BANCROFT LIBRARY LIBRARY CATALOGUE SLIPS. United States. Department of the interior. ( U. S. geological survey.) Department of the interior | | Monographs | of the | United States geological survey | Volume XX | [Seal of the depart- ment] | Washington | government printing office | 1892 Second title: United States geological survey | J. W. Powell, director | | Geology | of the | Eureka district | Nevada | with an atlas | by | Arnold Hague | [Vignette] | Washington | government printing office | 1892 4. xvii, 419 pp. 8 pi. Hague (Arnold). United States geological survey | J. W. Powell, director | Geology | of the | Eureka district | Nevada | with an atlas | by | Arnold Hague | [Vignette] | Washington | government printing office | 1892 4. xvii, 419pp. 8 pi. [UNITED STATES. Department of the interior. (U. S. geological nuney). Monograph XX.) United States geological survey | J. W. Powell, director | | I Geology | of the | Eureka district | Nevada | with an atlus | by | Arnold Hague | [Vignette] | ? Washington | government printing office | 1892 4. xvii, 419 pp. 8 pi. S [UNITED STATES. Department of the interior. (17. S. geological euney.) Monograph XX.] [Monograph XX.] The publications of the United States Geological Survey are issued in accordance with the statute approved March 3, 1879, which declares l hat "The publications of the Geological Survey shall consist of the annual report of operations, geo- logical and economic maps illustrating the resources and classification of the lands, a.nd reports upon general and economic geology and paleontology. The annual report of operations of the Geological Survey shall accompany the animal report of the Secretary of the Interior. All special memoirs and reports of said Survey shall be issued in uniform quarto series if deemed neceasary by the Director, hut otherwise iii ordinary octavos. Three thousand copies of each shall be published lor scientific exchanges and for sale at the price of publication; and all literary and cartographic materials received in exchange shall be the property of the United States and form a part of the library of the organization : And the money resulting from the sale of such publications shall be covered into the Treasury of the United States." The following joint resolution, referring to all government publications, was passed by Congress July 7, 1882: "That, whenever any document or report, shall be ordered printed by Congress, there shall be printed, in addition to the number in each case stated, the 'usual number' (1,900) of copies for binding and distribution among those entitled to receive them." Except in those cases.in which an extra number of any publication has been supplied to the Sur- vey by special resolution of Congress or has been ordered by the Secretary of the Interior, this office has no copies for gratuitous distribution. ANNUAL REPORTS. I. First Annual Report of the United States Geological Survey, by Clarence King. 1880. 8. 79 pp. 1 map. A preliminary report describing plan of organization and publications. II. Second Annual Report of the United States Geological Survey, 1880-'81, bv J. W. Powell. 1882. 8 C . Iv, 588 pp. 62 pi. 1 map. III. Third Annual Report of the United States Geological Survey, 1881-'82, by J. W. Powell. 1883. 8. xviii, 564 pp. 67 pi. and maps. IV. Fourth Annual Report of the United States Geological Survey, 1882-'83, by J. W. Powell. 1884. 8. xxxii, 473 pp. 85 pi. and maps. V. Fifth Annual Report of the United States Geological Survey, 1883-'84, by J. W. Powell. 1385. 8. xxxvi, 469 pp. 58 pi. and maps. VI. Sixth Annual Report of the United States Geological Survey, 1884-'85 ) by J. W. Powell. 1885. 8. xxix, 570 pp. 66 pi. and maps. VII. Seventh Annual Report of the United States Geological Survey, 1885-'86, by J. W. Powell. 1888. 8. xx, 656pp. 71 pi. and maps. VIII. Eighth Annual Report of the United States Geological Survey, 1886-'87, by J. W. Powell. 1889. 8. 2v. xix, 474, xii pp. 5:! pi. and maps; 1 p. 1. 475-1063 pp. 54-76 pi. and maps, IX. Ninth Annual Report of the United States Geological Survey, 1887-'88, by J. W. Powell. 1889. 8. xiii, 717 pp. 88 pi. and maps. X. Tenth Annual Report of the United States Geological Survey, 1888-'89, by J. W. Powell. 1890. 8. 2 v. xv, 774 pp. 98 pi. and maps; viii, 123 pp. XI. EleventhJAnnual Report of the United States Geological Survey, 1889-'90, by J. W. Powell. 1891. 8. 2 v. xv, 757 pp. 66 pi. and maps ; ix, 3">1 pp. 30 pi. and maps. XII. Twelfth Annual Report of the United States Geological Survey, 1890-'!U, by J. W. Powell. 1891. 8 2 v. xiii, 675 pp. 53 pi. and maps ; xviii, 576 pp. 146 pi. aud maps. MONOGRAPHS. I. Lake Bonneville, by Grove Karl Gilbert. 1890. 4. xx, 438 pp. 51 pi. 1 map. Price $1.50. II. Tertiary History of the Grand Canon District, with atlas, by Clarence E. Button, Capt., U. S. A. 1882. 4. xiv, 264 pp. 42 pi. and atlas of 24 sheets folio. Price $10.00. III. Geology of the Comstock Lode and the Washoe District, with atlas, by George F. Becker. 1882. 4. xv, 422pp. 7 pi. and atlas of 21 sheets folio. Price $11.00. IV. Comstock Mining and Miners, by Eliot Lord. 1883. 4. xiv, 451 pp. 3 pi. Price $1.50. I II ADVERTISEMENT. V. The Copper-Bearing Rocks of Lake Superior, by Rolanil Duer Irving. 1883. 4. xvi,464pp. I'll. 29 pi. and maps. Pricefl.85. VI. Contributions to the Knowledge of the Older Mesozoic Flora of Virginia, by William Morris Fontaine. 188.3. 4. xi, 144 pp. 54 1. 54 pi. Price $1.05. VII. Silver-Lead Deposits of Eureka, Nevada, by Joseph Story Curtis. 1884. 4. xiii, 200 pp. 16 pi. Price $1.20. VIII. Paleontology of the Eureka District, by Charles Doolittle Walcott. 1884. 4. xiii,29S pp. 241. 24 pi. Price $1.10. IX. Brachiopoda and Lamellibrancbiata of the Raritan Clavs and Greensand Marls of New Jersey, by Robert P. Whittield. 1885. 4. xx, 338 pp. 35 pi. 1 map. Price 81. 15. X. Diuocerata. A Monograph of an Extinct Order of Gigantic Mammals, by Othniel Charles Marsh. 1886. 4. xviii, 243pp. 561. 56 pi. Price $2.70. XI. Geological History of Lake Lahontan, a Quaternary Lake of Northwestern Nevada, by Israel Cook Russell. 1&85. 4. xiv, 288 pp. 46 pi. and maps. Price $1.75. XII. Geology and Mining Industry of Leadville, Colorado, with atlas, by Samuel Franklin Em- inons. 1886. 4. xxix, 770 pp. 45 pi. and atlas of 35 sheets folio. Price $8.40. XIII. Geology of the Quicksilver Deposits of the Pacific Slope, with atlas, by George F. 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The Penokee Iron-Bearing Series of Northern Wisconsin and Michigan, by Roland D. Irving and C. R. Van Hise. XXI. The Tertiary Rhynchophorous Coleoptera of North America, by S. H. Scudder. XXII. Geology of the Green Mountains in Massachusetts, by Messrs. Punipelly, Wolff, and Dale. In preparation : Mollusca and Crustacea of the Miocene Formations of New Jersey, by R. P. Whitfleld. Sauropoda, by O. C. Marsh. Stegosauria, by O. C. Marsh. Brontotheridae, by O. C. Marsh. Report on the Denver Coal Basin, by S. F. Eminons. Report on Silver Cliff and Ten-Mile Mining Districts, Colorado, by S. F. Eiumons. The Glacial Lake Agassiz, by Warren Upham. BULLETINS. 