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At least 937 records · Page 52Linked to original sources
USGS2010

Factors influencing reporting and harvest probabilities in North American geese

We assessed variation in reporting probabilities of standard bands among species, populations, harvest locations, and size classes of North American geese to enable estimation of unbiased harvest probabilities. We included reward (US10,20,30,50, or100) and control (0) banded geese from 16 recognized goose populations of 4 species: Canada (Branta canadensis), cackling (B. hutchinsii), Ross's (Chen rossii), and snow geese (C. caerulescens). We incorporated spatially explicit direct recoveries and live recaptures into a multinomial model to estimate reporting, harvest, and band-retention probabilities. We compared various models for estimating harvest probabilities at country (United States vs. Canada), flyway (5 administrative regions), and harvest area (i.e., flyways divided into northern and southern sections) scales. Mean reporting probability of standard bands was 0.73 (95 CI 0.690.77). Point estimates of reporting probabilities for goose populations or spatial units varied from 0.52 to 0.93, but confidence intervals for individual estimates overlapped and model selection indicated that models with species, population, or spatial effects were less parsimonious than those without these effects. Our estimates were similar to recently reported estimates for mallards (Anas platyrhynchos). We provide current harvest probability estimates for these populations using our direct measures of reporting probability, improving the accuracy of previous estimates obtained from recovery probabilities alone. Goose managers and researchers throughout North America can use our reporting probabilities to correct recovery probabilities estimated from standard banding operations for deriving spatially explicit harvest probabilities.

Journal of Wildlife Management↗
USGS1997

Potential for new nickel-copper sulfide deposits in the Lake Superior region

Scientists from the U.S. Geological Survey are evaluating the potential for undiscovered sulfide deposits containing varying amounts of nickel, copper, platinum-group metals, and cobalt in the Lake Superior region as part of an ongoing effort to assess the mineral potential of the United States. Similarities between rocks of the Midcontinent rift and rocks that host the Voisey Bay nickel-copper-cobalt deposit in Labrador, Canada, and the Noril'sk nickel-copper-platinum-group-metals deposits in Russia suggest a high potential for such sulfide deposits in rocks associated with the 1.1-billion-year-old Midcontinent rift in the Lake Superior region.

