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F. G. Poole

Publications and source records attributed to F. G. Poole.

At least 19 recordsLinked to original sources
USGS2009

Sulfur- and oxygen-isotopes in sediment-hosted stratiform barite deposits

Sulfur- and oxygen-isotope analyses have been obtained for sediment-hosted stratiform barite deposits in Alaska, Nevada, Mexico, and China to examine the environment of formation of this deposit type. The barite is contained in sedimentary sequences as old as Late Neoproterozoic and as young as Mississippian. If previously published data for other localities are considered, sulfur- and oxygen-isotope data are now available for deposits spanning a host-rock age range of Late Neoproterozoic to Triassic. On a ??34S versus ??18O diagram, many deposits show linear or concave-upward trends that project down toward the isotopic composition of seawater sulfate. The trends suggest that barite formed from seawater sulfate that had been isotopically modified to varying degrees. The ??34S versus ??18O patterns resemble patterns that have been observed in the modern oceans in pore water sulfate and water column sulfate in some anoxic basins. However, the closest isotopic analog is barite mineralization that occurs at fluid seeps on modern continental margins. Thus the data favor genetic models for the deposits in which barium was delivered by seafloor seeps over models in which barium was delivered by sedimentation of pelagic organisms. The isotopic variations within the deposits appear to reflect bacterial sulfate reduction operating at different rates and possibly with different electron donors, oxygen isotope exchange between reduction intermediates and H2O, and sulfate availability. Because they are isotopically heterogeneous, sediment-hosted stratiform barite deposits are of limited value in reconstructing the isotopic composition of ancient seawater sulfate.

Geochimica et Cosmochimica Acta↗
USGS2004

Comparison of some sediment-hosted, stratiform barite deposits in China, the United States, and India

Shifts in world barite production since the 1980s have resulted in China becoming the world's largest barite-producing country followed by the US and India. Most barite produced for use in drilling fluids is derived from black shale- and chert-hosted, stratiform marine deposits. In China, Late Proterozoic to Early Cambrian marine barite deposits occur on the oceanic margins of the Yangtze platform, in the Qinling region in the north and the Jiangnan region in the south. Most US ore-grade deposits are in the Nevada barite belt; most commercial deposits occur in Ordovician and Devonian marine rocks along the western margin of the early Paleozoic North American continent. Production in India is predominantly from a single Middle Proterozoic deposit in a sedimentary basin located on Archean basement in Andrah Pradesh.The geologic and geochemical characteristics of the deposits are consistent with origins from a variety of sedimentary-exhalative processes, with biogenic processes contributing to the concentration of some seafloor barite. Linear distributions of clusters of lenticular deposits suggest a geographic relationship to syndepositional seafloor fault zones. Sulfur isotope data of the barite deposits range from values that are similar to coeval seawater sulfate to significantly higher ??34S values. Strontium isotope values of continental-margin-type deposits in Nevada and China are less radiogenic than those of cratonic-rift deposits (e.g. Meggen and Rammelsberg). Comparison of Lan/ Cen ratios of barite in the Qinling region of China with marine chert ratios suggests a relationship to hydrothermal fluids, whereas ratios from the Jiangnan region and Nevada can be interpreted as reflecting a biogenic influence.The California Borderland provides a potential modern analog where hydrothermal barium is being deposited on the seafloor in fault-block-bounded basins. Anoxic to dysaerobic conditions on some marine basin floors result from upwelling, nutrient-rich currents and high productivity in surface waters. In this setting, biogenic processes could contribute to the concentration of barium from hydrothermal sources. ?? 2003 Published by Elsevier B.V.

Ore Geology Reviews↗
USGS2003

Reinterpretation of the stratigraphy and structure of the Rancho Las Norias area, central Sonora, Mexico

New geologic mapping and fossil data in the vicinity of Rancho Las Norias, 30 km east of Hermosillo, Sonora, Mexico, show that rocks previously mapped as Precambrian instead are Paleozoic. Previous geologic maps of the Rancho Las Norias area show northeast-directed, southwest-dipping reverse or thrust faults deforming both Precambrian and Paleozoic rocks. The revised stratigraphy requires reinterpretation of some of these faults as high-angle normal or oblique-slip faults and the elimination of other faults. We agree with earlier geologic map interpretations that compressional structures have affected the Paleozoic rocks in the area, but our mapping suggests that the direction of compression is from southeast to northwest. Published by Elsevier Ltd.

