An analysis of gravity data in Area 12, Nevada Test Site
Open-File Report
69-309
By: R. R. Wahl
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Abstract
The gravity data available from Healey and Miller (1963a) were augmented by new observations along three profiles through two new drill holes in Area 12; UEI2t #1 and UEI2p #1. The data were interpreted to allow evaluation of the geologic structure prior to the planning and excavation of two proposed tunnel complexes, Ul2t and Ul2p.
Density values for each of six rock units were determined to allow a two-dimensional analysis of the gravity data along the above-mentioned profiles. The surficial rocks of Quaternary and Tertiary age and the Tertiary volcanic rocks have a weighted average density of 1.86 gm/cc. The density of the caprock at Rainier and Aqueduct Mesas ranges from 2.17 gm/cc at UEI2p #1 to 2.27 gm/cc at UEI2t #1. The Gold Meadows stock and the associated Precambrian quartzite have an arithmetic average density of 2.60 gm/cc for all samples measured. The middle Paleozoic dolomite in Area 12 has an arithmetic average density of 2.75 gm/cc. The clastic rocks of Paleozoic age have an arithmetic average density of 2.60 gm/cc.
Interpretation of the residual gravity data indicates a maximum thickness of about 2,800 feet for all Tertiary volcanic rocks. A normal fault striking N. 30 ? E. disrupts the pre-Cenozoic surface at UEI2p #1 and 0.4 mile east of UEI2t #1. The throw within rock of Paleozoic age is about 400-500 feet. Another normal fault that strikes about N. 20 ? E. is located about 1.5 miles east of UEI2p #1. The throw of this fault is at least 1,100 feet in rocks of pre-Cenozoic age.
Elevation contours representing the pre-Cenozoic surface in Area 12 show a maximum relief of about 2,000 feet.
Suggested Citation
Wahl, R.R., 1969, An analysis of gravity data in Area 12, Nevada Test Site: U.S. Geological Survey Open-File Report 69-309, Report: iii, 23 p.; 3 Plates: 42.76 x 29.41 inches or smaller, https://doi.org/10.3133/ofr69309.
ISSN: 2331-1258 (online)
Study Area
| Publication type | Report |
|---|---|
| Publication Subtype | USGS Numbered Series |
| Title | An analysis of gravity data in Area 12, Nevada Test Site |
| Series title | Open-File Report |
| Series number | 69-309 |
| DOI | 10.3133/ofr69309 |
| Year Published | 1969 |
| Language | English |
| Publisher | U.S. Geological Survey |
| Description | Report: iii, 23 p.; 3 Plates: 42.76 x 29.41 inches or smaller |
| Country | United States |
| State | Nevada |
| Other Geospatial | Area 12, Nevada Test Site |