in width; at the crossing knee-deep, and flowing over a pebbly bed. Its source lies far to the south, in the State of Chihuahua; thence flowing north, it empties, about 30 miles from our place of crossing, into Lake Sta. Maria. This lake is shown, by the examination of the boundary commission, to be in close proximity to the larger Lake Guzman, from which it is separated by a range of mountains. These lakes, though thus separated, belong to the same general basin, receiving the drainage of a large tract of country—the San Miguel and its tributaries entering on the north, and the ie, GEOLOGY. Sta. Maria on the south. The waters of these lakes having no outlet, are strongly impregnated with saline substances, so as to be unfit for drinking. The adjoining mountains on our route are of igneous character, being composed of vesicular and amygdaloid trap, forming more or less continuous ridges, ranging north and south. Associated with the fact of running water in this region, we see the country characterized by an unwonted appearance of fertility and verdure, not alone confined to the immediate borders of the stream, but extending over the hills and plains adjoining. Our route, after crossing the Sta. Maria river, takes a course 8. 70° W., (mag.,) passing over country characterized as above, bounded by mountain ridges of less height above the general surface than those before passed. The greatest development of mountain range lies to the west. The various rock exposures exhibit most abundantly forms of amygdaloid trap ; more rarely we meet with local exposures of limestone strata, or variable metamorphic products. Conspicuously in view in our direct course are the mountains in which the silver mines of Corralitas are located, consisting of an assemblage of rounded and peaked summits of various heights, rising from 500 to 1,500 feet above the adjoining plain. These mountains occupy an area of about 5 miles in length from north to south, and 2 to 3 miles in width. They rise isolated in the midst of a broad alluvial plain, sloping gradually on the east and west towards the respective valleys of the Sta. Maria and Corralitas rivers. A wide intervening depression also separates them from higher mountain ranges north and south. The latter mountains present a marked contrast in their precipitous sides and exposed rock of a basaltic character to the uniform smooth outline of the mineral-producing mountains. In these latter, indeed, the geological formation is everywhere concealed from view by a variable deposite of earth and gravel, thickly covered with a growth of grass. It is this fact which has probably given to these mines their Spanish appellation of ‘‘ Minas del mineral de la Escondida,’’ or hidden mines. The mines at present worked occupy the most northern point of the mountains, though mine- ral indications and abandoned excavations are common over the exposed face of the whole mountain range. The various excavations bring to view a very uniform character of formation, first passing through a variable layer composed of angular fragments of rock, imbedded in a dry brown earthy medium. The superficial rock exhibits a siliceous limestone of very close compact texture and dark blue color ; to this succeeds the true silver-bearing rock, being a form of suberystalline limestone showing the action of internal heat, of a much softer texture than the preceding, and of a whitish gray color, (specimen rock, No. 99.) In this latter rock are exposed the veins of argentiferous galena, frequently extending into the upper siliceous rock, but acquiring its greatest thickness and richness in this lower forma- tion. The veins of mineral penetrate this rock in the’form of variable sheets, dipping regularly at an angle of 45° to the northwest. Further details in reference to the character and working of these mines, with such reliable mining statistics as could be procured, will be found under a separate head. From the mines, by a gradual and continuous descent over a wide grassy plain, scattered with low mezquite bushes, we have in view at the lowest depression the valley of the San Miguel or Corralitas river, and the towns of Baranca and Corralitas. This plain, though usually dry, CORRALITAS—BARANCA. 13 supports a fine growth of nutricious grasses, and the mezquite bushes, which are scattered over its surface, are the main dependence for the necessary supply of charcoal for smelting operations. To first view, this would seem to offer but a poor supply of this needful article, showing in such situations only a shrubby growth; but owing to a remarkable peculiarity of this variable and wide-spread shrub, it is found that, when growing in such exposed situations, instead of develop- ing a distinct trunk, it forms thick underground stems. These being grubbed up by a class of peon laborers, are disposed in piles to dry, when they become fit for conversion into a superior article of charcoal. At a distance of 20 miles over the above described plain we reach the valley of the San Miguel river ; on the eastern bank of which, at a distance of three miles apart, lie the towns of Corralitas and Baranca. We here encounter a beautiful limpid stream and a fertile valley. At Corralitas, this river, as seen by us in the month of February, and again in April, 1852, had an average width of 30 feet, and 2 feet in depth, flowing over a sandy or pebbly bed between shallow alluvial banks. The season of high water is said to be in September, corresponding with the close of the rainy season ; at which time a large portion of the adjoining bottom-land is overflowed, the greater part of which is susceptible of cultivation. The width of this alluvial belt is variable, being occasionally spread out in low marshy tracts, 3 to 5 miles wide ; at other places contracted by the encroachment of mountains on either side. Some 16 miles above Baranca, to the south, are the remains of ancient and extensive structures, known as ‘‘ Casas Grandes,’’ still occupied by a flourishing agricultural settlement under the same name. A similar character of mountain ranges, as before noticed, bound the valley on either side; being, however, composed exclusively of igneous rock, the higher peaks showing generally a basaltic structure. The towns of Corralitas and Baranca are built up exclusively with a view to mining operations, the ore being transported to these places for smelting and refining. Living ina state of constant warfare with hostile Indians, the raising of cattle, or even the cultivation ot the soil, is confined to a bare supply of necessaries. Abandoned fields and deserted ranchos are frequently met with, showing a quite recent period of greater prosperity, the decline of which is most evidently due, not to the natural incapacity of the country, but the inefficiency and degeneracy of its population. In a direction W.N.W. from Corralitas, and about 24 miles distant, is the town of Janos. Our road to this place, after crossing the Corralitas river, leads at first over the wide grassy bottom-land of its western side, here nearly 5 miles in width. From this we pass over a ridge projecting into the valley below, and descend again on its opposite slope, following near the course of the lower valley, and passing over a shrubby plain similar to that before described, forming a sort of table-land gradually sloping toward the river. The town of Ianos is situated on a branch of this main stream flowing from the southwest. On reaching the banks of this latter stream, we find a mere rippling brook running over a pebbly bed. A short distance below, its waters are drawn off for the purpose of irrigating the gardens and cultivated fields which occupy the delta formed at the point of junction of the Janos branch with the San Miguel river. The town is situated on the gravelly table-land on the left side of the stream overlooking the river bottom, and set off in the background by a range of high mountains shutting out the view westward. Our route leads directly toward this western mountain range, which is crossed at a low depression, thence descending into still another wide basin plain, 14 GEOLOGY. extending in its greatest length from north to south, and bounded on the west by the clearly defined range of the Sierra Madre. The course we travelled thence lies W.N. W., inclining towards this mountain range, and cross- ing diagonally the wide basin plain intervening between this and the Janos range of mountains. About 10 miles from Janos we come upon a singular depressed valley, sunk some 50 feet below the gravelly plain, having a lower alluvial belt about a quarter of a mile in width, which is coursed by a limpid brook, and bordered by a scattering timber growth. This stream is said to have a lagoon source some three miles to the southwest; thence flowing northeast 10 or 15 miles, it terminates in a marshy lake surrounded by mountains; thus show- ing a character similar to that before noticed in reference to Lake Guzman and Sta. Maria on a smaller scale. From this point, following a continuous course W.N.W. (mag.,) the road passes over a gently undulating swell, composed of gravelly table-land, thence crossing a wide, open, alluvial basin, similar in character to those before described. We then approach the high mountain range of San Luis., Our progress toward the moun- tain base leads by a gradual ascent till a near approach brings to view deep gullied stream beds, connected with the drainage of the mountain valleys, and terminating on the alluvial plains below. Near their sources in the mountains these ravines contain running water, more or less copious, according to the character of the season. On reaching the first rocky spurs from the main range, the country assumes a most pictu- resque character. Clumps of live oak (Quercus Emory) edge the ravines, and are scattered along the mountain slopes. Cedar of a shrubby growth is also frequent, and the usual mountain shrub- bery serves to give a character of freshness and verdure to the scenery. Directly at the mountain base, and forming its projecting spurs, a reddish form of porphyritic basalt makes its appearance, showing a precipitous columned face and tabled summit. In the recesses of the ravines, as exposed by the mountain torrents, a variable deposite of igneous conglomerate is met with, flanking the central rocky mass. This central nucleus, as exhibited along the sides and summit of the mountain range, is an igneous volcanic product of ? quite recent origin, and characterized by Professor Hall as ‘‘ feldspathic lava,’’ exhibiting a granitic appearance. (No. 86.) At the point where the old road crosses the ridge, called the ‘‘San Luis Pass,”’ the ascent is quite abrupt, rising from the plain below 800 to 1,000 feet. The summit crest commands a most extensive and grand view. Looking eastward, the eye takes in at a glance the wide alluvial plain over which we have been passing, encircled by its irregular mountain boundaries, showing plainly its basin character, and in which here and there stand out isolated mountains, as islands in the broad expanse.* To the north and south is a continuation of the main ridge, more broken to the north, and apparently forming slopes of easier ascent than the one passed over by us. Quite possibly at several places there may be an easy transition from the plains on one side to those of the oppo- _ site slope. To the south the range is more continuous, of a rugged character, and increased height. * This description was written before the line under the treaty of 1853 was run. It will have been seen in the preceding part of this work that good passes were found to the north and within the limits of the United States. W. 4H. £E. SIERRA MADRE OR NATER SHED. 15 Westward we look down on another alluvial plain, less distinctly bounded by mountain ranges, and extending to a great distance from north to south. On its western limits, ata distance of about ten miles, this plain abruptly terminates by a slightly elevated terrace, the descent from which to the lower level of the San Bernardino valley forms the well known Pass of Guadaloupe. Here, then, we have the means of estimating the true character of this great water-shed, in its connexion with the present line of boundary both to the north and south. Considerable confusion has arisen from the vague terms and expressions employed by writers to describe the peculiarities of this part of the central axis of the North American continent. There has been wanting in their popular descriptions the elements of a general principle, appli- cable alike to all great dividing ridges. Geological science alone furnishes this element, giving, in the general result of its observations, the best means of elucidating all the points involved, and clearly explaining the several local peculiarities exhibited. In most of the descriptions hitherto given of this portion of the dividing ridge, we hear in frequent use the stereotype expressions that at or near the point under examination the range of the Rocky mountains becomes ‘suddenly depressed,’’ or ‘‘ flattened out,’’ to form the great Mexican plateau. Again, that at some imaginary point south of this great change of topo- graphical features rises another distinct range, called the Sierra Madre, continuing thence to form the line of cordilleras extending to the extreme of the continent. Now, such descriptions as these embody no clearly defined principle of geological science, and ? contain, moreover, errors of fact. The Spanish name of Sierra Madre (literally mother mountains) is the general term in use to describe what is called a dividing ridge with us, and its special application to the range under consideration is due to the important character of this divide as the mother range of the continent. Now, it is well known that all extended continental ranges are due to a line of internal dis- turbance, of varying intensity at different points, but in all alike characterized by the protrusion of various igneous products, together with the uplifting of adjacent stratified deposites, either altered in texture by the action of internal heat giving rise to the various metamorphic products, or showing the action of an uplifting force only in changes of inclinatian or dip of the strata. Most naturally, then, in view of the numerous and varied agencies at work, should we expect changes of character at different points of the same range, corresponding to points of greater or less intensity of the internal disturbance, or the different products erupted or exposed to altera- tion. Hence occur elevations and depressions, and variety of formation in the course of the same continued range. With this principle in view, we have a ready explanation of all the peculiarities exhibited in the portion of the range under examination. Thus the igneous products are mostly of modern origin, exhibiting various volcanic products in the form of granitic lavas, porphyritic basalts, and amygdaloid traps. These products show a very variable character of exposure, forming ranges irregular in their direction, and differing in composition. These several mountain ranges cover more or less the entire face of the country, including the dividing ridge only as one member of the general series. 16 GEOLOGY. The natural explanatory inference from these facts is, that the internal force, here represented in the continued mountain range, was diffused over a large space, and not centralized on one particular line. Hence arises no great prominence of one central chain, but a number of inde- pendent ranges, serving to equalize the general elevation and give the character of an elevated plateau to the surface of the country. Again, the same irregular action of the internal force, and especially the preponderance of recent eruptive products, favors a varied direction of the mountain ranges, by means of which areas are circumscribed and basins formed for the reception of aqueous depositions. Here, then, we see the origin of those extensive plains and stretches of table-land to which our attention has been so frequently directed in the preceding sketch. These same characters probably apply more or less closely to many other localities connected with the general dividing range, whether north or south of the point we are examining. We are now prepared to descend the western slope of this dividing ridge, and note the pecu- liarities of feature presented on our route westward. Decending, then, by an equally steep slope as the eastern ascent, and about the same height, we come upon the alluvial plain below. The lowest depression of this plain is composed of a light alluvial soil, and thence sloping gently upward to the west, exhibits a gravelly deposit, till, at a distance of about eight miles from the base of the mountain just left, we come upon the abrupt descent of the Guadalupe Pass. : This noted pass, which has been so frequently traversed on the line of emigrant travel to California, is now so well known as hardly to need a detailed description. “4 This pass has been properly characterized as the first step of considerable descent from the Mexican plateau to the heads of valleys leading to the Californian gulf. It has now been clearly established that at a point farther to the north, near the parallel of 32° latitude, the descent westward may be accomplished by a more gradual slope, and without leaving the basin of drain- age pertaining to the Gila river. The geological structure exposed in this mountain pass is similar to that before noted as occurring in the upper slope of the Sierra Madre, including feldspathic lava, granitic in texture, associated with basalt, stratified porphyry, and closely cemented breccias. These several forms, variously associated, serve to give a remarkable diversity and broken character to the rock exposure, presenting a confused outline of mingled crests, peaks, and ra- vines. Through these the road has to work its way by sharp turns and very steep descents. On attaining a lower level we pass down a ravine, gradually widening, which finally spreads into a small valley, watered by a fine running stream, and beautifully shaded by large sycamore and cotton-wood trees. This valley is closely hemmed in by steep rocky walls, marked by intricate ravines, and rendered picturesque by a varied assemblage of live oak, cedar, and other verdant shrubbery. In emerging from the higher points of the mountain range, the walls of this caiion exhibit various forms of stratified porphyry running into a breccia. The character of stratification has, at several points, a close resemblance to altered sedimentary deposits, showing a reddish color and a very uniform character of dip. We finally leave this valley, mounting up a steep bank, composed of gravelly table-land, rising 200 feet above the bed of the stream, thence passing by a gradual and continuous slope toward the main valley of the San Bernardino. The table-land here has all the usual characters of this SAN BERNARDINO TO SANTA CRUZ. 17 formation in other parts, not differing essentially from that of the Rio Bravo or Gila valleys, and terminates by an abrupt bank, bounding the alluvial basin below. This basin, forming, as it is said, the head of the Yaqui river, here shows a wide flat plain, extending from north to south, and having a breadth of three to five miles. On its western edge is situated the deserted settlement of San Bernardino, Adjoining this rancho are numer- ous springs, spreading out into rushy ponds, and giving issue toa small stream of running water. The valley is covered thickly with a growth of coarse grass, showing in places a saline character of soil. The timber growth is confined to a few lone cotton-wood trees scattered here and there. Signs of previous cultivation are limited, this settlement having been engaged principally in stock raising. The numerous bodies of wild cattle now running at large over this section of country are the remains and offspring of domestic herds, now widely scattered and hunted by Indians. The western side of the valley is precisely similar to its opposite, showing the same general character of gravelly table-land. This leads by a gentle ascent to a low point in the dividing ridge separating the valleys of San Bernardino and Aqua Prieto. ‘ A remarkable tower-shaped peak rises in the centre of this ridge, a short distance south of the road, forming a conspicuous landmark. This ridge is seen to be composed of one or more of the variable forms of volcanic products so often noticed heretofore ; the prevailing character is here a reddish brown granitic mass, The descent on the opposite (western) side of the ridge to the alluvial bed of the Aqua Prieto is over a long, tedious slope, the gravelly table-land giving place to extensive tracts of clay or loam, supporting a patchy growth of coarse grass. The ‘‘ Black Water’’ valley, at its lowest depression at this point, contains no constant running stream, its course being mainly oceupied with low saline flats or rain-water pools. Extensive lagoons are said to occur in this valley a short distance south of where the road crosses. The main tributary to this valley comes from the west, and is followed to its head on the line of wagon-road. Its bed consists of a wide ravine, coursing through pebbly strata, variously marked by the washings and drift deposits, caused by the occasional strong current derived from local rains. At other times its bed is entirely dry. The timber growth along its borders consists of hackberry and walnut. At its source there is a fine spring, issuing from ledges of stratified porphyritic rock, identical in character with that noticed at the foot of the Guadalupe Pass. The stratification is inclined to the northeast, and along the line of its tilted ledges the spring issue forms frequent pools of limpid water. From this point we pass in a circuitous course to the southwest, winding among rocky spurs, and thence passing up an upland valley, agreeably diversified with groves of live oak and covered with luxuriant and nutritious mountain grasses. On this route we pass gradually to a divide which leads, on its western aspect, to an eastern branch of the Upper San Pedro valley. The country here begins to assume most attractive features. To the north and west rise high mountain ridges clothed with pine and oak groves ; the intervening country is everywhere car- peted with fine grama grass, the nutritious quality of which is exhibited in the well-conditioned character of the numerous wild horses and cattle that luxuriate over this favored region. Water 3M 18 GEOLOGY. : is frequent in the valleys, and everything indicates a capacity for cultivation, the grazing capa- bilities being unequalled by any tract heretofore passed over. Beyond this the San Pedro valley spreads out in diverging branches to the east and west, thus drawing tributary a very extended mountain drainage. It is this latter character which sufficiently accounts for the fact that the San Pedro is the only branch of the Gila River, coming from the south, which furnishes an uninterrupted stream of running water along its whole course. At the point where the main valley of the San Pedro is reached we find an alluvial belt, variable in width, and occasionally marshy. These bottoms are flanked by terraced table-land of unequal heights, composed of a hard gravelly soil, and supporting a close sward of grama grass, giving a peculiarly smooth shorn look to the general face of the country. Occasional exposures of igneous rock, or the projecting spur of some mountain ridge, serve to diversify the scene; and quite constantly in the higher branch valleys is exposed a form of igneous conglomerate. This latter formation is exposed in irregular bluffs along the edges of these valleys, presenting washed faces and precipitous walls crowned with terraces. These higher points are frequently set off with the remains of deserted dwellings, plainly located with a view to defence. Other eminences, commanding extensive views, are occupied by rocky breastworks, serving the double purpose of watch-towers and strongholds of retreat. Associated with these are also extensive rocky enclosures, in which the cattle were secured. All these points are suggestive of the condition of constant warfare to which this commencing civiliza- tion was subject, and under which it was at last obliged to succumb. These upland valleys are only sparsely wooded by occasional cotton-wood or walnut trees. As we approach the mountains, however, the timber growth becomes more abundant, and the lower ridges are occupied by extensive groves of oak, which, on the higher points, are associated with pine and cedar. From the head of the ‘‘ Nutria’’ (southwest) branch of the San Pedro, up which our road passes, we commence the steep ascent of the mountain ridge lying between the Santa Cruz and San Pedro valleys. The character of this range is exactly similar to what we have before de- scribed as pertaining to all the higher mountains passed over on our route, west of the Sierra Madre. The height of the pass leading to Santa Cruz is not less than 1,000 feet above the respective valleys on either side, being equally steep and rugged on either slope. The same ridge, ex- tending toward the south and southwest, forms a continuous line of high mountains, lying between the San Pedro and Santa Cruz valleys; the preferable route for crossing is probably that taken by Col. Cooke in 1846. The upper route, being the one more commonly followed, strikes the Santa Cruz valley near its head source. The direction of this valley is at first nearly due south, giving the idea that its drainage is on the line of the rivers flowing south to the California Gulf. It is indeed so laid down on most of the maps of this region, but this is manifestly incorrect. About three miles south of the town of Santa Cruz the valley makes a sharp elbow; thence doubling on its former course, it continues north and northwest, being the same valley in which, lower down, are SANTA CRUZ TO TUCSON. 