The Stratigraphic Section in the Vicinity of Eureka, Nevada GEOLOGICAL SURVEY PROFESSIONAL PAPER 276 The Stratigraphic Section in the Vicinity of Eureka, Nevada By T. B. NOLAN, C. W. MERRIAM, and J. S. WILLIAMS GEOLOGICAL SURVEY PROFESSIONAL PAPER 276 Revision of the pre- Tertiary stratigraphy of east-central Nevada UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1956 UNITED STATES DEPARTMENT OF THE INTERIOR Douglas McKay, Secretary GEOLOGICAL SURVEY W. E. Wrather, Director For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C. - Price $1.00 (paper cover) CONTENTS Page Page Abstract_ _____________________ 1 Silurian system.___________________________ 36 Introduction. _--___-______--___- 2 Roberts Mountains formation.__________ 36 Acknowledgments- --.-_---___-_-. 3 Lone Mountain dolomite__________... 37 Structural setting._______________ 3 Devonian system.__________-_-_-__--_____. 40 Economic significance. _-__._. 5 Nevada formation_________--______--. 40 Cambrian system.________________ 5 Beacon Peak dolomite member. 42 Prospect Mountain quartzite.. 6 Oxyoke Canyon sandstone member... 43 Pioche shale_______--_-_-_.__. 7 Sentinel Mountain dolomite member. 43 Eldorado dolomite___________ 9 Woodpecker limestone member. 44 Geddes limestone.___________ 11 Bay State dolomite member.--...--. 45 Secret Canyon shale._________ 12 Devils Gate limestone._________________ 48 Lower shale member. .... 13 Meister member.__________________ 49 Hayes Canyon member.____________ 49 Clarks Spring member.._ 14 Devonian and Mississippian systems. ________ 52 Hamburg dolomite.___-_.____ 16 Pilot shale________-__-_-___--__---_-_. 52 Dunderberg shale.___________ 18 Carboniferous systems_.____-__-______-__- 54 Windfall formation.__________ 19 Mississippian system._________--,___-_- 54 Catlin member._________ 20 Joana limestone,___________________ 54 Bullwhacker member. 21 Upper Mississippian formations.. ______.. 56 Ordovician system.______________ 23 Chainman shale.___.___-_..-_____. 59 Eastern facies._____-__-.__-_. 23 Diamond Peak formation.__________ 60 Pogonip group...________ 23 Pennsylvanian system.-_____---___------__- 61 Goodwin limestone...____ 25 Ely limestone.______-____.-_--_____.-__ ,61 Late Paleozoic (Permian?) rocks.____________ 63 Ninemile formation. _____ 27 Carbon Ridge formation.____-_-_-_____- 64 Antelope Valley limestone. 28 Garden Valley formation_____._-___-_. 67 Eureka quartzite_______ 29 Cretaceous system.____________---____-_-__ 68 Hanson Creek formation. _ 32 Newark Canyon formation._____________ 68 Western facies_.___.-_-____ 34 References cited.__________________________ 70 Vinini formation.________ 34 Index..-..--_-_-_--.--.----_---------_-_-. 73 ILLUSTRATIONS Page PLATE 1. Map of central Nevada, showing location of places referred to in the text___________-___-__-_-_-___ In packet 2. Stratigraphic sections of Lower and Middle Paleozoic rocks in the vicinity of Eureka, Nev______________ In packet FIGURE 1. Sections of Carboniferous sedimentary rocks at Tyrone Gap, Eureka,' and Diamond Peak.._______________ 4 2. Sketch of geology between Ruby Hill and Adams Hill_:___..____-___________-_____________-__-_.___________ 15 in THE STRATIGRAPHIC SECTION IN THE VICINITY OF EUREKA, NEV. By T. B. NOLAN, C. W. MERRIAM, and J. S. WILLIAMS ABSTRACT Eureka quartzite, of probable Middle Ordovician age, and it, The stratigraphic section at Eureka, Nev., as defined by King, in turn, is unconformably overlain by the Hanson Creek forma­ Hague, and Walcott, has been used as a standard in the central tion of Late Ordovician age. The Hanson Creek formation is Great Basin for more than 75 years. Detailed mapping, which composed of dolomite to the east, but is limestone in the west­ has led to a better understanding of the geologic structure of ern sections. Except for the Eureka quartzite this eastern this area, together with continued paleontologic study has sequence is composed almost exclusively of limestone or dolomite. modified some of the earlier conclusions about the section. The western Ordovician sequence, in contrast, contains only a Revisions and changes in nomenclature and age assignments small amount of carbonate rocks; it is made up chiefly of bedded consequent on this recent work are here presented. chert, quartzite, and graptolite-bearing shales. These beds These new conclusions concerning the stratigraphy are in are included in the Vinini formation, and are about eqrivalent accord with the concept of two major elements in the geo­ in age to the Ninemile and Antelope Valley formations of the logic structure of central Nevada: one is the development, at eastern sequence. least twice during Paleozoic time, of linear swells or positive Silurian sedimentary rocks are known with assurance only in areas that caused marked lateral changes in sedimentation in an eastern facies; their absence in western-facies sections may the seaways and locally resulted in nondeposition and even be due either to erosion or nondeposition. In the Eureka region, erosion of earlier deposited sediments. The other is the