Lake Superior↗
USGS2003

Petroleum geology and resources of the West Siberian Basin, Russia

The West Siberian basin is the largest petroleum basin in the world covering an area of about 2.2 million km2. The basin occupies a swampy plain between the Ural Mountains and the Yenisey River. On the north, the basin extends offshore into the southern Kara Sea. On the west, north, and east, the basin is surrounded by the Ural, Yenisey Ridge, and Turukhan-Igarka foldbelts that experienced major deformations during the Hercynian tectonic event and the Novaya Zemlya foldbelt that was deformed in early Cimmerian (Triassic) time. On the south, the folded Caledonian structures of the Central Kazakhstan and Altay-Sayan regions dip northward beneath the basin?s sedimentary cover. The basin is a relatively undeformed Mesozoic sag that overlies the Hercynian accreted terrane and the Early Triassic rift system. The basement is composed of foldbelts that were deformed in Late Carboniferous?Permian time during collision of the Siberian and Kazakhstan continents with the Russian craton. The basement also includes several microcontinental blocks with a relatively undeformed Paleozoic sedimentary sequence. The sedimentary succession of the basin is composed of Middle Triassic through Tertiary clastic rocks. The lower part of this succession is present only in the northern part of the basin; southward, progressively younger strata onlap the basement, so that in the southern areas the basement is overlain by Toarcian and younger rocks. The important stage in tectono-stratigraphic development of the basin was formation of a deep-water sea in Volgian?early Berriasian time. The sea covered more than one million km2 in the central basin area. Highly organic-rich siliceous shales of the Bazhenov Formation were deposited during this time in anoxic conditions on the sea bottom. Rocks of this formation have generated more than 80 percent of West Siberian oil reserves and probably a substantial part of its gas reserves. The deep-water basin was filled by prograding clastic clinoforms during Neocomian time. The clastic material was transported by a system of rivers dominantly from the eastern provenance. Sandstones within the Neocomian clinoforms contain the principal oil reservoirs. The thick continental Aptian?Cenomanian Pokur Formation above the Neocomian sequence contains giant gas reserves in the northern part of the basin. Three total petroleum systems are identified in the West Siberian basin. Volumes of discovered hydrocarbons in these systems are 144 billion barrels of oil and more than 1,300 trillion cubic feet of gas. The assessed mean undiscovered resources are 55.2 billion barrels of oil, 642.9 trillion cubic feet of gas, and 20.5 billion barrels of natural gas liquids. The largest known oil reserves are in the Bazhenov-Neocomian total petroleum system that includes Upper Jurassic and younger rocks of the central and southern parts of the basin. Oil reservoirs are mainly in Neocomian and Upper Jurassic clastic strata. Source rocks are organic-rich siliceous shales of the Bazhenov Formation. Most discovered reserves are in structural traps, but stratigraphic traps in the Neocomian clinoform sequence are pro-ductive and are expected to contain much of the undiscovered resources. Two assessment units are identified in this total petroleum system. The first assessment unit includes all conventional reservoirs in the stratigraphic interval from the Upper Jurassic to the Cenomanian. The second unit includes unconventional (or continuous), self-sourced, fractured reservoirs in the Bazhenov Formation. This unit was not assessed quantitatively. The Togur-Tyumen total petroleum system covers the same geographic area as the Bazhenov-Neocomian system, but it includes older, Lower?Middle Jurassic strata and weathered rocks at the top of the pre-Jurassic sequence. A Callovian regional shale seal of the Abalak and lower Vasyugan Formations separates the two systems. The Togur-Tyumen system is oil-prone; gas reserves are insignificant. The principal o

Bulletin↗
USGS2012

Mercury bioaccumulation studies in the National Water-Quality Assessment Program--biological data from New York and South Carolina, 2005-2009

The U.S. Geological Survey National Water-Quality Assessment Program conducted a multidisciplinary study from 2005–09 to investigate the bioaccumulation of mercury in streams from two contrasting environmental settings. Study areas were located in the central Adirondack Mountains region of New York and the Inner Coastal Plain of South Carolina. Fish, macroinvertebrates, periphyton (attached algae and associated material), detritus, and terrestrial leaf litter were collected. Fish were analyzed for total mercury; macroinvertebrates, periphyton, and terrestrial leaf litter were analyzed for total mercury and methylmercury; and select samples of fish, macroinvertebrates, periphyton, detritus, and terrestrial leaf litter were analyzed for stable isotopes of carbon (δ13C) and nitrogen (δ15N). This report presents methodology and data on total mercury, methylmercury, stable isotopes, and other ecologically relevant measurements in biological tissues.

New York, South Carolina↗
USGS1978

Geology of the Arco-Big Southern Butte area, eastern Snake River Plain, and potential volcanic hazards to the radioactive waste management complex, and other waste storage and reactor facilities at the Idaho National Engineering Laboratory, Idaho

The Arco-Big Southern Butte area of the eastern Snake River Plain, Idaho, includes a volcanic rift zone and more than 70 Holocene and late Quaternary basalt volcanoes. The Arco volcanic rift zone extends southeast for 50 km from Arco to about 10 km southeast of Big Southern Butte. The rift zone is the locus of extensional faults, graben, fissure basaltic volcanic vents, several rhyolite domes at Big Southern Butte, and a ferrolatite volcano at Cedar Butte. Limited radiometric age data and geological field criteria suggest that all volcanism in the area is younger than 700,000 years; at least 67 separate basaltic eruptions are estimated to have occurred within the last 200,000 years. The average volcanic recurrence interval for the Arco-Big Southern Butte area is approximately one eruption per 3,000 years. Radioactive waste storage and reactor facilities at the Idaho National Engineering Laboratory may be subject to potential volcanic hazards. The geologic history and inferred past volcanic events in the Arco-Big Southern Butte area provide a basis for assessing the volcanic hazard. It is recommended that a radiometric age-dating study be performed on rocks in cored drill holes to provide a more precise estimate of the eruption recurrence interval for the region surrounding and including the Radioactive Waste Management Complex. It is also recommended that several geophysical monitoring systems (dry tilt and seismic) be installed to provide adequate warning of future volcanic eruptions.

