Elko County Research Articles

Ranch Resource Differences Affecting Profitability of Crested Wheatgrass as a Spring Forage Source

A representative cow-calf ranch operation in Elko County, Nev., was modeled using a linear programming procedure to determine effects of selected ranch resource differences on profitability of seeding crested wheatgrass. Net present value (NPV) results suggest seeding crested wheatgrass as a spring forage can be a profitable investment if there are associated increases in calf weaning weights of 9.07 kg and increases in calving rates of 5 percentage points. Amount of meadow hayland, deeded range, and BLM forage available to the representative ranch were increased and decreased 50%. NPV’s of the crested wheatgrass investment are greater for ranches with excess meadow hay and excess deeded range. NPV’s are lower for ranches with limiting resources of meadow hayland, deeded range, and BLM forage. Herd size and profit potential on many western ranch operations are limited by availability of high quality, low cost early spring forage. Increased infestation of rangeland with low quality forage species may decrease the amount of spring forage produced. Overgrazing of the perennial grass community during the 1880’s destroyed much of the native understory, with degraded stands of sagebrush remaining (Young et al. 1979). Also, domination of rangeland by late maturing range species may delay early spring usage of the range. Given a permanent physical shortage of early spring forage, an operator may choose to buy hay, lease pasture, or graze other forage sources earlier than desired to maintain stand productivity. However, depending on costs and returns, it may be more profitable for the operator to maintain a smaller herd size and have excess ranch forage later in the grazing season. One possible investment alternative to inadequate spring forage is to remove existing forage and seed the rangeland with an earlier maturing grass. The adaptability of crested wheatgrass (Agropyron deserrorum) as a forage source on western range operations has been established, as more than 5 million ha have been seeded in the U.S. (Dewey and Asay 1975). Crested wheatgrass has its high

Hydrogeology of a Possible Geothermal System near Deeth, Nevada: ABSTRACT

Study of a possible geothermal system near Deeth, Elko County, Nevada, included geologic mapping, hydrogeochemical analyses, and geophysical interpretation. Geologic and geophysical methods emphasized structure, particularly Paleozoic thrust faults overprinted by Miocene listric normal faulting. Hydrogeochemical analyses showed geothermal fluids to be sodium-bicarbonate water, probably of meteoric origin. The geothermal model is convection cells caused by deep circulation along the Marys River fault zone. The reservoir is fractured rock along the fault zone. Silica geothermometry predicts a reservoir temperature of 165°C (329°F). A Paleozoic sedimentary range block is separated by the Marys River fault zone from a Tertiary basin-fill sequence to the east. Allochthonous western facies rocks at Twin Buttes were emplaced along the Roberts Mountains thrust. Eastward-thrusted upper Paleozoic units are exposed in the Peko Hills. A thick, bimodal, Oligocene-Pliocene volcanic sequence covers the area's northwest corner. The Miocene Humboldt Formation is a tuffaceous, fluviatile lacustrine basin-fill unit that onlaps the range block and thickens basinward. Quaternary hot-spring deposits are localized along the Marys River fault zone. The Miocene-Pliocene Marys River fault zone is a north-trending, down-to-the-east, normal fault system. A shear zone may be present where the fault zone undergoes right separation. Hydrogeochemical, thermal water, and heat-flow anomalies are localized along the fault zone. The proposed model calls for deep circulation of meteoric water along the Marys River fault zone. Surface water from the Marys River percolates down the fault and is heated to approximately 165°C (329°F). Thermal water migrates laterally, then rises back up the fault. Upwelling thermal water creates the three observed thermal anomalies. Leakage of geothermal fluid into discontinuous sand and gravel channels of the Humboldt Formation gives rise to broad, low-temperature anomalies. The high-temperature reservoir is fractured rock along the Marys River fault zone. End_of_Article - Last_Page 559------------

Relationship of Roberts Mountains Thrust to Oil and Gas Exploration in Nevada: ABSTRACT