19 located the towns of Tubac and Tucson; thence leading toward (though probably hardly ever reaching) the Gila River, near the Pimo settlements. The situation of the town of Santa Cruz is highly picturesque, lying embosomed amid lofty wooded mountains. Its soil is fertile, abundantly watered, and susceptible of easy irrigation ; its elevation gives it a cool temperature, suited to the production of northern fruits and cereal grains. A cut-off, over the mountain range intervening between the two courses of the river, leads, by a distance of 18 miles, to a lower part of the valley, maintaining in the main the same gen- eral features, but showing a marked change in the climate. This latter fact becomes still more apparent in our progress downward, as shown by the comparative forwardness of vegetation. Thus a short journey of three days (or 80 miles) from Santa Cruz, between February 27th and March Ist, 1852, showed a difference in the advance of vegetation equal to a full month in time; so that while at Santa Cruz the cotton-wood trees were barely budding, the first day’s journey displayed their loose catkins, the second the opening leaf, and the third the full leaf. Greater aridity also characterizes the lower portion of the valley, and the live 01k, so common above, gives place to heavy growths of mezquite. The adjoining mountains on either hand become in great measure bare of trees, and present steep ledges of igneous rock exposed along their broken range. The immediate edges of the valley are flanked by a conglomerate forma- tion, similar to that noticed on the Upper San Pedro. Accompanying these changes the stream contracts, and finally, in certain points along its course, ceases to run, and the usual desert features of all waterless tracts in this region are exhibited. We thus pass the settlements of Tomocacori, Tubac, San Xavier, and Tucson, together with numerous deserted ranchos occupying various points along the valley. After leaving Tubac, which is situated about midway between Santa Cruz and Tucson, the valley expands into a wide open basin, the mountains receding on either hand, and the dry valley, now almost exclusively occupied by mesquite, is bordered by a wide stretch of gravelly table-land. On this table-land we meet, for the first time on our route, that most remarkable vegetable production, the Cereus giganteus. Further on it becomes abundant, its stiff trunks and branched arms rising up here and there like sentinels, and giving a most peculiar character to the landscape scenery. Approaching the town of San Xavier, noted for its superb church, contrasting strangely with the mud hovels surrounding it, we again come upon running water, with its constantly asso- ciated fertility and verdure. In this vicinity occur rocky knolls, composed of a dark-colored trap-rock, which formation becomes still more largely developed in the vicinity of Tucson, form- ing extensive ridges having a tabulated form and very irregular outline. The settlement of Tucson occupies the lowest line of constant running water, and consequently the last fertile basin lying in the course of this valley. Below this, on the north, succeeds the extensive desert tract lying between Tucson and the Gila River. In pursuing our course down the valley, the adjoining table-land gradually merges into the desert plain over which our road passes. Hardly, however, did it seem to deserve the name of a desert at the time of our crossing it. Owing to the refreshing influence of recent rains, a rapid growth of evanescent flowers gave its otherwise barren surface the aspect of a flower gar- den, regaling both the sense of sight and of smell with a profuse and varied assemblage of tints and scents. Water sufficient for our animals was found in ravines by the side of the road, and 20 GEOLOGY. a journey of eighty miles, otherwise dreaded, was, by an agreeable disappointment, rendered highly pleasant. Our journey was made in the first week in March ; doubtless another month might have changed its features materially. Our course lies quite regularly to the northwest, a broken line of mountains lying on our left, while to our right lies the extensive high mountain range northeast of Tucson. Directly in our course is a singular pinnacled peak, being the ‘‘ half-way point’’ between Tucson and the Gila; approaching this, we pass by a gradual ascent over a gentle ridge, forming a de- pressed point in a continuous mountain range extending from the pinnacled peak, on our left, northeast toward the Gila valley. Near the summit of this ridge we pass small alluvial tracts, then occupied by a luxuriant growth of young grass, and cut up by deep gullies containing abundant supplies of rain water. The rock exposure here has a more ancient appearance than any before passed, indicating an approach to the granite ranges of the Californian Cordilleras. We descend the northern slope of this ridge, passing over extensive clay flats washed by recent rains into frequent gullies, these finally centering in one form the irregular bed of a rain stream leading direct to the Gila river. The portion of the Gila valley thus reached is where the river, emerging from the high mountains occupying the mouth of the San Pedro, spreads out into the extensive alluvial bot- toms, occupied in part by the settlements of the Pimo and Maricopa Indians. The gravelly table-land here forms a gentle slope, leading from the distant mountains, and indenting the alluvial belt below. This latter consists of an upper level, supporting a shrubby growth of mezquite, and a lower bottom subject to river overflows. On these upper portions the Indians usually construct their dwellings, thus overlooking the lower cultivated fields. ‘The amount of land here capable of cultivation is quite extensive, forming a belt on each side of the river often several miles in width, and extending east and west for 20 miles or more. The stream of water, then at its average height, (in early March,) measured about 40 yards in width with an average depth of 2 feet, the volume, however, being considerably diminished by the extensive irrigating ditches drawn from above. The line of the river bank is at this season set off with lagoons and marshes, and everywhere bordered with a dense willow growth, rendering it difficult of approach. The dams, which serve the purpose of drawing off the irrigating water, are constructed of old willow trunks and snags; these, in the course of time, entangling the loose soil and sediment borne down by the river, furnish a bed for the willow growth, thus becoming more permanent with age. From a rock knoll of true granite, abutting on the river on the American side, a fine view is obtained of the general character and external features of this interesting locality. The character of the Gila valley, from this point down to its mouth, did not come under my personal inspection. All accounts represent a great uniformity of general features already sufficiently detailed. Thus we have a succession of basins, limited by mountain barriers, through which the river forces its way, forming cafions of greater or less extent. These basins are again occupied by more or less extensive stretches of gravelly table-land, representing the desert features of this region; through these are marked the alluvial tracts, MINERAL PRODUCTS. 21 ; 5 ec ; - varying in width and character according to the geological conditions surrounding them; through this the river works its sinuous course, with a swift current and turbid water, till it empties into the Colorado of the West. IV.—MINERAL PRODUCTIONS OF THE REGION OF COUNTRY, IN CONNEXION WITH THE MEXICAN BOUNDARY LINE, FROM THE MEXICAN GULF COAST TO THE COLORADO OF THE WEST. {Norr.—This report was written before the treaty of 1853, and applies more particularly to the old boundary under the treaty of Gaudalupe Hidalgo. ] The mineral productions of the region of country, in connexion with the United States and Mexican boundary line, are necessarily various, as corresponding to the different geological formations. The detailed examinations necessary to furnish a satisfactory estimate of the real value of this class of products are still wanting, and the peculiarities of the country itself place great obstacles in the way of arriving at clear results. Among the most important, which we may here briefly enumerate, are: First. Such as are connected with the various forms of igneous and metamorphic rocks, including Copper, Gold, Silver. Second. Such as pertain to the stratified or alluvial deposites, including Coal, Salt, Gypsum. E FIRST CLASS. Copper is quite frequently found in connexion with porphyritic rocks. The most usual form of the ore is that of green malachite and red oxide. The locality best known is that of Santa Rita del Cobre, which was profitably worked about 20 years ago. Analysis of ore from this locality exhibited a yield of 75,%,°; per cent. of copper.—(See analysis by Professor T. Antisell.) No mine of copper is at present worked in any part of the region under examination. Gotp is said to be sparingly found at various localities, in connexion with diluvial deposites, derived from adjacent igneous rocks. It is here met with in a finely disseminated state, and has never yet been found in sufficient quantities to yield a fair return for the labor expended. It would seem here to belong to the same character of formation as that of Mexico, associated with forms of porphyry, and never to approach in richness the deposits of California; such, indeed, we would expect in the general absence of metamorphic slates and quartz veins, so well known to be the most prolific source of gold in other regions. But one locality of the true gold- producing rocks was met with on our route, and that was at the furthest western point, near the Pimo villages, on the Gila.—(Specimen rock, Nos. 97 and 98.) Sizrver.—Silver ore is found at several localities, mostly on the Mexican side of the line. It has also been found in the Organ Mountains and various portions of southern New Mexico. The localities best known in Mexico adjoining the boundary line occur at Corralitas and Presidio del Norte, in the State of Chihuahua, and at Santa Rosa, in the State of Coahuila. The only one at present successfully worked is that at Corralitas, before referred to. The ore from which the silver is obtained is a form of Argentiferous Galena, containing very variable proportions of silver. According to the statement of the principal proprietor of these mines, Mr. Flotte, the average yield of the best mineral is 0.50 per cent. of silver ; analysis of a single specimen by Professor Antisell gave only 0.03 of one per cent., a discrepancy difficult to account for, except on the supposition that the ore varies remarkably in the relative amount of contained silver. 22 GEOLOGY. The working of these mines is carried on in a very rough manner. The excavations simply commence with the surface exposure of the veins, thence following them down by rude and irregular shafts, inclined according to the dip of the vein, at an angle of 45° to the northwest. The ore is extracted by blasting, both the mineral and the refuse material being brought up on men’s backs. Where the depth is such as to cause an accumulation of water the mine is abandoned, The richest of these distinct mining excavations is that called ‘*San Pedro.’’ This, when visited in 1852, had attained a depth of eighty yards. The mineral vein, as exposed along the line of excavation, exhibited a very variable thickness, from one to twelve inches ; the character of the ore and its specific gravity also varied at different points.—(See description and analysis by Professor T. Antisell.) The mode of extracting the silver is by a double process of smelting and refining. By the former the ore is reduced, by the means of a common furnace, to the form of an alloy of lead and silver. In the refinery the lead is removed by burning it out in a blast furnace, leaving the silver in the shape of irregular cakes, weighing about eight ounces each. The refining process occupies about twelve hours. The following information in reference to the working of two of the principal mines and reducing establishments and the amount of silver produced is furnished by the proprietor, Mr. Luis Flotte, of Baranca. The mine of San Pedro employs about forty men, whose wages average $10 per month. The amount of ore extracted by this number of men monthly is from 160 to 200 loads, of 300 pounds each. This is calculated to yield from 24 to 32 ounces of silver per load. The average monthly expense of working this mine is about $1,000. The mine of Leon employs about the same number of men, and requires the same expense of working, viz: $1,000 per month. The amount of mineral extracted from this mine is about 500 loads per month, of 300 pounds each, estimated to yield three ounces of silver to the load. This ore is chiefly valued as a flux to assist in the reduction of the richer mineral. Smelting Establishments and Refineries. There are two of each of these establishments in operation at Baranca. The number of men employed in all the necessary labor, including hauling the mineral, manufacture of charcoal, &c., is 125. The average monthly expense is $2,000. When in full operation, the amount of ore smelted is 180 loads of San Pedro ore, and 500 loads of Leon mineral, of 300 pounds each. ‘Total, 204,000 pounds per month. The yield of silver for this amount of ore would be an average of 420 pounds, at $16 per pound, equal to $6,620, leaving a profit for capital invested of $2,620 per month. The total amount of silver produced at this mining location for six years ending January 1, 1852, as given by the two proprietors, is— Mr selimsehlotte; at) Barancay.. cfscsascstost aactasiees en tenesesiiicsneeosenecaeenctis $340,000 Sefior Don José Maria Zuloaga, at Coralitas .............sscsccecsereceveeseeees 146,000 MB Otallenserisiesnches sceneathoaselsenisesesenacess DisGadewsnnesaueceet 486,000 MINERAL PRODUCTS. 23 Coat.—A remarkable form of coal, closely resembling cannel coal, is found in connexion with the cretaceous strata on the Rio Grande, being exposed at several points along the course of the river from the mouth of the Pecos to Laredo. The character of the formation and economic value of the product, as an article of fuel, will be given in the report of Mr. Schott. Sar occurs in connexion with salt lakes, occupying depressed portions of the wide desert tracts, to which the term of Llano Estacado is applied. The product is more or less pure, and in greater or less abundance, according to obvious local causes. Gypsum occurs in connexion with marls, belonging either to the upper Tertiary, or alluvial series of deposits. In such situations it frequently forms very extensive beds, composing the main bulk of local table-land exposures. In concluding this report, I have to express my special obligations to Professor James Hall, of Albany, who has kindly favored me with his views of the geological collections of the survey, and otherwise rendered assistance in making out this report. Similar acknowledgments are due to Professor John Torrey, of New York, in reference to the botany. Especially, in this final conclusion of my duties on the Mexican boundary survey, are my sincere thanks due to Major W. H. Emory, with whom I have been directly associated, in field and office duties, for the last five years, a length of time signalized by repeated and considerate acts of kindness on his part, as my superior officer, and gratefully remembered on mine. Respectfully submitted. €) C) PARRY, MDs Botanist and Geologist U. S. B. C. I consider the present a proper place to insert the analysis of minerals, not only of those referred to by Dr. Parry in the above memoir, but those which were collected in the new Terri- tory subsequently to his withdrawal from the commission. In the Organ Mountains, near Fort Fillmore, and at several other places along our route, silver mines have been opened by enterprising Americans, but I have not obtained analyses of the minerals procured at them, for the obvious reason that the experience of the miner will be a more valuable test of the value of the mine than any which can be afforded by specimens. Nothing can be a more fallacious test of the value of a mine than the analysis of pieces of ore taken at random from the metallic vein, as most of these have been. Its true value can only be arrived at by actually working the mine, which, for the purpose of experiment, may be carried on upon a very limited scale. Those familiar with the localities will see in the analysis that specimens from veins of known value are here exhibited as yielding a very low per cent. of precious metal. These specimens are therefore not fair examples of the whole. When at Janos, I observed the inhabitants collecting nitre from the soil by the rudest process, and was informed that all the powder used in blasting at the mines of San Pedro was manufac- tured from the nitre thus obtained. The soil, in many places almost destitute of vegetation, is no doubt surcharged with this substance, and a portion of soil was collected to be analyzed, and 24 GEOLOGY, has been mislaid. In view of the difficulty experienced in obtaining this substance in time of war, the subject is well worth the attention of government. Many of the earths and rocks were placed in the hands of my lamented friend and classmate, Professor J. W. Baily, for microscopic examination. His state of health did not permit him to go entirely through with the examination. He, however, had made some progress, and I here give a short arid characteristic note from that eminent and beloved gentleman, which gives an interesting summary of the results of his investigations up to that time. WEE West Pornt, N. Y., April 2, 1856. Major W. H. Emory, Commissioner U. S. M. Boundary Survey. Dear Mason: This time we have some luck. ‘Three of the specimens last sent prove quite interesting. They are Nos. 18 and 19, from cretaceous strata, Leon creek and Leon spring, West Texas, and No. 23, travertin-like crust, from bed of San Pedro The specimens Nos. 18 and 19 are interesting, as containing a considerable number of fossil Polythalamia, (microscopic cal- careous shcells,) and still more so from yielding fine green sand casts of the same minute forms. This fact of the occasional formation of green sand in the cavities of minute shells was discovered by Ehrenberg, and I have verified it in specimens from several American localities. I would be glad to get a good supply of Nos. 18 and 19 for further study. The travertin-like crust, No. 23, has an organic basis. When treated with chloro-hydric acid, it leaves a spongy mass, greater than the original volume, and composed of plants belonging to the genera Oscillatoria, Hydrocoleum, &c. There are several of these plants which delight in calcareous waters, and always incrust themselves as in the specimens you have sent. 3 With regard to the moss agates, I cannot satisfy myself that the filamentous mosses in them are really of confervoid origin. If they were, it is now impossible to distinguish a single vegetable cell. I incline to the belief that they are rather concre- tionary deposits of oxide of iron, which may possibly have had organic nuclei to collect upon; but if so, these last have disappeared. The cretaceous earths attached to the Texian fossils will be well worth further study, and any which have specks of green sand in them will be particularly interesting. Yours, very truly, J. W. BAILEY. New York, 13 Mercer street, January 31, 1854. Three samples forwarded for analysis : No. 1. Silver ore from San Pedro mine. No. 2. Ore from copper mines. No. 3. Ore from Leona mines. No. 1.—Argentiferous galena ; partly granular, chiefly fibrous; specific gravity 603. It contains iron pyrites, dissemi- nated in small cavities. The amount of silver was determined by moist analysis. Two grammes of ore were treated with nitric acid ; to the clear solution hydrochloric acid was added—the resulting cloride of silver fused. The lead was determined as carbonate, by adding carbonate of soda to the solution, after separating the silver. Some adhering earthy matters remained undissolved by the nitric acid. Analysis yielded in 100 parts : Mmsoltib edsihica tes a oxo cal ye ee ah a 4. 50 IQEC) Soe ss Se eS Sect soe SSeese aes Stokes 82. 20 Ul Ya ee ce eg rm ee 12.79 Oxide.of iron; and traces) Of. copper) = ——— = 2 =, Do — Je aig Oe B 2 5 ee Se SS = gi ee ee a gicgmen a eae anae SSeS = OG Gr ae wes gee = aa —— = SS Se Te errs fe nga cee a | ie aires, F: a « in ae SN SSS oo —"~— = aS ee ma a ——. ime aaah <= ae eit er SS * Se Re SSS SS x; eS aS ao a am > a Su oS — Es 2a See RS ee Sey D5 A. Dark-colored igneous rock of vesicular or close texture, disposed in vertical columns or horizontal masses. B. Volcanic breccia in evenly horizontal strata, light-colored and of crumbling earthy texture. a. Emory’s Peak, 2,500?’ above the waters of the river, having the appearance of a crater. Rumor had led us to expect, in connexion with this chasm, an extensive river fall, but such did not prove to be the case. Rapids, indeed, do occur sufficiently severe to render a safe passage by boats a virtual impossibility, but no distinct fall from an upper to a lower ledge of rocks was encountered by the surveying party. Indeed, from a priori reasoning, we should hardly expect to find such a feature in this location, where the strata are of such uniform texture, and where the evident marks of such long continued abrading forces tend to level the river bed. All the rapids seen along the course of the river are connected either with a talus, thrown down from the projecting cliffs, or with the irregular deposit brought down from the beds of tributary streams. PRESIDIO DEL NORTE TO SAN VINCENTE. 57 Within this cafion there is rarely a foothold visible along the line of the ordinary water level, and at no place for the whole distance of ten miles would it be practicable to make a safe descent to the water’s edge, still less to ascend. The ‘‘ facile descensus’’ would here be truly “¢ Averni.”’ SECTIONAL VIEW OF THE GREAT CANON OF THE RIO RRAVO DEL NORTE, NEAR SAN CARLOS. =—-— ~< 10 mutes Ss Sor eee (as 7, Set A. Perpendicular walls of limestone rock, having a gentle dip to the west, giving increased height to the wal's of the cafion, along the eastern course of the river. B. Cross section of the cafion, showing the general shape of the chasm. (Same scale, horizontal and perpendicular.) Note.—For 300 read 800. It would be barely possible, in a time of high water, to conduct a boat safely through this stupendous chasm. A strong wooden boat, which accomplished the entire distance from El Paso to this place in the service of the survey, being here cast adrift, was found in broken fragments along the river course below. There are rumors among the Mexicans living near here of the attempted passage of this cafiton by some daring individuals, but no authentic record of a successful result. A perpendicular cross section of this cafion exhibits a rather peculiar feature, at least such as is not noticed elsewhere: thus, instead of a regular slope or perpendicular descent of the cation walls on either side, we have an expansion of the breadth of the caiion at two distinct points, above and below. The vertical cross section would thus correspond to that of a pitcher, showing first a flaring top, then a contraction, and again bulging out below; the peculiarity consists in this lower expansion, but is evidently susceptible of a ready explanation. Thus, it may be regarded as due to the irregular action of river flood and recession, acting along its pent-up course in such a way as to exert a greater denuding effect on the sides of the chasm than on its lower bed. Professor Hall has suggested that such a shape would be apt to result, in such situations, from the gradual diminution of the body of running water, naturally connected with increasing land elevations. The average width of the stream within this caiion is probably about 100 feet ; and when we come to include herein the immense floods that in other places spread out the river overflows for miles, we can appreciate its terrible energy when pent up within such narrow limits. Sufficient has, doubtlessly, been said on this most remarkable feature in the course of the Rio Bravo ; its details, however, will have a general application to what is to succeed, and render a more elaborate notice of the successive cafions unnecessary, all of which resemble the above in general aspect, but none equal it in extent and grandeur. 8M 58 GEOLOGY. In order to reach the lower basin in the course of the Rio Grande, beyond the San Carlos canon, you have to make an extensive detour, and pass again up the San Carlos creek about ten miles to the ‘‘Oid Presidio of San Carlos.’