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Map showing large structures interpreted from geophysical data in the vicinity of New Madrid, Missouri
This is one of a series of five seismotectonic maps of the seismically active New Madrid area in southeast Missouri and adjacent parts of Arkansas, Kentucky, and Tennessee (table 1). We cannot legibly show all the seismotectonic data on a single map, therefore each of the five maps in this series groups a different type of related information. Rhea and others (1994) summarized the background and purpose of the seismotectonic map folio.
Map showing locations of geophysical survey and modeling lines in the vicinity of New Madrid, Missouri
This is one of a series of five seismotectonic maps of the seismically active New Madrid area in southeast Missouri and adjacent parts of Arkansas, Kentucky, and Tennessee (table 1). We cannot legibly show all the seismotectonic data on a single map, therefore each of the five maps in this series groups a different type of related information. Rhea and others (1994) summarized the background and purpose of the seismotectonic map folio.
Geophysical log signatures of lower Tertiary and upper Cretaceous rocks in the Powder River Basin, Wyoming and Montana
No abstract available.
Stratigraphy and tectonic history of the Tucson Basin, Arizona, based on re-examination of cuttings and geophysical logs of the Exxon State (32)-1 well
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Preliminary report on geophysics of the Verde River headwaters region, Arizona
This report summarizes the acquisition, data processing, and preliminary interpretation of a high-resolution aeromagnetic and radiometric survey near the confluence of the Big and Little Chino basins in the headwaters of the Verde River, Arizona. The goal of the aeromagnetic study is to improve understanding of the geologic framework as it affects groundwater flow, particularly in relation to the occurrence of springs in the upper Verde River headwaters region. Radiometric data were also collected to map surficial rocks and soils, thus aiding geologic mapping of the basin fill. Additional gravity data were collected to enhance existing coverage. Both aeromagnetic and gravity data indicate a large gradient along the Big Chino fault, a fault with Quaternary movement. Filtered aeromagnetic data show other possible faults within the basin fill and areas where volcanic rocks are shallowly buried. Gravity lows associated with Big Chino and Williamson Valleys indicate potentially significant accumulations of low-density basin fill. The absence of a gravity low associated with Little Chino Valley indicates that high-density rocks are shallow. The radiometric maps show higher radioactivity associated with the Tertiary latites and with the sediments derived from them. The surficial materials on the eastern side of the Big Chino Valley are significantly lower in radioactivity and reflect the materials derived from the limestone and basalt east of the valley. The dividing line between the low radioactivity materials to the east and the higher radioactiviy materials to the west coincides approximately with the major drainage system of the valley, locally known as Big Chino Wash. This feature is remarkably straight and is approximately parallel to the Big Chino Fault. The uranium map shows large areas with concentrations greater than 5 ppm eU, and we expect that these areas will have a significantly higher risk potential for indoor radon.
Geophysical constraints on the Virgin River Depression, Nevada, Utah, and Arizona
Gravity and aeromagnetic data provide insights into the subsurface lithology and structure of the Virgin River Depression (VRD) of Nevada, Utah, and Arizona. The gravity data indicate that the Quaternary and Tertiary sedimentary deposits hide a complex pre-Cenozoic surface. A north-northwest-trending basement ridge separates the Mesquite and Mormon basins, as evidenced by seismic-reflection, gravity, and aeromagnetic data. The Mesquite basin is very deep, reaching depths of 8?10 km. The Mormon basin reaches thicknesses of 5 km. Its northern margin is very steep and may be characterized by right steps, although this interpretation could change with additional gravity stations. Most of the young (Quaternary), small-displacement faults trend within 10? of due north and occur within the deeper parts of the Mesquite basin north of the Virgin River. South of the Virgin River, only a few, young, small-displacement faults are mapped; the trend of these faults is more northeasterly and parallels the basement topography and is distinct from that of the faults to the north. The Virgin River appears to follow the margin of the basin as it emerges from the plateau. The high-resolution aeromagnetic data outline the extent of shallow volcanic rocks in the Mesquite basin. The north-northwest alignment of volcanic rocks east of Toquop Wash appear to be structurally controlled because of faults imaged on seismic-reflection profiles and because the alignment is nearly perpendicular to the direction of Cenozoic extension. More buried volcanics likely exist to the north and east of the high-resolution aeromagnetic survey. Broader aeromagnetic anomalies beneath pre-Cenozoic basement in the Mormon Mountains and Tule Springs Hills reflect either Precambrian basement or Tertiary intrusions. These rocks are probably barriers to groundwater flow, except where fractured.
Deep electrical geophysical measurements across the Carlin Trend, Nevada
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Annotated bibliography of geophysical methods for characterizing mine waste, late-1994 through early-2000
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Bathymetric, geophysical and geologic sample data from Medicine Lake, Siskiyou County, northern California
In September, 1999, the U.S. Geological Survey acquired high-resolution bathymetry, seismic reflection profiles, and geologic sample data from Medicine Lake, a high altitude (2,036 m) lake located within the summit caldera/basin at Medicine Lake volcano (MLV), a dormant Quaternary shield volcano located in the Cascade Range, 50 km northeast of Mt. Shasta. It last erupted less than 1000 years ago.The purpose of this work was to assess whether sediments in the lake might provide a high-resolution record of the climate, volcanic and geochemical (particularly mercury) history of the region. We are still working with our data to assess whether the sediments are appropriate for further study. This report provides a summary of what we have learned to date.
Preliminary Precambrian basement map showing geologic-geophysical domains, Wyoming
No abstract available.
Application of geophysical techniques to minerals-related environmental problems
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Basement geophysical interpretation of the National Petroleum Reserve Alaska (NPRA), Northern Alaska
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Anchorage Urban Region Aeromagnetics (AURA) Project — Preliminary geophysical results
No abstract available.