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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 667 records · Page 37Linked to original sources
USGS1997

Deep structure of Medicine Lake volcano, California

Medicine Lake volcano (MLV) in northeastern California is the largest-volume volcano in the Cascade Range. The upper-crustal structure of this Quaternary shield volcano is well known from previous geological and geophysical investigations. In 1981, the U.S. Geological Survey conducted a teleseismic tomography experiment on MLV to explore its deeper structure. The images we present, calculated using a modern form of the ACH-inversion method, reveal that there is presently no hint of a large (> 100 km 3 ), hot magma reservoir in the crust. The compressional-wave velocity perturbations show that directly beneath MLV's caldera there is a zone of increased seismic velocity. The perturbation amplitude is +10% in the upper crust, +5% in the lower crust, and +3% in the lithospheric mantle. This positive seismic velocity anomaly presumably is caused by mostly subsolidus gabbroic intrusive rocks in the crust. Heat and melt removal are suggested as the cause in the upper mantle beneath MLV, inferred from petro-physical modeling. The increased seismic velocity appears to be nearly continuous to 120 km depth and is a hint that the original melts come at least partly from the lower lithospheric mantle. Our second major finding is that the upper mantle southeast of MLV is characterized by relatively slow seismic velocities (−1%) compared to the northwest side. This anomaly is interpreted to result from the elevated temperatures under the northwest Basin and Range Province.

California↗
USGS1983

Mineral resource potential map of the Blanco Mountain and Black Canyon Roadless Areas, Inyo and Mono Counties, California

On the basis of geologic, geochemical, and geophysical investigations and a survey of mines and prospects, the mineral resource potential for gold, silver, lead, zinc, tungsten, and barite of the Blanco Mountain and Black Canyon Roadless Areas is judged to be low to moderate, except for one local area that has high potential for gold and tungsten resources. A geochemical survey detected moderately anomalous amounts of lead, copper, and zinc and less anomalous concentrations of tungsten, gold, and silver. Elements in anomalous samples were grouped as suites known to form in various ore deposits. Four element suites that may be indicative of mineralization are recognized in the White Mountains: (1) lead, zinc, and silver in carbonate rocks; (2) copper, barite, and lead in veins and replacement bodies; (3) tungsten, molybdenum, and bismuth in skarns; and (4) gold and arsenic in mineralized quartz veins. The assessment of the areas of resource potential was made in part by the application of ore deposit models to the geochemical results. A mineral deposit survey by the U.S. Bureau of Mines indicates that there are no properties with identified mineral resources in the Blanco Mountain Roadless Area. There is one active placer claim. In the Black Canyon Roadless Area, two properties have 40,000 tons of indicated and inferred low-grade gold, silver, or lead-bearing rock. Five properties near this roadless area have 150,000 tons of indicated and inferred low-grade gold, silver, lead, zinc, or tungsten-bearing rock. About 90 percent of this tonnage is estimated to occur at the Mirage-Mariposa and the Hope mines. The roadless areas have no known resource potential for geothermal energy, coal, oil, or gas.

California↗
USGS1982

Mineral resources potential map of the Lost Cove and Harper Creek Roadless Areas, Avery and Caldwell counties, North Carolina

A geologic, geophysical, and geochemical investigation and a survey of mines, quarries, and prospects have been conducted to evaluate the mineral resource potential of the Lost Cove and Harper Creek Roadless Areas, Avery and Caldwell Counties, North Carolina. The study area lies within the Blue Ridge physiographic province and is predominatly underlain by Precambrian age plutonic and metasedimentary rocks of low metamorphic grade. All surface and mineral rights are Federally owned. Permit areas for uranium prospecting cover about 85 percent of the area. Uranium-rich rock in the Lost Cove and Harper Creek Roadless Areas occurs widely in the Wilson Creek Gneiss and to a minor extent in the Grandfather Mountain Formation. Vein-type deposits and other occurrences of uranium in foliated rocks in the Wilson Creek Gneiss have uranium resource potential. Speculative resources of uranium in vein-type deposits and in supergene-enriched foliated rocks are estimated to total 4 to 8 million pounds of U 3 O 8 . Mineral resources having low to moderate potential are gold and minerals of thorium, beryllium, niobium, and copper. Stone has a low economic potential; lead, molybdenum, and titanium have low resource potential. These conclusions are based on results of prospect examination, radiometric survey, geochemical survey of stream sediments, saprolite, and bedrock.