? This now deserted adobe structure is situated on the eastern side of the valley, occupying gravelly table-land, and overlooking the alluvial bottom, which shows the remains of former cultivation in extensive lines of irrigating ditches. The cultivation carried on by the present inhabitants of San Carlos is confined to the upper part of the valley. These cultivated fields extend some five miles, and present a rich belt of alluvial soil, abundantly watered and consequently fertile. On leaving the San Carlos valley, we pass by a southeast course over an upland, gently undulating plain, set off by occasional rocky knolls, and encircled by mountains mostly of voleanic formation. Our course thence, inclining more to the northeast, leads over broken swells of the limestone range pertaining to the cafion above described. Thus, by a series of steep descents, the lower basin of the Rio Grande is gained at a point some distance below the mouth of the San Carlos cation, and nearly opposite the range of the Chisos mountains. The general character of the valley here presents the usual features of gravelly table-land, flanking a narrow alluvial belt along the winding course of the river. The bottom-land here is again bordered by cotton-wood and willow growth. Towards the exit of the river, from the San Carlos cafion above, the general aspect of the valley is modified by irregular outbursts of eruptive trap rocks, confusedly alternating with volcanic breccias. The general course of the river through this basin is easterly ; the bottom-land is of limited extent, and generally barren. At several points here are seen Indian fords and broad trails leading from upper Texas into Mexico. These beaten paths are unmistakable indications of the route pursued by the Camanches on their extensive foraging expeditions. These routes, both to the north and south, are comparatively open, and are apparently deter- mined by the depressions that occur in the elsewhere uninterrupted line of mountains. The continuation of our land route down the river compelled us to cross, with our pack train, at one of the Indian fords called ‘‘ Vado F'leche,’’ thence taking along the Texan side to turn the spur of the mountain range forming the San Vincente cation. This range is exclusively composed of cretaceous limestone, similar in texture to that in the San Carlos cafon above. It differs from that, however, in being of less height and extent, and in showing, in place of a regular western dip, a distinct anticlinal axis, the dip being quite abrupt on either side. Cretaceous fossils, identical with those found at San Carlos, serve plainly to characterize this formation. The cafion of San Vincente is very abrupt and of considerable height ; the ridge adjoining is also very broken, exhibiting steep descents and branch chasms, which rendered the survey extremely arduous. The passage through this catinon was accomplished by our India-rubber boats, one of which was, however, capsized in shooting a sharp rapid. On emerging from this range, the Rio Grande opens on the San Vincente basin, in which, on the Mexican, side is situated the now deserted Fort San Vincente. This basin differs from all others yet seen in being exclusively formed of low ledges of a dark-color :d stratified rock, showing low bluff ranges 30 to 50 feet high. These ridges have a very uniform dip of 15° to the northeast ; they occupy in great measure the place of the usual PRESIDIO DEL NORTE TO SAN VINCENTE. 59 gravelly table-land, forming along the line of strike open valleys. Arid and bleak sterility characterizes this formation, to which the scant and sandy bottom-land is hardly an exception. Fossils are occasionally copiously imbedded in these ledges ; among which principally Ostrea, Ammonites, and Turritella occur, aud show that the formation belongs to the upper cretaceous series. At some points there is an evident approach to the lower Tertiary formation. VIEW OF PRESIDIO DE SAN VINCENTE AND SIERRA CARMEL The eastern limits of this basin are marked by the extensive and elevated range of the Sierra Carmel, presenting directly in front an unbroken wall composed of a light-colored limestone. This shows a dip to the east. Its western aspect exhibits a line of perpendicular escarpment rising in several peaked knobs to a great height. The line of mountain wall thus exposed presents a series of terraced elevations, dividing horizontally the abrupt face of rock exposure. Along these terraced lines, and associated with the talus there accumulated; is a growth of dark-green shrubbery, strongly contrasting with the ochreous-colored wall, which forms the background. This mountain range further to the southeast exhibits an extensive development of igneous rock, showing in the distance a very rugged outline. The occurrence of { hese several ranges forces the river from its east and southeast course, and gives it an abrupt turn to the north. The mountain barrier is thence passed at a lower eleva- tion of the main range forming the Carmel cation. The river here cuts through the limestone strata, showing a distinct dip to the northeast ; after a course of 8 miles, the river emerges on the eastern slope of the Carmel range. To accomplish the same distance with our mule train a detour of 40 miles was necessary, leading again to the river at the point where it emerges from the mountains. The operations of the surveying party being here suspended, our route hence led southward to the Mexican settlement of Santa Rosa, thence to Eagle Pass. 60 GEOLOGY. The eastern slope of the Sierra Carmel shows the strata of cretaceous limestone inclining eastward at an angle of about 20°; its exposed face is variously marked up by irregular trenched valleys and abrupt points and ledges, due to the natural denuding forces of water drainage and atmospheric action. This slope terminates in an irregular valley below, having its drainage to the north, and leading direct to the Rio Grande. Further south is conspicuous the extensive igneous development of the mountain range, rising in jagged peaks to an Alpine height, and presenting in the forest growth, which clothes its sides, agreeable features of verdure, contrasting strangely with the river valley and its bare outline of desert hills. The most northern outlier of this igneous formation is the singular peak known as the “¢ Picotena.’’? Lying at a distance of about 5 miles from the river, it rises abruptly from amid the surrounding limestone ranges, shooting up a sharp conical peak of basaltic structure. This peak, by its height and external features, presents a most striking landmark. The country stretching to the north and east in the course of the river is less interrupted by high mountain ranges than has yet appeared on the line of our route, and presents features precisely similar to those before noticed in connexion with the lower valley of the Pecos. Igneous exposures disappear altogether, or are of very limited extent, and the limestone strata are but little disturbed. The numerous deeply cut valleys leading to the river are bounded by abrupt walls, rendering travelling, except in the direct line of their drainage, next to impossible. In attempting to follow down the river with pack animals, the only practicable course was to follow up to near its head one of these tributary ravines, thus reaching the general table sum- mit, and then to pass over to and down another ravine leading to some uncertain point of the river below. By this plan it not unfrequently happened that, in order to make a distance of 5 or 6 miles by the line of the river, a detour of 30 miles or more was necessary. Each of these detours, moreover, leads over a country destitute of water, except the uncertain rain water retained in rocky wells, which generally occupy positions inaccessible to animals. This character of country continues hence uninterruptedly to the mouth of the Pecos river, about 80 miles distant, presenting great uniformity in the general external and geological features of country. Our course led along the eastern base of the Sierra Carmel, bringing to view, in connexion with its larger development of igneous formation, a section of country extremely picturesque, including well watered valleys, timbered mountains, and upland plains covered with a luxuriant growth of nutricious grass. Indian traces abound in these vicinities, and the deep recesses of the adjoining mountains afford secure retreats, where the animals plundered from the Mexican settlements are driven to recruit, in preparation for their passage across the Rio Grande into Texas. To this character of country again succeed ranges of cretaceous mountaius, showing a general easterly dip of strata, and connected with upland basin plains mostly waterless. At a distance of about a hundred and fifty miles south from the Rio Grande we reach a system of elevated basins, having frequently a drainage distinct from the valley of the Rio Grande, forming extensive inland lakes fed by numerous rivers. The noted Bolson Mapimi is the largest example of this lagoon formation. Several, however, of these lagoons on the northern edge of this elevated area give rise to tributaries which empty into the Rio Grande, Of this latter class, the ‘‘ Laguna Agua Verde’’ SAN VINCENTE TO EAGLE PASS. 61 is an example. Along the line of one of these valleys last mentioned our route led, thus threading our way through the mountain barriers, forming the northern line of the Santa Rosa range, thence emerging on this charming valley a short distance above the town of Santa Rosa. The route thence to the Rio Grande at Eagle Pass is over an open country, occupied by low swells of cretaceous limestone, thus merging into that character of country pertaining to the region of central Texas. For further details of the lithological character and fossil contents of the various rock ex- posures above alluded to, reference may be had to the lists of Mr. Conrad and Professor Hall. A very interesting paper from the latter gentleman also contains important generalizations, derived from examination of the various geological specimens collected in this and other expeditions. The numerous illustrations of scenery from various sources will supply all that can be desired in regard to the general aspect of the region under consideration. CHAPTER LM. GEOLOGICAL OBSERVATIONS ON THE COUNTRY ALONG THE BOUNDARY LINE LYING BETWEEN THE 111TH DEGREE OF LONGITUDE AND THE INITIAL POINT ON THE RIO COLORADO. [By Arthur Schott, Assistant U. 8. B. C.] Geographical terms for this section of the boundary line would be Sonorian or Pimerian, as it runs through the northwestern part of Sonora, which also bears the old Spanish name of Pimeria Alta (High Pimeria ;) and since it intersects both meridians and parallels in an oblique direction, it is called, in geodetic language, ‘‘ azimuth line.’’ This line lies entirely on the eastern slope of the basin of the Gulf of California, and falls on the divide separating the waters of the Gila from the streams of Northern Sonora, which, after flowing in a southwesterly course, empty into the Gulf of California. The hypsometrical and general geological features can only be expressed approximately, for circumstances prevented actual measurements. At the eastern end of the azimuth line is the Sierra del Pajarito, from the highest point of which an imaginary line drawn to the Rio Colorado would give a grade of about 22 feet to one mile, or its equivalent, 0.41 to 100. The highest point may be set down at about 5,200 feet above the level of the sea. This point does not, however, reach the pine region, which in this latitude may be considered as occurring at an elevation of not less than 6,000 feet. A monoto- nous simplicity is a characteristic of the topographical features of Northwestern Sonora; and but for a close examination, there would only be disclosed a mere dualism of diluvial drift and pluto-volcanic mountains. The drift covers many of the mountain ranges almost to the tops, particularly those which approach the bottom-lands of the Colorado. The northwestern part of the line runs over what may be called a veiled country ; for of the mountains, only their crests are to be seen above the desolate sand-flats of the general level of the surface. It is through these forsaken barrens that the Rio Colorado, with its timbered bottom, winds its course towards the waters of the Gulf. Comparing the geological edifice with the structure of animal organism, the mountain ranges jutting up through this vast level of drift represent the skeleton ; the diluvial main the sinew and muscle ; and the alluvial deposits the tegument or epidermis. The last mentioned is poorly represented. The scant vegetable cover facilitates, however, the observations of the geologist. Alluvium is seen first and as the uppermost stratum ; except at the extremities of the line, there is, however, but very little to be met with. As might be expected, it abounds most in the bottom-lands of the Colorado ; but, strange to say, it is even in greater abundance on the: highest mountains than on the plains. It frequently collects in such quantity in the little valleys and in the cavities of the broken sides of the mountains as to give rise to a more complete develop- COUNTRY WEST OF THE 111TH MERIDIAN OF LONGITUDE. 63 ment of vegetable life. The plains exposed to the drifting sand as well as to climatic severities are almost wholly deprived of an alluvial coat. A few traces may be looked for at the so-called ‘« Playas,’’ (depressions in the plains.) What little rain may fall collects here, and bringing down with it the lighter particles of the surrounding soil, affords a foothold for vegetation, which presents, however, more a mass of equals than a diversity of species and genera. Often, apparently, this premature effort of nature to develop vegetation is sadly counterbalanced by the saline character of the soil, which causes the prevalence of corresponding forms, as obione, salicornia, salsola, chenopodium, and others, in the place of algarobia, prosopis, or even salix, the usual types in analogous localities. The plains lying between the mountain ranges are formed of a more or less uniform deposit of loose diluvial sand, its composition not differing essentially from that of the adjoining mountains. This diluvial main may, therefore, be called the debris of the adjacent mountains and of the underlying mas. As to the formation of this diluvial main, we incline to the opinion that it is the residue of a sea once a connecting link between the waters of the Atlantic and Pacific. Changes in the constituents of this deposit certainly occur ; but they are of a local character, besides having a certain uniformity. Fragments of quartz, mica, feldspar, and other similar elements of crystal- line and igneous rock, associated with calcareous particles, constitute the formation of that vast region of deserts stretching from the eastern foot of the California Cordilleras to the table-lands bordering even the Rio Bravo. This section of country may thus be viewed as the bed of an ocean variously intersected by numerous reef-like or dyke-shaped mountain ranges. In the immediate vicinity of the mountains, isolated beds of pebbles are sometimes seen, the lithological character of which indicate their origin. These pebbly beds, however, must not be confounded with similar ones occurring occasionally about the centre of the desert basins and frequently along the dry water-courses. The former are the disintegration of the rocks, unmoved from their original locality, whilst the latter are gatherings of an immense area. The latter bear evidence of being brought from the most opposite and most remote geographical quarters ; pieces of limestone representing both the carboniferous and cretaceous periods with tertiary and even traces of lime recently precipitated ; these fragments are mingled with agate, chalcedony, semi-opal, opal, jasper, slates, silicia, breccias, and crystalline and amorphous conglomerates ; here, also, are silicified, agathized, or opalized fragments of wood side by side with pieces merely incrusted—scarcely metamorphosed or entirely unchanged, and of quite a recent geological date ; semi-opal, formed entirely of shell, whose age is readily recognized by the numerous nummulites associated with it ; agate, with neat fragments of encrinitic or coraline forms ; jasper or horn- stone, which, under a common lens, discloses both the texture and grain of coniferous wood ; opal, exhibiting traces of the structure of fossil-wood, with distinct annular concentric rings, but no marks of the grain could be detected; glass-opal, and hyalite, containing casts of some forms of the coral age pisolites, in appearance like a toadstone, which are either unchanged or metamorphic. The deserts of both sides of the Colorado and along the Gila abound with these pebbly beds, surrounded by and. occasionally entirely buried in the sand. To the scientific observer they are pearls of this vast terrestrial ocean, which once formed the bottom of a sea, whose currents in all probability collected these pebbly deposits, Since the 64. GEOLOGY. water has receded, an ocean of a more subtile character sweeps over this area. Arial currents are now driving the shifting sand from place to place as the waters of the sea once did. Besides the general inclination of the western slope of the Sierra Madre towards the Gulf of California, an increased inclination of stratum is perceptible around the bases of the intersecting sierras. This does not, however, affect the mean ascent of the main land, and may be ascribed solely to the deposition of debris, as the angle formed by the inclination of the diluvial deposits was observed (particularly in the valley of the Santa Cruz river) to be = 2.5°. The general ascent already referred to is conclusive proof of the action of upheaval forces since the deposition of the quaternary or diluvial drift. A straight line over its surface from the valley of the Colorado to the foot of the Sierra del Pajarito, where it ceases, gives a grade of 12.44 per mile, or 0.23 ft. in one hundred, In some valleys heading on the slopes of this sierra this deposit may be seen; but its occurrence in such localities being exceptionable, does not affect the mean angle of inclination of the stratum. The height to which this diluvial main rises, in its approach to the Sierra Madre, gives a striking peculiarity to the features of the country. But for it the rugged crests of the sierras would be scarcely accessible. : If the climatic conditions were favorable, these now bleak and forbidding mountains would present a region teeming with vegetable and animal life. Instead of that, this country now lies an arid waste. The few periodical streams descending from the mountain sides share a similar fate, for no sooner do they reach this drift than they disappear from the surface, sinking to unknown depths, and leaving only in the vicinity of the mountains slight marks of rudimentary drainage, clumps of shrubbery bordering dry water-courses. The vegetation peculiar to the diluvial main is similar to that of the corresponding localities on the eastern side of the Sierra Madre and west of the Colorado. Besides smaller and more inconspicuous forms, are the Larrea, Fouquiera, Obione, and other chenopodiaceous shrubs ; there are also a variety of leguminous plants, numerous members of the Cacti family, and some few bushes and trees, all well known to the traveller whose fortune has led him through these desert regions. In passing to the consideration of the underlying strata—those upon which the diluvial deposits rest—a deep step is made at once; constituents of the secondary age seem to be wanting. Crystalline rocks of primary and transition age—more or less metamorphic—constitute the bed upon which the diluvial deposit lies. This bed does not occur as an even or slightly inclined plane, for its surface is variously broken by eruptive masses. These upheavals have not only disturbed and protruded through the primary and metamorphic strata, but carried with them- selves masses of the latter above the level of the supercumbent deposits. Thus are formed the mighty sierras now representing the frame-work of our geological edifice, most of which may be distinguished as Pluto-volcanic. With the hypsometrical features of these sierras, better called cordilleras, three important peculiarities are connected. These are, 1st. Parallelism among themselves, with the Gulf of California, and with the Pacific coast. 2d. Articulation. 3d. General petrographic relation- ship. SPANISH TOPOGRAPHICAL EXPRESSIONS. 65 The parallelism is a fact now better understood than the natural laws which effected it. The linear extension of the axis may be supposed to be the result of electro-magnetic forces combined with the action of tidal currents, together with other causes, such as isothermal, isoclinic, and isodynamic currents. We offer the following explanation, founded on our own observations : After the first formation of the dykes and reefs composing the sierras, the result of vol- canic forces, acted upon by electro-magnetism, sedimentary strata commenced to be formed. The igneous forces, however, at this time prevailed, and as a consequence, the strata of that era exhibit a crystalline character. By the increase of volcanic detritus and sedimentary material, the igneous ejections were confined to certain fissures only, whilst the action of aqueous forces became more general. The crust thereby becoming more and more firm and overlaid, the molten masses had to seek other outlets, determined, perhaps, by the character of the sedi- mentary rocks through which they led. To the stratification, lamination, and cleavage of the sedimentary rocks, as determining the subsequent direction of these volcanic forces, we may ascribe the formation of the catenary mountain ranges and dykes, and the cellular system of their intermediate bases. The mountain ranges are mostly one-sided upheavals of metamorphic strata; the dykes, on the contrary, are essentially volcanic eruptions. The two classes of mountains are seen in a diversified combination of volcanic, plutonic, and aqueous or sedimentary rocks ; syenitic and granitic lavas; trachyte and trap still exhibiting clear traces of lamination, cleavage, and strati- fication ; granite, gneiss, syenitic, and various transition slates. How far this view may agree with the observed geognostical data, the special survey will show. Before entering on this subject, we propose some remarks on a few Spanish terms which define their objects with a precision that could hardly be otherwise arrived at except by much circum- locution. These words are— Cordillera, which means a long, continuous range of mountains, composed of several ridges, sometimes united by cross spurs, and intersected by passes or narrow valleys. The essential characteristic of this word is, that it means a mountain composed of two or more ranges forming one orographical body, just as several strings twisted together make a cord. The words cord and cordillera are formed from the same stem. Sierra, a saw, indicates a mountain range with a serrated crest. A cross section of either sierra or cordillera is very small compared with its longitudinal axis. Cuchilla,—This signifies a branch or outrunner of a sierra, which it usually resembles in its physiographical character. Its sharply edged crest, in all probability, suggests its name— cuchilla meaning knife. Picacho means a sharp peak rising conspicuously above a surrounding mass of mountains ; its height bears the same proportion to its width that the longitudinal axis of a sierra does to its cross section. Puerto—a gate, or gap, and also a post. In its topographical application, a pass over or through a mountain range. Cajion implies a defile or mountain pass without any outlets on either side. Loma is a long mountain, or ridge of hills, with a somewhat smooth and flat surface. Lomita is the diminutive form of the same word. ’ Mesa is a table-land, table-mountain, or a flat-top ridge. Mesilla is the diminutive. 9M 66 GEOLOGY. Malpais—iiterally, bad land; the ‘‘Mauvais terre’ of the French. In Sonora it is exclu- sively applied to mesas, lomas, or any more or less elevated plateau formed of igneous rock, here mostly a compact or vesicular trap or basalt. Ciénaga is a valley, or depression in a plain, where the water collects, and can only escape by an obstructed outlet. Such a place is usually miry and boggy. Charco means a hole in clay, or stratum of rock, where water collects, and from which it cannot run. Tinaja is a water-hole, found in the crevices of rocks and ravines, difficult of access. The primary meaning of this word is an unglazed earthen jar, burned so as to allow exudation. The water thus oozing through evaporates and keeps that remaining inside cool. Beginning at the intersection of meridian 111° and parallel 31° 20’, we proceed to the con- sideration of the various sierras crossed by the line. The Sierra del Pajarito (little bird) shows crystalline transition rocks, metamorphic and unchanged ; also, trachytic strata, or metamorphic forms of granitic and syenitic rocks,(z.) Some of the more elevated portions exhibit a rough cellular surface, whilst the lower are smooth and more compact. The tint is light pink, or flesh color. This rock contains much glassy feldspar, and, occasionally, particles of augite, indicating the frequent occurrence of a syenitic granite. A fine-grained, white, metamorphic syenite, consisting of minute particles of hornblende and white feldspar, occur on some of the cuchillas on the north side. On the lower parts of the west slope talcose (argillaceous) and quartzose slates are met with, though trachyte dykes range through in every direction ; in the bottom and slopes of the valleys the igneous rocks prevail. In one place a solid mass of trachyte is cut through by an arroyo, forming a puerto, flanked on both sides by vertical walls of eruptive (A and c) rocks fifty feet thick. The mountains on both sides slope towards this gap at an angle of 35 to 40 degrees. Here, and other localities along the foot of this sierra, pudding stone, volcanic breccia, feldspathic porphyry, and trapitic amygda- Joid rocks abound. Some of the water-beds are lined with a singular formation, (B,) and apparently of a later age than those just mentioned. At first sight it may be considered a fresh-water deposit, overlying or placed alternately with volcanic breccia. SECTIONAL VIEW OF THE VALLEY DE LOS JANOS. Occasionally traces of stratification, and even cleavage, are visible, especially in its upper part ; its lower portion is cemented into a solid mass, Its color is a light brown, or dark ash- gray. The outer crust looks as if it had been subjected to a process of calcination, for it readily crumbles or exposes a marl or chalk-like substance that could be easily scratched out with the finger. There were no means at hand to identify this as carbonate of lime; yet we were VALLEY OF LOS NOGALES. 