Publications

The Western Earth Surface Processes Team (WESP) of the U.S. Geological Survey (USGS) conducts geologic mapping and related topical earth science studies in the western United States. This work is focused on areas where modern geologic maps and associated earth-science data are needed to address key societal and environmental issues such as ground-water quality, potential geologic hazards...

Gravity and magnetic surveys were performed along the western flanks of the Santa Rita Mountain range located in southeastern Arizona to develop an understanding of the relationship between surface fault scarps within the basin fill sediments and theirgeophysical response of the faults at depth within the bedrock. Data were acquired for three profiles, one of them along the northern...

Open-File Report 01-450 contains a digital geologic map database of the Sunnymead 7.5’ quadrangle, Riverside County, California that includes: ARC/INFO (Environmental Systems Research Institute, http:/www.esri.com) version 7.2.1 coverages of the various elements of the geologic map. A Postscript file to plot the geologic map on a topographic base, containing a Correlation of Map Units...

Open-File Report 01-449 contains a digital geologic map database of the Steele Peak 7.5’ quadrangle, Riverside County, California that includes: ARC/INFO (Environmental Systems Research Institute, http://www.esri.com) version 7.2.1 coverages of the various elements of the geologic map. A Postscript file to plot the geologic map on a topographic base, and containing a Correlation of Map...

This study used powder X-ray diffraction, with Rietveld quantification software to quantify and characterize the mineralogy of the 83 samples collected from two stratigraphic sections measured by the U.S. Geological Survey at the Dry Valley mine in the Meade Peak Member of the Phosphoria Formation. Analyses show extensive variability of carbonate substitution in the fluorapatite...

Using gridded high-resolution aeromagnetic data, the performance of several automated 3-D depth-to-source methods was evaluated over shallow control sources based on how close their depth estimates came to the actual depths to the tops of the sources. For all three control sources, only the simple analytic signal method, the local wavenumber method applied to the vertical integral of the...

This report provides brief petrographic descriptions of rock samples collected from the vicinity of the Hayward Fault, Northern California. Two groups of rock samples are represented here: A set of six samples that were used for laboratory measurements of P- and S-wave velocity , strength, density, and porosity. This group was examined using standard petrographic microscope, scanning...

No abstract available.

Structural geology is an important component in regional-, district- and orebody-scale exploration and development of sedimentary rock-hosted Au deposits. Identification of timing of important structural events in an ore district allows analysis and classification of fluid conduits and construction of genetic models for ore formation. The most practical uses of structural geology deal...

The geologic map of the Tucson-Nogales 1:250,000 scale quadrangle (Peterson and others, 1990) was digitized by U.S. Geological Survey staff and University of Arizona contractors at the Southwest Field Office, Tucson, Arizona, in 2000 for input into a geographic information system (GIS). The database was created for use as a basemap in a decision support system designed by the National...

This investigation of the Eagle Mountain Mine area, though cursory, revealed new structural, alteration, and stratigraphic relations. Eagle Mountain ores were previously an important source of iron to the western U. S. Ore (where fresh) is magnetite-pyrite rock forming two stratabound horizons virtually continuous for 11 km. Gneissic basement rocks are overlain by two sedimentary units...

This Open-File Report contains a digital geologic map and map database of the Lakeview 7.5' quadrangle, Riverside County, California, that includes: 1. ARC/INFO (Environmental Systems Research Institute) version 7.2.1 double-precision coverages of the various elements of the geologic map 2. A Postscript file to plot the geologic map on a topographic base, and containing a Correlation of...