1. On Hypersthene-Andcsite and on Triclinic Pyroxene in Augitic Rocks, by Whitman Cross, with a Geological Sketch of Buffalo Peaks, Colorado, by S. F. Einmons. 1883. 8. 42 pp. 2 pi. Price 10 cents. 2. 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Geological Map of Northeast-Central Sheet Sheet VIII. Geological Map of Southwest-Central Sheet Sheet IX. Geological Map of Southeast-Central Sheet Sheet X. Geological Map of Southwest Sheet .' Sheet XI. Geological Map of Southeast Sheet Sheet XII. Geological Cross-sections Sheet XIII. VIII LETTER OF TRANSMITTAL. DEPARTMENT OF THE INTERIOR, UNITED STATES GEOLOGICAL SURVEY, Washington, I). C., June 30, 1891. SIR : I have the honor to transmit herewith a report on the Geology of the Eureka District, Nevada. To yourself and to the Hon. Clarence King, under whose direction the field work was commenced, I am greatly indebted for the personal interest taken in the investigation, and also for the generous facilities afforded me both in the field and office. Very respectfully, your obedient servant, ARNOLD HAGUE, Geologist in Charge. Hon. J. W. POWELL, Director, U. S. Geological Survey. PREFACE. The survey of the Eureka District was authorized by the Hon. Clarence King, the first Director of the United States Geological Survey, and the field work, for the most part, was done during his administration. The field season was confined to the summer and autumn of 1880, and was limited to five months, the work being brought abruptly to a close early in December owing to the inclemency of the weather. Visits of a few days' duration were made by different members of the party during the two following years, but these were simply to verify previous observations or to correct apparently conflicting statements. This monograph is purely geological in its scope and is mainly a careful study and survey of a comparatively small block of mountains, which may be designated the Eureka Mountains, but which should not be confounded with the Eureka mining district, as several other well known but less important mining districts also lie wholly within this mountain area. As it was unmapped and only occasionally visited by geologists, little had been accomplished, except for the immediate purposes of mining, toward investigating its structure or solving its many geological problems. The Eureka region was known to occupy an exceptionally broad expanse of mountains, affording fine geological sections if carefully worked out, and of special interest for the purposes of comparative study in other regions of the Cordillera. In this direction scarcely anything had been accomplished. The field work, as planned, could not have been completed in the Xil PREFACE. * allotted time except for the untiring energy and interest of all those connected with the survey. In the geological work I was fortunate in having the cooperation of two thoroughly equipped assistants, both of whom have since attained honorable distinction by published writings in their special lines of research. To Mr. Charles D. Walcott was assigned the collection of the paleontological material, while Mr. Joseph P. Iddings was engaged in work- ing among both volcanic and sedimentary rocks. The report appears in two parts, one a volume of text, the other an accompanying atlas of topographical and geological maps and cross sec- tions, and as the text is, in great measure, explanatory of the atlas, the two can be considered only as parts of the same work. A paper embodying the more important results obtained at Eureka was prepared in 1882 and published in the Third Annual Report of the Survey as an abstract of the final monograph. It was accompanied by a geological map similar to sheet iv of the atlas. The volume of atlas plates bears the imprint of 1883, but is now issued in complete form for the first time. In its more essential features the present report was pre- pared several years ago, but the completion of the manuscript has been delayed from time to time for various unforeseen reasons, mainly by press- ure of other duties. It presents, as concisely as is consistent with clearness and completeness, the principal geological facts gathered in the field and such general deductions as have been drawn from their study. I haye endeavored to make each chapter complete in itself, and this has necessitated the repetition of certain observations, as a large number of facts are more or less related to the subjects discussed in the different chapters. It is an advantage, however, to the special reader, to have such facts as he may need brought together under one grouping, and not to feel obliged to search through the volume for them. The atlas consists of thirteen sheets. The preparation of the topo- graphical map was intrusted to Mr. F. A. Clark, who employed three able assistants in the field Mr. G. H. Wilson, assistant topographer with the plane table; Mr. Gr. Olivio Newman, in charge of triangulation, and Mr. Morris Bien, assistant topographer. A special paper by Mr. Iddings, upon the microscopical petrography of I'liEFACE. XIII the eruptive rocks of the Eureka District, appears as an appendix to this report. It presents the results of a careful examination of several hundred thin sections prepared from a large number of rocks, representing every variety known to occur in the region. It is a concise statement of results of a systematic study of the material and is of great interest, bearing directly upon many geological questions connected with eruptive masses. Mr. Iddiiigs's report is illustrated by six plates, four of which are reproductions of photomicrographs, showing some interesting features in structure of fine groundrnass, and two of drawings of minute crystals and microscopic objects found in the rocks. At the time these photomicrographs were produced they were superior to anything which had been done in this class of illus- tration. Mr. Walcott's report upon the "Paleontology of the Eureka District" was published as Monograph VIII of the U. S. Geological Survey, in 1884. It gives the results of a detailed study of the organic forms obtained throughout a wide range of geological formations, the region having proved an exceptionally rich one in paleontological material from Cambrian, Devo- nian and Carboniferous rocks. In addition to the descriptions of many forms new to science and the identification of over five hundred species, the report contains notes, more or less full, upon many species which presented