Journal of South American Earth Sciences↗
USGS2003

Formation of modern and Paleozoic stratiform barite at cold methane seeps on continental margins

Stratiform (bedded) Paleozoic barite occurs as large conformable beds within organic- and chert-rich sediments; the beds lack major sulfide minerals and are the largest and most economically significant barite deposits in the geologic record. Existing models for the origin of bedded barite fail to explain all their characteristics: the deposits display properties consistent with an exhalative origin involving fluid ascent to the seafloor, but they lack appreciable polymetallic sulfide minerals and the corresponding strontium isotopic composition to support a hydrothermal vent source. A new mechanism of barite formation, along structurally controlled sites of cold fluid seepage in continental margins, involves barite remobilization in organic-rich, highly reducing sediments, transport of barium-rich fluids, and barite precipitation at cold methane seeps. The lithologic and depositional framework of Paleozoic and cold seep barite, as well as morphological, textural, and chemical characteristics of the deposits, and associations with chemosymbiotic fauna, all support a cold seep origin for stratiform Paleozoic barite. This understanding is highly relevant to paleoceanographic and paleotectonic studies, as well as to economic geology.

Geology↗
USGS2003

Middle Devonian to Early Carboniferous event stratigraphy of Devils Gate and Northern Antelope Range sections, Nevada, U.S.A

The classic type section of the Devils Gate Limestone at Devils Gate Pass is situated on the eastern slope of a proto-Antler forebulge that resulted from convergence of the west side of the North American continent with an ocean plate. The original Late Devonian forebulge, the site of which is now located between Devils Gate Pass and the Northern Antelope Range, separated the continental-rise to deep-slope Woodruff basin on the west from the backbulge Pilot basin on the east. Two connections between these basins are recorded by deeper water siltstone beds at Devils Gate; the older one is the lower tongue of the Woodruff Formation, which forms the basal unit of the upper member of the type Devils Gate, and the upper one is the overlying, thin lower member of the Pilot Shale. The forebulge and the backbulge Pilot basin originated during the middle Frasnian (early Late Devonian) Early hassi Zone, shortly following the Alamo Impact within the punctata Zone in southern Nevada. Evidence of this impact is recorded by coeval and reworked shocked quartz grains in the Northern Antelope Range and possibly by a unique bypass-channel or megatsunami-uprush sandy diamictite within carbonate-platform rocks of the lower member of the type Devils Gate Limestone. Besides the Alamo Impact and three regional events, two other important global events are recorded in the Devils Gate section. The semichatovae eustatic rise, the maximum Late Devonian flooding event, coincides with the sharp lithogenetic change at the discordant boundary above the lower member of the Devils Gate Limestone. Most significantly, the Devils Gate section contains the thickest and most complete rock record in North America across the late Frasnian linguiformis Zone mass extinction event. Excellent exposures include not only the extinction shale, but also a younger. Early triangularis Zone tsunamite breccia, produced by global collapse of carbonate platforms during a shallowing event that continued into the next younger Famennian Stage. The Northern Antelope Range section is located near the top of the west side of the proto-Antler forebulge. Because of its unusual, tectonically active location, unmatched at any other Nevada localities, this section records only four regional and global events during a timespan slightly longer than that of the Devils Gate section. The global semichatovae rise and late Frasnian mass extinction event are largely masked because of the depositional complexities resulting from this location.

Nevada↗
USGS1980

Quantitative analysis versus semiquantitative optical emission spectrographic analysis of chromium, nickel, zinc, vanadium, and molybdenum in organic-rich Paleozoic marine strata, Western United States

Comparison of analytical results between the quantitative method and the semiquantitative six-step optical-emission spectrographic method commonly shows significantly lower values for the semiquantitative method. The lower values are most obvious for splits from the same samples of fine-grained organic-rich rocks where the concentrations of the metals chromium, nickel, zinc, vanadium, and molybdenum are greater than about 200 ppm (parts per million). Samples compared are Paleozoic marine rocks from the Western United States; they include the Permian Phosphoria Formation (Idaho, Montana, Utah, Wyoming), Mississippian Chainman Shale (Nevada and Utah), Mississippian Heath Formation (Montana), Mississippian Doughnut Formation (Utah), Devonian Woodruff Formation (Nevada), and Ordovician Vinini Formation (Nevada). The semiquantitative method consistently underestimates the concentration of the five metals studied by a factor of 1.7 to 2.7 and, thus, cannot be considered reliable for determining the concentration of metals in these rocks if the reported semiquantitative values exceed about 100 ppm. It is noteworthy that the most comprehensive analytical and statistical studies of metal concentrations in black shales of the United States have used the semiquantitative six-step optical-emission method of analysis.