The Roberts Mountain thrust is the oldest and probably the largest of many eastward-moving regional thrust plates that make up much of the Basin and Range province. The fault can be traced from the state of Washington through central Nevada into California. Movement commenced during Late Devonian-Early Mississippian time (Antler orogeny), probably as a result of plate collision and subduction farther west along the margin of the eastern Klamath geanticlinal arc. Ordovician to Devonian age, eugeosynclinal, highly organic (2 to 5%), dark-colored shales, siltstones, cherts, and limestones--the western siliceous facies--perhaps originally totaling 20,000 ft (6,100 m) are thrust over eastern-facies carbonate and clastic shelf deposits. Movement along the thrust continues sporadically into middle Permian, by which time much of the eugeosynclinal rocks were eroded eastward as a flysch. These clastic deposits of Mississippian, Pennsylvanian, and Permian age are deposited along with shallow-marine units in local basins and sags. Outcrops of thin-bedded, oil-bearing shales (25 gal/ton) and black cherts of the western siliceous facies Vinni Formation are present at Roberts Mountain. This unit is a potential source, seal, and possible reservoir rock, averaging several thousand feet in thickness, which floors many of the Miocene valley basins west of the leading edge of the thrust. Oil potential is considered to be good although fewer than 15 wells have been drilled in the area. Many had oil shows but none has tested the Vinni or the overlying Cretaceous-Eocene sedimentary units at depth. Free oil has flowed from perforations at approximately 7,200 ft (2,195 m) from possibly Mississippian or Devonian dolomites in the Amoco-Getty 3 Blackburn Unit, (Sec. 8, T27N, R52E, Pine Valley, Eureka County, Nevada). This s the first substantial oil recovery from the Paleozoic rocks in any valley basin other than Railroad Valley in the Nevada portion of the Basin and Range. Oil appears to be of Paleozoic source. In some valleys the overlying Cretaceous and Tertiary units may provide additional source, seal, and reservoir rocks. East of the thrust trace, in several valley basins, Paleozoic source and reservoir rocks are present and intertongue with the flysch of the Roberts Mountain thrust. In some valleys, these units are also overlain by sedimentary Cretaceous and Tertiary rocks which may also be potential source, reservoir, and seal for any oil accumulations. Noncommercial Tertiary and Paleozoic free oil and gas have been recovered in several test wells drilled in T29N, R55E, Huntington Creek valley basin, Elko County, Nevada. Local horst and graben structures, combined with Tertiary truncation similar to that found productive at Trap Spring and Eagle Springs fields, are present in valley basins both east and west of the thrust. End_of_Article - Last_Page 564------------

Characterization of Carlin-Type Gold Ore by Photoacoustic, Raman, and EPR Spectroscopy

Low-grade carbonaceous gold ore (0.01 to 1.8 oz/ton of gold) from the Carlin mine in Elko county, Nevada, has been characterized by a variety of analytical and spectroscopic techniques with emphasis on vibrational spectroscopy. A particular concern was determining the nature of the carbon-containing material in the ore. It was found that in addition to the anticipated carbonate, finely disseminated elemental carbon is present in amounts ranging from 0.062 to 0.43 wt. %. Contrary to previous reports, no detectable amounts of humic acid materials or organic hydrocarbons are present in any of the samples investigated.