in their characters or geographical distribution information not heretofore published. The work is illustrated by over five hundred and fifty accurate drawings of fossils, arranged on twenty-four plates. Four plates represent the fauna of the Cambrian, two that of the Silurian, ten that of the Devonian, and eight that of the Carboniferous. All specific identifica- tions of organic forms from Eureka referred to in this work were made by Mr. Walcott. After the completion of the field work for the Eureka map, Mr. J. S. Curtis began his investigations of the ore deposits found on Ruby Hill. The surface maps published by Mr. Curtis were taken from the atlas sheets accompanying this monograph. Mr. Curtis's report appeared in 1884 as Monograph VII of the U. S. Geological Survey, and is entitled "Silver-Lead Deposits of Eureka, Nevada." It is a valuable work and one which forms an important part of the scientific memoirs relating to the Eureka District. XIV PKEFACE. The writer's acknowledgments are due to many gentlemen, superin- tendents of mines and others, who rendered valuable assistance in furnishing information in regard to the country, and who generously afforded every facility in the prosecution of the work. Special thanks are due to Mr. R Kickard, formerly superintendent of the Richmond Mining Company, and to Mr. Thomas J. Read, superintendent of the Eureka Consolidated Mining Company. June 6, 1891. ARNOLD HAGUE. OUTLINE OF THIS VOLUME. CHAPTER I. The area covered by the geological survey of the Eureka Mountains embraces a region of country 20 miles square. The mountains are situated on the Nevada plateau and form a somewhat isolated mass, surrounded on all sides by the broad detrital valleys so characteristic of the Great Basiu. These valleys which encircle the mountains have an average elevation above sea level of 6,000 feet. Rising above them the highest peaks attain altitudes varying from 9,000 to 10,500 feet. In strong contrast with most of the Great Basin ranges, the Eureka Mountains present a rough and rugged appearance, with varied topographical features. CHAPTER II. Sedimentary rocks belonging either to the Paleozoic or Quaternary age form the greater part of the mountains and valleys. Quaternary beds present little of geological interest, although they extend over wide areas, being mainly superficial accumulations composed of detrital material brought down from the mountains and deposited along their flanks and out over the broad plains. A great thickness of limestone, sandstone, and shale, which make up the Paleozoic series of rocks, was laid down under varying conditions of depth of water and rapidity of deposition with only one well recognized unconformity from base to summit. In this region the Paleozoic age was a time of comparative freedom from dynamic movements. Eureka presents no direct evidence as to the time mountain building took place other than that the region was elevated into a broad conti- nental land mass after the deposition of the Upper Coal-measure limestone. Reasons are assigned for supposing that all the Great Basin ranges owe their origin to a post-Jurassic movement. The folding, flexing, and faulting which outlined the mountains broke up this mass of sediments into six sharply denned orographic blocks, each with well marked structural peculiarities. These mountain blocks have been designated as follows: Prospect Ridge, Fish Creek Mountains, Silverado and County Peak group, Mahogany Hills, Diamond Mountains, and Carbon Ridge and Spring Hill group. Taken together these six blocks present a compact mass of mountains, the result of intense lateral com- pression and longitudinal strain. Profound longitudinal faults extend the entire length of the moun- tains, showing a displacement of beds of over 13,000 feet. The Paleozoic sediments measure 30,000 feet in thickness, with Cambrian, Silurian, Devonian, and Carboniferous, all well represented by characteristic fauna. In these four periods fourteen epochs have been recognized. CHAPTER III. Cambrian rocks measure 7,700 feet, divided into five epochs, as follows: Pros- pect Mountain quartzite, Prospect Mountain limestone, Secret Canyon shale, Hamburg limestone, and Hamburg shale. The Middle, Lower, and Upper Cambrian are all exposed. On the crest of Prospect Ridge, at the base of the Cambrian limestone, occurs the Olenellus shale, the oldest fossiliferous strata recognized in the Great Basin. Hamburg Ridge carries a Potsdam fauna both at its base and summit. Conformably overlying the Cambrian come the Silurian rocks, 5,000 feet in thickness. They fall readily into three epochs, two limestones and an intervening body of quartzite. They have been designated Pogonip limestone, Eureka quartzite, and Lone Mountain limestone. The qnartzite XV 4 xvi OUTLINE OF THIS VOLUME. is easily distinguished from both the coareo sands and grits of the Cambrian below and the Carbon- iferous conglomerate above. An unconformity of deposition exists between the Eureka and Lone Mountain epochs. Both the Trenton and Niagara formations are included within the Lone Moun- tain epoch. CHAPTER IV. By imperceptible gradations limestones of the Lone Mountain epoch pass upward into those of the Devonian period. Devonian rocks occupy a larger area in the District than those of any other period, and present a greater thickness than either the Cambrian or Silurian. They measure 8,000 feet, divided into two epochs : A bluish limestone the Nevada limestone and an argillaceous black shale the White Pine shale. The limestone carries a rich invertebrate fauna from base to summit. The black shale is characterized by a flora which, though fragmentary, is suffi- ciently well preserved to identify the genera as belonging to the Upper Devonian. The Carboniferous rocks measure 9,300 feet, which, however, does not quite represent their full development, the uppermost beds having undergone more or less erosion. They have been divided into four epochs, as follows : Diamond Peak quartzite, Lower Coal-measure limestone, Weber con- glomerate, aud Upper Coal-measure limestone. As the limestone is in general favorable to the preser- vation of organic remains, fossil-bearing strata occur throughout the beds. Three salient features mark the life of the Lower Coal-measures. First, the occurrence near the base of the limestone of a fresh- water fauna; second, the varied development of the Lamellibranchiates a class which has here- tofore been but sparingly represented in the collection of Carboniferous fossils from the Cordillera ; third, the mingling near the base of the horizon of Devonian, Lower Carboniferous, aud Coal-measure species in gray limestone directly overlying beds characterized by a purely Coal-measure fauna. In the first range to the east of the Eureka Mountains