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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, gravi
Authors
Victoria E. Langenheim, J. M. Glen, R.C. Jachens, G. L. Dixon, T.C. Katzer, R. L. Morin

Age and paleoenvironmental significance of mega-invertebrates from the "San Pedro" Formation in the Coyote Hills, Fullerton and Buena Park, Orange County, Southern California

The "San Pedro" Formation in the Coyote Hills contains an invertebrate fossil as-semblage of 184 taxa from 158 localities. The fauna consists of two annelids, 174 mollusks (80 bivalves, 94 gastropods, and three scaphopods), five arthropods, and three echinoids, along with other minor constituents recognized by not specifically identified during the present study. These fossils are divided into thr
Authors
Charles L. Powell, Dave Stevens

Preliminary maps of Quaternary deposits and liquefaction susceptibility, nine-county San Francisco Bay region, California: a digital database

This report presents a preliminary map and database of Quaternary deposits and liquefaction susceptibility for the nine-county San Francisco Bay region, together with a digital compendium of ground effects associated with past earthquakes in the region. The report consists of (1) a spatial database of fivedata layers (Quaternary deposits, quadrangle index, and three ground effects layers
Authors
Keith L. Knudsen, Janet M. Sowers, Robert C. Witter, Carl M. Wentworth, Edward J. Helley, Robert S. Nicholson, Heather M. Wright, Katherine H. Brown

Geologic map and digital database of the Apache Canyon 7.5' quadrangle, Ventura and Kern counties, California

The Apache Canyon 7.5-minute quadrangle is located in southwestern California about 55 km northeast of Santa Barbara and 65 km southwest of Bakersfield. This report presents the results of a geologic mapping investigation of the Apache Canyon quadrangle that was carried out in 1997-1999 as part of the U.S. Geological Survey's Southern California Areal Mapping Project. This quadrangle was chosen fo
Authors
Paul Stone, P. M. Cossette

Digital geologic map of the Coeur d'Alene 1:100,000 quadrangle, Idaho and Montana

Between 1961 and 1969, Alan Griggs and others conducted fieldwork to prepare a geologic map of the Spokane 1:250,000 map (Griggs, 1973). Their field observations were posted on paper copies of 15-minute quadrangle maps. In 1999, the USGS contracted with the Idaho Geological Survey to prepare a digital version of the Coeur d’Alene 1:100,000 quadrangle. To facilitate this work, the USGS obtained the
Authors
Steven R. digital compilation by Munts

Operational guidelines (version 1.0) for geological fieldwork in areas endemic for Coccidioidomycosis (Valley Fever)

Coccidioidomycosis (Valley Fever) is a disease caused by the inhalation of the arthroconidia (spores) of Coccidioides immitis, a fungus that lives in the soils of southwestern United States. Although large numbers of people are exposed to the arthroconidia and are consequently infected, very few individuals contract the more serious forms of the disease. Earth scientists working in field areas whe
Authors
Frederick S. Fisher, Mark W. Bultman, Demosthenes Pappagianis

Basement structure beneath Langford Well Lake basin, Fort Irwin, California, based on inversion of gravity data

Gravity data were used to study the basement structure of Langford Well Lake basin at the U.S. Army National Training Center, Fort Irwin, California. Figure 1 shows the location of the study area. During 1996 and 1999, 290 new gravity stations were measured. These data were merged with existing data to produce a depth-to-basement map, which, in turn was converted to a structure map of the basement
Authors
Robert L. Morin

Principal facts for gravity stations in the Antelope Valley-Bedell Flat area, west-central Nevada

In April 2000 the U.S. Geological Survey (USGS) established 211 gravity stations in the Antelope Valley and Bedell Flat area of west-central Nevada (see figure 1). The stations were located about 15 miles north of Reno, Nevada, southwest of Dogskin Mountain, and east of Petersen Mountain, concentrated in Antelope Valley and Bedell Flat (figure 2). The ranges in this area primarily consist of norma
Authors
Eleanore B. Jewel, David A. Ponce, Robert L. Morin

Geologic map database of the El Mirage Lake area, San Bernardino and Los Angeles Counties, California

This geologic map database for the El Mirage Lake area describes geologic materials for the dry lake, parts of the adjacent Shadow Mountains and Adobe Mountain, and much of the piedmont extending south from the lake upward toward the San Gabriel Mountains. This area lies within the western Mojave Desert of San Bernardino and Los Angeles Counties, southeastern California. The area is traversed by a
Authors
David M. Miller, David R. Bedford