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USGS1998

Contributions to the gold metallogeny of northern Nevada

Nevada is one of the Earth's premier gold producing regions, accounting for approximately 64 percent of the U.S and nine percent of the world total. The impact of these mines on nearby local economies and on our national balance of payments is profound, and will continue well into the next century. Of principal importance in this region are giant sedimentary-rock-hosted (Carlin-type) deposits. These are some of the world's largest deposits, but yet are poorly understood. Other sedimentary-rock hosted deposits in the region, the distal-disseminated Ag-Au type, are genetically related to shallow plutonic complexes. Hot-spring gold-silver systems associated with Tertiary volcanic rocks represent a third type of precious metal deposit in northern Nevada. These deposits, despite being generally smaller than sedimentary-rock-hosted gold deposits, are also important gold-silver resources. Aspects about the geologic and metallogenic setting of gold-silver deposits in northern Nevada are addressed in the twenty-two chapters that compose this volume. The volume is organized along four themes: (1) crustal structure; (2) Carlin-type deposits; (3) pluton-related gold-silver deposits near Battle Mountain; and (4) hot-spring gold-silver deposits. This Open-File Report, the result of ongoing geologic and mineral-resource investigations, provides a basis for mineral exploration, for land-use planning decisions, and for environmental questions in northern Nevada.

Open-File Report↗
USGS1998

Contributions to the gold metallogeny of northern Nevada

Nevada is one of the Earth's premier gold producing regions, accounting for approximately 64 percent of the U.S and nine percent of the world total. The impact of these mines on nearby local economies and on our national balance of payments is profound, and will continue well into the next century. Of principal importance in this region are giant sedimentary-rock-hosted (Carlin-type) deposits. These are some of the world's largest deposits, but yet are poorly understood. Other sedimentary-rock hosted deposits in the region, the distal-disseminated Ag-Au type, are genetically related to shallow plutonic complexes. Hot-spring gold-silver systems associated with Tertiary volcanic rocks represent a third type of precious metal deposit in northern Nevada. These deposits, despite being generally smaller than sedimentary-rock-hosted gold deposits, are also important gold-silver resources. Aspects about the geologic and metallogenic setting of gold-silver deposits in northern Nevada are addressed in the twenty-two chapters that compose this volume. The volume is organized along four themes: (1) crustal structure; (2) Carlin-type deposits; (3) pluton-related gold-silver deposits near Battle Mountain; and (4) hot-spring gold-silver deposits. This Open-File Report, the result of ongoing geologic and mineral-resource investigations, provides a basis for mineral exploration, for land-use planning decisions, and for environmental questions in northern Nevada.

Open-File Report↗
USGS1918

Shorter contributions to general geology, 1917

Contents: A. Baked shale and slag formed by the burning of coal beds / G.S. Rogers B. The Newington moraine, Maine, New Hampshire, and Massachusetts / F.J. Katz and Arthur Keith C.A comparison of Paleozoic sections in southern New Mexico / N.H. Darton D. Wasatch fossils in so-called Fort Union beds of the Powder River Basin, Wyo., and their bearing on the stratigraphy of the region / C.H. Wegemann E. Geologic history indicated by the fossiliferous deposits of the Wilcox group at Meridian, Miss. / E.W. Berry F.A fossil flora from the Frontier formation of southwestern Wyoming / F.H. Knowlton G. The stratigraphic position and faunal associates of the orbitoid Foraminifera of the genus Orthophragmina from Georgia and Florida / C.W. Cooke G. Orbitoid Foraminifera of the genus Orthophragmina from Georgia and Florida / J.A. Cushman H. The Pliocene history of northern and central Mississippi / E.W. Shaw I. Stratigraphy in northwestern Maine and southeastern New Hampshire / F.J. Katz J. The Flaxville gravel and its relation to other terrace gravels of the northern Great Plains / A.J. Collier K. The Helderberg limestone of central Pennsylvania / J.B. Reeside L. Stratigraphy of the Hanna Basin, Wyo. / C.F. Bowen