Carboniferous rocks extend for miles along the edge of the valley, in which well developed coal seams occur. CHAPTER V. This chapter is devoted to the descriptive geology of the sedimentary rocks. Each orographic block is described in detail, beginning with Prospect Ridge, where the oldest rocks occur, followed by the other blocks according to the succession of strata. It gives a connected description of the country and points out the relations of the different mountain masses to each other. CHAPTER VI. A discussion of the Paleozoic rocks follows, based upon the facts presented in the earlier chapters. It is shown that during Paleozoic time a pre-Cambrian continent existed in western Nevada which furnished to an ocean lying to the eastward an enormous amount of detrital material. It is pointed out that the Eureka region was situated not far from the eastern border of this land mass, and that a large part of its coarse conglomerates aud mechanical sediments must have been offshore deposits. . The geological record affords proof of elevation and depression th roughont Paleozoic time with intervals of shallow water and proximity of land areas between periods of relatively deep seas. Fresh-water life, plant remains, and coal seainb at different horizons furnish additional evidence of shallow water and offshore deposits. A study of Paleozoic rocks in other parts of southern and western Nevada exhibit nearly similar geological conditions as regards sequence of beds. This is especially well shown both at White Pine and in the Highland and Pifion ranges. The sequence of strata, both to the north and south, indicates a closer agreement with the conditions of sedimentation at Eureka than the many exposures situated but a short distance eastward of the latter area. The structural relations of the, different orographic blocks to each other and the outbursts of igneous rocks are well brought out in cross-section. An instructive feature at Eureka is the close relationship between the anticlinal and synclinal folds to the profound north and south faults. CHAPTER VII. Pre-Tertiary igneous rocks play a very subordinate part. They may be classed under three heads: Granite, granite-porphyry, and quartz-porphyry. The granite occupies a limited area on Prospect Ridge. Both the granite and quartz-porphyries occur as dikes. Structural varia- tions in the dikes are mainly dependent upon the chilling effect of cold contact walls upon a rapidly OUTLINE OF THIS VOLUME. XVII cooling molten mass. The width of the (like has much to do in determining the physical conditions governing crystallization. A8 regards the age of the dikes little is known other than that they pene- trate Siluriaii strata. CHAPTER VIII. The Eureka District offers no direct proof of the age or duration of volcanic energy, although evidence based upon observations elsewhere in the Great Basin points to the conclusion that the lavas belong to the Tertiary period, and probably the greater part of them to the Pliocene epoch. They broke out in four ways: First, through profound fissures along meridional lines of displacement; second, following lines of orographic fracture, they border and encircle large uplifted masses of sedimentary strata ; third, they occur as dikes penetrating the sedimentary rocks; fourth, they occur in one or two relatively large bodies, notably Richmond Moun- tain and Pinto Peak, along lines of displacement. The sequence of lavas was hornblende-andesite, hornblende-mica-andesite, dacite, rhyolite, pyroxene-andesite, and basalt. The lavas display a great variety of volcanic products in both chemical and mineral composition. They are all derived from a common source, a homogeneous molten mass. They are due to a process of differentiation by molec- ular change within the molten mass under varying conditions of pressure and temperature. Starting with a magma of intermediate composition, the extreme products of such a differentiation are rhyolite and basalt. CHAPTER IX. In the Eureka District the ores occur in sedimentary rocks belonging to the Cambrian, Silurian, and Devonian periods, and may be found in all horizons, except the Secret Canyon and Hamburg shale, from the base of the Prospect Mountain limestone to the summit of the Nevada limestone. Through 17,000 feet of strata ores have been deposited in sufficiently large bodies to encourage mining exploration. The most productive deposits have been found in Cambrian rocks, but this is owing to orographic and structural conditions rather than the geological age of strata or chemical nature of sediments. Nearly all the more productive mines are included within the beds which form the Prospect Mountain uplift between the Hoosac and Spring Valley faults. The ore followed the rhyolite and is consequently Pliocene or post-Pliocene age. All the ores came from below and were originally deposited as sulphides. They were subsequently oxidized by atmospheric agencies, mainly surface waters percolating through the rocks. In Appendix A, Mr. C. D. Walcott gives a systematic list of fossils from each formation found at Eureka. In Appendix B, Mr. Joseph P. Iddings discusses the microscopical petrography of the crystal- line rocks. It is a thorough study of the mineral and structural character of the rocks and is illus- trated by several plates. MON XX II GEOLOGY OF THE EUREKA DISTRICT. BY ARNOLD HAGUE. CHAPTER I. GENERAL DESCRIPTION. The Eureka District is situated on the Nevada plateau in the central part of the state of Nevada, midway between the basin of Lake Lahontan westward and the basin of Lake Bonneville eastward. The area covered by the geological and topographical survey embraces a region of country 20 miles square, lying partly in the county of Eureka and partly in the county of White Pine. The meridian of 116 west from Greenwich passes just westward of the center of the examined area, and the 39 30' parallel of north latitude crosses Ruby Hill, the seat of the present activity in precious-metal mining. Nevada plateau. On the Nevada plateau the broad central north and south valleys, lying between meridional mountain ranges, reach an aver- age altitude of 6,000 feet above sea-level, the country falling away grad- ually on both sides till at Salt Lake, in Utah, the altitude is 4,250 feet, and at Carson and Humboldt Lakes, in Nevada, 3,800 feet above sea level. These valleys, however, compared with those of the depressed areas adjoin- ing the plateau, are relatively narrow, with few marked exceptions, seldom measuring more than 10 or 12 miles in width. In general the broader physical features of the Great Basin ranges are much the same all the way MON xx 1 1 2 <1 EULOGY OF THE EUKEKA DISTRICT. from the bold escarpment of the Sierra Nevada of California to the precip- itous wall of the Wasatch Mountains