67 inclined to the belief that the whole mass of apparent fresh-water deposit was cemented by this material, which also formed the matrix of the volcanic breccia. The trapitic and amygdaloid rocks (F) appeared everywhere, no matter how great the elevation, slightly blended with carbonate of lime, as if it had been precipitated there by water. This calcareous precipitation was espe- | \ ah, y : | / i\ \ \X\ ee g Se wee ( | f | / | | ira | | VALLEY OF ‘‘ LOS NOGALES.”’ cially perceptible in the vesicular cavities of every trachytic or basaltic boulder, and also in the fissures of the rocks and in the dells where these latter are imbedded. On the east slope, in the valley of ‘‘Los Nogales,’ (Walnuts,) similar strata line the various 68 GEOLOGY, water-courses, sometimes forming a continuously winding low bank, or terrace, on both sides, and sometimes covering the slopes of the adjoining mountains, composed of metamorphic rock. On the hill-sides there are beds of this formation dipping towards the valley, and exhibiting, by decurrent, undulating lines, a shaly, laminated texture. On the easternmost limits of this valley the same formation is still more developed ; and it can be seen in all the valleys to the south and southeast of the Sierra de Santa Barbara, which is a part of the cordillera embracing the Sierra del Pajarito. The volcanic breccia, in many of the ravines, form walls of from forty to fifty feet in height, varying from an angle of forty-five degrees to perpendicu- larity. Pieces of this breccia, heated ina log fire, and then thrown into cold water, showed much effervescence, without fracture. North and northwest of this mountain range, bearing east and west, the Sierra Janos rises up in bold terraces of dark-brown amygdaloid trap and porphyry, the broader terraces being nearer the base. These gigantic shelves are bordered with rocks projecting out in the most fantastic shapes. They incline toward the main body of the sierra—deep and lateral valleys intervening. A huge block, exhibiting on its south and west side gigantic walls, with distinct stratification and cleavage intersecting at right angles, constitute at once the centre mass and the peak. The rectilinear fissures are visible at a distance of ten or fifteen miles, and giving the igneous walls more the appearance uf mason-work than the result of volcanic action. This sierra’s vernacular name, ‘‘Janos,’’ bears no reference to its petrographic character. The word signifies, in the language of the Papago Indians inhabiting this country, an arbores- cent shrub of the bignoniaceous order, belonging to the genus ‘‘Chilopsis.’’ Its frequent occurrence here in the water-beds in this vicinity may have originated the name. On the northern slope of the Sierra Janos another group of mountains occur, known as the Sierra Atascosa. Its bearing is the same as that of the Sierra Janos, and its longitudinal axis is common to this sierra and that of Sierra del Pajarito. All these three links of the cordillera have both dip and strike alike, the dip being to the east. Its petrographic character is similar to that of the Sierra Janos, and, being closely connected orographically, may be considered its twin. The cordillera formed by these three mountains terminates with the Sierra Atascosa, which is separated by a narrow and rugged valley from the Sierra del Babuquibari, lying to the northwest. This valley is of some importance, not only for its valuable fresh-water springs, but also as affording the only means of communication between the settlements of the Santa Cruz River valley and the coast regions along the Gulf of California. A rancho was once established at these springs, bearing the Papago name of Aribaca, or, more properly, Aribac. The settlement has, however, been abandoned long ago, in consequence of the repeated depre- dations of the Apaches. The northwestern part of the sierra is composed of igneous rocks, towering up into peaks of the most grotesque form, and bearing, not inappropriately, the name of ‘‘Malpais.”’ Atascosa means ‘‘miry,’’ which probably has reference to a previous state; it now presents the appearance of being an upheaved, boiling, volcanic pool. This sierra and that of Janos have about the same elevation above the Santa Cruz valley. Springs abound about the Sierra del Pajarito, but their drainage being, for the most part, below the surface, it requires a well-practised eye to detect their presence, particularly during the dry season, which occurs in April, May, June, and sometimes July. There is a considerable THE ARIZONA MINES. 69 development of vegetation on this sierra ; the rough surface of its sides is covered with a dense growth of shrubbery, of which some are quite trees, and grass is luxuriant in all the valleys. There are several species of oak, and on the summit is found a cedar; though this ridge does not fully reach the pine region. This sierra partakes of all the physiographical features of the Santa Barbara, Santa Cruz, and other links of the Sierra Madre further east. The Sierra del Pajarito, with its dependencies already referred to, constitute one and the same mountain system, properly characterized by the word Cordillera, and, taken collectively, are known as the Arizona Mountains. This word probably belongs to the soft Papago language, but we could not learn its meaning. The Arizona Mountains are rich in silver, copper, and gold ; evidences of numerous and well-worked mines are still to be met with. The eastern slope of the Sierra del Pajarito (Los Nogales) is especially worthy of exploration with reference to a development of its mineral production. Specimens of silver from this locality were analyzed, and the result will be found in its proper place. The Sierra del Pajarito constitutes a part of the divide already referred to, and has been inten- tionally dwelt upon at length for the purpose of referring the other sierras to it as a standard of comparison in consequence of its typical character, both as to its hypsometrical and geologi- cal features. Looking westward from the peak of the Sierra del Pajarito, a rugged net of mountain ranges is spread out, made up of metamorphic rocks; and though the single sierras do not rise very high, they form a very bold mountain relief by the close, uninterrupted texture of the inclined plane which constitutes them. (See outline sketches Nos. 34 and 35 of the azimuth line.) At a distance of about sixteen miles another cordillera is visible, between which and the Sierra del Pajarito very little drift occurs ; and this is confined only to the intervening valleys, where mesas and lomas, forty to fifty feet in height, are formed by the drainage from the sur- rounding mountains. Near where the drainage from the east slope of the Sierra de la Escon- dida joins that coming from the southwest side of the Sierra del Pajarito, a point just south of SECTION ON THE NORTH SIDE OF THE CERRO DE SONORA. the line, permanent water is to be found. It is under a cleft of igneous rocks, and does not pro- perly deserve the name of a spring, but is rather a tinaja supplied by water trickling through the rocks from water-holes above. From the character of this place is taken the name Escon- dida, (agua escondida meaning hidden water,) a term which is generally applied to the whole sierra. In its orographical character, this sierra is but a volcanic dyke,(a) towering up into an isolated, rugged crest of igneous rocks, composed of amygdaloid, porphyritic, end trachytic com- pounds, intersected and overlaid by contorted and overthrown crystalline strata of a coarsely- grained and frequently disintegrating feldspathic syenite(z.) This syenite is sometimes meta- 70 GEOLOGY. morphic, at other times unchanged ; sometimes it is quartzose, and imperfectly mixed with large scales of silvery mica, in other places feldspar prevails. This sierra is scarcely more than one mile wide where the line crosses it ; both sides are bor- dered by the upheaved and contorted crystalline beds just alluded to. We ascended to the top of this sierra, near where the singular-looking peak that marks the Escondida towers up, and found it to exceed in barrenness either of the sierras—Pajarito, Janos, or Atascosa. Portions of the terrace-like slopes, and also the plateau, are covered with patches of white or pearl-colored chalcedony, investing the rocks with a scoria-like crust of that silicious fossil. The southern part exhibits a more horizontal arrangement, leading to the supposition of having been formed under water ; for here are extensive table-lands, ridges, lomas, and mesas, composed partly of black vesicular or compact trap, and partly of real quaternary banks. The topography of the country seems to indicate here the confluence of numerous mountain streams and torrents coming from every direction. (See sketch No. 40 of azimuth line.) The line crosses a little to the north of a conspicuous peak(p)—the highest point of the whole range—and falling on the Mexican side, we gave it the name of ‘‘ Cerro de Sonora.”’ Immediately west of the Sierra de la Escondido a low group of granite hills(c) occur, furnishing several temporary, as well as permanent, water places, apparently well known to the natives— Papagos and Apaches. Some are mere tinajas ; others real springs, though liable to become dry before the setting in of the rainy season. While encamped here we experienced a heavy hail and thunder storm ; in a few minutes water came rushing down the ravines in a torrent, five feet deep, carrying everything before it, and giving us unmistakable proof how little time it requires to submerge all the valleys around under a most terrible flood of rain-water. This mountain group was called ‘‘ Granizo,’’ (hail,) and is so designated in the maps-from the cir- cumstance of the surveying parties being overtaken here by one of those hurricanes peculiar to these regions. A flat valley, nine miles wide, separates the Sierra de la Escondida and the adjoining Granizo group from the Sierra Verde, which is a southern spur or branch of the Sierra del Babuquibari, north of the line. The plateaus bordering the dry water-courses of this valley furnish fine grass, and are sparsely covered with well-developed hackberry and liveoak. The Sierra Verde, so called because of the verdure encountered in the shelter of its rocky valleys, seems to be formed exclusively of feldspathic granite, similar to that already mentioned as occurring on the east slope of the Sierra Escondida. The strike-side faces southwest, and with a width of scarcely more than a mile, this sierra does not present any petrographic novelties. Its longi- tudinal axis ranges southeast and northwest, and joins the bold walls of igneous rocks belonging to the Sierra Babuquibari. At its southern end mounds of dark, vesicular trap crop out of the diluvial main. Here water finds its way to the surface, forming a spring known as the ‘‘ Pozo Verde, ’’ (Green Well ;) the bunches of rush, which at once conceal and mark the water, in all probability gave rise to the name. Almost due north of the Sierra Verde lies the picacho of the Sierra del Babuquibari, which is one of the orographical phenomena of the country, its peculiarity being such as to attract espe- cially the attention of the red man. ‘The Papagos consider this huge mountain obelisk their palladium ; here they take refuge in times of famine, drought, or war. Babuquibari is said to signify ‘‘ water on the mountain.’’ The word is certainly formed from babu (water) and ari COMMENCEMENT OF THE DESERT. 71 (rock or mountain.) Its great height, added to its spire-like top, causes it to act as a conductor to the clouds, and thereby gather an unusual quantity of rain, which is retained for a long time in its numerous rugged and inaccessible recesses. (See outline sketch No. 39, azimuth line.) Viewing the country westward from the Sierra Verde, a wide plain is visible, bounded at a distance of fifteen miles by a mountain range traversing the country with the invariable bearing southeast and northwest. The eastern half of this plain is favored with a more than usual cover of vegetable life— abounding in grass, a dense growth of brushwood, and mesquite; the western part, a low flat, was entirely destitute of vegetation, which seemed to have been destroyed by small trogloditic quadrupeds of the order Rodentice. Although this plain had received copious showers of rain a few days previous to our visit, singularly enough no life was given to the naked and barren flat. A change, and not to its advantage, is here perceptible in the physiographical features of the country, and becomes quite decided in the next mountain range, which is unlike all the sierras eastward, and which presents an isolated group rising out of the diluvial main. Notwithstanding its lesser extension, the Sierra de la Union presents no peculiarity in its petrographic character—being a compound of igneous and metamorphic rocks. The lat- ter constitutes the greater portion. On the east slope feldspathic granite in a disintegrating and somewhat metamorphic state occurs; on the west is a quaternary granite, similar to that mentioned as occurring on the Sierrita del Granizo. The backbone or central mass is formed of igneous amygdaloid and porphyritic rocks, here and there overlaid and concealed by crystalline strata. Thus far there has been but little room for the diluvial deposits, so broken up is this region by the continuous succession of mountain ranges; but westward, great basins of quaternary and alluvial deposits form the main in which the sterile mountains lie imbedded and completely isolated by this vast sea of drift. Of the sierras ranging eastward, parts of them are so entirely submerged as to appear detached and isolated mountains, their connexion being traceable only by their general bearing. The country passed over may be viewed as a narrow strait, traversed by long mountain reefs, and that, in part, as a c»ast of shoal water dotted with rocky islands. The influence of the climate of the Gulf coast, as far as the Sierra de la Union, is quite apparent; on its west slope two leguminous trees, the Palo verde and Arbol de hierro of the Mexicans, Cercidium floridanum and Olneya Tezota, three large Cerei, two gigantic Echinocacti, and other desert forms, now appear in prevailing numbers. The line, after crossing a desert of about seventeen miles, strikes a comparatively low and narrow sierra, composed chiefly of porphyry and amygdaloid rock. This sierra presents two vertical. peaks, rising up like a pair of horns, which constitute natural monuments for the line as it falls between them. It is a northerly continuation of the Cordillera Cobota, so called by the Papago Indians, who have several fixed settlements here. There is a cafion in this sierra, near the line by which the west side is easily gained, and in which are seen masses of crystalline rock ; igneous strata, however, prevail. The name ‘‘ Lindero’’ (boundary or landmark) was given to this sierra, because of the line falling between the two conspicuous peaks before mentioned. The sierras Arteza and Sofi lie, respectively, southeast and northwest; the former in the United States, the latter in Mexico, both well known and famous among the natives as being 72 GEOLOGY. remarkably auriferous; especially Sofi, once a mining settlement of the Mexicans. It was abandoned at the time of the California gold fever. The latter subsiding, the old settlers, dis- appointed on the Pacific coast, are now returning again. The Papagos claim this region, and, from the time they first learned to appreciate the value of gold to the present day, have con- tinued to prospect successfully. A desert of sixteen or eighteen miles in extent separates the Sierra de los Linderos from that of la Nariz. Though these sierras are nearly related in petrographic character, there exists one striking difference. The former is, at least where it was crossed, a true volcanic dyke, bordered in some places by upheavals of crystalline strata; its crest of eruptive rocks seems to have been forced through a mass similar to itself. The latter, though consisting also of trachyte and trapitic masses, appears only a simple upheaval; its crest, comparatively smooth, is the upturned edge of a bed of igneous masses, dipping northeast; its strike faces the west, at an angle of 60 to 70 degrees. The surface (8) of the east slope is covered with a thick layer of loose boulders, of a black or dark-brown vesicular trap. On the strike, stratification (A) is visible, even at a considerable distance, the layers varying in thickness from five to twenty-five feet. SX SS, 8 thes RRR Wr ARS SS wan VERTICAL SECTION OF THE SIBZRA DE LA NARIZ. This sierra ranges in a slightly curved line from southeast to northwest, and joins about eight miles north of the line the Sierra del Ajo, of which it is, in fact, only a spur. A little to the north of where the line strikes, quite a depression occurs, the range here not being more than fifty feet above the drift. A valley of about fifteen miles wide separates the Sierra de la Nariz from the Sierra de la Laguna on the north. Its petrographic character seems to be similar to the de la Nariz, having the same strike, dip, and stratification. Trap mounds accompany both sierras, cropping out along their bases to a height of thirty or forty feet above the level of the valley. There are no springs to be found about any of these mountains; holes of water or ponds, (charcos and lagunas of the Mexicans,) formed in beds of clay, are the only dependence for water, and are not to be relied on during the whole season. The surveying parties being unexpectedly fortunate in finding an abundance of water here, the sierra was called La Laguna (de la Esperanza ;) it seems but an eastern branch of the Sierra del Ajo. Northwest from the Sierra de la Nariz this latter sierra, a bold and high mountain.range, is visible. As we have been told, it takes its name, (del Ajo,) garlic, from its structure, appearing as the consolidation of various branches forming a cordillera. Although composed most probably of volcanic rocks, similar to that of ranges just referred to, it is quite different in its other features. As seen from the southwest, a huge central block of metamorphic, or, more probably, igneous rock constitutes the strike side. This block, exhibiting traces of horizontal stratification, is divided into two almost equal parts by a protruding mass of rocks, which, though lithologically almost the same, show a vertical columnar structure instead of a horizontal stratification. On the sides and about the base numerous isolated and volcanic peak SIERRA DEL AJO. 73 tower up, but they all, undoubtedly, have the same origin, The main body of this sierra, resembling the bulbous head of garlic, has been dignified with the name of that plant. This SOUTH SIDE OF THE SIERRA DEL AJO, AND PART OF CI®NAGA DE SONOYTA. growth of both the sierra and the garlic. It forms a subdivide, but the separated waters unite before they are lost in the waste of sand along the Gulf coast. A wide valley spreads out from the west foot of the Sierra del Ajo; being hemmed in on all sides by mountains, and having only one (and that somewhat obstructed) outlet, this is desig- 10 M 74. GEOLOGY. nated, in Spanish, asaciénaga. As the sierra heretofore referred to strikes the eye with a dark- brown or even black aspect, on the other hand the sierras southwest,-composed of metamorphic crystalline rock, (feldspar prevailing,) meet the view in a robe of glaring white, dazzling under the rays of a Sonorian sun. It is common to the traveller to distinguish these two classes of mountains as the black and white, so opposite is their general appearance. At the western foot of the Sierra Juchibabi, which bounds the valley on the south and near the old Mission of Sonoyta Chloritic slates and greenstone appear—these are, however, but local. A branch ranging north shows throughout the same light-colored feldspathic crystalline rock. ‘The ridge east of the ciénaga is but a slight swell of the diluvial plains, and affords an open and travelled pass to Presidio de Altar. Besides numerous deep charcos and even small lagoons in its lower part, this ciénaga is blessed with a small stream fed in its outset by a number of small springs. These springs afford a constant flow of water, which proves their deeply-seated source. The water is clear, of a bluish hue, but warm and slightly brackish. Notwithstanding this permanent supply, the little river of Sonoyta continues but about a mile as a running stream. There was a mission founded here, but it has long since shared the fate of all similar establishments of this desolate and remote region. ‘The inhabitants now consist mainly of Papagos, who have a few miserable huts, and irrigate a small patch of ground. The Sierra del Ajo, rising up at the northeastern corner of Ciénaga de Sonoyta, is remarkable for establishing, by a natural monument, a true boundary between the coast and the interior. In its northwestern continuation auriferous and argentiferous copper ores abound. The gold and silver product in this location is said to be sufficient to defray all expenses of mining and assaying, leaving the copper a net gain. These mines have been long known to the Papagos and Mexicans, but were not worked for want of capital and security against the Apaches. Some Californians, under the name of ‘‘ Arizona Company,’’ have now ‘‘ prospected’’ the country between Sonoyta and the Gila. They commenced to build roads, make water-tanks, introduce labor, and, notwithstanding these initiatory expenditures, anticipate a prosperous business. Following the bed of the Sonoyta river, a narrow but smooth pass leads to another ciénaga, which, having but little water, assumes the general aspect of the desert. The course of the Sonoyta river is traceable through it, but the water, except in two or three places, does not come to the surface, and it is necessary to dig for it everywhere during the dry season. Felds- pathic crystalline mountains border also the ciénaga except on the west, where the river finds an outlet for the flood of water that may sometimes rush down its usually dry course. The sierra partakes very decidedly, in its physiographical character, the features of the Great Colorado desert. It is a Papago name, and signifies little mountain gap or pass. Upon some rising ground in the west end of the last-mentioned ciénaga there is a settlement, or, more properly, cattle rancho, the inhabitants of which are favored with spring water flowing out in abundance from a dozen little springs. These springs come out in a line from a considerable bank, which seems to have been formed by sediment, perhaps carbonate of lime, which they themselves have precipitated. The water resembles, both in appearance and mode of issue, that of Sonoyta, and there would be in all probability no error committed in assigning their thermal and mineral properties to a common source. West of Quitobaquita the line passes over a broad ridge dipping east and west before reaching the Cerros de la Salada. SONOYTA—SIERRAS PINACATE—TULE. 75 This group, like all the adjoining mountains, consists of crystalline feldspathic rock. The present structure of the Salada hills indicates a general geognostical disturbance of the relative position they must have once sustained. They vary in relative height, and the rocky parts are often covered with debris. The relative position as well as the direction of the sierras between this place and Sonoyta show a deviation from the parallelism so characteristic of north- western Sonora. The water of the Rio Sonoyta appears above ground for the last time near Quitobaquita. On the southeast side of the Cerros de la Salado fresh palatable water can be got in its bed by digging to a depth of about three feet. Just below, it becomes so salt that even famishing mules will not touch it. This salt water has given its name to the adjoining mountains. From this point southward the country is open, presenting to the view a bold and isolated mountain group at some distance, known as Sierra Pinacate. Its name, signifying beetle, does not seem to have reference to any peculiarity in appearance or formation. In consequence of the entire absence of water, the Sierra Pinacate is almost inaccessible ; it is, however, celebrated throughout Sonora for wonderful and inexhaustible layers of rock-salt, which is said to be stored up in immense masses, arranged in diversified strata and of a variety of colors. This Pinacate, in all probability, bears a close geological relationship to the Cerros de la Salada. West of the Salada hills a wide, waterless desert stretches out, studded with numberless isolated little peaks and a variety of mounds, composed of the crystalline feldspathic rock or igneous masses—the latter is either trapitic, amygdaloid, or porphyritic. Southward, this desert is bounded by low ridges or, rather, gradual risings of the diluvial main ; north and west by bold volcanic sierras. A rugged cordillera, known as the Sierra Tule, limits this desert on the west, and breaks off what would be otherwise an uninterrupted continuation of the great Colorado waste. There are playas near the centre of this desert plain, and sometimes just after a rain charcos of drinkable water. Towards the Sierra del Tule, there is an ascent over an immense bed of dark versicular trap, from which rise small black and white hills or mounds. These gradually increase in size and number in the vicinity of the mountains, and assume an elongated shape, with the usual bearing S.E. and N.W. Finally they unite with the latter, and form spurs of the main mountain mass.