ex­ however, there is considerable variation between the factions istence of many thrust faults of large displacement that have that are exposed. To the west and north, the Roberts Mountains brought notably different sedimentary facies into juxtaposition formation, as much as 1,900 feet in thickness, rests on the with one another. An understanding of the revised stratig­ Hanson Creek formation. It contains a Middle Silurian fauna raphy, and the structural setting in which the sedimentary and is succeeded conformably in this part of the area by the rocks occur, probably is helpful in exploration for both metallif­ Lone Mountain dolomite, which reaches a thickness o* 2,200 erous deposits and petroleum accumulations. feet. The Lone Mountain just west of Eureka contains, near The Cambrian sedimentary rocks have been divided into 8 the top, an Upper Silurian fauna. In the sections east of Eureka, formations, 2 of which are made up of 2 members each. They the Roberts Mountains formation appears to be absent, f».nd the have a total thickness of about 7,400 feet and include strata interval between the Hanson Creek formation and strata of assigned to the Lower, Middle, and Upper Cambrian. The Devonian age is occupied by thick-bedded poorly fossfiferous increase in the number of formations from the 5 units originally dolomites that have been included within the Lone Mountain described at Eureka has been accompanied by a more precise dolomite. assignment of the present and earlier fossil collections to the Rocks of Devonian age are more widely distributed tha"1 those appropriate stratigraphic units and hence by a more accurate of any of the other Paleozoic systems; individual section'' range determination of faunal sequences. from 3,000 to about 5,000 feet in thickness. All the sections The following Cambrian formations are distinguished: the exposed in the Eureka region belong to the eastern facies, as Prospect Mountain quartzite and the Pioche shale are the Early beds of this age are not known in the plate above the Foberts Cambrian formations; the Eldorado dolomite, the Geddes lime­ Mountains thrust. An unconformity that probably is widespread stone, and the Secret Canyon shale (with a lower shale member separates these rocks from the Lone Mountain dolomite below; and an upper Clarks Spring member) are of Middle Cambrian the contact with sedimentary rocks of Mississippian age above age; the Hamburg dolomite is Middle Cambrian at the base and is conformable and is regarded as falling within a sequence of probably Late Cambrian above; and the Dunderberg shale and black calcareous shales. The thinner sections to the north the Windfall formation (with a lower Catlin member and an and northeast appear to be not the result of erosion therefore, upper Bullwhacker member) are of Late Cambrian age. but to ba caused by either nondeposition or by a slower rate of In contrast with the rocks of Cambrian age, of which only deposition in this direction. one sequence of facies was recognized, there are two very dif­ Three formations have been recognized as of Devonian age. ferent facies or Ordovician rocks in the Eureka district; they The lowest of these is the Nevada formation. Over mucb of the have been brought together by a major thrust—the Roberts region five members may be mapped; they are, in ascending Mountains thrust. The two are thought to have been deposited order: the Beacon Peak dolomite member, the Oxyoke Canyon in separate seas which developed through the formation of a sandstone member, the Sentinel Mountain dolomite memt 3r, the positive area or swell early in the Ordovician and acted as a Woodpecker limestone member, and the Bay State dolomite barrier between the seaways. member. As is true of the carbonate rocks of late Ordovician The eastern sequence, which rests with apparent conformity and Silurian age, the older carbonate units of the Nevada forma­ on the Cambrian strata, is composed of five formations with tion are relatively richer in limestone westward; this change a total thickness of more than 2,500 feet. Three of these, the probably reflects the proximity of a shoreline in that direction. Goodwin limestone, Ninemile formation, and Antelope Valley Five faunal zones have been recognized in the Nevada forma­ limestone, make up the Pogonip group of Early and Middle tion: two are of early Devonian age; the upper three are assigned Ordovician age. They are overlain imconformably by the to the Middle Devonian. STEATIGRAPHIC SECTION IN VICINITY OF EUBEKA, NEV. The Devils Gate limestone overlies the Nevada formation. however, contains at least one marked unconformity. The basal Through part of the area it may be subdivided into a lower limestone member contains a fauna of probable Wolfcamp age. Meister member and an upper Hayes Canyon member. The The three upper members contain scant fosnls; some poorly Devils Gate limestone decreases in thickness notably to the preserved pelecypods in the red beds are somewhat suggestive north and east. Of its six included faunal zones, three are of early Mesozoic forms.