of Utah, the distance across the widest part in an east and west line being about 425 miles. These ranges form long, narrow mountain uplifts with sharply defined limits, rising with more or less abruptness above dreary intervals of desert. Their nearly uniform trend and the remarkable parallelism of the lines of upheaval of the older sedimentary ridges present the most marked feature of the region. In width they seldom exceed 8 miles, but frequently extend in an unbroken line for more than 100 miles in length, with serrated peaks and ridges rising from 2,000 to 6,000 feet above adjacent valleys. For the most part they possess a simple topographical structure and a simple drainage system. They are characterized, more especially the lower ranges, by absence of trees, and in many cases are nearly bare of all vegetation, presenting rough, rugged slopes of naked rock. On the higher parts of the plateau the ranges, reaching a greater alti- tude, partake more of an Alpine or sub-Alpine character. Precipitation of moisture is more abundant, as seen both in the more frequent rains of slimmer and snows of winter. A greater precipitation produces larger and more frequent streams, and a continued moisture favors a varied vegeta- tion the spurs and ridges being more or less covered with a dwarfed and stunted forest growth, and the long slopes with nutritious grasses. These salient features distinguish the ranges of the Nevada plateau from those of Lake Lahontan and Lake Bonneville Basins, which present a more arid and desolate aspect. A striking feature of nearly all these ranges is their isolated position, only a few of them presenting outlying spurs or low lines of rolling foothills. Occasionally inferior ridges of sedimentary beds stretch diagonally across valleys from one range to another, com- pletely shutting in the intermediate valley, and still more frequently out- bursts of volcanic rocks in irregular flows serve to unite in confused masses bodies of sedimentary formations otherwise distinct. Midway between the Sierra and the Wasatch stand the East llum- boldt Mountains, the most prominent range in the Great Basin. They lire- sent, not only by reason of the greater number of rugged and commanding peaks, many of them attaining an elevation over 11,000 feet above sea EUREKA MOUNTAINS. 3 level, but by their broad, massive proportions, long, unbroken ridges, and Alpine character, the boldest uplift on the Nevada plateau. Next west from the Humboldt occurs the Diamond Range, followed by the Pinon Range, with the broad Diamond Valley lying between them. Southward the southern extremities of these two ranges enter the Eureka District and form a part of its mountainous region. On the plateau, among the more marked exceptions to the long narrow ranges which rib the surface of the country, may be mentioned the Rob- erts Peak Group, connecting the Wahweah with the Pinon Range, the White Pine Mountains, and the subject of the present report, the moun- tains of the Eureka District. Eureka Mountains. The Eureka District forms a rough mountain block standing out prominently by itself, except for its narrow connections with both the Pinon and Diamond Ranges, almost as completely isolated from its neighbors as the longer parallel ranges. As a mountain mass, however, although well deserving such a distinction, it has never received any definite appellation which would include all its members, it being made up of por- tions of several ranges and short uplifted blocks sp intimately connected and inosculated as to form both topographically and geologically a single group, hemmed in on all sides by the characteristic detrital valleys. To the north Diamond Valley, which may be taken as a type of the higher valleys of the Great Basin, extends for over 40 miles in an unbroken plain, the lowest part of the depression being covered in winter by a broad, shal- low sheet of water, which, upon evaporation, presents during the greater part of the year a hard, level floor, strongly impregnated with salt. Con- siderable quantities of salt for metallurgical purposes have been collected from the shores of the small lakes at the northern end of the valley. To the south of the district lies the broad basin of Fish Creek Valley, con- necting with Newark Valley on the east side of Diamond Range, while the Antelope Valley cuts off" the Eureka District on the west side from the neighboring mountains. All these valleys stand at about the same elevation above sea level, and offer to the eye a monotonous olive-gray color derived from a vigorous growth of the Artemcsia tridenlata which covers all the low- lands except the central portions of the broader basins. 4 GEOLOGY OF THE EUREKA DISTRICT. It is doubtful if any urea of equal extent iu Nevada possesses more varied physical features with such strongly marked contrasts than the Eu- reka District. In close proximity may be seen long serrated ridges, broad summits, gently inclined tables of nearly horizontal sedimentary beds, with abrupt escarpments along canyon walls, and highly tilted strata in rough irregular spurs. And, as might be expected in a country made up of indi- vidual blocks and parts of ranges and so interlocked as to form one broad mass, the region is characterized by broad shallow basins, long narrow ravines, and winding valleys, presenting a more than ordinarily accidented surface with an intricate structure. Above the broad base of the surround- ing sage-brush valleys rise many prominent peaks from 2,500 to 4,500 feet. Diamond Peak, in the northeast corner of the district, at the southern ex- tremity of Diamond Range, is the culminating point, measuring 10,637 feet above sea level, and, with the exception of the high summits in the East Humboldt Range, is one of the loftiest peaks on the Nevada plateau. Prospect Peak, on the central ridge, and the second point in the district, measures 9,604 feet, while Atrypa Peak, to the southwest on the same ridge, has an altitude of 9,063 feet above sea level. Other points are White Cloud Peak, the highest point on a broad plateau-like ridge, 8,950 feet; Alpha Peak, 8,985 feet; and Woodpecker's Peak, 8,598 feet; all of them being formed of sedimentary rocks. Among volcanic mountains may be mentioned Richmond Mountain, just east of the town of Eureka, which rises to a height of 8,392 feet, and Pinto Peak, an isolated cone in the center of the district, reaches an altitude of 7,880 feet above sea level. Up to the time of the rapid development of the mining interests upon Ruby Hill and Prospect Mountain, the slopes and ridges about Eureka were exceptionally well supplied with an arborescent growth, a condition which was due partly to the number of high peaks but in great part to broad masses of mountains acting as condensers of desert moisture. To- day, so great has been the demand for wood B,nd charcoal in the reduction of lead ores, that the mountains are as bare of trees as any part of the Great Basin. Several species of pines, dwarfed junipers (Juniperus occiden- talis), and mountain mahogany (Cercocarpus Icedifoliits), which attains a height of over 20 feet, are, or rather were, the prevailing trees, but are now SOIL CLIMATE. 