Geology of a skarn-breccia orebody at the Victoria Mine, Elko County, Nevada

The copper orebody at the Victoria mine occurs in a breccia pipe emplaced in Permian limestone and calcareous sandstone. The mineralized part of the breccia appears to be due to collapse. Elsewhere, the breccia consists of mixed lithologies in a rock-flour matrix, and in some places, clasts are rounded and show rare graded bedding; these factors imply emplacement by upward-streaming. Monzonite porphyry dikes intruded the pipe during brecciation. Zonation and paragenesis in the district and downward within the pipe proceed from limestone to talc- and tremolite-bearing assemblages to diopside to garnet (averaging 77% andradite). Brecciation took place repeatedly during silication: tremolite clasts were cemented by diopside, diopside hornfels clasts were cemented by coarser diopside, and then by diopside and calcite, at which point brecciation ceased. Finally, garnet, calcite, quartz, and sulfide ore cemented the breccia. Copper is concentrated in an arcuate zone at one end of the breccia pipe. Late alteration of diopside produced saponite, talc, and local serpentine, whereas garnet altered to mixtures of hematite, calcite, quartz, and chlorite. The sequence is divided into (1) early contact metamorphism, (2) main-stage iron metasomatism and copper deposition, and (3) late-stage alteration, nearly isochemical except for the addition of CO 2 and H 2 O.

Geology of the Tuscarora geothermal prospect, Elko County, Nevada

The Tuscarora geothermal prospect is located at the north end of Independence Valley in northern Nevada. Thermal springs issue from Oligocene tuffaceous sediments near the center of an area of high thermal gradient. The springs, are associated with a large siliceous sinter mound and are currently depositing silica and calcium carbonate. Measured fluid temperatures range up to 95 °C, and chemical geothermometers indicate a reservoir temperature of 216 °C. The Independence Valley contains 35- to 39-m.y.-old tuffs and tuffaceous sediments which overlie Paleozoic clastic and volcanic rocks and are overlain by Miocene lava and pyroclastic flows. The rocks have been deformed by normal faults trending north-south and northwest and by folds trending north-south which have been active in the Pleistocene.

The Economic Effects of Three Changes in Public Lands Grazing Policies

Linear programming was used to analyze the impact of potential changes in federal policies. The amount of federal grazing used by ranchers was found to be relativley unresponsive to grazing fee increases. However, allotment reductions and adjustments in the allowed season of use for federal grazing had a large impact on the quantity of beef supplied and the net income of the ranches studied. Leased grazing for privately owned domestic livestock has been an important use of public lands throughout Nevada. Availability of federal grazing leases plus relatively low grazing fees led to the development of extensive range resource use by the livestock industry. Mitchell and Garrett (1977) reported range property values closely related to availability of federal grazing permits. Of the 56 ranches surveyed in northeastern Nevada, only four did not use federal lands; and, the average ranch depended upon federal range for about 49% of its annual feed requirements. Recently Bureau of Land Management (BLM) and U.S. Forest Service (FS) proposed increasing fees for grazing on public rangelands to the fair market value (FMV) of private leases. Other proposals include elimination of early spring grazing and/or a temporary reduction of grazing to rejuvenate overgrazed range resources. Because of the large amount of federal grazing lands in Nevada, these changes in public lands policies could have a significant effect on Nevada’s livestock industry. The purpose of this paper is to present estimates of the economic impact on a sample of 36 ranches in Elko County of three public land use policy changes: (1) increase in BLM and FS grazing fees; (2) elimination of spring grazing on BLM range; and, (3) reductions in BLM grazing allotments of 20, 40, and 60%.

Lower Permian of the Central Cordilleran Miogeosyncline

This study of Lower Permian rocks in northeastern Nevada and northwestern Utah was undertaken to provide a basis for interpretation of Early Permian history of the Cordilleran Miogeosyncline. The area of study extends from the western margin of the miogeosyncline, along the eastern edge of the old Antler highlands, eastward into the Salt Lake Desert west of Salt Lake City (Fig. 1), where outcrops of Permian rocks are few. It extends along the miogeosyncline in Nevada from northern Lincoln County into northern Elko County. The base of the Permian was selected as the lower stratigraphic limit for this study. The base of the Kaibab Limestone was selected as the upper limit, although the Lower-Upper.*** Permian boundary occurs above it (Baird and Collinson, 1975), because it forms a reliable horizon for correlation and marks the commencement of a new depositional cycle in this region. Work concerning Lower Permian rocks of the central Cordilleran Miogeosyncline includes that of Steele (1959, 1960) and Bissell (1960, 1962a, 1962b, 1964, 1967, 1970, 1974), which are regional in scope, and that of Stevens (1965), Collinson (1968), Zabriskie (1970), and, Marcantel (1975), which presents more details in smaller areas. Many different facies, the distribution of which generally has been credited to various highs depocenters, troughs, basins, highlands, or shelves, often on the basis of tenuous data have been recognized.