Idaho, Montana, Nevada, Utah, Wyoming↗
USGS1979

Metals in Devonian kerogenous marine strata at Gibellini and Bisoni properties in southern Fish Creek Range, Eureka County, Nevada

A kerogen-rich sequence of siliceous mudstone, siltstone, and chert as much as 60 m thick on ridge 7129 in the southern Fish Creek Range, referred to as Gibellini facies of the Woodruff Formation, has been evaluated on the surface and in drill holes principally for its potential resources of vanadium, zinc, selenium, molybdenum, and syncrude oil content. The strata are part of a strongly deformed allochthonous mass of eugeosynclinal Devonian marine rocks that overlie deformed allochthonous Mississippian siliceous rocks and relatively undeformed autochthonous Mississippian Antler flysch at this locality. The vanadium in fresh black rocks obtained from drill holes and fresh exposures in trenches and roadcuts occurs chiefly in organic matter. Concentrations of vanadium oxide (V2O5) in unoxidized samples range from 3,000 to 7,000 ppm. In oxidized and bleached rock that is prevalent at the surface, concentrations of vanadium oxide range from 6,000 to 8,000 ppm, suggesting a tendency toward enrichment due to surficial weathering and ground-water movement. Zinc occurs in sphalerite, and selenium occurs in organic matter; molybdenum appears to occur both in molybdenite and in organic matter. Concentrations of zinc in unoxidized rock range from 4,000 to 18,000 ppm, whereas in oxidized rock they range from 30 to 100 ppm, showing strong depletion due to weathering. Concentrations of selenium in unoxidized rock range from 30 to 200 ppm, whereas in oxidized rock they range from 200 to 400 ppm, indicating some enrichment upon weathering. Concentrations of molybdenum in unoxidized rock range from 70 to 960 ppm, whereas in oxidized rock they range from 30 to 80 ppm, indicating strong depletion upon weathering. Most fresh black rock is low-grade oil shale, and yields as much as 12 gallons/short ton of syncrude oil. Metahewettite is the principal vanadium mineral in the oxidized zone, but it also occurs sparsely as small nodules and fillings of microfractures in unweathered strata. In fresh rock, bluish-white opaline-like silica (chalcedonic quartz) fills microfractures, and is believed to have originated by diagenetic mobilization of opaline silica from radiolarian tests and sponge spicules. As revealed by microscopic study, the Gibellini facies originally consisted of siliceous muds, slimes, and oozes high in organic constituents. The organic matter is amorphous flaky and stringy sapropel, and probably includes remains of bacteria, phytoplankton, zooplankton, and minor higher plants. Recognizable organic remnants include radiolarian tests, sponge spicules, conodonts, brachiopod shells, algae, and humic debris. Diagnostic radiolarians indicate a Late Devonian age for the Gibellini facies of the Woodruff Formation. Some pyrite is disseminated through the rock and may be primary (syngenetic) but significant pyrite and marcasite occur in chalcedonic quartz veinlets and appear to be diagenetic. In fresh rock, black solid bitumen and liquid oil fill voids and microfractures. These early phase hydrocarbons probably were released during diagenesis from complex nonhydrocarbon molecular structures originating from living organisms, and formed without any major thermal degradation of the kerogen. Gas chromatographic analysis of the saturated hydrocarbon fraction indicates a very complex mixture dominated by branched and cyclic compounds. Conodont and palynomorph color alteration, vitrinite reflectance, and other organic geochemical data suggest that the organic matter in the rock is thermally immature and has not been subjected to temperatures greater than 60?C since deposition in Devonian time. All of these characteristics are consistent with the interpretation of a relatively low temperature and a shallow-burial history for the Gibellini facies on ridge 7129.