5 found only in a few areas preserved by their owners for future use, at no distant day. Not only have the Eureka Mountains lost their forests, but the neighboring mountains for long distances have been devastated to fur- nish fuel for the smelting furnaces. Some idea may be obtained of the enormous consumption of wood from the statement that 10,000 bushels of charcoal are required daily for the smelting furnaces when the works are running their usual force, and that for five or six years the daily consump- tion was rather over than under that amount. Soil. Nature presents a barren, arid appearance. Perennial streams in the ravines are exceptional, other than those found on the slopes of Diamond Peak. Fresh water springs lie scattered about the mountains and fur- nish a scanty supply of water, barely sufficient to meet the wants of the people. A few deep wells have been successfully sunk in the broader valleys. Vegetation is everywhere limited, and is mainly confined to bunch grasses on the mountain slopes and sage brush in the open valleys. As the valleys are mainly filled with coarse detrital material from mountain slopes, soils suitable for agricultural purposes occupy very small areas, and are found only in the broader basins. In the favored spots where water for irrigation purposes can be readily obtained, all the more hardy vegetables grow well, and are of excellent quality, but nearly all crops suffer from early frosts. In no sense can the country be regarded as an agricultural one, and cultivation of the soil is remunerative to the farmer only by reason of the very high prices received for his produce. climate. A rigorous winter, a long hot summer, a dry atmosphere, with a light precipitation of moisture, are characteristic climatic features of the Eureka District. In summer, rainfalls are limited to showers, frequently very severe, but of short duration, and what are commonly known as cloud- bursts are by no means uncommon during late July and early August. The clouds, late in the afternoon, centering over Prospect Peak, break with such force that many people caught without warning have been drowned. In July, 1874, a severe storm and flood destroyed seventeen lives, and carried off property to the value of many thousands of dollars. During the period of our survey careful meteorological observations were made throughout the summer. Snow fell in the month of May no 6 GEOLOGY OF THE EUEEKA DISTRICT. less than eight times, and again on June 10 and 11 In summer the days are warm, and for the most part cloudless; the nights cool. The daily variation between the maximum and minimum thermometers was always very considerable, frequently showing a difference of 40 F. For the three summer months of June, July, and August, of 1880, the maximum ther- mometer in the shade stood over 90 F. on eighteen days, or one day in six. As the climate is very dry, the heat was seldom oppressive, except in some inclosed basin or valley. As early as August 30, the thermometer fell below the freezing point, and on October 9 a light fall of snow covered both mountain and valley. History. In the summer of 1864 the first locations of mining property were made in New York Canyon, on the easteni side of Prospect Mountain, near the present " 76 " Mine. This property was known as the Eureka Mine, and although it never fulfilled the expectations of its original owners, it transferred its name to the very successful property on Ruby Hill and subsequently gave a name to the town, to the mining district, to the county, and finally to the neighboring group of mountains. The original property gave so little promise that the district was finally abandoned. In mining operations very little was accomplished until the spring of 1869, when im- portant discoveries were made on Ruby Hill and active, intelligent work was undertaken. The Champion and Buckeye claims on the south side of Ruby Hill were the first properties located, and soon afterward the ground was broken on the now famous Richmond and Tip Top Mines. From that time forward mining operations on Ruby Hill have gone on steadily, and to-day the Eureka District is the most successful mining region in the state of Nevada. Success on Ruby Hill was quickly followed by active enter- prise developing mining locations on both slopes of the ridge of Prospect Mountain, in Secret Canyon, and in the Silverado Hills in the southwest corner of the district. Estimates of the value of the ore production of the district since the first shipment of crude bullion in 1869 are as follows : From 1869 to 1873 $10,000,000 From 1873 to January, 1883 50,000,000 Total 60,000,000 H1STOKY OF THE DISTRICT. 7 One-third of this amount, according to the best estimates, was gold, and two-thirds silver. The product in lead is not so easily determined, but it is not far from 225,000 tons, an amount sufficient to affect the market price of lead in all the great commercial centers of the world. Around this industry has grown up the town of Eureka, which is the center of population and trade for this part of the state. It is a long, narrow settlement, lying in the main northern drainage channel of the mountains, and sheltered on the east side by Richmond Mountain. Here are located the smelting furnaces of both the large companies. The Eureka and Palisade Railway, 88 miles in length, connects the town with the Central Pacific Road at Palisade. Branch tracks connect with the Eureka Consolidated and Richmond furnaces, the former at the lower, and the latter at the upper end of the town, and these again by a somewhat sinuous course with the principal mines, which are situated about two and one-half miles southwest of Eureka. There are an imposing, well built court house, three or four churches, and several blocks of brick stores and warehouses in the town. It supports two daily papers, which have a considerable influence and a wide circulation throughout the state. Ruby Hill, the only other town of any importance in the district, is a flourishing place, nearly the entire population being actively engaged in mining in the immediate neighborhood. It is built on the north and east sides of an isolated hill which bears the same name, and on which are located all the more prominent mines, including the Albion, Richmond, Eureka Consolidated, Phoenix, and Jackson properties. On the slopes to the north are situated the Bullwhacker and