Jurassic Suprastructure in the Delano Mountains, Northeastern Elko County, Nevada

K-Ar dating of a granitic stock in the Delano Mountains, northeastern Elko County, Nevada, documents probable Jurassic tectonism. Permian(?) sedimentary rocks have been cut by low-angle bedding-plane faults and synchronously and (or) later have been folded into one major, and several other minor, broad, symmetrical, open folds. Emplacement of a granitic stock at 135 m.y. B.P. through the previously deformed strata and subsequent Tertiary normal faulting added to the structural complexity of the area. It is suggested that the relatively moderate pre-Tertiary deformation in the Delano Mountains represents the upper tectonic level of a pre-Cretaceous (Jurassic) suprastructure in Elko County and vicinity.

New Mississippian Formation in Northeastern Nevada and Its Possible Significance: GEOLOGIC NOTES

The allochthonous Tripon Pass Limestone (new name) in the Windermere Hills, northeastern Elko County, Nevada, consists of 1,550 ft of clastic limestone and interbedded argillite, quartz siltite and arenite, and quartz-chert arenite. The Tripon Pass Limestone overlies the Devonian Guilmette Formation, probably disconformably, and is overlain conformably by the Diamond Peak Formation. The Tripon Pass Limestone contains Kinderhookian (Early Mississippian) conodonts; those at the top of the formation are latest Kinderhookian. Sedimentary structures in the Tripon Pass Limestone suggest that at least part of the formation was deposited by turbidity currents. Turbidity current activity probably resulted from tectonism in part of the Cordilleran miogeosyncline contemporaneous with an early stage of the Antler orogeny in the Cordilleran eugeosyncline on the west. Allochthonous rocks tentatively assigned to the Chainman Formation, structurally separate from the Tripon Pass Limestone and associated formations, also contain Kinderhookian conodonts. If the conodonts reflect the true age of the Tripon Pass Limestone (and lowermost Diamond Peak Formation) and Chainman Formation, which is probable, then complex facies relations between Mississippian terrigenous clastic and carbonate rocks in the Cordilleran geosyncline are implied. Such relations can be clarified only by detailed lithostratigraphic and biostratigraphic work, but clarification may lead to the discovery of petroleum reservoirs.