North Carolina↗
USGS1983

Mineral resource potential map of the Sugarloaf Roadless Area, San Bernardino County, California

Geologic, geochemical, and geophysical investigations and a survey of mines and prospects indicate that the Sugaloaf Roadless Area contains subeconomic graphite and magnesian marble resources. Parts of the area have a low potential for the occurrence of additional low-grade graphite resources, but there is no potential for additional magnesian marble resources within the roadless area. Sand, gravel, and construction stone other than carbonate rocks are found in the roadless area, but similar or better quality materials are abundant and more accessible outside the area. The roadless area has no identified energy mineral resources, but parts of the area have a low to moderate potential for low-grade uranium resources. There are no identified metallic mineral resources within the area, and there is no evidence of a potential for the occurrence of such resources. No previously unknown mineral occurrence was located during this study.

California↗
USGS2000

Seismic-reflection investigations of the Texas Springs Syncline for ground water development, Death Valley National Park

The U.S. Geological Survey has completed an integrated geologic and geophysical study of the Texas Springs syncline for the National Park Service with the intention of locating a new production water well near existing water-collection and distribution facilities. Subsurface information was required to determine which, if any, sites within the syncline would be favorable for a well. About 4.2 km (2.6 mi.) of high-resolution seismic-reflection data were collected across and along the Texas Springs syncline. Two of our three lines, designated DV-1 and DV-3, cross the syncline, whereas the third line (DV-2) runs parallel to the north-northwest-trending syncline axis.

Open-File Report↗
USGS1979

Goal-seismic computer programs in BASIC: Part I; Store, plot, and edit array data

Processing of geophysical data taken with the U.S. Geological Survey's coal-seismic system is done with a desk-top, stand-alone computer. Programs for this computer are written in an extended BASIC language specially augmented for acceptance by the Tektronix 4051 Graphic System. This report presents five computer programs used to store, plot, and edit array data for the line, cross, and triangle arrays commonly employed in our coal-seismic investigations. * Use of brand names in this report is for descriptive purposes only and does not constitute endorsement by the U.S. Geological Survey.

Open-File Report↗
USGS1996

Hydrogeologic assessment of shallow clastic and carbonate rock aquifers in Hendry and Collier counties, southwestern Florida

Direct-current electrical resistivity data were collected from 109 vertical electrical sounding sites in Hendry and Collier Counties, southwestern Florida. Selected direct-current electrical resistivity surveys, together with available borehole geologic and geophysical data, were used to determine the approximate areal extent of the shallow clastic aquifers composed of thick sands and carbonate lithologies. Results indicated that a complex pattern of shallow sands, clays, and carbonate lithologies occur throughout the area. Buried channel sands were found as deep as 50 meters below land surface in some places. The channels contain unconsolidated fine- to medium-grained quartz sand interbedded with sandy limestone, shell fragments, and gray-green sandy clay. Both surface and borehole geophysical techniques with lithologic data were necessary to approximately locate and define layers that might behave as confining layers and to locate and define the extent of any buried sand aquifers. The borehole geophysical data were used to analyze the zones of higher resistivity. Direct-current electrical resistivity data indicated the approximate location of certain layer boundaries. The conjunctive use of natural gamma and short- and long-normal resistivity logs was helpful in determining lithologic effects. Geohydrologic sections were prepared to identify potential locations of buried channels and carbonates containing freshwater. Buried channel sands and carbonate rock sections were identified in the subsurface that potentially may contain freshwater supplies.

Florida↗
USGS1986

Structural deformation and sedimentation in an active Caldera, Rabaul, Papua New Guinea

Recent seismic and tectonic activity in Rabaul Caldera, Papua New Guinea, suggests that magma is accumulating at a shallow depth beneath this partially submerged structure and that a new volcano may be developing. Changes in onshore elevation since 1971 (as much as 2 m on south Matupit Island) indicate that rapid and large-scale uplifts have occurred on the seafloor near the center of the caldera. The frequency of seismic events within the caldera has also increased during this period. Earthquake locations define an elliptical ring surrounding the center of this uplift within the caldera. A marine geophysical survey in 1982 by the U.S. Geological Survey's R/V "S.P. Lee" in Rabaul Caldera shows the development of a bulge in the seafloor near the center of the caldera. High-resolution seismic reflection profiles show that this bulge consists of two domal uplifts bounded and separated by two major north-south-trending fault zones. Deformed sediments overlie these zones; a prominent slump flanks the area of the bulge. Five major acoustic units were identified in the seismic reflection profiles: an acoustic basement and four sedimentary units consisting of irregularly layered, cross-layered, contorted, and well-layered sequences. The acoustic basement is probably composed of crystalline volcanic rocks, and the layered acoustic units are probably sediments, primarily ash deposited in different environments. The cross-layered, irregularly layered, and contorted units appear to have been deposited in a dynamic environment subjected to strong currents, seismicity, and/or mass wasting, while the well-layered units were deposited in a low-energy environment. Locally, well-layered sequences interfinger with the other sedimentary units, indicating a transitional environment that alternated between high-energy and low-energy depositional processes. A submarine channel cuts most of the acoustic units and appears to be the conduit for sediment transport out of the caldera; it occupies an older buried channel north of the caldera that is presently being exhumed. In the south, active erosion of well-layered sediments is taking place. What are believed to be several young volcanic cones also disrupt the depositional layers. We conclude that the bulge in the seafloor and the associated fault zones are a result of emplacement of magma at a shallow depth. Contorted sediment and slumps adjacent to the bulge are probably the result of uplift and seismic activity. The pattern of seismicity appears to reflect increased magma pressure at depth beneath the caldera floor. This activity may eventually lead to an eruption. ?? 1986.