Williamsburg mines, while to the southward of Ruby Hill, on Prospect Ridge, are found the Dunderberg and Hamburg properties and others of more or less importance. CHAPTER II. GEOLOGICAL SKETCH OF THE EUREKA DISTRICT. Sedimentary rocks, belonging either to the Paleozoic or Quaternary period, form by far the greater part of the mountains and valleys of the Eureka District. The beds of the Quaternary present but little of geological interest, and although they extend over wide areas they are, in most instances, superficial accumulations composed of detrital material brought down from the mountains and deposited along their flanks, concealing the underlying rocks of the foothills. Igneous rocks play a most important part in the geological history of the region, but nevertheless do not form an imposing feature of the individual mountain uplifts, appearing either as ex- travasated masses along lines of faulting, or as larger bodies encircling and lying outside the main blocks of sedimentary formations. The older crys- talline rocks offer a still less marked topographical feature of the country, occupying very limited areas in the older Paleozoic limestones, where they appear as intruded masses exposed by erosion. It is doubtful if within the province of the Great Basin there can be found any region of equally restricted area surpassing the Eureka District in its grand exposures of Paleozoic formations, especially of the lower and middle portions. The great thickness of limestone aiid sandstone of which the Paleozoic is composed was laid down under varying conditions of depth of water and rapidity of deposition, with only one well recognized unconformity from its base to summit. In this region the Paleozoic age was a time of compara- tive freedom from dynamic movements. Most geologists who have given any attention to the history of the Great Basin ranges substantially agree that the movements that finally built up the mountains began after the close of Paleozoic time, and that between the Carboniferous and the close 8 AGE OF MOUNTAIN BUILDING. 9 of the Jurassic period took place the folding, flexing and faulting of the beds which outlined the structural features of nearly all the meridional ranges between the abrupt walls of the Wasatch and those of the Sierra Nevada. At Eureka no direct evidence is offered as to the time when this mountain building took place other than that the region was finally lifted above the ocean after the deposition of the Upper Coal-measures. So far as the mountains themselves are concerned, there is a total lack of evidence that the blocking out of the ridges did not begin at the close of the Paleozoic period, but, on the other hand, all observations tend to show that whenever and by whatever causes the other Great Basin ranges were uplifted, the same orographic conditions which prevailed elsewhere held true for the Eureka Mountains. In other words, the Eureka Mountains were a part of a more extended geological province. According to the conclusions of Mr. Clarence King, 1 based upon the observations of the geologists of the Fortieth Parallel Exploration, the mountains west of the Havallah Range and the meridian of 117 30' belong to a post-Jurassic upheaval, and to the west of this line there existed during Paleozoic time an elevated continental area which fumished the material accumulated in an ocean basin to the east. At the close of the Paleozoic this oceanic area, stretching as far eastward as the Wasatch, was lifted up into a broad laud-mass, and the former continental region sank below the water and in turn became an ocean basin. From the Wasatch westward to this ancient shore line the mountain ridges exhibit much in common in their structural and physical features, being made up in great measure of Paleozoic strata, whereas from this boundary westward the ranges show a marked contrast in the nature of their sedimentation and bear ample paleontological evidence of their Mesozoic age. Over this latter area, not- ably in the West Humboldt, Piute, and Augusta Mountains, limestones characteristic of the Triassic and Jurassic have been described in detail by the geologists of the Fortieth Parallel Exploration, 2 while to the east of this shore line no Mesozoic rocks occur. Mr. King assigns excellent reasons for 1 Geological Exploration of the Fortieth Parallel, vol. i, Systematic Geology, p. 733. Washing- ton: 1878. "Geological Exploration of the Fortieth Parallel, vol. n. Descriptive Geology, pp. 657, 711, ami 724. Washington. 1877. 10 GEOLOGY OF THE EUEEKA DISTRICT. the opinion that all the Great Basin ranges across Utah and Nevada were uplifted at the same time under identical dynamic influences, and conse- quently owe their origin mainly to a post-Jurassic movement. This indicates a marked unconformity between the Carboniferous and Triassic, but it neither necessitates nor precludes the beginning of mountain building over the Paleozoic area at the time of the uplifting of the conti- nental laud-mass from beneath the ocean. Nowhere throughout this region, any more than at Eureka, have the Great Basin ranges as yet offered any direct evidence of folding accompanying this elevation, yet it would seem highly probable that some crumpling of strata might have taken place before the main blocking out of the mountain ridges at the close of Jurassic time. Most of the Great Basin ranges are narrow, longitudinal ridges, and while they present much in common as to their origin and primary struc- ture, each possesses its own special physical features due to local dynamic conditions. Most of them are formed by direct lateral compression result- ing in anticlinal folds, occasionally accompanied by synclines. Some of them are simple mouoclinal ridges, representing one side of an anticlinal axis. Still others exhibit great complexity of structure with both folding and faulting along the meridional axes of the ranges, with which are asso- ciated transverse faults and folds striking obliquely across the topograph- ical trend of the uplifted mass. Orographic Blocks. The Eureka Mountains lie near the western edge of what was at one time the Paleozoic ocean. The nearness of these uplifted beds to an older pre-Paleozoic continent is in some measure indicated by the relatively great amount of disturbance of strata and plication of mountain masses as compared with the more gently inclined strata, and simplicity of structure found farther to the eastward. Unlike the ordinary type of nar- row ridges, the Eureka Mountains exhibit a solid mountain mass over 20 miles in width, including several uplifted blocks whose length does not greatly exceed their width. Taken together they present a compact mass of mountains thrown up by intense lateral compression accompanied by longitudinal strain. The forces which brought about the elevation of the mountains produced an intricate structure with powerful flexures and folds and broke up this immense thickness of sediments into individual blocks PALEOZOIC SECTION. 