Thrust Sequences in the Windermere Hills, Northeastern Elko County, Nevada

Paleozoic and Mesozoic (Triassic) rocks in the Windermere Hills comprise several informally named sequences, all of which are believed to be allochthonous. The Chainman Sequence is the structurally lowest one seen and contains only the Chainman Formation of Kinderhookian (Mississippian) age. Above the Chainman Sequence is the Black Mountain Sequence which contains the Devonian Nevada and Guilmette Formations, an unnamed Kinderhookian limestone formation, and the Diamond Peak Formation whose base is Kinderhookian. The overlying Thousand Spring Sequence consists of two parts. The lower part of the sequence contains imbricate slices of eugeosynclinal and transitional belt rocks which are unconformably overlain by the upper part with Permian clastic rocks assigned to the Strathearn, Buckskin Mountain, and Carlin Canyon Formations, and the Triassic Dinwoody and Thaynes Formations. West of Highway 93, the Summer Camp Sequence, which contains Upper Ordovician eugeosynclinal belt rocks, is thrust over the Thousand Spring Sequence. East of the highway, the HD Summit Sequence, with Permian clastics, is over the Thousand Spring Sequence. The relations between the Summer Camp and HD Summit Sequences are unknown. The isolated Wilkins Siding Sequence contains Pennsylvanian rocks and may constitute a thin thrust sheet between the Chainman and Thousand Spring Sequences. Poorly defined domes and basins fold the pre-Cenozoic rocks and thrusts and were probably formed by the interaction of two sets of folds, of unknown significance. Small asymmetrical folds close to thrusts predate the domes and basins and were probably produced in response to southeasterly movement of thrust sheets during the Antler Orogeny and in post-Early Triassic time. Thrusts are accompanied by predominantly brittle deformation. High-angle faults are mostly normal; they occur throughout the area and postdate all other structures. Rocks in the thrust sequences of the Windermere Hills provide a fragmented record of Ordovician to Triassic deposition and deformation in different parts of the Cordilleran Geosyncline. Paleozoic eugeosynclinal and transitional belt rocks were first thrust southeastward during the Antler Orogeny. Permian and Triassic rocks were subsequently deposited unconformably on the thrust sheets, and post-Early Triassic thrusting moved the whole succession southeastward again to the site of the Windermere Hills. Other sequences contain rocks of various ages deposited in different tectonic environments, all juxtaposed in the Windermere Hills by post-Triassic thrusting.

Oligocene or Younger Thrust Faulting in the Ruby Mountains, Northeastern Nevada

A klippe of unmetamorphosed Devonian carbonate rocks rests on the Harrison Pass intrusive body south of Toyn Creek in the central Ruby Mountains, Elko County, Nevada. This klippe and other klippen of Carboniferous strata—first mapped by R. P. Sharp (1942)—that rest on lower Paleozoic strata are believed to represent a once-continuous thrust sheet that developed after emplacement of the intrusive body. This intrusion of coarse-grained granodiorite to quartz monzonite is exposed over an area of about 45 square miles. Potassium-argon and lead-alpha age determinations on four samples of the intrusive body establish Oligocene or younger age for the thrusting. Potassium-argon age determinations on biotites from the four samples range from 29 to 36 m.y. with a possible analytical error of ±10 percent. Lead-alpha age determinations (all with a possible analytical error of ±10 m.y.) on zircon showed 40 m.y. for three of the samples and 30 m.y. for the fourth. Lead-alpha and potassium-argon dates on a fifth sample collected by R. R. Coats also fall within these ranges. The agreement of the radiometric dates indicates a lack of thermal activity subsequent to the emplacement of the intrusion and establishes a maximum age of Oligocene for the thrust faulting. The present distribution of thermally metamorphosed Paleozoic rocks in the Ruby Mountains seems to preclude the possibility that the thrust plate originated within the Ruby Mountains. Sharp suggested a western source with displacement of from 7 to 10 miles.

Stratigraphy and Correlation of Late Precambrian Rocks of Pilot Range, Elko County, Nevada, and Box Elder County, Utah

Approximately 3,300 feet of metasedimentary rocks believed to correlate lithologically with Units C, D, E, F, and G of the late Precambrian McCoy Creek Group (Misch and Hazzard, 1962) is exposed in the Pilot Range. Unit G is disconformably overlain by Lower Cambrian Prospect Mountain Quartzite (restricted). These Precambrian rocks were regionally metamorphosed to slate, argillite, phyllite, metasiltstone, and quartzite. The rocks of Unit G show the effects of subsequent static thermal metamorphism of biotite grade. The Precambrian rock units have characteristic heavy-mineral assemblages that are useful in correlation.