—(See outline sketch No. 58, of azimuth line.) The black and white rocks which constitute this mountain appear in one place closely packed or pressed together ; in another they shoot up as separate branches. The dip and strike with the stratification and cleavage are contorted, and in most places entirely obscured ; at another PLUTO-VOLCANIC PEAKS STUDDING THE MAL-PAIS EAST OF THE SIERRA TULE. place again they are traceable even at a distance of a mile. This is a mountain block—the upheaved corner of a bed of feldspathic syenite or granite changed into granitic lava or regular 76 GEOLOGY. trachyte, containing numerous large crystals of glassy feldspar. The singular aspect of this mountain is produced by the protusion of crystalline rocks through a bed of black vesicular trap. The morphological features of these walls of rock bear a resemblance to the ice formations of the Polar seas. Similar causes have effected similar results; there, we have the consolidation of aqueous masses ; here, the crystallization of pluto-volcanic rock. Similar in outline, there are, on the one hand, ice-fields, hammocks, packs, and icebergs; on the other, vast beds of trachytic lava, contorted peaks of porphyritic or amygdaloid rocks, upheaved edges of immense beds of metamorphic masses forced upon each other—broken, crushed, and shattered—and formed over again. a; : The whole of both the icy and rocky world, each one floating half submerged upon an ocean— the one upon the salt waters, and the other upon the residue of a quaternary sea. 'The moving medium is also somewhat analogous to the masses acted upon. There are the oscillatory move- ments of the sea with one, and the folding of the earth’s crust with the other. That metal is to be looked for in mountains like that of Sierra del Tule is doubtful. A piece of copper ore, however, was picked up by one of the party off one of the highest— almost inaccessible—peaks. Our duties were such as would not permit of an examination for ores of any kind; yet had their been any indications of their occurrence—such as oxides and sulphates of copper or lazur and malachite—they would certainly have attracted our attention. (For analysis of piece discovered, see page 25.) This, consisting like the last-mentioned sierra of several ranges, would be more properly called cordillera. The petrographic features of these sierras are similar, and there is not much doubt but that they originated from a common upheaving focus. This sierra is the last of the ranges traversing the State of Sonora. Westward from its crest a few rocky peaks only are visible, rising out of the diluvial main like out-posted reefs along a seacoast, and are in all probability the tops of submerged sierras. The tinajas altas, or water-holes, in the volcanic crevices of this mountain are famous; they are the principal places in the surrounding country where the traveller between the Colorado and the springs of Sonoyta may expect to find water. After leaving this sierra, the Colorado desert proper is entered upon, stretching in an unbroken sheet of drifting sand to the foot of the California Cordilleras, a distance of about 130 miles. The distance in a direct line from the Tinajas to the Colorado is about 45 miles ; about midway, there is a slight swell of the sand traversing the desert, and which may be considered an under- ground sierra. Reviewing the mountain ranges passed over, we find that they invariably dip to the east, with their strike facing west; each sierra and cordillera may, therefore, be considered as one page in the great book of creation. Few of them have been fully opened so as to permit a satisfactory reading of their pages; whilst their greater number still remain closed, with just one edge turned up. Our belief is, that when the time for further revelations come, the axis of disturbance will develop itself in the eastern base of the California Cordilleras, and these mysterious sheets will be turned from west to east. The sierras Santa Cruz, Pajarito, and Santa Barbara, have disclosed a part of their geological history, while others, especially those on the confines of the desert, have hardly commenced to do so. Earthquakes are not uncommon in the basin of the California Gulf. There are two solfataras now known at the eastern foot of the south California Cordilleras, both still in activity; and SUMMARY. 77 the lower Colorado js constantly changing not only its bed but also its numerous bends. Below the mouth of the Gila there is but one place where the river remains unchanged, which is so remarkable a fact that the navigators of this river named it the ‘‘ Permanent Bend.’’ Considering such facts, we cannot doubt that the regions here spoken of have not yet passed through all the phases of their destiny. We do not, however, believe any general and violent catastrophe indispensable for further geological developments. A long continuance and perhaps imperceptible rising of the country, a simple increase of elevation, and especially an enlarge- ment of the angle of grade by which the horizontalism of the quaternary main would be dis- turbed, should it become subjected to these forces, would aid the torrents of the mountains and the sweep of rial currents to clear the surface of the country from its desert burden. CHAPTER. PHYSICAL AND GEOLOGICAL DESCRIPTION OF THE COUNTRY FROM THE INITIAL POINT ON THE PACIFIC TO THE JUNCTION OF THE GILA AND COLORADO. The data on which these results are based are derived from personal observation and col- lections continuously made during my stay in that region from July, 1849, to March, 1851. This period was variously occupied in different sections of this region, including an interrupted residence in the vicinity of San Diego ; an expedition of three months’ continuance to the mouth of the Gila River ; a land journey up the Pacific coast as far as Monterey; a residence during the fall and winter months of 1850-51 at the Mission of San Luis Rey ; together with various minor excursions to the mountains east, north and south of San Diego. The region of country thus covered by my observations includes portions of territory lying between 32° and 36° N. latitude and 114°-121° W. longitude. The district, however, to which my attention was mostly confined is indicated on the accompanying geological map, and popu- larly known under the title of Southern California. The separate heads under which I propose to embrace the general information pertaining to the subjects assigned me are— I.—The general physical features of country. Il.—Geology and mineral productions. IIlI.— Botany. IV.—Agricultural capacities. I.—THE GENERAL PHYSICAL FEATURES OF COUNTRY. The most marked external feature which serves to give character to the region under exami- nation is seen in the occurrence of a mountain range parallel and in close proximity to the ocean, presenting in its various elevations and the differences which characterize its two slopes (eastern and western) a great diversity of scenery within a small compass of territory. The range itself, in its geographic relations, must be regarded only as an inferior link in the great mountain chain extending along the entire northwest coast to the extremity of the California peninsula. To the part at present under consideration the local but not very precise term of the Cordilleras of California has been applied. Directing our attention to this portion of the mountain range, considered as a whole, it will be remarked that, while the general direction of the range is parallel to the coast, this feature is worked out in detail so variously that it would be difficult, from a single point of view, to decide on the true direction from noting the supposed axis of greatest elevation. This is, per- haps, owing to a peculiar feature of the range, which, instead of consisting of continuous ridges or sierras, as they are termed, are made up of an irregular series of rounded or ridge-formed SOUTHERN CALIFORNIA. 79 peaks, sloping gradually towards each longitudinal extreme, with their more or less tapering spurs interlocking with those of adjoining ridges, but scarcely ever in a continuous line, This view of the range will serve as a useful key to explain many of its peculiarities. Thus, as one fact in connexion with the general features of scenery, it will be noticed, that though the bareness of vegetation would seem to favor extensive views, they are seldom, even from the higher points, of that commanding character such as may serve to give a true idea of the elevation attained, or to strike the mind with those ideas of grandeur elsewhere connected with wide-spread mountain scenery. The horizon is, in fact, shut in, and the view confined to a limited sphere, by the varied direction of these mountain spurs. Roads and passes are also readily found, and routes can be modified with comparative ease by selecting the interlocking spaces to pass from one range to another, or by crossing spurs at their lower depressions. Another fact connected with this character of the range is a marked tendency in the main valleys to assume a basin shape, apparently encircled by mountains, and fringed on all sides by branch valleys, affording a choice of travelling routes in every direction. We also frequently meet with upland plains of a similar character, where the more extended view takes in distant mountains, in which, though a more determined general direction of the range is apparent, the approach to a basin feature is not lost. Connected with the same general cause, streams find their way by very devious courses, and on the western slope, particularly, are seldom followed in any direct line of travel. In reference to the two slopes of this mountain range, an important point connected with their “distinct external features is to be noted in the fact that the axis of greatest elevation, or the true divide, is much nearer to the eastern than the western base. Thus, supposing the moun- tains to have an average width of 60 miles, the centre of this line would invariably fall far on the western slope, the real water-shed being pretty constantly marked within ten miles of the eastern base, thus leaving a proportional difference between the length of the two slopes of five to one at least ; hence, as a natural consequence, the eastern slope is more abrupt and precipitous, the western more gradual and circuitous ; the streams of the former dash down a limited descent, and are soon lost in the absorbent debris at the base; the streams of the latter, flowing more leisurely, and drawing as tribute in their winding course a more abundant supply, frequently embody sufficient force to reach the ocean. Confining the attention more closely to the Pacific or western slope, we are led to observe in its wider dimensions that it is made up of quite a number of parallel minor ranges, comprised in the general series, forming intervening depressions, and marked off by spurs, in the above- mentioned basin-shaped valleys; towards the summits these valleys are more contracted in breadth, and attain wider dimensions as you approach the coast. At the higher elevations, the mountain sides are usually bare and rocky, but the immediate summit assumes a more verdant character, being clothed more or less with pine and Alpine oaks. The ranges adjoining the coast are smooth in outline, slope up gradually into vertebrated ridges, and are covered with a dense, brownish shrubbery, giving a singular, smooth a~pect to their distant outline. Moisture is more abundant and the streams more copious towards the higher elevations, while the wider coast valleys, unfed by perennial streams, are, during the greater part of the year, destitute of running water, the issue from occasional springs becoming speedily evaporated in the dry atmosphere. 80 GEOLOGY. These different ridges vary somewhat in geological structure, and, as we shall have occasion to notice hereafter, serve to give an additional variety to the mountain scenery. However viewed, nakedness is the prevailing character, the exceptions being few and far between. The summit ridge, attaining a variable height above the sea of 3,000 to 5,000 feet, presents in its wintry covering of snow, and its richer verdancy of summer growth, some of the finer features of California scenery. Without possessing.a marked Alpine character, it approaches it in a sparse growth of pines, and other coniferze ; while the frequent fogs bathing its sides favor the growth of lichens and mosses almost unknown in the lower regions, except in a few evan- escent forms during the rainy season. The view to the west takes in the bold outline of treeless ranges stretching in a dim line seaward. Looking towards the east, the less obstructed view traces the line of diminished vegetation, plainly and somewhat abruptly marked, in going downward on the steep slope. Irregular mountain peaks, and ranges of a dull, ashy color stand out in view in close proximity, and below all stretches the brown plains of the desert, extending to the hazy marked line of the Colorado river. ; Descending from the summit westward, you pass down luxuriantly grassed valleys, edged with scattering pine and oak groves, and watered by cold, perennial streams, until an abrupt descent to a lower level brings you again into wider basin-shaped valleys, bounded on all sides by rocky ridges. The streams spread out into low grassy or sedgy marshes, and the pine growth gives place to the lowland oak, with its peculiar undergrowth. Continuing thus by a series of, gentle swells and abrupt descents, you pass almost insensibly the different ranges, till the smooth, brown outline of the coast range indicates your proximity to the sea, In the summer season you wind down broad valleys, marked by the dry, pebbly beds of winter streams ; herbage is dry and wiry, and water confined to a few willow-shaded marshes or isolated springs. Opening on the sea, you traverse dry moorland hills, dropping down to the sea-level in the bed of some wide, sandy valley, which, with its sides bounded by precipitous walls of coarse sand and pebbles, finally spreads out into wide saline flats, cut up by tide estuaries, and terminates on the ocean beach, Proceeding from the same summit ridge in the opposite direction (eastward) from its pine fringed heights and rich green sward, you drop by a steep descent into pent-up valleys bounded by ashy-colored mountains. The streams which flow in the upland ravines are soon lost in their thirsty beds. The valleys near their exit from the mountains slope in a regular plane, covered by wide and dry beds of streams. Occasionally the passage of an irregular mountain chain is marked by a rude defile, cutting through mica slate, or highly micaceous granite. Thus winding with occasional passages over ridges of the same character, flanked with rough pebbles, the desert opens before you, its table-land being generally gained by a steep ascent from the deep bed of some dried up stream, along the course of which the geological tertiary formation is strongly marked in thick layers of marl or sand, surmounted by a varying bed of rounded pebbles. Over the desert waste, furrowed occasionally by the dry sandy beds of rain streams, you pass insensibly down till the lake formation of ‘‘ New River’’ comes into view. Here the soil acquires a sedimentary character ; fresh-water shells are scattered here and there. The imme- diate lake edges and lower depressions are bordered by a growth of mezquite, while, in its SOUTHERN CALIFORNIA. 81 proper season, large patches of annual grama grass relieves the desert of its barren aspect, and transfers the mind to scenes of neatly trimmed pleasure grounds set off with verdant shrubbery. The next stretch mounts again to the pebbly strewn table-land of the desert, from which you descend further by the steep sandy bluff which bounds the bottom land of the Colorado river. STREAMS AND WATER-COURSES. A consideration of the character of the various streams and water-courses in this region belongs properly to the view of its external features, and derives especial interest from the intimate relations they sustain to climate and agricultural resources. On the western slope the various streams, each draining a very limited area, are remarkable more for their number than their magnitude. Having their main sources near the mountain summit, they pursue their tortuous course towards the sea, following all the irregularities interspersed by the separate mountain ranges and their projecting spurs. By these devious courses the descent is finally accomplished without occasioning falls or cascades, which are so commonly associated with mountain streams elsewhere. Their volume being necessarily dependent on the supply from local rains, they generally attain their greatest bulk towards the close of the rainy season, when the melting snows at their sources combine with frequent showers below to swell their volume. As the dry season ad- vances they gradually contract their dimensions, till in the month of July most of the streams _ near their mouth become absorbed in their porous sandy beds. The exception to this general fact is seen only in those streams which, having their sources in the higher mountain ridges, receive a sufficiently constant supply to exceed the amount lost by evaporation. The drying up of the stream beds is a gradual process, necessarily modified by the compara- tive dryness of the atmosphere, as also by the relative absorbent or retentive character of their beds. The point at which water ceases to flow is quite variable ; its more usual upward limit being marked at or near the passage of the stream from the first rocky ranges into the Tertiary formation. The point, however, as before stated, is by no means a fixed one ; thus, during the night it extends further downwards than in the daytime; in cloudy weather, for the same reason, its course is more prolonged than under aclear sky. In the stream beds themselves, however dry, water is generally found a short distance below the surface. The descent of these streams in the rainy season may be either a gradual process in the pro- gressive saturation of their sandy beds, or the saturation being accomplished by previous showers, the irruption may be sudden. A fine example of this sudden appearance was observed in the San Diego river, in December, 1849; when, after a rainy night, by which its sandy bed was completely saturated, the upper stream suddenly appeared in the fourm of a foaming body of water, moving onward at the rate of a fast walk, carling round the river bends, absorbing the pools, and soon filling its shallow bed with a brimming swift current. An instance of the more gradual descent was seen on the following season, December, 1850, when, from the abseuce of local rain, its downward progress was slow and interrupted. The facts connected with this supply of running water seems to deserve particular attention in this region, where its presence or absence is synonomous with barrenness or fertility. 11 M 82 GEOLOGY, The streams of southern California are, in truth, the life-blood of its agriculture, and the means to be adopted to extend this supply can only be efficiently based on a clear understanding of all their separate relations, both as to atmospheric conditions and geological structure. In many of the old mission establishments extensive lines of masonry were constructed, by means of which the streams were tapped a short distance above their place of sinking, and a vigorous irrigating supply conveyed to the lower portions of the valley, thus rendering productive lands otherwise useless for all the common purposes of cultivation. It is therefore in the true character of these streams—with reference to their sources, their beds, the elevation and geological structure of their banks and bottoms—that we are to look for the fairest general idea of the agricultural capacities of this region. But it must further be remarked that it is not to these mountain sources alone that we must look for the needful supply of water; occasional springs in the lowest portions of valleys fre- quently furnish a constant flow sufficient to meet the demands of cultivation over a limited area. Thus, the extensive mission of San Luis Rey, proverbial for its vertility, depended almost entirely upon such sources of supply. Similar examples in other parts, though rare, may furnish useful indication, in directing the location of artificial means of supply, by the con- struction of Artesian wells. Referring to the character of the streams on the eastern mountain slope, we have before noticed their abruptness, also the rapid diminution of volume which they undergo in their steep descent. The excessive dryness of the atmosphere, and the more absorbent character of the strata through which they pass, serves to exaggerate all their peculiarities, as compared with the opposite slope. The streams, equally as vigorous at their sources as those of the other slope, are quickly absorbed in their course, and none at any time acquire sufficient volume to be entitled to the name of river affluents. Thus, though the existence of wide and deeply cut streain beds show the occasional agency of powerful streams, derived from the rapidly embodied force of copious rains, yet their rare occurrence and short continuance only serve, in the main, to give an exaggerated feature of barrenness and desolation to a region where, during the greater part of the year, scanty supplies of water are only attainable from stinted and unwhole- some springs. The point at which water ceases to flow is extremely variable, and exhibits a singular inter- mittent character: thus, in the morning you may cross over quite a large brook, and at the same place, by noon, find it entirely dried up, to show itself again when the diminished evaporation, at night, allows the ground, instead of the atmosphere, to receive its aqueous tribute. Often you meet with streams, near the lower mountain slope, present at one point of their course and absent at another, thus constantly varying, according to the relative absorbent or retentive character of their beds. On the desert plains, the stream courses are marked by wide beds, with more or less abrupt banks, cutting through strata of sand, marl, or coarse gravel. Near the mountain base they exhibit steeply inclined plains, strewn with a variety of rounded and angular pebbles. In the re-entering angles, formed by the irregular projection of mountain spurs, these plains often attain an elevation of nearly one-half the mountain height, and are taken advantage of in the selection of passes. But the point of all others which has attracted most attention, in reference to the distribution SOUTHERN CALIFORNIA. 