Idaho↗
USGS1994

A search for paleoliquefaction and evidence bearing on the recurrence behavior of the great 1811-12 New Madrid earthquakes

In the winter of 1811-12, three of the largest historic earthquakes in the United States occurred near New Madrid, Missouri. Seismicity continues to the present day throughout a tightly clustered pattern of epicenters centered on the bootheel of Missouri, including parts of northeastern Arkansas, northwestern Tennessee, western Kentucky, and southern Illinois. In 1990, the New Madrid seismic zone/central United States became the first seismically active region east of the Rocky Mountains to be designated a priority research area within the National Earthquake Hazards Reduction Program (NEHRP). This professional paper is a collection of papers, some published separately, presenting results of the newly intensified research program in this area. Major components of this research program include tectonic framework studies, seismicity and deformation monitoring and modeling, improved seismic hazard and risk assessments, and cooperative hazard mitigation studies.

Professional Paper↗
USGS2021

Vulnerability assessment and adaptation planning for projected changes in water quality and quantity for protected areas in the upper Midwest

Climate change and the extreme weather associated with it can be a major challenge to natural resource managers charged with the protection, restoration, recovery, and management of wetlands and wildlife habitats. Forecasting the potential impacts of climate changes will be important for decision-makers and land managers seeking to minimize impacts to habitats, infrastructure, and wildlife populations and prepare for the future. In collaboration with U.S. Fish and Wildlife Service (FWS) managers, we developed a climate change vulnerability assessment to spatially evaluate climate vulnerabilities across the Midwest region. To create the vulnerability assessment, we convened resource managers and scientists working across the region to determine the components and scope of the vulnerability assessment. The vulnerability assessment was watershed-based and composed of 15 indicators of climate change and five indicators that reflect the capacity of a watershed to buffer against the effects of climate change. The indicators were selected by FWS managers to have broad applicability across systems and programs in the FWS. To facilitate usability, we created an online application that allows users to generate customizable vulnerability assessments. We then integrated the assessment into a process for engaging in climate change adaptation thinking as a precursor to formal planning, implementation, and monitoring of adaptation actions. The process we designed focused on understanding the components of the system, assessing climate change vulnerabilities, creating and describing possible climate change scenarios, and identifying impacts and adaptation options for each scenario. We piloted this process in a virtual workshop setting with FWS managers and biologists on the topic of managed wetland systems. This work is currently being used by the FWS to better understand regional vulnerabilities and adaptation strategies and to advance integration of climate science into formal planning processes.

Illinois, Indiana, Iowa, Michigan, Minnesota, Miss↗
USGS2017

A physics-based earthquake simulator and its application to seismic hazard assessment in Calabria (Southern Italy) region

The use of a newly developed earthquake simulator has allowed the production of catalogs lasting 100 kyr and containing more than 100,000 events of magnitudes ≥4.5. The model of the fault system upon which we applied the simulator code was obtained from the DISS 3.2.0 database, selecting all the faults that are recognized on the Calabria region, for a total of 22 fault segments. The application of our simulation algorithm provides typical features in time, space and magnitude behavior of the seismicity, which can be compared with those of the real observations. The results of the physics-based simulator algorithm were compared with those obtained by an alternative method using a slip-rate balanced technique. Finally, as an example of a possible use of synthetic catalogs, an attenuation law has been applied to all the events reported in the synthetic catalog for the production of maps showing the exceedance probability of given values of PGA on the territory under investigation.