The Barstovian Camp Creek fauna from Elko County, Nevada

The Barstovian Camp Creek fauna from Elko County, Nevada

Some Notes on Birds of Elko County, Nevada

Some Notes on Birds of Elko County, Nevada

Patterned Sedimentation of Pennsylvanian and Permian Marine Strata in Part of the Cordilleran Area: ABSTRACT

Repetitive to cyclic sedimentary patterns characterize many sequences of marine rocks of Pennsylvanian and Permian age in parts of eastern Nevada and western Utah. The assemblages accumulated in different (at End_Page 350------------------------------ times connected) depocenters of the miogeosyncline. Ely Limestone (Pennsylvanian) exhibits rhythmic arrangement of skeletal to bioclastic, calcarenitic, matrix, and micritic limestones with some interbedded calcareous sandstones. The sedimentary cyclic pattern occurs in stratigraphic sections totaling 1,000 to 1,500 feet, particularly in the Burbank Hills, Confusion Range, and Leppy Range of western Utah, and in the Cherry Creek Mountains, Butte Mountains, Pequop Mountains, Diamond Range, and Pancake Range of Nevada. Ferguson Mountain Formation (Wolfcampian) of northeastern Nevada and part of adjacent Utah is approximately 2,000 feet of alternating reefoid, bioclastic matrix, and micritic limestones arranged in a remarkable pattern in which this tetrad is repeated numerous times by patterned sedimentation. Farther south in east-central Nevada and west-central Utah the Riepe Spring Limestone and restricted Arcturus Formation (both Wolfcampian) aggregate 1,000 to 2,000 feet of cyclically arranged reefoid, bioclastic-lithoclastic, matrix, and micritic limestones with which occur interbedded calcareous quartzose sandstones. The Leonardian-age Pequop Formation crops out in a large area of eastern Nevada and western Utah; essentially all sections studied display patterned or rhythmic sedimentation of bioclastic, skeletal, matrix, and micritic limestones. Butte Mountains and Pequop Mountains of Nevada contain finest stratigraphic sections; the one at Moorman Ranch near U.S. Highway 50 about 35 miles northwest of Ely is a remarkable arrangement of about 2,500 feet of criquinites, fusulinid coquinites, sandy matrix limestones, and micrites. A normal triad of criquinites with fusulinids, sandy matrix limestones, and micritic limestones typifies the section in rhythmic succession. Marine strata of Guadalupian age in western Utah and eastern Nevada include, in ascending order, the Loray Formation, Kaibab Limestone, Plympton Formation, Indian Canyon Formation, and Gerster Formation. The Loray contains shale, siltstone, dolosiltites, evaporitic dolomites, and petroliferous limestones arranged in cyclic manner; this succession evidently formed in marine to non-marine environments under transgressive-regressive conditions. The overlying Kaibab, Plympton, and Indian Canyon do not display marked pattern sedimentation. Gerster Formation normally is less than 1,000 feet thick, but where more than 4,000 feet thick in south-central Elko County, Nevada, it consists of cyclically arranged tetrads of skeletal, matrix, and micritic limestones, and arenaceous criquinites. Evidence suggests that periodicity of diastrophism of marginal and intra-basin landmasses substantially controlled the pattern of sedimentation in depocenters of the Late Paleozoic miogeosyncline. Marine oscillations and concomitant transgressive-regressive sedimentation across the broad shelves, banks, basin, troughs, and evaporite pans established a pattern of carbonate deposition. Rhythmic activity of the Antler-Sonoma orogenic belt, Northeast Nevada Highland, West-Central Utah Highland, Ely Uplift, and others provided detritus and otherwise initiated and controlled patterned sedimentation. End_of_Article - Last_Page 351------------

