Gravity data for the state of Nevada on magnetic tape

Abstract

Gravity data assembled for a state gravity map to be published by the Nevada Bureau of Mines are available from the EROS data center on magnetic tape. The first 18 files of the tape contain principal facts for individual data points, organized by 1° x 2° quadrangle. The approximately 71,000 individual data points are from numerous sources including the Defense Mapping Agency data base and U.S. Geological Survey files. Each data record contains geographic position, observed gravity, terrain correction, Bouguer gravity anomaly (p = 2.67 g/crn3), and isostatic residual anomaly (Airy Heiskanen, T = 25 km, A/? = 0.4 g/cm3). The 19th and 20th data files are 2 km square grids of complete Bouguer and isostatic residual gravity values based on the data in the preceding files. The 9-track magnetic tape is written at 1,600 bytes-per-inch (BPI) in ASCII format with an 80-character record and 4,000-character (50 record) block size. Gravity sources These Nevada gravity data consist primarily of data from the Defense Mapping Agency (DOD) data base (available from the National Geophysical and Solar-Terrestrial Data Center, Boulder, Colorado 80303). Additional data from U.S. Geological Survey (USGS) files in Denver, Colorado and Menlo Park, California are included. Most of the USGS data are documented in published Bouguer gravity anomaly maps and principal facts reports for the following 1° x 2° quadrangles in Nevada (see appendix for source DOD references

Maps of the thickness of Cenozoic deposits and the isostatic residual gravity over basement for Nevada

“…parts of northwest and northeast Nevada) are covered only by observations along profiles spaced tens of kilometers apart. Uncertainties in reduced gravity values resulting from errors in observed gravity, location, elevation, and terrain correction are estimated to be less than 1 mGal (1 mGal=10 m/s ) for most stations, but uncertainties may be significantly greater for gravity values from stations in areas of rugged topography (Saltus, 1988a). The data have been used to produce a Bouguer gravity anomaly map with a reduction density of 2.67 g/cm (Saltus, 1988b), an isostatic residual gravity map based on an Airy-Heiskanen model for buoyant support of topography, and various derivative gravity maps of Nevada (Saltus, 1988c).…”

“…Data Sources, Reductions, and Accuracies Basic gravity data are from Saltus (1988a) and comprise approximately 71,000 point observations. These data are distributed unevenly over the state ( fig.…”

Basin genesis associated with strike‐slip faulting in the Basin and Range, southeastern Nevada

“…The sediments that fill the depression are of alluvial facies and have a distinct density contrast with the Precambrian through Paleozoic rocks that frame the basin. Using regional gravity data compiled previously by Saltus [1988], the complete Bouguer anomaly was contoured around the region of the Lake Mead fault system. A northeast trending rhomboid minimum is constrained by the Lake Mead fault system (Figure 6).…”

Major results of geophysical investigations at Yucca Mountain and vicinity, southern Nevada

“…Gravity data for the southwestern part of the NTS and vicinity were released by Jansma and others (1982) and included gravity and magnetic data along three profiles across Yucca Mountain. The data from the four 1:250,000-scale maps have since been recompiled and extended south to 35" 30'N, north to 38" 30'N, and west to 118" 30'W using subsets of the gravity data releases for California (Snyder and others, 1981) and Nevada (Saltus, 1988). A Bouguer gravity map of the southern Great Basin is shown ( fig.…”