Journal of Volcanology and Geothermal Research↗
USGS1988

Geophysical instrumentation near Parkfield

The geophysical instrumentation operated by the U.S Geological Survey and others near Parkfield is designed to monitor ongoing tectonic processes that generate earthquakes and to record the strong shaking that results from larger shocks and its effects. this discussion focuses on the former objectives; the latter is discussed in the next section "Ground Shaking and Engineering Studies on the Parkfield Section of the San Andreas Fault Zone." Because scientists expect the anticipated earthquake to resemble the historic Parkfield earthquakes, and in particular that in 1966, the data from the 1966 shock were used to site instruments for optimun benefit before, during, and after the next shock. the primary feature used for siting was the "1966 rupture zone," which is shown as the orange fault traces on the maps in this section. This zone defines the extent of surface tectonic cracks in 1966 and includes the source areas for fore shocks to the 1934 and 1966 earthquakes (north end of the zone) as well as for apparent precursory fault creep in 1966 (near center of the zone). Scientists believe that if precursors to the next shock are observed, they most likely will be near the 1966 rupture zone.

California↗
USGS1981

Preliminary report on geophysics ground follow-up of the 1977 airborne survey in the Wadi Bidah District, Kingdom of Saudi Arabia

Reconnaissance geologic and geochemical sampling was made during the 1978 field season at most of the 50 or so electromagnetic anomalies detected in the 1977 airborne electromagnetic (AEM) survey of the Wadi Bidah district. These Phase 1 studies also included reconnaissance geophysical traverses of nine of the AEM conductors. In addition the AEM anomalies were classified on the basis of this reconnaissance work into a list of priority targets for use in economic studies, and six AEM anomalies were selected for further studies. During Phase 2 conducted in the 1979 field season, ground geophysical work consisting of electromagnetic (EM), self-potential (SP), and selected magnetic surveys were carried out in the six targets selected in the Phase 1 studies. These target areas in aggregate cover about 30 km 2, and are approximately half of the Wadi Bidah Class 1 and Class 2 priority targets found during the 1977 airborne electromagnetic (AEM) survey of parts of the Arabian Shield. The results indicate possible extension of known reserves at the Rabathan area (AEM anomaly B-29), with possible potential for mineralization in the area extending 15-20 km north (anomaly B-13), where the geologic and geophysical environment is similar. An important observation is that mineralization in the B-29 (Rabathan) zone is coincident with narrow SP anomalies superimposed on the larger, broader, and more formational-type SP anomalies encountered in both areas B-29 and B-13. AEM anomaly B-25-26 areahas geophysical characteristics that show in the groundwork and that make it an attractive drill target. EM and SP anomalies are associated, in part, with magnetic anomalies and with exposures of significant limonitic gossan. Wadi al Khadra prospect, not included in the 1977 AEM survey, and the AEM anomaly B-25-26 area were also high-mineralization-potential products of the Phase 2 studies. Target area B-35 remains an unknown quantity, and AEM anomaly B-24 is almost certainly due to a carbonaceous schist. Geochemical results, along with detailed geologic mapping and the geophysical data, indicate several potential mineralized targets. Further detailed geophysics (EM and SP) will assist in understanding the geophysical data thus far collected. Further ground follow-up studies are recommended.

Open-File Report↗
USGS2018

Characterizing the subsurface geology in and around the U.S. Army Camp Stanley Storage Activity, south-central Texas

Several U.S. Geological Survey projects, supported by the National Cooperative Geologic Mapping Program, have used multi-disciplinary approaches over a 14-year period to reveal the surface and subsurface geologic frameworks of the Edwards and Trinity aquifers of central Texas and the Arbuckle-Simpson aquifer of south-central Oklahoma. Some of the project achievements include advancements in hydrostratigraphic mapping, three-dimensional subsurface framework modeling, and airborne geophysical surveys as well as new methodologies that link geologic and groundwater flow models. One area where some of these milestones were achieved was in and around the U.S. Army Camp Stanley Storage Activity, located in north­western Bexar County, Texas, about 19 miles north­west of downtown San Antonio.