Calabria region↗
USGS2011

Geologic map of Big Bend National Park, Texas

The purpose of this map is to provide the National Park Service and the public with an updated digital geologic map of Big Bend National Park (BBNP). The geologic map report of Maxwell and others (1967) provides a fully comprehensive account of the important volcanic, structural, geomorphological, and paleontological features that define BBNP. However, the map is on a geographically distorted planimetric base and lacks topography, which has caused difficulty in conducting GIS-based data analyses and georeferencing the many geologic features investigated and depicted on the map. In addition, the map is outdated, excluding significant data from numerous studies that have been carried out since its publication more than 40 years ago. This report includes a modern digital geologic map that can be utilized with standard GIS applications to aid BBNP researchers in geologic data analysis, natural resource and ecosystem management, monitoring, assessment, inventory activities, and educational and recreational uses. The digital map incorporates new data, many revisions, and greater detail than the original map. Although some geologic issues remain unresolved for BBNP, the updated map serves as a foundation for addressing those issues. Funding for the Big Bend National Park geologic map was provided by the United States Geological Survey (USGS) National Cooperative Geologic Mapping Program and the National Park Service. The Big Bend mapping project was administered by staff in the USGS Geology and Environmental Change Science Center, Denver, Colo. Members of the USGS Mineral and Environmental Resources Science Center completed investigations in parallel with the geologic mapping project. Results of these investigations addressed some significant current issues in BBNP and the U.S.-Mexico border region, including contaminants and human health, ecosystems, and water resources. Funding for the high-resolution aeromagnetic survey in BBNP, and associated data analyses and interpretation, was from the USGS Crustal Geophysics and Geochemistry Science Center. Mapping contributed from university professors and students was mostly funded by independent sources, including academic institutions, private industry, and other agencies.

Texas↗
USGS2010

Proceedings of the 25th Himalaya-Karakoram-Tibet Workshop

For a quarter of a century the Himalayan-Karakoram-Tibet (HKT) Workshop has provided scientists studying the India-Asia collision system a wonderful opportunity for workshop-style discussion with colleagues working in this region. In 2010, HKT returns to North America for the first time since 1996. The 25th international workshop is held from June 7 to10 at San Francisco State University, California. The international community was invited to contribute scientific papers to the workshop, on all aspects of geoscience research in the geographic area of the Tibetan Plateau and its bounding ranges and basins, from basic mapping to geochemical and isotopic analyses to large-scale geophysical imaging experiments. In recognition of the involvement of U.S. Geological Survey (USGS) scientists in a wide range of these activities, the USGS agreed to publish the extended abstracts of the numerous components of HKT-25 as an online Open-File Report, thereby ensuring the wide availability and distribution of these abstracts, particularly in the HKT countries from which many active workers are precluded by cost from attending international meetings. In addition to the workshop characterized by contributed presentations, participants were invited to attend a pre-meeting field trip from the Coast Ranges to the Sierra Nevada, to allow the international group to consider how the tectonic elements of the Pacific margin compare to those of the Himalayan belt. Following the workshop, the National Science Foundation (NSF) sponsored a workshop on the 'Future directions for NSF-sponsored geoscience research in the Himalaya/Tibet' intended to provide NSF Program Directors with a clear statement and vision of community goals for the future, including the scientific progress we can expect if NSF continues its support of projects in this geographic region, and to identify which key geoscience problems and processes are best addressed in the Himalaya and Tibet, what key datasets are needed, and how NSF can best support the evolving need for interdisciplinary investigations. This workshop also has clear societal relevance. Recent earthquakes have brought international attention to active tectonics and earthquake hazards in the HKT region. Prominent examples include the Mw 7.8 Kokoxili (Qinghai, China) earthquake of 2001, the Mw 7.6 Kashmir (Pakistan) earthquake of 2005, the Mw 7.9 Wenchuan (Sichuan, China) earthquake of 2008, and this year the Mw 6.9 Yushu (Qinghai, China) earthquake. Geological and geophysical field work conducted both before these earthquakes, as well as in response to them, has helped to define the active faults and regional tectonics in the HKT region. The research presented at this workshop provides the framework necessary for improved seismic hazard assessments in this region. The organizers gratefully acknowledge the support of NSF's Continental Dynamics Program and its Office of International Science and Engineering, through award EAR-0965796. We thank San Francisco State University's Sheldon Axler, Dean of the College of Science and Engineering, and Toby Garfield, Director of the Romberg Tiburon Center, for use of their conference facilities; and the Department of Geosciences, particularly Deb Shulman and Miriam Knof, for administrative support. The California Academy of Sciences generously hosted a reception for visiting delegates, and Brad Ritts (Chevron Exploration Technology Company), Todd Greene (California State University, Chico) and John Shervais (Utah State University) together co-led the pre-conference field trip. Technical editing of this volume was led by Roxanne Renedo (U.S. Geological Survey) with assistance from Margaret Milia (Stanford University). We are grateful to the U.S. Geological Survey (USGS) Earthquake Hazards Program and the USGS Menlo Park (California) Publishing Service Center for making this online report possible.