Professional Paper↗
USGS1980

Shorter contributions to stratigraphy and structural geology, 1979

PART A: A system of anticlines lies along the trend of the sinuous course of the Colorado River for a distance of 97 km in the central Grand Canyon. Similar anticlines occur in some perennially wet side canyons. The anticlines are most abundant and well developed along northeast-trending reaches of the main canyon where it is floored by the Cambrian Muav Limestone. Dips of the folded strata are as great as 60?, and the folding locally extends more than 250 m from the river. Low-angle thrust faults in the limbs of the anticlines parallel the river and have formed in response to folding of the comparatively brittle carbonate strata. High-angle reverse kink bands, along which rocks are displaced up toward the river, also parallel the anticlines and have develop2d in response to the upward bulging of the canyon floor. The river anticlines are an unloading phenomenon. They result from lateral squeezing toward the river of saturated shaly parts of the Muav Limestone and underlying Bright Angel Shale. The driving mechanism for the deformation is a stress gradient that results from a difference in lithostatic load between the heavily loaded rocks under the 650-m-high canyon walls and the unloaded canyon floor. Saturation appears to weaken the shaly rocks sufficiently to allow deformation to take place. River anticlines are not present in the eastern Grand Canyon, where the Cambrian rocks also occur at river level. Their absence is explained by a lack of shaly rocks that could flow when saturated. PART B: The current interest in contemporary tectonic processes in the Eastern United States is turning up abundant evidence of crustal movements in late geologic time. Topographic analysis of the highland areas from the southern Blue Ridge to the Adirondack Mountains indicates that most of the landforms owe their origin to erosion of rocks of different resistance rather than to tectonic processes. Most areas of high relief and high altitude have been formed on resistant rocks. The Cambrian and Ordovician belt, containing mostly shale and carbonate rock, on the other hand, forms an extensive lowland from Alabama to the Canadian border and girdles the Adirondack Mountains. Differences in altitude can be explained by the presence of resistant rocks outside the belt; these resistant rocks form local base levels on the streams that drain the belt. A few areas may have undergone local uplift at a higher rate than areas nearby--for example, the Piedmont region northwest of Chesapeake Bay. Most estimates of erosion rates, based on the load transported by streams and of uplift rates, based on removal during a known period of time, are of the same order of magnitude, averaging almost 4x 10^-2 millimeters per year. Rates of uplift, based on study of tilted Pleistocene beaches and repeated geodetic traverses, are at least an order of magnitude higher for comparable areas. Tectonic uplift of the highlands has been slow and involves mostly warping or tilting on a large scale. Erosion rates keep up with or exceed the rate of uplift and have been sufficient to mask evidence of faulting or other differential movements. The high rates of uplift that are inferred on tilted water planes in the glaciated regions or that are measured by differences in repeated geodetic traverses cannot have been sustained for long periods of time. PART C: The Hanson Creek Formation southwest of Eureka, Nev., in the Bellevue Peak Quadrangle is composed of three lithostratigraphic members: (1) a basal dark-gray dolomite, (2) a middle silty thin- to thick-bedded, locally nodular, dark-gray, light-yellow-mottled limestone topped by light-gray dolomite, and (3) an upper dark-gray dolomite, which is herein named the Combs Canyon Dolomite Member. Detailed geologic mapping and accompanying fossil collecting prove that the same lithostratigraphic and biostratigraphic sequence is present in the Mountain Boy Range and 11 km to the south near Wood Cone Peak. Minor differences in

Professional Paper↗
USGS1919

A contribution to the geology of northeastern Texas and southern Oklahoma

The region in central and northeastern Texas and southern Oklahoma known as the Black and Grand prairies abounds in features of interest to physiographers, geologists, and paleontologists, and the pioneer investigators of this region must have experienced renewed satisfaction in each day's exploration. The reports of Joseph A. Taff, Robert T. Hill, and others, published chiefly under the auspices of State and Federal surveys, represent with approximate accuracy at most places the general distribution of the outcrops of the formations in this region, and contain detailed descriptions of many sections that constitute a mine of useful information. The reader of the present paper is urged, therefore, to hold as most important the general excellence of the earlier reports of these authors and to relegate the inaccuracies and mistakes to which his attention will be called to the relatively unimportant place in which they belong, remembering at the same time that a future generation of investigators may find our own shortcomings as great as those we now criticize.

Oklahoma;Texas↗