Texas↗
USGS2016

Regional geophysics of western Utah and eastern Nevada, with emphasis on the Confusion Range

As part of a long term geologic and hydrologic study of several regional groundwater flow systems in western Utah and eastern Nevada, the U.S. Geological Survey was contracted by the Southern Nevada Water Authority to provide geophysical data. The primary object of these data was to enable construction of the geological framework of the flow systems. The main new geophysical data gathered during the study were gravity observations, and existing aeromagnetic data were also compiled. These data resulted in regional maps of the isostatic gravity and aeromagnetic fields of the area. The isostatic gravity map shows a north-south grain to most of the area, which was imparted by post-20 Ma basin-range tectonism; whereas the aeromagnetic map shows an east-west grain to the area, imparted by Eocene to lower Miocene calc-alkaline calderas and source intrusions. To de-emphasize surface and near-surface features and to gain greater insight into contributions from deeper sources, the isostatic gravity anomalies were upward continued by 3 km and the aeromagnetic data were transformed to their magnetic potential ("pseudogravity"). Identification of maxima of the horizontal gradients in the gravity and magnetic-potential data helped define deep-seated crustal blocks that are characterized by major changes in density and magnetization. Maps showing these maxima were useful in defining large faults, especially range-bounding faults, and margins of igneous bodies and calderas. A gravity inversion method was used to separate the isostatic residual anomaly into pre-Cenozoic basement and young basin fill. Inasmuch as the primary aquifer in the area is sedimentary basin fill, this method is especially valuable for hydrogeologic analyses because it estimates the thickness of the fill. As befits its name, the geology of the Confusion Range of Utah has been a point of contention for many years, so we looked at it in greater detail in the course of our regional study. The northern part of the range is underlain by a large gravity high, which continues south through the Conger Range, Burbank Hills, and northern Mountain Home Range. This is the "structural trough" reported in the literature that was mapped as the axial part of a Sevier synclinorium and contains the maximum thickness (7 km) of high-density carbonates in the area, thus the largest high gravity anomaly.

Utah↗
USGS1984

Aeromagnetic, Bouguer gravity, and interpretation maps of the Sheep Hole-Cadiz Wilderness Study Area (CDCA-305), San Bernardino County, California

The Federal Land Policy and Management Act (Public Law 94-579, October 21, 1976) requires the U.S. Geological Survey and the U.S. Bureau of Mines to conduct mineral surveys on certain areas to determine their mineral resource potential. Results must be made available to the public and be submitted to the President and the Congress. These maps presents the results of a mineral survey of the Sheep Hole-Cadiz Wilderness Study Area (CDCA-305), California Desert Conservation Area, San Bernardino County, California. The U.S. Bureau of Mines conducted a mineral survey of the Sheep Hole-Cadiz Wilderness Study Area, which encompasses approximately 200,000 acres including enclosed private lands, in south-central San Bernardino County, California. The U.S. Bureau of Mines studied the mineral resources of mines, prospects, and mineralized areas; geologic, geochemical, and geophysical investigations were conducted by the U.S. Geological Survey. The study area is located in the Mojave Desert 13 miles east of Amboy, California, 20 miles east of Twentynine Palms, California, and 90 miles east of San Bernardino, and encompasses parts of the Dale Lake, Bristol Lake, Cadiz Valley and Cadiz Lake 15-minute quadrangles. Its borders are defined by the Amboy Road and a gas pipeline service road on the northwest, the unimproved Cadiz Valley access road on the east, State Route 62 along the south, and the Iron Age mine road and an unimproved powerline service road on the west. Major access from the east and west is provided by State Route 62 and access from the north is provided by the Amboy Road. Companion reports to this one describe the mineral resource potential (March and others, 1982), the geology (Howard and John, 1984), and hydrothermal alteration studies (Raines, 1983).

California↗
USGS2007

Geosoft eXecutables (GX's) Developed by the U.S. Geological Survey, Version 2.0, with Notes on GX Development from Fortran Code

Introduction Geosoft executables (GX's) are custom software modules for use with the Geosoft Oasis montaj geophysical data processing system, which currently runs under the Microsoft Windows 2000 or XP operating systems. The U.S. Geological Survey (USGS) uses Oasis montaj primarily for the processing and display of airborne geophysical data. The ability to add custom software modules to the Oasis montaj system is a feature employed by the USGS in order to take advantage of the large number of geophysical algorithms developed by the USGS during the past half century. This main part of this report, along with Appendix 1, describes Version 2.0 GX's developed by the USGS or specifically for the USGS by contractors. These GX's perform both basic and advanced operations. Version 1.0 GX's developed by the USGS were described by Phillips and others (2003), and are included in Version 2.0. Appendix 1 contains the help files for the individual GX's. Appendix 2 describes the new method that was used to create the compiled GX files, starting from legacy Fortran source code. Although the new method shares many steps with the approach presented in the Geosoft GX Developer manual, it differs from that approach in that it uses free, open-source Fortran and C compilers and avoids all Fortran-to-C conversion.

Open-File Report↗