Open-File Report↗
USGS2020

Causes of land change in the U.S. Interior Highlands, 2001–2011

The causes of land change from 2001 through 2011 for the Interior Highlands region of the south-central United States were assessed using satellite imagery, historical land-use and land-cover data, and digital orthophotos. The study was designed to develop improved regional land-use and land-cover change information, including identification of the proximate causes of change. The four leading causes of land change involved various stages of forest change: harvest (376,497 hectares), reforestation (105,150 hectares), stand loss to fire (98,875 hectares), and thinning (54,029 hectares). The study provides baseline spatial data for understanding human and ecological dynamics in the region. The spatial data, including metadata, are available in the data release associated with this report at https://doi.org/10.5066/P9W4SF05.

Missouri, Arkansas, Oklahoma, Kansas↗
USGS1998

Monitoring the water quality of the Nation's large rivers: Rio Grande NASQAN Program

The U.S. Geological Survey (USGS) has monitored the water quality in the Rio Grande Basin as part of the redesigned National Stream Quality Accounting Network (NASQAN) since 1995 (Hooper and others, 1997). The NASQAN program was designed to characterize the concentrations and transport of sediment and selected chemical constituents found in the Nation's large rivers-including the Mississippi, Colorado, and Columbia in addition to the Rio Grande. In these four basins, the USGS currently (1998) operates a network of 40 NASQAN sites, with an emphasis on quantifying the mass flux for each constituent (the amount of material moving past the site, expressed in tons per day). By applying a consistent flux-based approach in the Rio Grande Basin, the NASQAN program is generating the information needed to identify regional sources for a variety of constituents, including agricultural chemicals and trace elements, in the basin. The effect of the large reservoirs on the Rio Grande can be observed as constituent fluxes are routed downstream. The analysis of constituent fluxes on a basin-wide scale will provide the means to assess the influence of human activity on water-quality conditions in the Rio Grande.

Colorado, New Mexico, Texas↗
USGS1986

Geochemical maps showing distribution and abundance of bismuth and beryllium in the nonmagnetic fraction of stream-sediment concentrates, Silver City 1 degree by 2 degrees Quadrangle, New Mexico and Arizona

These maps (Maps A and B) show the distribution and abundance of bismuth and beryllium in the nonmagnetic fraction of heavy-mineral concentrates from stream sediments collected in the Silver City 1 o x 2 o quadrangle, New Mexico and Arizona. Geochemical maps showing the distribution and abundance of nine other selected key elements and the mineral flourite in the Silver City quadrangle are also part of this folio (Watts and Hassemer, 1980; Watts and others 1986a-i). These maps contribute to the assessment of mineral resources within Silver City 1 o x 2 o quadrangle by (1) showing regional patterns of elements enriched in heavy-mineral concentrates, thereby providing clues to regional patterns of mineralization; (2) showing new areas containing enriched metals, not previously known from mining activity; and (3) providing supportive data to the interpretive and summary maps (Watts and Hassmer, 1986) and the mineral resource assessment (Richter and others, 1983). Background information that pertains to published components of the Silver City Folio is also available (Richter and others, in press).