83 of water on this desert plain, is to be noted in that singular feature, to which the name of ‘New River’’ has been applied by the Californian emigrants. The idea naturally conveyed by this name is that of a running stream, arising in the desert and flowing towards the Colorado river, but its true character is quite the reverse; the current itself, which is by no means constant and at all times irregular, is in the opposite direction, or from the Colorado, while its bed, instead of exhibiting the features of a regularly washed stream bank, shows only a chain of lagoons or marshes irregularly connected, and often spreading over extensive tracts, or at other times contracted within narrow beds. Its novelty, moreover, is sufficiently disproved by the presence of heavy mezquite growth, and other plants and shrubbery usually associated with the presence of water in this region. Indeed, all the singular features in the case are now sufficiently accounted for, in the ascertained fact (first suggested by Major Emory from barometric observations) of the existence of a natural depression, at this point, below the level of the Colorado river at high water. The connexion between the overflow of the one and the appearance of the other has been frequently observed, though the exact course of this connexion has not yet been traced out. Still, all the facts in the case derive their full explanation by referring it to this peculiarity of the Colorado river, which, seeking an outlet for its swollen waters, spreads them in fertilizing deposits to such a great distance from its usual bed. LAKES AND LAGOONS. Mountain lakes are of very rare occurrence in any part of the region under examination. The only body of water that I am acquainted with really deserving the name of a lake, is found on the western slope of the mountains, near the parallel of 33° 30! north latitude, and some twenty-five miles distant from the ocean. It is about five miles long, by from two to four in breadth. It has no outlet, and its waters are consequently brackish. It is also apparently shallow, and exhibits along its banks marks of recent and continuous recession, plainly indi- cating a gradual exsiccating process. What adds to the interest of this latter fact, is the explanation it seems to offer of the original condition of some of the more fertile basin valleys, which exhibit all the characters of a lacustrine origin, to which they now owe, in a great measure, their fertility. A fine example of this may be noticed in the rich and extensive valley known as the San Bernardino. It is seen encircled by high mountains on all sides, and seems to have derived its subsequent drainage by the Santa Anna river, which is now observed passing through an elevated range of tertiary mountains towards the ocean. On the desert plain of the eastern side of the mountains, report speaks of one or more extensive salt lakes, but no opportunity was afforded for a personal examination of their true character or extent. The fresh water lakes and lagoons belong to the ‘‘ New River’’ formation, which has been sufficiently noticed above. Il.—GEOLOGY AND MINERAL PRODUCTIONS. Directing the attention more especially to the geological structure of this region, we have to consider the same mountain range, in its line of greatest elevation, constituting a central axis from which we may trace on each side the diversities that churacterize its extended flanks. By reference to the accompanying geological map and sections, three main facts will particu- 84 GEOLOGY. larly claim our attention, and serve at the same time as the most natural division by which to unfold the entire subject. Ist. The great preponderance of crystalline metamorphic granite pertaining to the older paleozoic series of rocks. 2d. The entire absence of any member of the lower paleozoic, or secondary rocks, in their regular stratified character. 3d. The existence of extensive Tertiary deposits, forming a more or less extended flank, on each side of the mcuntain range. Ist. In reference to the preponderating granite formation, as exhibited in the central axis, and main development of the mountain range, we shall notice a considerable diversity of form and structure, but all evidently pertaining to the same general formation of metamorphic rocks in their different exposures. Illustrative specimens are characterized by Professor Hall in the accompanying list, to which reference may be had for special characters, The central axis is represented by a somewhat variable mottled granite, composed of various proportions of quartz, feldspar, mica, and hornblende, frequently containing imbedded crystals of tourmaline. The «xposed mass varies greatly in the degree of aggregation of its component materials, assuming in some places a close sienitic texture, while in others a larger proportion of feldspar renders it more readily decomposable by disintegrating causes—its exposed face easily crumbling into a coarse, granitic sand. At other points the preponderance of mica, confusedly mixed in large scales, serves to give a very irregular form to the external rock exposures. Belonging also to the same series, we find, particularly on the eastern side of the range, mica and talcose slates associated with quartz veins. The irregular rocky range immediately adjoining the coast, and also probably composing the numerous rocky islands extending at variable distances seaward along the same line from north- west to southeast, present a distinct form of eruptive rock, described by Professor Hall as ? “ greenstone, with soft chloritic spots, or blotches,’ and ‘‘ porphyry, or porphyritic greenstone.”’ This character of rock forms the first extensive range of mountains east of San Diego Bay, and attains an elevation in some of the higher peaks of 2,500 feet above the sea. Further to the north, in the vicinity of San Luis Rey, several isolated peaks exhibit a basaltic structure, weathering into peaked domes, with abrupt columnar faces. Professor Hall considers all the rocks of this series as of quite recent origin, compared with the central granite series above mentioned. As sustaining this view, we observe further north, in continuation of this range, near Santa Barbara, evidences of disturbed Tertiary rocks associated with similar or more recent igneous exposures. The isolated mountain peaks and ranges adjoining the Colorado River exhibit a sienitic texture, which, by exposure to the dry atmosphere, acquires a deep brown, polished face, giving a peculiar and forbidding aspect to the bare mountain scenery These sienitic rocks are frequently associated with gneiss, exhibiting a very distinct stratified character, occupying a position external to the adjacent igneous rocks. The immediate junction of the Gila and Colorado Rivers is marked by a singular geological formation. It is composed of an irregular series of rounded knolls, attaining a height of thirty to eighty feet above the river level. SOUTHERN CALIFORNIA. 85 The summit and sides of these knolls are strewn over with the erratic fragments which pertain to the continuous desert formation, and which conceal the central nucleus, except in the deep cleft made by the passage of the Colorado just below its junction with the Gila. At this point we see the central nucleus forming an irregular breccia, composed of variously sized blocks, frequently massive. The rock is a form of greenstone, streaked with epidote. The cementing material is apparently derived from the natura] decomposition of the contained rock. On the western side, near the level of low water, there is an underneath exposure of a dark-colored mass, composed of epidote, with talc—the latter being occasionally granular. This material is seen shooting upward into the superincumbent breccia in the form of veins, and would seem to hold some close relation with the disturbing cause below. The external features of this singular formation we have endeavored to represent in sectional sketches.—(See part 1, pages 128, 129.) The Tertiary formation.—The Tertiary formation which flanks the mountain range on the west extends to the Pacific coast, forming a belt of variable extent and thickness, and composed of various stratified deposits. The strata adjoining the sea occasionally presents abrupt ocean bluffs, washed by the waves at high tide; through the same formation the various streams cut their way, forming deeply trenched valleys. The strata thus exposed in the sides of valleys exhibit a slight dip toward the sea, and are seen to be composed of alternate beds of coarse sand, clay, or marl, with occa- sional beds of interstratified pebbles, all smoothly rounded, and variable in size. SECTION OF LIGNITE BLUFF NEAR SAN DIEGO. th ab a SH rie, oo ot hs sei . A : A. Ss = er —— oo” so” Hobo w A. Coarse, feruginous sand, with occasional interstratified pebbles, weathering very irregularly into fantastic shapes, forming miniature peaks and ridges. B. Coarse, white sand, in even, horizontal strata. C. Drab-colored sandstone. D. Fine-grained sand, varying in color from buff to light-gray, containing thin seams of sulphuret of iron. E. Tough clay, containing an irregular seam of lignite, with smaller portions of mineralized bitumen. In the vicinity of San Diego, and plainly exposed in the steep bluffs which bound the lower part of the river valley at this place, is observed a distinct fossiliferous layer, having a thickness of about thirty feet. Its lower members, resting on micaceous sand or clay, are not more than twenty feet above the present sea level. The contained fossils are made up mainly of silicified casts of marine shells, imbedded in a calcareous medium of more or less close texture. The individual forms of fossil species are quite numerous, though the number of distinct species is not great; the most abundant and widely spread is a species of Turritella.—(See Plate No. XIX, fig. 8.) 86 GEOLOGY, This formation is distinctly traceable at various points up the coast, and in the neighborhood of Santa Barbara is seen to form mountain masses. Wherever noticed, it is overlaid by various — sandy layers, forming an upper capping of very variable thickness. The irregular layer of interstratified pebbles, so frequently seen in hill-sides, seems hardly capable of being referred to any distinct place in the general Tertiary series. Their most abundant occurrence, however, near the mouths of valleys opening on the sea, sufficiently indi- cate that they are derived from the combined agency of river transportation and tide-washing— having attained their present position by subsequent land elevations. The junction of this Tertiary formation with the adjoining granite or igneous rocks is seen in a general thinning out of the former, which, at last, barely mantling the protruding rocks, is blended with the result of present decomposing agencies. Natural terraces and table summits.—Another interesting geological feature, observable in the post Tertiary strata adjoining the coast, is the existence of natural terraces and table summits, of various elevations, and their evident connexion with ancient sea levels—thus indicating suc- cessive periods of land elevations. A series of at least three of these terraces is distinctly noticeable near the initial point of boundary on the Pacific. The highest of these is exhibited in that striking landmark appropriately named ‘‘Table ? Mountain.’’ Visible, far out at sea, and attaining an elevation of not less than one thousand feet above the present sea level, it presents a distinct outline of abrupt slopes terminated by a regular flat table summit. As it now stands in its isolated character, and not far from the sea beach, it appears to be altogether unique, though, doubtless, more extended and accurate obser- vation of height and situation would show its connexion with some of the higher terraced elevations adjoining the interior mountain slopes. The next step in the descending series is represented in the average level of the post Tertiary bluffs and hills near the coast, say at a present elevation of two hundred to four hundred feet above the sea. The irregular character of the deposit, at various points, and the evidence of long-continued denuding influences, have necessarily obscured the general level; or, as we may suppose, the land elevation at this period was itself irregular or alternating with periods of depression. It may further be remarked, as substantiating this latter view, that the deposits here exhibited are those most abundantly characterized by the presence of transported rounded pebbles, irregularly distributed, as we have seen, along the course of valleys of denudation. The third well marked terrace formation in the descending, or more recent series, occurs in close proximity to the present sea beach, and is characterized by a more alluvial deposit, and also the first appearance of recent marine shells, strewn irregularly over its surface in comminuted fragments. ee a Se ee S eee oy ——— Se ee — —_—_-—_—_ ) ‘ a 9 re a = = ae van | | } | ! | i | | | UNITED STATES AND MEXICAN neve NUE YS UY aes UNDER THE ORDERS OF LIEUT. COL. W. H. EMORY, MAJOR FIRST CAVALRY, AND UNITED STATES COMMISSIONER. GEOLOGY AND PALAONTOLOGY OF THE BOUNDARY: JAMES HALL, OF ALBANY, NEW YORK: ——————— a aaa SSS et ee atcnyothinilibed pioret ie. “Wn “tt ee 3 NS) | titi pest bea ‘eeewinaatittehst ta pullin ta is eon lr TS i OE oe ; : > ® = b \ _ = ; PD ; . & rae Bikes 3, PALE DDG Se TRA ‘ ‘“ i ee faptty ties Lapa wl ob. ati : a H ve cali mi pag ur meeovareal ; e , |) een Sc WETSS | ‘ v rs a a Api aw uf con ’ 7 2 4 OS =e : f “9 p434- és : t Ba: ee oa My “3 iid = : = LP aed tig il ¥ “8 teaewintir bint p: Seth 3 a ; ; “Aaj ay - Me = + H sta i < > ve i : ‘ Z 7 ty tyes Oa : 5 : ‘ cto oa sa a bn ; La . >t q r% e , 7 : ay - hia ; af a 6 mld tal eae Ape x as hi eT A Svs > hl Ai. oe l — ” . . % sae i ig ' i Pon Pde, . “a 7 7 7 ~ - 9 ’ R a et iy ™ anil sd ar ae ce * Were th salt Ope OR I ie e “ . aap | ¢ be e » 7 - roy th ‘ : , ’ ; oy: et Sy idee F wei ay) eee ie wie! > f ‘ “ : co - . . “ mm, Ay i & : / . a ’ : 4 H af , . a . 7 : pens = . Pa = s~ a & ; 1 Seat Paley OR reer ers A me, i ke ee . - F : >. ‘ . wean yj ae Saeed trv'ed A lnesteaith, Ae ieakipat< ots, Ka Ant Er SR A ; ye oe ad isn. 4 : t ame =a ae “79 : : : > ~ — a) ® . ¥ ! sh WK \ : 7 7! ei : = 4 ~ ‘ , le a 24 . ba sms} GEOLOGY AND PALAONTOLOGY. Colonel W. H. Emory, Commissioner for the United States and Mexican Boundary Survey. Str: In accordance with your direction, I herewith transmit to you my report relating to the Geology and Paleontology of the Boundary Survey. The collections of the original survey were placed in my hands, in 1853, by Dr. C. C. Parry, of the Boundary Commission. These consisted of a series of rocks, minerals, and fossils, collected along the line of the survey, and along the route travelled through Texas. The fossils consisted chiefly of Cretaceous and Tertiary species ; and some of these had previously been submitted to Mr. Conrad, who described several species in the Proceedings of the Academy of Natural Sciences, of Philadelphia. There were still in the collection a considerable number of undescribed species ; and although placed in my hands for final arrangement and disposition, I preferred that Mr. Conrad should complete the work he had begun, and accordingly trans- ferred the new species to him for description. In the meantime, I had the drawings made and arranged as far as practicable previous to May, 1854. At this time an examination of some collections that had remained in Washington brought to light other species, and the number of figures and plates were increased by these additions. The collections of the Survey of the New Boundary, in 1854 and 1855, have also contributed several new species to those previously described, and these I have likewise submitted to Mr. Conrad,* in order that the descriptions might, as far as practicable, possess a unity of character and design. The collections have largely contributed to our knowledge of the extent and character of the Cretaceous formation in the southwest. . This information, taken in connexion with the results which have been obtained in the west and northwest, enable us to determine with a great degree of accuracy the character and relations of the different members of the Cretaceous period, as developed in the United States. The collections of Paleozoic fossils contain specimens from the upper carboniferous or coal measure limestone, which is known to become extensively developed in the west and southwest. A single specimen of Asaphus (Isotelus) indicates the existence of lower silurian strata, and since the specimen is scarcely worn, it cannot have been transported from a distance. It is the first specimen of undoubted lower silurian age that has fallen under my observation in all the collections that have been made in the southwest. I should not, however, omit to remark, that a specimen of coral found in the same locality (though exhibiting no decided marks of trans- * Except the few species of Echinoderms, which, at the request of Mr. Conrad, I have described in their proper place, one only being a new species. 104 GEOLOGY AND PALZONTOLOGY. portation) is apparently identical with specimens found in the immense drift deposits far to the northward, in Nebraska and at other places; and although quite possible that both the trilobite and the coral have been derived from the extreme northern exposures of the older rocks, I am nevertheless prepared to expect that these formations will be found nearly coextensive with the carboniferous limestones. Although there are among the collections of the Boundary Survey several specimens which appear referable to a position below the carboniferous limestones, and in the later collections some silurian or devonian corals, yet in the absence of other information than that furnished by the specimens, which do not bear evidence of having been freshly broken from the rocks, I do not feel warranted in drawing any general conclusions. This subject is one of the greatest interest for future explorers in that region. The specimens of igneous and metamorphic rocks from the eastern and central portions of the route travelled are all unlike those so well known in the eastern part of the United States ; and it is not until we approach the range of the Cordilleras that we find specimens bearing all the lithological characters and associations of the metamorphic rocks of the Appalachian chain. We are constrained to believe, not only from the evidences of this collection, but from others previously examined, that the metamorphic rocks of this intermediate region are to a great extent newer than those of Silurian and Devonian age, which we know to be the age of a large part of the metamorphic portions of the Appalachian chain. This conclusion, or we may say suggestion, is deduced from the differences in lithological character, as well as from the fact, already stated, that the upper carboniferous limestone is the most conspicuous unaltered rock of the region, while in some places this rock itself, as well as strata of more recent date, appear to pass into a metamorphic condition. In regard to this carboniferous limestone, it should also be borne in mind that it is not the carboniferous limestone of the Mississippi valley which attains this force farther west, but a limestone high in the coal series, and which has become thus developed, while we are yet ignorant of the existence of the lower carboniferous limestone in that part of the country. The collections of the Boundary Survey, when compared with those made in traversing the country along lines farther to the northward, present a great similarity of aspect and litho- logical character. The cretaceous belt, bordering the metamorphic and igneous region which succeeds in turn, and in the midst of which are large areas of limestone just mentioned, and also some smaller areas of cretaceous rocks, which have now been traced quite to the central part of the great basin to the west of the first mountain chain, and have more recently been determined in California. We have the means of knowing, therefore, the general geological structure of the country, from near the northern limits of the United States to Mexico. ; The first part of my report, constituting the observations upon the specimens collected, and the general results regarding the geographical distribution of the formations along the line of the Boundary Survey, are essentially the same that I transmitted to you in 18543; but which, in consequence of the change in the boundary line making a re-survey necessary, were not published at that time. I have since reviewed the whole collection, with all the additional information derived from MEXICAN BOUNDARY LINE. 105 other sources, and comparison of other collections from rocks of the same age, and particularly those of the cretaceous period from western localities and from New Jersey. These results are given in the chapter upon the relative position of the cretaceous fossils of the Boundary Survey with other known cretaceous formations in the United States. The relations of the carboniferous limestone of the Rocky Mountain range, I have endeavored to make more clear by a few pages upon the carboniferous rocks, and a section of the principal members belonging to that period, as known in the Mississippi valley. The specimens from the Tertiary formation of the southwest, although indicating a general similarity to the formations of Nebraska, are nevertheless insufficient to give the means of care- ful comparison and reliable conclusions. Our knowledge of the geological formations of the west is now so rapidly progressing, and the materials accumulating in such abundance, that whatever may be presented to-day as new and in advance of previous knowledge, will to-morrow be regarded only as a historical record of our progress. The facts here presented, and the conclusions deduced from these and other collections which I have heretofore examined, may serve as a contribution towards a more perfect elucidation of the geology of this great central region, which has been traversed by the Boundary Survey commission. I have the honor to remain, very respectfully, your obedient servant, JAMES HALL. 144M 106 GEOLOGY AND PALAONTOLOGY. OBSERVATIONS UPON THE CHARACTER AND GEOLOGICAL AGE OF THE SPECIMENS OF ROCKS AND MINERALS SUBMITTED TO MY EXAMINATION FROM THE COLLECTIONS OF THE UNITED STATES AND MEXICAN BOUN- DARY SURVEY. I. Specimens from the Gulf Coast, Texas, as far as El Paso, including all those from the east side of the Rio Grande. 1. Calcareous sandstone, branch of the Guadaloupe river below San Antonio. This rock is apparently of Tertiary age, and presents nothing peculiar in its character, except its loose aggregation and numerous dark siliceous specks or grains. 2. Calcareous conglomerate, fifteen feet thick, These specimens bear the character of the Tertiary sandstones known in Kansas and Nebraska. They are sometimes highly calcareous. The sandstone varies in character from loosely aggregated and incoherent sand to a compact calcareous sandstone or quartz rock, for the grains sometimes appear to have been cemented by fluid silica. From information obtained in connexion with these specimens, the strata to which they pertain occur in outliers of greater or less extent, the original formation having been subjected to extensive denudation. The similarity in lithological character and association suggests a probable identity in age between these beds and those of the Mauvaises Terres of Nebraska; and that the Tertiary is probably co-extensive with the cretaceous formation from Nebraska to Texas and New Mexico. : 3 and 4, Argillaceous, buff-colored limestone, a thickness of fifty feet, ascertained in sinking a well, while the entire thickness of the rock is much greater. This rock is used for buildings in San Antonio. It has the same lithological character as the stratum which elsewhere contains Inoceramus mytiloides.—I. problematicus. , 5, A yellow granular limestone of similar character, but more compact than the limestone of Timber creek, New Jersey. The specimen containsa species of cardium. The rock from which this specimen was obtained occurs about twenty miles further to the west than Nos. 3 and 4, and is penetrated in reaching a more compact stratum below. These specimens are from the lower part of the cretaceous formation. a. Specimens from the table-land on Devil's river. 6. Light gray limestone with cretaceous fossils. Painted caves. 7. A more granular limestone than the preceding, resembling No. 5 in character, and con- taining valves of an Ostrea. Painted caves. 8. Compact, reddish brown granular limestone, containing Nodosaria. This rock, on its weathered surface, is of the character of the preceding, but more compact and crystalline in its texture. 9. Compact, subcrystalline, yellowish limestone ; sometimes of a brownish yellow. Table- land beyond Devil’s river. 10. Vesicular trap from isolated hills and ridges rising from the table-land. MEXICAN BOUNDARY LINE. 107 11. Compact, light ash-colored limestone, containing cretaceous fossils; among which are Lima Wacoensis, Trigonia Emoryi, Gryphea Pitcheri, and other species. Camanche crossing, Camanche springs. b. Specimens from the Limpia range of mountains, between the Pecus river and Rio Grande. 12. Brown porphyritic trap rock, with crystals of Adularia. 13. Coarsely crystalline igneous rock, (trap-like in some parts,) composed in a great propor- tion of crystallized feldspar or Adularia, having a chatoyant lustre on the cleavage faces. This rock forms the central part of the mountain range. 14. Compact quartz rock, of a slightly reddish tint, with minute cavities. 15. Compact white opaque quartz, approaching chalcedony in its characters. These specimens from the Limpia range are of igneous origin, the quartz rock having been derived doubtless from the gelatinous silica produced by volcanic waters. We have no evidence from the facts before us that any part of the range consists of Metamorphic stratified rocks. They are mostly of reddish-brown porphyry and a coarse granitic aggregate, of which Adularia forms a large part. Some specimens of milky quartz appear as if due to depositions from hot springs. c. Stratified rocks to the northwest of the Limpia range. 16. Compact, fine grained limestone, dipping to the southwest. 17. Same as the preceding. 18. Limestone of similar character to the preceding, containing remains of crinoidal columns and shells. 