Occurrences of sepiolite in Utah and Nevada

Sepiolite (2MgO.3SiO 2 .4H 2 O) occurrences in 4 mining districts were investigated by field and laboratory techniques to determine the geological environment. In the Maxfield Mine, Big Cottonwood Canyon, Salt Lake County, Utah, sepiolite occurs in carbonates of the Madison Formation (Mississippian) as paper-thin, white veinlets in a larger ore vein containing pyrite, galena, sphalerite, calcite, and quartz. White to tan sepiolite, calcite, and chalcedony, in veins up to 6 in. wide, occur in an unnamed Permian carbonate formation in the Ferber Mining district, Elko County, Nevada. In the Gold Hill, Utah, mining district, the sepiolite occurs within the Ochre Mountain Limestone [Mississippian] in the Cane Springs Mine, where the sepiolite is associated with sulfide ore minerals in a silicated limestone matrix. In the Mineral Range, Beaver County, Utah, white sepiolite, in veins up to 1 in. wide, is found with calcite and quartz in a carbonate bed of the Kaibab Formation (Permian). The analytical data were obtained on the sepiolite specimens by chemical, X-ray diffraction, infrared-absorption, and optical analyses. Similarities in the sepiolite occurrences, widely separated geographically, indicate a common mode of genesis. In all cases where field relations could be studied, the following similarities were noted: 1) the host rock is a carbonate, partly or wholly dolomite; 2) calcite and quartz and/or opal occur with the sepiolite veins; 3) intrusive rocks are found in the vicinity; 4) sulfide minerals are present with the sepiolite or are found in the area. It is believed the sepiolites were formed by low-temperature hydrothermal solutions during the last stages of the sulfide-mineral deposition in carbonate beds.

Paleozoic Sequences and Thrust Slices of the Seetoya Mountains, Independence Range, Elko County, Nevada

Three stratigraphic sequences of lower Paleozoic rocks in the Seetoya Mountains east of Tuscarora, Nevada, are of partly equivalent age. The highest sequence is Lower Silurian and younger, composed of bedded cherts, quartzite, volcanic rocks, and graptolitic shales, deposited in a western eugeosynclinal belt, and thrust southward or southeastward for some scores of miles. Each of two lower sequences includes the same five Ordovician and Silurian formations which differ markedly in thickness and slightly in lithology. They are predominantly carbonate rocks with some quartz sandstones, deposited in an eastern miogeosynclinal belt. The upper of these latter sequences has been thrust about 6 miles southward or southeastward. The eastern sequences were folded, faulted, and eroded, probably in pre-Carboniferous or Permian time. Siltstones, laid unconformably on the southern of the two eastern sequences, may have been derived from rising lands in the eugeosynclinal belt. Thrusting of uncertain age carried a thick plate of allochthonous rock of the western belt southerly or southeasterly. Presence of younger rocks beneath the thrust in the south suggests that there was a regional southward slope at this time. A second thrust, which developed within the eastern belt, carried parautochthonous rocks and may be a subsidiary thrust initiated by movement of the overriding rocks of the western belt. This thrust shows a close similarity to the peel thrusts of the Western Alps. Block faulting during Tertiary is largely responsible for the present-day north-south trend of the range.

Carboniferous Cherts, Turbidites, and Volcanic Rocks in Northern Independence Range, Nevada