Arizona, New Mexico↗
USGS1986

Geochemical maps showing distribution and abundance of tin in two fractions of stream-sediment concentrates, Silver City 1 degree by 2 degrees Quadrangle, New Mexico and Arizona

These maps (Maps A and B) show the distribution and abundance tin in the nonmagnetic and magnetic fractions of heavy-mineral concentrates from stream sediments collected in the Silver City 1 o x 2 o quadrangle, New Mexico and Arizona. Geochemical maps showing the distribution and abundance of 10 other selected key elements and the mineral fluorite in the Silver City quadrangle are also part of this folio (Watts and Hassemer, 1980; Watts and others 1986a-i). These maps contribute to the assessment of mineral resources within Silver City 1 o x 2 o quadrangle by (1) showing regional patterns of elements enriched in heavy-mineral concentrates, thereby providing clues to regional patterns of mineralization; (2) showing new areas containing enriched metals, not previously known from mining activity; and (3) providing supportive data to the interpretive and summary maps (Watts and Hassmer, 1986) and the mineral resource assessment (Richter and others, 1983). Background information that pertains to published components of the Silver City Folio is also available (Richter and others, in press).

Arizona, New Mexico↗
USGS1986

Geochemical maps showing distribution and abundance of manganese in two fractions of stream-sediment concentrates, Silver City 1 degree by 2 degrees Quadrangle, New Mexico and Arizona

These maps (Maps A and B) show the distribution and abundance of maganese in the nonmagnetic and magnetic fractions of heavy-mineral concentrates from stream sediments collected in the Silver City 1 o x 2 o quadrangle, New Mexico and Arizona. Geochemical maps showing the distribution and abundance of 10 other selected key elements and the mineral fluorite in the Silver City quadrangle are also part of this folio (Watts and Hassemer, 1980; Watts and others 1986a-i). These maps contribute to the assessment of mineral resources within Silver City 1 o x 2 o quadrangle by (1) showing regional patterns of elements enriched in heavy-mineral concentrates, thereby providing clues to regional patterns of mineralization; (2) showing new areas containing enriched metals, not previously known from mining activity; and (3) providing supportive data to the interpretive and summary maps (Watts and Hassmer, 1986) and the mineral resource assessment (Richter and others, 1983). Background information that pertains to published components of the Silver City Folio is also available (Richter and others, in press).

Arizona, New Mexico↗
USGS1986

Geochemical maps showing distribution and abundance of barium in two fractions of stream-sediment concentrates, Silver City 1 degree by 2 degrees Quadrangle, New Mexico and Arizona

These maps (Maps A and B) show the distribution and abundance barium in the nonmagnetic and magnetic fractions of heavy-mineral concentrates from stream sediments collected in the Silver City 1 o x 2 o quadrangle, New Mexico and Arizona. Geochemical maps showing the distribution and abundance of 10 other selected key elements and the mineral fluorite in the Silver City quadrangle are also part of this folio (Watts and Hassemer, 1980; Watts and others 1986a-i). These maps contribute to the assessment of mineral resources within Silver City 1 o x 2 o quadrangle by (1) showing regional patterns of elements enriched in heavy-mineral concentrates, thereby providing clues to regional patterns of mineralization; (2) showing new areas containing enriched metals, not previously known from mining activity; and (3) providing supportive data to the interpretive and summary maps (Watts and Hassmer, 1986) and the mineral resource assessment (Richter and others, 1983). Background information that pertains to published components of the Silver City Folio is also available (Richter and others, in press).