11 accompanied by profound longitudinal faults, several of which extend the entire length of the mountains, and have played a most important part in bringing about the present orographic conditions. Although these mountain masses stand so intimately related to each other that it is frequently difficult to draw sharp topographical lines between them, the Eureka Mountains may be divided into six blocks with well marked structural and geological differences. These blocks may be desig- nated as follows: Prospect liidge. Fish Creek Mountains. Silverado and County Peak group. Mahogany Hills. Diamond Mountain. Carbon Ridge and Spring Hill group. Paleozoic Section. As already mentioned, the Eureka Mountains lie just eastward of the old shore line. In this and the following chapters the evidence is presented, derived from the history of the rocks themselves, to show the close proximity of a land area when the beds were laid down. The nature of these off-shore deposits near the western border of an old Paleozoic sea form one of the principal objects of this investigation. Much of the material, such as the coarser conglomerates, must necessarily have been off-shore deposits The sedimentary rocks which make up the mountains present a great development of limestones, quartzites, sandstones, and shales, comprising many thousands of feet of Cambrian, Silurian, Devonian, and Carboniferous beds. From the lowest exposed members of Cambrian strata to the top of the Coal-measures there are represented a series of sedimentary deposits 30,000 feet in thickness. Nowhere within the limits of the Eureka district can there be found any one exposure which shows the beds with- out a break in their continuity, the longest unbroken section representing about one-third of the entire sequence of strata, yet the region offers in so many instances such continuous exposures of beds and so many in which the series of strata overlap each other with such a constant repetition of beds, that the reconstruction of the entire section is easily made out when the individual parts are carefully compared and studied. The reason why there is no one unbroken section may be readily understood by a glance 12 GEOLOGY OF THE EUREKA DISTRICT. at the map which shows how the sedimentary strata have been broken up into separate mountain blocks, each made up of a portion of the entire thickness of beds. In the four grand periods of Paleozoic time represented at Eureka, 14 epochs have been recognized : 5 in the Cambrian, 3 in the Silurian, 2 in the Devonian, and 4 in the Carboniferous. With a single exception local geographical names have been employed to designate the different epochs into which the Cambrian, Silurian, and Devonian have been divided. Heretofore, throughout the Great Basin the division of the larger periods into epochs has not been deemed necessary, the individual horizons not having been studied sufficiently in detail to require it. The exception is made in favor of the Pogonip limestone, a name first applied by the Geological Exploration of the Fortieth Parallel to the belt of limestone which forms the base of the Silurian. In the Carbon- iferous period a large quartzite body at the base of the series has been designated the Diamond Peak quartzite, but for the remaining epochs the well known names Lower Coal-measures, Weber conglomerates, and Upper Coal-measures are retained, notwithstanding some serious objection to the use of the term Coal-measures in this region. Each of the six blocks expose several thousand feet of strata, and while they frequently overlap each other no two of them represent precisely the same horizons, although the Diamond Range includes within its strata the beds which make up the Carbon Ridge and Spring Hill blocks. The six blocks essentially correspond to the following periods : Prospect Ridge : Cambrian and Siluriau. Fish Creek Mountains : Silurian. Silverado and County Peak: Silurian and Devonian. Mahogany Hills: Devonian. Diamond Mountain : Devonian and Carboniferous. Carbon Ridge and Spring Hill: Carboniferous. In the subjoined section, which may be best designated as the Eureka section, the relative thickness and general lithological characters are given for all the geological divisions which have -been made of the sedimentary rocks. A plane of unconformity in the Silurian is indicated by double dividing lines between the Eureka quartzite and Lone Mountain limestone. EUEEKA SECTION. Eureka Section, Nevada, 30,000 feet. 13 I 0>' i 500 Light colored blue and drab limestones. 2,000 Coarse and fine conglomerates, with angular fragments of chert; reddish yellow sandstone. layers of 3,800 Heavy bedded dark blue and gray limestone, with intercalated chert ; argillaceous beds near the base. bauds ot 3,000 Massive gray and brown quartzite, with brown and green shales at the summit. DEVONIAN, 8,000 feet. White Pine shale 2,000 Black argillaceous shales, more or less arenaceous, with intercalations of red and reddish brown friable sandstone, changing rapidly with the locality; plant impressions. 6,000 Lower horizons indistinctly bedded, saccharoidal texture, gray color, pass- ing up into strata distinctly bedded, brown, reddish brown, and gray in color, frequently finely striped, producing a variegated appearance. The upper horizons are massive, well bedded, bluish black in color ; highly fossiliferous. SILURIAN. 5,000 feet. Lone Mountain limestone 1, 800 Black, gritty beds at the base, passing into a light gray siliceous rock, with all traces of bedding obliterated; Trenton fossils at the base; Haly sites in the upper portion. 500 Compact, vitreous quartzite, white, blue, passing into reddish tints near the base; indistinct bedding. 2,700 Inters tratitied limestone, argillites, and arenaceous beds at the base, pass- ing into purer, fine grained limestone of a bluish gray color, distinctly bedded ; highly fossiuferous. CAMBRIAN, 7,700 feet. 350 Yellow argillaceous shale, layers of chert nodules throughout the bed, but more abundant near the top. 1.200 Dark gray and granular limestone; surface weathering, rough and ragged ; only slight traces of bedding. 1,600 Yellow and gray argillaceous shales, passing into shaly limestone; near the top, iuterstratined layers of shale and thinly bedded limestones. Prospect Mountain limestone. . . 3,050 Gray, compact limestone; lighter in color than the Hamburg limestone, traversed with thin seams of calcite ; bedding planes very imperfect. Prospect Mountain quartzite . . . 1.500 Bedded brownish white quartzites, withering dark brown; ferruginous near the base; intercalated thin layers