Research Article| May 01, 1962 Carboniferous Cherts, Turbidites, and Volcanic Rocks in Northern Independence Range, Nevada JOHN J FAGAN JOHN J FAGAN City College of New York, New York, N. Y Search for other works by this author on: GSW Google Scholar Author and Article Information JOHN J FAGAN City College of New York, New York, N. Y Publisher: Geological Society of America Received: 03 Mar 1960 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1962, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1962) 73 (5): 595–612. https://doi.org/10.1130/0016-7606(1962)73[595:CCTAVR]2.0.CO;2 Article history Received: 03 Mar 1960 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation JOHN J FAGAN; Carboniferous Cherts, Turbidites, and Volcanic Rocks in Northern Independence Range, Nevada. GSA Bulletin 1962;; 73 (5): 595–612. doi: https://doi.org/10.1130/0016-7606(1962)73[595:CCTAVR]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Rocks of eugeosynclinal origin in the northern Independence Range, Elko County, Nevada (Wildhorse and Bull Run quadrangles) compose the Schoonover Formation which includes eight named and two unnamed members. The formation is, in part, Mississippian, and about 9000 feet in maximum thickness. The rocks, allochthonous with respect to a Carboniferous and Cambrian terrane of miogeosynclinal facies, have been folded and thrust from the northwest during the late Mississippian or post-Mississippian but prior to the Miocene. Principal rock types include (1) argillaceous lutites, (2) bedded cherts, (3) arenites and conglomerates, and (4) andesite lavas.The bedded cherts appear to have been pelagic accumulations of siliceous organic debris, mostly radiolarian fragments, on the sea floor. Bedded cherts grade from those clearly composed of solid organic debris to those in which the finer radiolarian fragments have merged into a featureless silica continuum. Partial solution and interstitial crystallization during diagenesis and accompanying compaction are considered the essential mechanisms of lithification.The arenites show graded bedding and flute casts and consist mainly of poorly sorted, poorly rounded quartz grains and once-argillaceous finer material. They are turbidites intermittently deposited by currents from the west. The cherts are products of brief flourishings and settlings of siliceous plankton. Layers of pebbly mudstone (tilloid) record chaotic submarine slides into the relatively deep-water site of sedimentation. The source of the turbidites and slide deposits was a tectonic land not far to the west, composed of rocks formed in the eugeosyncline. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Permian Rocks of Parts of Nevada, Utah, and Idaho

Detailed study and measurement of 30 stratigraphic sections, and reconnaissance of numerous other sections of Permian marine rocks of the eastern half of Nevada, western half of Utah, and central to south-central Idaho indicate that certain revisions in nomenclature are justified. This area in the eastern Great Basin contains excellent sections of Late Paleozoic marine rocks, most of which contain diagnostic fusulinid faunas. Within the Permian system representatives of the Wolfcampian, Leonardian, and Guadalupean time-equivalents are areally extensive. In most of eastern Nevada and part of western Utah a widespread regional disconformity separates Permian from Pennsylvanian rocks, and commonly this is represented by absence or truncation of strata of medial to late Pennsylvanian age. This disconformity is slight or missing in the Oquirrh Formation of Utah and southern Idaho, the Wood River Formation of central Idaho, and certain limestones and related sedimentary rocks of east-central Idaho. The Ferguson Mountain Formation, mostly Wolfcampian in age but locally of late Virgilian age at the base and early Leonardian age at the top, is of wide areal extent and at its type locality in eastern Elko County, Nevada, contains one of the most prolific Wolfcampian fusulinid faunas in the eastern Great Basin. It is conformably overlain by the Pequop Formation, Leonardian in age, also rich in fusulinids. The Pequop is unconformably overlain by the Loray Formation, a dolomitic and gypsiferous sequence laid down in retreating epeiric seas. The Park City Group includes, in ascending order, Kaibab Limestone, Plympton Formation, and Gerster Formation. These are of late Leonardian to Capitanian age. The Indian Canyon Formation comprises sandy, cherty, and dolomitic rocks beneath the Gerster and above the Plympton, but was not originally included in the Park City Group. In southern Nevada, basin facies include the Bird Spring Formation (Pennsylvanian), conformably overlain by the Spring Mountain Formation (Wolfcampian and Leonardian age). Shelf facies to the east consist, in ascending order, of: Callville Limestone (Pennsylvanian), and Pakoon Limestone (Wolfcampian), Queantoweap Sandstone, Hermit Formation, Coconino Sandstone, Toroweap Formation, and Kaibab Formation (the last two are of Leonardian to early Wordian age). Kaibab Formation also is in the basin. Permian rocks in this area, and to the north, are disconformably overlain by early Triassic sedimentary rocks (Moenkopi or Thaynes Formations). Carbonates predominate in the stratigraphic sections and are bioclastic, matrix, micritic, detrital, and combined types. Sediments accumulated in different repositories of the miogeosyncline; with varying degrees of tectonism in the Antler-Sonoma orogenic belt on the west, intra-geosynclinal highlands, and shelves to the east, numerous lithologic associations formed, including evaporites.