Arizona, New Mexico↗
USGS1990

Map showing distribution of cadmium and antimony in the nonmagnetic fraction of heavy-mineral concentrates, Richfield 1° x 2° quadrangle, Utah

This map of the Richfield 1° x 2° quadrangle, Utah, shows the regional distribution of cadmium and antimony in the nonmagnetic fraction of drainage-sediment samples. It is part of a folio of maps of the Richfield 1° x 2° quadrangle, Utah, prepared under the Conterminuous United States Mineral Assessment Program. Other published geochemical maps in this folio are listed in the references (this publication). The Richfield quadrangle is located in west-central Utah and includes the eastern part of the Pioche-Marysvale igneous and mineral belt, which extends from the vicinity of Pioche in southeastern Nevada, east-northeastward for 155 miles into central Utah. The western two-thirds of the Richfield quadrangle is part of the Basin and Range province, whereas the eastern third is part of the High Plateaus of Utah, a subprovince of the Colorado Plateau. Bedrock in the northern part of the Richfield quadrangle consists predominantly of Late Proterozoic and Paleozoic sedimentary strata that were thrust eastward during the Sevier orogeny in Cretaceous time onto an autochthon of Mesozoic sedimentary rocks located in the eastern part of the quadrangle. The southern part of the quadrangle is largely underlain by Oligocene and younger volcanic rocks and related intrusions. Extensional tectonism in late Cenozoic time broke the bedrock terrain into a series of north-trending fault blocks; the uplifted mountain areas were eroded to various degrees and the resulting debris was deposited in adjacent basins. Most of the mineral deposits in the Pioche-Marysvale mineral belt were formed as a result of igneous activity in the middle and late Cenozoic time. A more complete description of the geology and a mineral-resource appraisal of the Richfield quadrangle appears in Steven and Morris (1984 and 1987). The regional sampling program was designed to define broad geochemical patterns and trends that can be utilized along with geological and geophysical data to assess the mineral-resource potential for this quadrangle. Reconnaissance geochemical surveys are valuable tools in mineral exploration, especially when used in conjunction with data obtained from other earth science disciplines. Identifying specific exploration targets generally involves additional, more detailed investigations.

Utah↗
USGS1990

Map showing distribution of silver in the nonmagnetic fraction of heavy-mineral concentrates, Richfield 1° x 2° quadrangle, Utah

This map of the Richfield 1° x 2° quadrangle, Utah, shows the regional distribution of silver in the nonmagnetic fraction of heavy-mineral concentrates of drainage-sediment samples. It is part of a folio of maps of the Richfield 1° x 2° quadrangle, Utah, prepared under the Conterminuous United States Mineral Assessment Program. Other published geochemical maps in this folio are listed in the references (this publication). The Richfield quadrangle is located in west-central Utah and includes the eastern part of the Pioche-Marysvale igneous and mineral belt, which extends from the vicinity of Pioche in southeastern Nevada, east-northeastward for 155 miles into central Utah. The western two-thirds of the Richfield quadrangle is part of the Basin and Range province, whereas the eastern third is part of the High Plateaus of Utah, a subprovince of the Colorado Plateau. Bedrock in the northern part of the Richfield quadrangle consists predominantly of Late Proterozoic and Paleozoic sedimentary strata that were thrust eastward during the Sevier orogeny in Cretaceous time onto an autochthon of Mesozoic sedimentary rocks located in the eastern part of the quadrangle. The southern part of the quadrangle is largely underlain by Oligocene and younger volcanic rocks and related intrusions. Extensional tectonism in late Cenozoic time broke the bedrock terrain into a series of north-trending fault blocks; the uplifted mountain areas were eroded to various degrees and the resulting debris was deposited in adjacent basins. Most of the mineral deposits in the Pioche-Marysvale mineral belt were formed as a result of igneous activity in the middle and late Cenozoic time. A more complete description of the geology and a mineral-resource appraisal of the Richfield quadrangle appears in Steven and Morris (1984 and 1987). The regional sampling program was designed to define broad geochemical patterns and trends that can be utilized along with geological and geophysical data to assess the mineral-resource potential for this quadrangle. Reconnaissance geochemical surveys are valuable tools in mineral exploration, especially when used in conjunction with data obtained from other earth science disciplines. Identifying specific exploration targets generally involves additional, more detailed investigations.

Utah↗