Open-File Report↗
USGS1978

Stable isotope studies of bedded barite at East Northumberland Canyon in Toquima Range, central Nevada

Several beds of barite occur in the Slaven Chert at East Northumberland Canyon in the Toquima Range of central Nevada. Most of the barite is internally laminated but shows massive weathering. However, rosette, disseminated, conglomeratic, and concretionary varieties also occur. New fossil evidence from conodonts and brachiopods indicates a Late Devonian age for the Slaven Chert at East Northumberland Canyon. Preliminary δ 34 S values of most disseminated and massive-laminated barite within the Slaven Chert average about 25 permil; these are within the range of values that is typical of sulfate from Late Devonian seawater and are distinctly different from δ 34 S values of most crosscutting hydrothermal barite veins in the area. Primary δ 34 S values of the bedded barite appear to be retained during recrystallization and hydrothermal alteration, suggesting that δ 34 S data of bedded barites could be developed into a useful stratigraphic tool. The δ 34 S values of rosette and concrectionary barites range from 29.1 to 56.3 permil and indicate that these varieties of barite formed in restricted microenvironments where extensive bacterial reduction of seawater sulfate occurred. The δ 18 O data on cherts associated with the barite beds and δ 14 C and δ 18 O data on carbonate beds within the Slaven Chert indicate that the depositional environment at tames had restricted communication with normal seawater of the open ocean.

Nevada↗
USGS1968

Summary of regional evidence for right-lateral displacement in the western Great Basin

Right-lateral displacement of 80 to 120 miles across the western Great Basin is indicated by the consistent disruption of sedimentary facies and thickness trends of formations ranging in age from late Precambrian to Mesozoic. Some of this displacement occurs as fault slip and some as a more pervasive large-scale drag (oroflexural bending).

California, Nevada↗
USGS1967

Bedded barite in East Northumberland Canyon, Nye County, Nevada

Bedded barite has been identified in the course of stratigraphic studies by the U.S. Geological Survey in and near East Northumberland Canyon, Toquima Range, Nye County, Nev. The barite beds are interlayered in black chert of probable Ordovician age. The barite rock is mostly dark gray and massive, has a specific gravity averaging about 4.0, and contains, by chemical analysis, 70.7 to 93.9 percent BaSO4.

Circular↗
USGS1967

Devonian of the Southwestern United States

The structural framework that controlled Devonian deposition consisted of, from west to east: (1) a eugeosynclinal area in northern California and western Nevada; (2) a miogeosynclinal area in southeastern California, eastern Nevada, and western Utah; and (3) a cratonic area in Arizona, eastern Utah, Colorado, New Mexico, and western Texas, east of a northeast-trending hinge line (Wasatch line). The eugeosyncline contains a fragmentary record of Middle Devonian rocks at least 4,000 feet thick characterized by thin-bedded chert, siliceous mudstone, and some limestone and volcanic rocks. The original thickness, however, probably exceeded 6,000 feet and probably included Lower and Upper Devonian rocks. The miogeosyncline contains Lower, Middle, and Upper Devonian rocks as much as 6,000 feet thick characterized by thick units of dolomite and limestone and some local interbeds of sandstone. A transitional zone perhaps 50 miles wide separates the eugeosynclinal and miogeosynclinal facies. The craton contains mostly Upper Devonian rocks, generally less than 1,000 feet thick, characterized by dolomite and limestone and local interbeds of sandstone and mudstone. Widespread crustal movements occurred during Late Devonian time. The Antler orogeny in Nevada initiated a culm facies in the geosyncline. Eugeosynclinal and transitional rocks including those of Devonian age were uplifted to form the Antler orogenic belt, and then were thrust eastward over autochthonous miogeosynclinal rocks in latest Devonian or earliest Mississippian time. Folding and faulting, and subsequent erosion on local uplifts, produced clastic deposits of Late Devonian age in Utah and southwestern Colorado. Devonian rocks in many parts of the geosynclinal area have been moved since Devonian time by large-scale, generally eastward thrusting, oroflexural bending and strike-slip faulting. Four major subdivisions of the Devonian System and related rocks are treated separately: 1) Lower Devonian (Gedinnian, Siegenian, Emsian) and related Upper Silurian (Ludlovian) rocks. 2) Middle Devonian (Eifelian and Givetian) rocks. 3) Lower Upper Devonian (Frasnian, to I ) rocks. 4) Upper Upper Devonian (Famennian, to II-VI ) and related lowermost Mississippian (Tournaisian, cu I ) rocks.

Conference Paper↗