Publications

The U.S. Geological Survey (USGS) collected 811 gravity stations on the Lake Mead 30' by 60' quadrangle from October, 1997 to September, 1999. These data were collected in support of geologic mapping of the Lake Mead quadrangle. In addition to these new data, gravity stations were compiled from a number of sources. These stations were reprocessed according to the reduction method...

Using a model of the topographic subsurface derived from drill hole and gravity inversion analysis of the basement rocks in Yucca Flat, Nevada Test Site (NTS), Nevada, a fault map and digital fault dataset were constructed based on offsets of the basement surface. Because these faults are, in large part, not present at the surface, they are interpreted to be inactive faults, older than...

The geology of the Thompson Falls 1:100,000 quadrangle, Idaho was compiled by Reed S. Lewis in 1997 onto a 1:100,000-scale greenline mylar of the topographic base map for input into a geographic information system (GIS). The resulting digital geologic map GIS can be queried in many ways to produce a variety of geologic maps. Digital base map data files (topography, roads, towns, rivers...

A three-dimensional inversion of gravity data from the Pahute Mesa–Oasis Valley region reveals a topographically complex pre-Tertiary basement surface. Beneath Pahute Mesa, the thickness of the Tertiary volcanic deposits may exceed 5 km within the Silent Canyon caldera complex. South of Pahute Mesa in Oasis Valley, basement is shallower ( 1 km) but between this valley and the Timber...

Permits to explore for and (or) develop mineral resources on forest land can be used to indicate locations and types of mineral-related activities on national forests. Permits for these activities require filing at the Forest Service a Notice of Intention (Notice) to conduct mineral exploration activities and (or) a Plan of Operation (Plan). A Plan of Operation is required is significant

Understanding patterns of historical erosion and deposition in San Francisco Bay is crucial in managing such issues as locating deposits of sediment-associated contaminants, and the restoration of wetland areas. These problems were addressed by quantitatively examining historical hydrographic surveys. The data from five hydrographic surveys, made from 1867 to 1990, were analyzed using...

The computer program WTAQ calculates hydraulic-head drawdowns in a confined or water-table aquifer that result from pumping at a well of finite or infinitesimal diameter. The program is based on an analytical model of axial-symmetric ground-water flow in a homogeneous and anisotropic aquifer. The program allows for well-bore storage and well-bore skin at the pumped well and for delayed...

Quantifying the hydraulic interaction of aquifers and streams is important in the analysis of stream base fow, flood-wave effects, and contaminant transport between surface- and ground-water systems. This report describes the use of two computer programs, STLK1 and STWT1, to analyze the hydraulic interaction of streams with confined, leaky, and water-table aquifers during periods of...

Surface and borehole geophysical methods were used to determine fracture orientation in crystalline bedrock at the Eastern Surplus Superfund Site in Meddybemps, Maine. Fracture-orientation information is needed to address concerns about the fate of contaminants in ground water at the site. Azimuthal square-array resistivity surveys were conducted at 3 locations at the site, borehole...

The magnetization in crustal rocks is the vector sum of induced in minerals by the Earth’s present main field and the remanent magnetization of minerals susceptible to magnetization (chiefly magnetite) (Blakely, 1995). The direction of remanent magnetization acquired during the rock’s history can be highly variable. Crystalline rocks generally contain sufficient magnetic minerals to...

This report comprises digital spatial data that constitute a partial transcription of the 1:250,000-scale Geologic map of Washington - southwest quadrant (Walsh and others, 1987); digital base material, symbolsets, and ARC Macro Language (AML) procedures to create a geologic map on a shaded-relief base from the digital spatial data; and Postscript and RTL plotfiles for such a geologic...

This report describes a digital map generated by the U.S. Geological Survey (USGS) to provide digital spatial mining claim density information for federal lands in Wyoming as of March 1997. Mining claim data is earth science information deemed to be relevant to the assessment of historic, current, and future ecological, economic, and social systems. There is no paper map included in this...