19. Similar limestone with remains of shells ; (Brachiopoda, etc.) 20. Limestone like the preceding, of a grayish blue color, containing fragments of Tere- bratula, etc., (probably Terebratula subtilita.) Although these specimens present no well marked fossil species, | am nevertheless quite con- vinced, from the character of the fragments preserved, that the rock is of the age of the upper carboniferous limestone. The condition and character of the rock with the fragmentary fossils is precisely identical with specimens from the neighborhood of the Great Salt lake and other western localities. They contain remains of small Terebratula in like manner ; and the numerous fragments of organic bodies which cover the weathered surfaces indicate sufficiently that the rock is in great measure composed of similar materials. Some of the specimens are quite com- pact, and others are granular in texture; they are traversed by minute veins, sometimes of calcareous spar, and sometimes of harder material. 21. Siliceous tufa, resembling trap tuff. It consists of an aggregation of finely divided siliceous matter, porous or minutely cellular in structure. It is represented as forming dykes in the limestone. Two specimens from Eagle spring. 22. Specimens similar to the last, but coarsely laminated, and with minute concretions ; brecciated, ete. Eagle spring. 23. Light-colored amygdaloid rock. Hagle spring. 24. Porphyritic trap. LHagle spring. 25. Brown porphyry ; compact. 108 GEOLOGY AND PALHONTOLOGY. 26. Brown porphyry; same as the preceding, except that it contains cavities, which are probably due to the weathering out, or solution of crystals from the mass. 27. Chalcedony mixed with Feldspathic lava. This rock has been formed by gelatinous silica penetrating scoria or other loose volcanic materials. 28. Chalcedony. Two specimens, associated with the preceding rocks. The volcanic products present numerous modified conditions, from the effect produced by silica’in solution, or in the gelatinous condition, having penetrated the mass. From this cause, and from the effects of heated water, not only the lithological aspect, but the color of the rock is often greatly modified. 29. A siliceous stratified rock, apparently a highly altered sandstone. From the Rio Grande, seventy miles below El Paso. 30. A porphyritic trap-like rock, perhaps a sedimentary rock altered by volcanic action. Seventy miles below El Paso. 31. Greenstone trap. Seventy miles below El Paso. 32. Volcanic breccia, a gray feldspathic mass with hornblende. Same locality as the last. 33. Volcanic breccia, becoming porphyritic; more compact and crystalline than the preceding. 34. Granitic mass; a volcanic granite, composed of feldspar and hornblende, with little quartz ; probably a further modification of the breccia by igneous action. Seventy miles below El Paso. The range east of the Rio Grande, seventy miles below El Paso, has furnished specimens of reddish and greenish compact porphyry, compact trap, a specimen of granitic structure con- sisting of feldspar, mica, and some earthy matter, but loosely aggregated, not unlike the products of recent igneous formations ; also several specimens of volcanic breccia loosely aggre- gated, and a single specimen of similar composition very compact in texture. From this locality there is also a specimen of carboniferous limestone, partially crystalline, and one side permeated by innumerable minute pores ; but it still preserves evidences of organic remains on its weathered surfaces. d. Specimens from the Tertiary Basin of the Rio Grande. 35. Selenite mixed with marl from a bluff composed of marl, gravel, and beds of selenite. The crystals occur in detached groups, but altogether form large beds. 36. Cretaceous limestone with Hzogyra texana, and Serpula. El Paso. 37. Argillaceous limestone with Jnoceramus, from the Rio Grande above El Paso. 38. Hornstone with seams, or a brecciated intermixture of limestone with hornstone, forming the summit of a mountain 1,200 feet high. The base of the mountain is composed of the upper carboniferous limestone. Near Frontera. 39. Black hornstone, surrounded by a lighter colored mass of the same. Near Frontera. 40. Feldspathic or granitic volcanic rock, composed mainly of Feldspar and Olivine. Two specimens from near Frontera. 41. Compact feldspar with a little glassy quartz: forming knobs and dykes running through the limestone strata; sometimes overlying and sometimes underlaying the latter rock. It is evidently of volcanic origin. No. 40 forms isolated knobs less intimately connected with the limestone than No, 41. MEXICAN BOUNDARY LINE. 109 The specimen marked ‘‘ Isolated knobs near Frontera,’’ consists of feldspar and olivine, and is a modern igneous product. The specimen marked ‘‘ Granite, north of Frontera,’ ? is asimilar aggregate, more compact and containing scales of mica. The mountain northeast of Frontera is partially composed of reddish feldspar with small grains of crystalline quartz; a kind of porphyritic rock. The position of this rock is remarkable and highly interesting. A sectional sketch of the mountain by Dr. C. C. Parry, represents it as resting on the upturned edges of the strata of carboniferous limestone, which form the base and greater portion of the mountain, and dip at an angle of 45°. The granitic aggregate rests on the sloping sides of the mountain, in the direction of the dip. At a little distance from this point, and apparently resting on the latter rock, occur cretaceous strata, highly inclined, as it the igneous mass had been forced out near the junction of the carboniferous and cretaceous beds. In other instances the igneous beds rest on the cretaceous deposits ; leaving no doubt that the eruption took place subsequent to the cretaceous period. The specimens from 35 to 41 inclusive, present the characters of the different members of a section across the Tertiary and cretaceous strata, to the upper carboniferous limestone ; with the associated igneous rocks which form separate and isolated masses, or are more or less entangled in the stratified limestone. e. Specimens from the Organ Mountain range, jifty miles north of the locality of Nos. 40 and 41. The elevation of this range is about 2,000 feet above the bed of the river. The specimens from the Organ Mountains consist of compact feldspathic granite with very little quartz, a few scales of green mica and hornblende, and numerous minute crystals of mag- netic oxide of iron. Notwithstanding the compactness of this mass, the character and mode of aggregation are so similar to some of the well-characterized volcanic products that it can scarcely be regarded as an ancient granite. Resting on this rock occurs very compact green- stone porphyry. A specimen from the western base of the mountain is a reddish lava-like porphyry with a finely porous or vesicular structure. 42. Granitic rock, composed of crystalline feldspar with a smaller proportion of quartz and hornblende. The specimen is less lava-like than No. 40, but it has the aspect of a very modern igneous rock. This constitutes the central portion of the mountain range. 43. Porphyritic greenstone, very compact, forming the mass partially surrounding No. 42. This rock occurs in distinct layers dipping at an angle of 82° W. 44, Brown porphyritic trap, overlying the granitic central mass of the mountain. 45. Reddish brown, compact, lava-like rock, containing minute crystals of feldspar; associated with Nos. 42, 43, 44, forming extensive masses. 46. Sulphuret and phosphate of lead, sulphuret of copper, and sulphate of baryta. There are several specimens all presenting the same general character, and obtained from a vein in the mountain range. 47. A coarse porphyry ; a red, coarse, loosely aggregated base. Near the San Antonio road, 48 Volcanic breccia. Near the San Antonio road. 49. Amygdaloidal trap; a common, grayish base with round vesicles. Tascate. 50. Porphyry. 110 GEOLOGY AND PALZONTOLOGY. 51. A porphyritic rock with chalcedony. 52. Compact, laminated porphyritic rock. 53. Compact, micaceous, gneissoid sandstone, slightly calcareous; dipS.8.E. 60°. This sandstone has the aspect of a cretaceous or tertiary sandstone. 54, Laminated, compact, argillo-calcareous rock, which has been subject to igneous action, and partially altered. The two preceding specimens are from strata overlaid by trappean rock, before noticed ; and their altered condition is doubtless due to this action. This fact places the date of these erup- tions subsequent to the cretaceous period, and perhaps posterior to the older Tertiary deposits. 55. Encrinital, subcrystalline, light-gray limestone, containing numerous fossil fragments ; belongs to the upper carboniferous period ; dip to the southeast. Cibolo creek. 56. Argillaceous sandstone with mica, fine-grained and thinly laminated. The age of this sandstone is doubtful, but it may be carboniferous. Cibolo spring. 57. Compact porphyry. Cibolo creek. 58. Limestone of the upper carboniferous period, forming high mountains; dip southeast. Presidio del Norte. This rock is similar to that from Cibolo creek, but more compact and less crystalline, and evidently has undergone a partial metamorphism. A specimen from the rapids of the Del Norte is of a bluish ashen color, very compact and fine-grained, with numerous crystalline points and lines which mark the presence of organic bodies. Although no fossils can be recognized in their specific character, yet the rock is so precisely of the character of the carboniferous limestone in numerous western localities as to leave no doubt of its trueage and geological position. The specimens from Buffa-silla, marked ‘‘ Aug. 10,’’ consist of the following : two specimens of vesicular lava, one of compact breccia, enclosing fragments of lava, and several specimens of trap tuff, enclosing quartz pebbles and fragments, and becoming, in one specimen, a sort of friable breccia. Another specimen from the same locality, marked ‘‘ Aug. 13,’’ is a compact, volcanic breccia, composed mainly of fragments of various volcanic materials. 59. Vesicular lava, Buffa-silla. A second similar specimen. 60. Compact lava, Buffa-silla. 61. Voleanic breccia, composed of fine white volcanic ashes, with pebbles and fragments. 62. Coarser breccia, with a coarser base than the preceding. The compact lavas are represented as lying below, and the breccias between these and the more cellular lavas above. Sometimes there are several successive series of these beds. 63. Granitic or compact feldspathic lavas, with quartz and hornblende in small proportions. Three specimens from the cajion of the Rio Grande. A specimen from the caiion of the Rio Grande, marked ‘‘ Aug. 27,’’ consists of a crystalline aggregation of quartz, feldspar, and carbonate of lime. Two other specimens, same date, from Puerto Peak, are granitic aggregations of quartz and feldspar, and appear much like a partially fused breccia. 64. Cemented volcanic ashes, with, occasionally, small vesicles, giving an amygdaloidal character. MEXICAN BOUNDARY LINE 111 Three specimens, showing variety (of 64.) 65. Breccia with a white base. 66. Lava, less compact than that below. The series shows the succession of compact lava, breccia, and less compact, or vesicular lava above. 67. A fragment including part of a cavity in amygdaloid, with green quartz. 68. Brownish porphyritic rock. This has the common character of the porphyry of the region. 69. Crystallized peroxide of iron, connected with the trap or lava deposits, 70. Porphyritic granite, apparently of very modern origin. 71. Sienite or porphyritic granite, varying but little from No. 70. It contains dark smoky quartz. 72. Reddish porphyry or porphyritic trap, associated with the preceding specimens. 73. Compact argillaceous limestone of the Cretaceous formation. 74. Compact, close, and fine-grained argillaceous limestone of the Cretaceous formation. 75. Exogyra texana, from above the Pecos river. 76. Argillaceous limestone, with Hxogyra, containing cavities filled with calcareous spar. 77. Fossil wood from Tertiary strata; Eagle Pass. Il. Specimens from the country west of the Rio Grande. 78. Sandstone, compact and fine grained. Cemialauke. This rock is said to form a mountain range in connexion with the conglomerates. The specimens are not sufficient to determine satisfactorily the geological age of the formation. 79. Carboniferous limestone with fossil remains. These specimens, (79,) from west of Salado, have evidently undergone partial metamorphism, though still preserving fragments of organic remains. One of them contains several imperfect shells, among which a Terebratula is distinguishable. 80. Porphyritic lava, connected with the preceding limestone; and breccia, connected with the same. 81. Compact trap, with a silicious incrustation covering the surface. 82. Amygdaloid. An extensive district is represented as covered by rocks like 81 and 82, on the southwest of Frontera. 83. Amygdaloid, similar to the preceding ; one hundred miles west of El Paso. 84. Specular iron ore. It occurs in loose masses, scattered over the Tertiary plains. 85. Chalcedony, associated with trap rocks. 86. Feldspathic lava, or compact trap tuff. Rocks of this character are represented as forming the dividing ridge and summit of the Sierra Madre near the Gaudaloupe Pass. 88. Quartz rock; some portions are granular, showing the passage from an arenaceous mass to a compact homogenous quartz rock. (This is, apparently a metamorphic stratified rock.) A specimen from the summit of the Gaudaloupe Pass presents the character of rounded 112 GEOLOGY AND PALMONTOLOGY. crystalline grains of quartz, in a paste of milky quartz. In many parts the granular structure is seen passing into the homogenous texture. This sandstone is associated with the carboniferous limestone. 89. A reddish colored stratified rock ; apparently an altered shale becoming porphyritic. 90. An argillaceous sandstone; the granular structure gradually merging into a compact chalcedonic mass. 91. Conglomerate, associated with the preceding specimens, 89 and 90. The rock has the aspect of a Tertiary conglomerate. 92. A compact granular mass of feldspar and olivine. p 93. A similar mass, colored by oxide of iron. The change of color perhaps due to infiltration of heated water. 94. Conglomerate, composed of quartz pebbles, trap, and other volcanic rocks, with much calcareous matter. The pebbles are somewhat angular. (A modern product.) 95. An earthy calcareous rock, associated with the preceding conglomerate. 96. Compact dark colored trap rock. 97. Talcous slate, with quartz veins. 98. Granite, fine, granular, consisting of quartz, feldspar, and mica, in nearly equal propor- tions, and having a more ancient aspect than the granite found associated. with the trap rocks. These two specimens (from the same locality) give the first indications of an approach to rocks of a character similar to those composing the Appalachian mountain chain; and which are like the products of metamorphic silurian strata. III. Specimens from the silver and lead-bearing rocks of the Corriletas. 99. A compact silico-calcareous rock, with a few scales of mica. It appears to be an impure subcrystalline limestone, and is associated with other specimens of limestone. This is repre- sented as forming the rock traversed by the veins of silver-lead ore. 100. Sulphuret of lead and silver. 101. Sulphuret and carbonate of lead. 102. Sulphuret of lead connected with a gray limestone. 103. Earthy carbonate of lead, said to contain silver. 104. Semi-crystalline limestone associated with the earthy carbonate of lead, which latter is represented as occurring in beds or veins, distinct from the sulphurets. 105. Limestone similar to the preceding, colored brown by oxide of iron. 106. Compact, silicious limestone, which has undergone some alteration from igneous action. 107. Compact, altered limestone, associated with the silver ores of the San Pedro mines. A specimen said to be associated with the silver of the San Pedro mine is a greenish, impure limestone, with light colored or white crystalline points. The weathered surface presents minute cavities, and it has altogether the appearance of an ordinary greenstone. On testing by acids, it effervesces strongly, and is evidently highly calcareous. 108. Cretaceous limestone containing shells of Exogyra, &c., from the foot of the mountain in which the silver ores occur. The cretaceous strata overlie the upper carboniferous limestones, and are shown to have been subjected to similar disturbances, so far as the elevation of the strata is due to such action. 109. Red oxide and green carbonate of copper.—Copper mines of New Mexico. MEXICAN BOUNDARY LINE. i 3 110. Green carbonate of copper.—Sonora. 111. Gray sulphuret and green carbonate of copper.—Copper mines of Presidio del Norte. 112. Sulphuret of lead and silver, with crystals of sulphate of lead.—Santa Rosa. The specimens from Santa Rosa are from veins, and do not furnish any of the associated rock. The specimens of rock from the Leon mine are a semi-crystalline limestone of a mixed gray and white color, with calcareous spar; and a crystalline limestone colored brown by oxide of iron. The other specimens from this locality are vein-stones or ores. In the vicinity of the mines of Corriletas, the limestone has undergone still farther meta- morphism, and some specimens which occur in the same connexion, and apparently of this age, assume a very crystalline character, and exhibit mica and some other minerals, which have been segregated from the mass during the progress of metamorphism. The specimens of limestone from the Escandido mines include one of a yellowish white color and crystalline texture, containing disseminated crystals of iron pyrites: this may be a vein- stone. Another specimen is of very compact, bluish, granular limestone, with thin pressed veins of spar, evidently having undergone some metamorphic action. This is labelled as coming from the foot of the mountain adjoining the mines. Other specimens marked as from the same locality contain large numbers of’ fossil shells, but in such a condition as to afford very unsatis- factory means of determining their age. They present, however, many features like those of the cretaceous limestones, and are probably beds of that formation, which have undergone partial metamorphism. , B. SPECIMENS COLLECTED ON THE ROUTE FROM THE PACIFIC COAST EASTWARD, INCLUDING THE TERTIARY OF THE COAST AND THE METAMORPHIC ROCKS OF THE CORDILLERAS; THE TERTIARY OF THE GREAT PLAIN EAST OF THE CORDILLERAS, AND THE METAMORPHIC ROCKS OF THE ISOLATED MOUNTAINS IN THE GREAT PLAINS. IV. Specimens from the coast Tertiary belt, from the neighborhood of San Diego. 1. Gray micaceous sandstone, with more or less of argillaceous matter, friable, or more or less compact. 2. Calcareous beds with shells, Turritella, Pectunculus, &c. 3. A fine chalk-like, tufaceous deposit, occurring in isolated beds. 4. Lignite, associated with clays and sands. V. Tertiary formations spreading over the plain east of the Cordilleras. 1, Sands and marls with clays, all more or less calcareous ; represented as forming extensive beds of considerable thickness, and cropping out in bluffs of several hundred feet high. 2. Shells of Ostrea vespertina, from the beds of the preceding series. 3. Calcareous tufa ; forming isolated masses or deposits. 4. Gypsum—Selenite. This mineral occurs in the clays and marls of the formation. 5. Common salt, forming on the borders of lakes from evaporation. The soil is more or less permeated with saline matter, which is carried downwards to the depressions in which occur the small lakes having no outlets. 15 M 114 GEOLOGY AND PALAONTOLOGY. 6. Sandstone. A fine-grained, friable, micaceous sandstone, occurring above the marls and clays, and represented as attaining a thickness of from 100 to 200 feet. The sandstone contains nodules of clay, which are often large and flattened, forming an irregular or interrupted layer. These nodules are frequently surrounded by pebbles or small gravel. These pebbles consist of quartz, porphyry, greenstone, jasper, &c., and sometimes form layers of conglomerate. From the evidences of drift action afforded in the specimens, it is probable that the formation may at some points present extensive beds of conglomerate. This sandstone is precisely of the same character as the Tertiary sandstone of the Mauvaises Terres of Nebraska. ‘ 7. Coarse sand and small pebbles cemented by calcareous matter, forming a conglomerate which has a thickness of 30 or 40 feet. 8. Fossil wood—an erratic mass found upon the plains. 9. Vesicular lava, having the cavities filled with earthy matter, and embracing small shells like Ceritheum, but too imperfect to be specifically identified. The table-land occupied by this Tertiary formation forms the plateau in which the rivers take their rise. VY. Specimens from the Coast Range. 1. A somewhat vesicular trap or greenstone, containing spots and blotches of soft green earth. 1. Greenstone porphyry. V1.—Specimens from the westerly part of the Cordilleras. . Chloritic rock, having a compact or scarcely laminated structure. . Chloritic or talco-chloritic rock, with hornblende, etc. . Black mica, with quartz veins.—Pine ridge, 16 miles E. of San Luis Rey. White quartz, with schorl. . Quartz and feldspar; granitic in its structure, and containing schorl.—Near Santa Isabel. . Feldspathic granite, very similar to the preceding specimens.—Near Acapulco. aware WwW bd VII.—Specimens from the central portion of the dividing range. 1. Granitic or sienitic rock, composed of quartz with black hornblende in blotches and a little mica.—From the bare peaks of the Cordilleras, near the boundary line. 2 Feldspathic granite, somewhat gneissoid. 3. Feldspathic gneissoid granite. 4, Gneiss. 5. Hornblende rock; dark colored. This rock is very similar in character to much of the rock of the Green mountain range. 6. Fine-grained syenitic rock, with hornblende in crystals on the surface. The specimens enumerated above, from 2 to 6 inclusive, are evidently from the same formation of metamorphic rocks in the exposures of the different beds. 7. Rose quartz; from a loose mass, though probably derived from this metamorphic belt. . 8. Black tourmaline; a loose mass. MEXICAN BOUNDARY LINE. 115 9. Crystalline quartz, with black tourmaline.—Near the dividing ridge of the Cordilleras ; east from San Diego. 10. Feldspathic granite, with mica in large plates. The locality south from No. 1 of this series, and belonging to the same (dividing) range. VIII.—Specimens from the eastern slope of the Cordilleras. 1. Coarsely crystalline granite, with much mica and feldspar.—Lower California. 2. Similar to the last, but with a less proportion of feldspar.—Lower California, near the boundary line. 3. Talcose slate, with Anthophyllite. 4. Quartz in veins in the talcose slate. IX.—Specimens from the isotated mountains in the great plain of the Cordilleras, near the mouth of the Gila, on the west side of the Colorado River. 1. Syenitic rock, composed of hornblende and feldspar. 2. Similar to the last, but finer grained. 3. A granitic mass, composed of quartz, feldspar, and mica, with black tourmalines. 4. A granitic mass, consisting chiefly of quartz with lamine of white mica The quartz con- tains garnets, 5. Gneiss or mica slate, finely granular and laminated, * 6, Epidote rock ; crystalline. 7. Epidote with talc; (two specimens ;) the tale in thin minute scales, and the epidote finely granular. 8. Epidote and tale; the epidote granular, but arranged in lamin, IX.—WMiscellaneous specimens not numbered. Specimens designated as follows : « August 25,’’ compact and amygdaloid traps. ‘*¢ August 29,’’ marked as the lower stratum, is amygdaloid, having the appearance of fine volcanic ashes, loosely cemented, and containing a few cavities filled with crystalline matter, and others empty. ‘¢ September 16,’’ volcanic tuff. “September 17,’’ green quartz in a cavity of amygdaloid. ‘¢ September 30,’’ specular iron ore connected with volcanic rocks. “¢ October 7,’’ reddish, porphyritic lava. ‘¢ November 8, Mount Carmel,’’ coarse syenitic aggregate. ‘¢ November 10,’’ reddish vesicular porphyry. ‘* Mareh 2, 1852,’’ siliceous rock, apparently indurated trap tuff. ‘March 26, 1852,” granitic lava, or trap tuff, with crystals of feldspar, mica, &c. **Summit of San Luis Mountains,’’ an indurated tufaceous mass, with cavities lined with quartz, ‘¢ Mouth of Guadaloupe river,’’ semi-metamorphie red shale. 116 GEOLOGY AND PALAONTOLOGY. “Conglomerate, mouth of Guadaloupe river,’’ breccia, probably of volcanic origin. ‘*Santa Cruz Pass,’’ compactly granular feldspathic rock, containing minute grains of mag- netic oxide of iron. Another specimen is of vesicular trap tuff, colored red by oxide of iron. “Rio Santa Cruz, above Tilbac,’’ semi-indurated volcanic ash; also a specimen of coarse breccia. “¢ Toneous rocks west of Salado’’—one specimen is compact, feldspathic lava ; the other com- pact, coarse breccia. _ ‘ ‘‘TLacuna Santa Maria,”’ finely vesicular trap, with siliceous incrustation. ‘¢ Twenty-five miles southwest of Frontera,’’ highly vesicular trap or amygdaloid. » ‘Baranca,”’ a granular amygdaloid. The enumeration of this collection of specimens enables us to deduce some general conclu- sions of great interest regarding the geological structure of the country between the Gulf of Mexico and the Cordilleras range of mountains. The specimens from the eastern part of this range, taken in connexion with what we know of its character in other places, and of the geology between this range and the Pacific ocean, are sufficient to give a very correct idea of the intervening space. A broad belt along the coast of the Gulf is occupied by deposits of very modern geological age, which may be referred to the same period as the drift and alluvium. This deposit consists of water-worn materials—as sand, gravel, pebbles, &c., which have been spread over the sur- face in a very regular and even manner, The general elevation of this belt is 300 feet above tide water, and varies little in its height for many miles in extent. In several places the denudation of this deposit discloses beneath it formations of the Lather Tertiary period. Approaching the borders of the high table-land which commences at the head of navigation on the rivers, the cretaceous formation appears at numerous points in the river beds and banks, and elsewhere where the superficial accumulations are removed. From the commencement of the table-lands westward, the specimens show the occurrence of a broad belt of the cretaceous formation, interrupted here and there by isolated dykes, or mounds of trap, or other igneous rocks of modern age. Basins of Eocene, marine Tertiary, likewise occur at intervals, resting upon the cretaceous beds. The specimens of the latter formation consist of limestones, some of them extremely compact and dark, and others light colored and friable. Various admixtures of these with more argillaceous matter, and greenish, calcareous sands, sometimes partially indurated, are of frequent occurrence. The numerous fossils collected from different localities leave no doubt in regard to the age of this formation.* In localities where the igneous rocks are protruded through the beds of this age, a greater or less degree of metamorphism has taken place. Sometimes we find a partial or entire induration of the contiguous masses, and often their metamorphism is so great as to render it eter to distinguish their age and relations from a simple examination of specimens. Towards the west the igneous rocks, which first appear in small, isolated knolls, gradually * T should not omit to notice in this place the very valuable and interesting work of Dr. F. Remer upon the fossils of the chalk formation in Texas, ‘‘ Kreidebildungen von Texas,’’ &c. This gentleman passed more than two years in the United States, a considerable part of which was spent in Texas. Previous to the publication of this work he had published a description of that country, with a geological map, &c. The collections now under consideration, though for the most part made at a distance from the principal localities cited by Dr. Roemer, correspond to a great extent with those described by him, and corroborate in the most satisfactory manner his views of the general geological structure of the country. MEXICAN BOUNDARY LINE. a ie" assume more importance, and extend into long belts. In the Limpia range these rocks present the character of a mountain chain, having an elevation of 6,000 feet, and extending several hundred miles north and south. The specimens from this range present the characters of erup- tive and metamorphic rocks. Notwithstanding the syenitic texture of some of the beds, they have still a modern aspect. ‘The different minerals are quite distinct from each other, not blended and imbedded as in the older metamorphic rocks, and their mode of aggregation is also unlike. In addition to this, the occurrence of igneous products of very modern age, which are intimately associated with these rocks, and apparently prevail in great quantity, induce us to regard all these as belonging to a system of eruption and of elevation of very modern date. We may, however, inquire what other evidences, if any, we have in the surrounding rocks as to the age of these igneous mountain ranges. The great table-land formed of the cretaceous rocks has on its eastern margin an elevation of not far from 1,000 feet. The surface of the country gradually rises to the westward, and near its junction with the igneous rocks of the Limpia range they have an elevation of 3,000 or more feet. On approaching the range, also, we find these beds of cretaceous age dipping at a high angle in various directions, showing great disturbance of the beds, apparently due to the elevation of intruded igneous masses. The beds of cretaceous rock have in some instances been indurated, and otherwise affected by the proximity or contact of igneous masses. We have, therefore, not only evidence of the general elevation of the country towards the great central range in the inclination of these beds, but we have the positive evidence of local disturbance and change due to the intrusion of these igneous masses which form isolated points or mountain chains. Beyond the Limpia range, in the neighborhood of El Paso, we have cretaceous rocks, con- taining numerous fossils. These beds rest upon carboniferous limestone, and all have a westerly dip—the carboniferous strata dipping at a much higher angle than the cretaceous. The rocks of both periods are complicated with volcanic and other igneous rocks ; and in some instances the latter have been protruded beneath the cretaceous beds, and rest upon the carboniferous limestone, which is but partially altered. The cretaceous beds of this locality are about 4,000 feet above tide water. Still farther west, in the vicinity of Corrilitas, cretaceous beds occur in connexion with par- tially altered limestones and igneous rocks, having an elévation of nearly 5,000 feet above the level of the sea. This is the most westerly point at which any cretaceous fossils have been found on the line of this expedition. The occurrence of cretaceous deposits in this region is of much interest when taken in con- nexion with similar discoveries further to the northward. Captain Frémont, in his explorations of 1843 and 1844, brought cretaceous fossils from the eastern slope of the Rocky mountains, Smoky Hill Fork of the Kansas river, in latitude 39°, longitude 105°. In the explorations of 1846 and 1847, Lieutenant Abert collected specimens of the same species of cretaceous fossils, Cnoceramus mytiloides, = I, problematicus,) at Poblazon, on the western slope of the Rocky Mountains, in latitude 35° 13’, longitude 107° 0! 2”.* * Professor Bailey, who identified the fossils in Lieutenant Abert’s collection, makes the following remarks: ‘* The fossils from Poblazon consist of gigantic Hippurites, casts from the cells of several species of Ammonites, valves of Inoceramus, identical with a species figured in Frémont’s Report, pl. IV, fig. 2,+ casts of small univalves and bivalves too imperfect for t Inoceramus (mytiloides) problematicus. 118 GEOLOGY AND PALAONTOLOGY. The same species of Inoceramus was brought from between the Big and Little Blue rivers, (tributaries of the Kansas river,) by Captain Stansbury. A collection from several points in Arkansas, made by Colonel Frémont in his late expedition, and sent to me for examination in 1854, contains also specimens of Inoceramus problematicus, associated with a few other fossils. The cretaceous fossils which occur in the vicinity of Corrilitas correspond in position, being on the eastern slope of the Rocky Mountains in nearly the same meridian of longitude? and between 31° and 32° of latitude. In each of these explorations the points mentioned were the farthest west at which cretaceous rocks with fossils were obtained. The identity of fossils, the occurrence of the same species of Inoceramus in all these localities, and its association at Poblazon with Hippurites, as in the collections of the Boundary Survey, indicate very clearly the same geological horizon for the strata of all these localities from the Kansas river to New Mexico. The dip of the strata in the localities is influenced by the igneous rocks in immediate prox- imity, and is therefore variable, often inclining to the west; while the general dip of the formation is in the opposite direction.* . To the west of the last named localities there occur various stratified, partially metamorphic rocks, some of which may be of cretaceous age ; but the information possessed warrants no more than a probable inference. One of the specimens is a somewhat coarse and rather loosely aggregated calcareous gray sandstone, and another is a partially metamorphic silicious slate. The principal features developed by this collection show the existence of a broad belt of cretaceous rocks, in almost uninterrupted continuity, along the Rio Grande, from below Laredo to beyond San Vincente. On either side are igneous rocks occupying a greater or less extent ; and beyond the junction of the Rio Pecos these igneous belts become of more frequent occurrence and of greater extent. The older tertiary deposits occupy isolated basins in- the cretaceous formation, and both are covered indiscriminately by the alluvium. In many places, these drift or alluvial deposits, consisting of waterworn materials, with saline efflorescences, gypsum, &c., are spread out over large areas of the cretaceous formation which forms the fundamental rock of the Llano Estacado or Staked Plain. The almost constant occurrence of the carboniferous limestone, with these igneous and meta- morphic belts, along a great north and south extent, taken in connexion with our knowledge of the existence of this formation on the west and northwest of the Mississippi valley and in Arkansas, offers almost conclusive evidence that nearly or quite all the intermediate space is occupied by the same strata underlying the cretaceous formation. We already know of a similar association of the carboniferous limestone, over a large extent of country, in the vicinity of the Great Salt Lake, and at intervals farther to the south ; and the facts, in connexion, afford a very probable inference that it occurs in similar associations from the southern boundary of the United States, or latitude 28°, to above the 42d parallel. determination, and teeth of sharks. These fossils prove that the strata ftom which they were taken belong to the cretaceous formation. The existence of vast beds of this formation on the east side of the Rocky Mountains, and extending from the upper Missouri to Texas, is well known. The occurrence of the same formation on the western side of the primary axis of the Rocky mountains, is quite interesting.”” : ‘The dip of the rocks at Poblazon is to the west, or from the Rocky Mountains ; and this proves that these mountains have been elevated since the deposition of the cretaceous beds. It is, therefore, probable that the cretaceous beds on both sides of the Rocky Mountains were made by the same ocean.”’ * The inferences in regard to dip, &c., are founded on observations and sections furnished by Dr. C. C. Parry. MEXICAN BOUNDARY LINE. ~ 119 The relative position of these cretaceous beds is precisely the same throughout Texas that it is along the valley of the Mississippi river, in the States of Tennessee, Arkansas, Illinois, and Missouri, where they rest upon the upper carboniferous strata. In an economical point of view, the most important results shown by this collection are the almost constant association of metalliferous products at the junction of the igneous with the metamorphic rocks of the carboniferous period, or perhaps sometimes with metamorphic rocks of more ancient date. The collection of silver lead ores and copper ores, from different veins, with the associated rocks, show that they are always near the junction of the igneous formations, and the superin- cumbent more or less altered limestones. The metalliferous veins, it would appear, always penetrate the limestones, which vary in character from gray or grayish blue granular beds with fossils, to light colored or nearly white crystalline limestones. The specimens which can be identified are clearly of carboniferous age, though some erratic specimens show that the older Paleozoic limestones may enter into this combination ; and possibly some of the cretaceous beds have become so altered as to be undistinguishable from the older rocks, though we have yet had no proof of extensive metamorphism in rocks of this age. These circumstances, nevertheless, do not affect the general inferences regarding the metal- liferous character of the rocks at or near the junction of the two systems. The facts before us warrant the conclusion that the conditions enumerated apply not only to the region actually travelled over, but also to the highly metalliferous regions farther to the south in the same range. These facts also suggest the importance of a more careful examination of this range in its northern extension, which we already know to have the same geological constitution, but which has scarcely been explored with a view to its economical resources. 120 GEOLOGY AND PALAONTOLOGY. OBSERVATIONS UPON THE IGNEOUS AND METAMORPHIC ROCKS, AND ASSO- CIATED MINERALS, IN THE BOUNDARY SURVEY COLLECTIONS. The preceding catalogue of specimens, with observations ‘upon their character and geological age, and a resumé of their geographical distribution, may very properly be followed by some notice of their relative positions in the series, and their correspondence with, or difference from, others of the same age in other parts of the country. From time to time, and from various sources, we have learned that large areas of the central portion of this continent are occupied by rocks of igneous or metamorphic character ; and that the plains and valleys present geological formations of different and more recent periods. We have also been made aware of the entire distinctness, in character and origin, as well as geographical separation, of the great mountain chain of the Cordilleras, or Sierra Nevada of the North, from the more easterly ranges of the Rocky Mountains. Physically, the great central mountain region, or Rocky Mountain chain, with its subordinate ranges, is clearly as distinct from the western chain, notwithstanding there may be numerous isolated peaks and short broken ranges, which form a partial connexion between them, Still, again, the Sierra Nevada and the coast range are recognized as geographically distinct. Geology has likewise proved these several mountain ranges to be of different origin and of different age. The Cordilleras, or Sierra Nevada, and the subordinate ranges, or isolated mountains dependent upon that stupendous chain, are all of the older metamorphic rocks, consisting of stratified rocks of Palaeozoic age, silurian, devonian, and perhaps, to some extent, of carboniferous strata, which have been changed from their original condition, and finally elevated into mountains. The lithological character and mineral products are identical with the rocks of the Appalachian chain, which form the great elevation from Canada and Nova Scotia to Alabama, on the eastern side of our continent. Their lithological characters and mineral products correspond likewise with rocks known to be of that age in other parts of the world. The series of specimens in the boundary collections, and the specimens in other collections, brought from this mountain range, exhibit all the varieties of mineral materials and differences of aggregation presented in a series of the rocks of the Appalachian formations. The auriferous gravel of California is derived from the quartz veins in the slates and other rocks of the Sierra Nevada, as the auriferous gravels of Canada, Virginia, the Carolinas, and Georgia are derived from the quartz veins of the Appalachian rocks. The auriferous quartz veins of California are the same in character, in age, and origin, as those traversing the metamorphic rocks of the great eastern chain from Canada to Georgia. There are even stronger, though more subtle, analogies between the rocks and minerals of these widely distant mountain regions, when submitted to the researches of the chemist. Rocks and compound minerals, while known by the same names, are often found, on careful analysis, to possess different proportions of certain elements ; or they may in one case contain an elementary mineral substance not known in the other. Now, even in this regard, the researches of chemistry have proved that certain mineral products of the one mountain chain are precisely similar to the same in the other. And we might go still further, and show that the order of succession among beds of a certain character is the same in both mountain chains, MEXICAN BOUNDARY LINE. 121 and prove also, by dynamic and chemical laws, that it could not have taken place in any other order, The present occasion does not require the details of comparison between these two ranges of the same age. Still, it is not a little interesting to know that two mountain chains, produced from the metamorphism of series of strata of the same age, now form, the one the eastern, and the other the western, outlines of our continent. The one has a direction from northeast to southwest, and the other, almost at right angles, from the northwest to the southeast, giving us the great breadth of continent at the north, and the narrow southern extremity. The coast range of mountains presents us with quite distinctive features in the specimens, and we know from many sources that it consists of recent igneous rocks and metamorphic strata of very modern age, the igneous products being chiefly greenstone or basalt, amygdaloid, and materials of similar character. Further east, the Cordilleras offer a striking contrast in the collections to those made along the route travelled from the coast of Texas to the westward. From the coast to the Rio Grande, the specimens from the Limpia range, from the Sierra Madre, and the Organ Mountains present no character similar to those from the Cordilleras. The granites are all of different aspect, with glassy feldspar, occuring in connexion with known volcanic products, as porphyry, greenstone, and mixtures of quartz, feldspar, and olivine, etc. There are among these no granites assuming a gneissoid structure; no granites with shorl, tourmaline, or garnets; no talcous (pholerite) slates, chloritic or mica slate rocks, as in the Cordilleras. The lithological aspect of the two collections is at once conclusive of their different age and origin. Whatever the Rocky Mountains may offer in other parts of their range, that passed over in the boundary survey gives no indication of the occurrence of the older metamorphic rocks, Indeed, the materials of purely igneous origin so largely preponderaie, that the few metamor- phic specimens appear quite subordinate ; while the observations accompanying the igneous specimens prove that they form nearly entire mountains which are crossed upon the route. We are aware that further to the north there are extensive mountains, which bear rather the character of metamorphic than of igneous products; but even these do not resemble the meta- morphic rocks of the western chain. In the specimens from this range, we see the predominating influence of volcanic action, and the result of the same action in the influence of heated waters holding silex in solution, by which the more porous masses have been penetrated and become solid, or so changed in color and condition that there is an almost infinite variety of these products of one prime source. 16M 2 GEOLOGY AND PALMONTOLOGY. OBSERVATIONS ON THE CARBONIFEROUS LIMESTONE OF THE BOUNDARY SURVEY COLLECTIONS, AND ITS RELATIONS WITH THE CARBONIFEROUS LIMESTONES OF THE MISSISSIPPI VALLEY. The carboniferous limestone, so often mentioned in the preceding pages, and which has been usually referred to in published reports as ‘¢ Carboniferous limestone,’”’ and as ‘‘ Lower carbo- niferous limestone,’’ is actually of the same age as the coal measures. This point we have but lately had the means of satisfactorily determining. Several species of fossils were known to characterize this formation over a wide extent of country, and from their associations the rock was referred simply to ‘‘carboniferous limestone,’ ’* without distinguishing the order of position among the different members of that series. Among these species were several known to occur in the coal measures of Ohio, Indiana, Illinois, Iowa, and Missouri, while none of them were characteristic of the lower carboniferous limestones. In the Missouri Geological Report of 1855, Professor Swallow has placed the limestones and shales of Weston and other localities, which contain these fossils, in the upper coal measures. At the same time, some of them are known to occur in the lower coal measures ; and, with our present knowledge, we are constrained to believe that certain species occur both in the upper and lower coal measures of the west. In order to understand fully the relations of this higher carboniferous limestone of the west to the other members of the series termed carboniferous, it is necessary to present the following section of these rocks, beginning with the upper member : Section of the carboniferous limestones and the coal measures in the valley of the Mississippi. “LOCALITIES. Localities of the upper carboniferous limestone, Ohio; Indiana. Illinois; Weston and Bellevue, Missouri; Great Salt Lake, Utah Territory ; near Santa Fé, and at the Pecos village, { Shales, shaly sandstones, sandstones, and seams of coal, with shaly and more compact limestone, constituting the upper coal measures. This limestone is designated as the upper carboniferous limestone, and constitutes the | New Mexico, etc. bess: carboniferous limestone of the Rocky Mountains. Coal measures below the limestone, being the middle and | Ohio, Indiana, Illinois, Missouri, etc...+.esseeeseeeeereccee lower coal measures of the Missouri report, and the | lower coal measures, in part, of Ohio and Pennsylvania. VI.—Kaskaskia, or Upper Archimedes limestone....+..es0e- Kaskaskia and Chester, Illinois; St. Mary’s, Missouri, etc.... V.—Gray, brown, or ferruginous sandstone ..... Bafarerslete -+-.| Below St. Genevieve, Missouri, between Prairie du Rocher and Kaskaskia, Illinois. IV.—St. Louis limestone, or concretionary limestone ..... ---| St. Louis, St. Genevieve, Missouri; Alton, Illinois; highest beds below Keokuk, Iowa. Arena ceOuUsi Ded isrejeisiesisiseisicctclecteie eeteteeinene podcondooH | III. ; Warsaw, or second Archimedes limestone........+...- + Warsaw and Alton, Illinois; Spergen Hill, Bloomington, Ind. Magnesian limestones s1sjelajesjesienoieieteleise ctinieonicieieeielere J Beds of passage, shale or marl, with geodes of quartz, etc. Il.—Keokuk limestone, or Lower Archimedes limestone..... Beds of passage, (cherty beds,) 60 to 100 fect ........ ate I.—Burlington limestone Oolitic limestone and argillaceous sandstone of the Che- | mung period. * Dr. Owen in his report upon the Chippewa land district, | Keokuk, Iowa; Warsaw, Illinois .... | Keokuk, Iowa; Quincy, Illinois; above St. Genevieve, Mo... Rapids of the Mississippi, above Keokuk .......+.. Burlington, Iowa; Quincy, Illinois; Hannibal, ete., Missouri... wee eerece Burlington, Iowa; Hannibal, Missouri... .ceeeessecesssoccee gives numerous sections of the carboniferous limestone in the Mississippi and Missouri valleys, and its connexion with beds of coal; but he does not speak positively with regard to the position of this rock or its distinction from the carboniferous limestones below. MEXICAN BOUNDARY LINE. 123 The limestones in the lower part of the section are those usually termed ‘‘ carboniferous limestone.’’ The group consists of distinct members, each marked by numerous characteristic fossils, and the whole together representing the phases of a calcareous formation, going on in an ocean, where the conditions of its bed and its limits were subjected to change. The limestones of this period are well developed in the valley of the Mississippi, from above Burlington, in Iowa, and Oquaka, in Illinois, as far south as below the towns of Kaskaskia and Chester, on the Illinois side, and St. Genevieve and St. Mary’s, on the Missouri side. Several of the members are known in Indiana, and one or more in Kentucky, Tennessee, and Alabama, and also in Arkansas. Throughout all this region these limestones, whether developed as the full series or in a single member, underlie the coal measures proper. In all the collections which I have examined from Texas and New Mexico, and from points further north in the same line, and particularly in the collections made by Captain Stansbury, on his route from the Missouri to the Great Salt Lake, and in that region, I have never observed fossils which are characteristic of any member of the lower carboniferous limestone. We have, thus far, no evidence of the occurrence of lower carboniferous strata among the Rocky mountains ; while at intervals from the northern limits of the United States along the range of the Rocky Mountains, and both east and west of the principal range, we have the upper carboniferous limestone everywhere more or less perfectly indicated by its characteristic fossils. Among these are Spirifer cameratus, S. lineatus, Terebratula subtilita, Productus Rogersi, P. semireticulatus, Zaphrentis Stansburyi, and others. From a recent comparison of specimens from Ohio, Illinois, Iowa, Missouri, Kansas, Texas, and New Mexico, I find the same association of species from numerous localities.* Ia the eastern and northern part of the State of Ohio, (and perhaps extending into Pennsyl- vania,) there are thin bands of limestone associated with the coal measures. These beds are usually shaly in character, often separated by wide vertical joints, and weather to a brown color. Although recognized at numerous points, I am not aware that these beds have been regarded as continuous, though they are doubtless indications of a continuous formation.