Preliminary results of gravity investigations of the Calico Hills, Nevada Test Site, Nye County, Nevada
A total of 211 recently established gravity stations supplement 128 existing regional stations in providing data for a detailed gravity interpretation of the Calico Hills area of the Nevada Test Site. Reduction of these data to complete Bouguer anomalies combined with a regional correction of -0.8 mGal/km N.15{sup 0} E. reveals an elliptical gravity high centered over the exposed Paleozoic rocks. The anomaly has an amplitude of about 7.5 mGal and extent of about 8 km, elongate in an east-west direction. A log from a 770-m drill hole and data from detailed surface geologic mapping, a seismic refraction line, electrical soundings, and magnetic traverses all provide some control on the interpretation of density variations or rock structure within the study area. Two nearly perpendicular gravity profiles interpreted by 2 1/2-dimensional modelling suggest the Calico Hills gravity anomaly can be entirely attributed to a lateral density contrast of 0.50 g/cm{sup 3} between Paleozoic rocks (= 2.60 g/cm{sup 3}) and the overlying Tertiary tuff (= 2.10 g/cm{sup 3}). This boundary can be constrained vertically to within several hundred meters and thus defines the domical structure of the Paleozoic rocks in this region. The strong contrast of this boundary produces anomalies that mask any gravity anomalies of smaller amplitude that might arise from structure internal to the Paleozoic rocks. Therefore, the existence of a relatively high- or low-density intrusive body in those rocks cannot be confirmed or denied.
- Research Organization:
- US Geological Survey, Denver, CO (United States)
- DOE Contract Number:
- AI08-78ET44802
- OSTI ID:
- 59821
- Report Number(s):
- USGS-OFR-81-101; ON: DE86008359
- Resource Relation:
- Other Information: PBD: 1981
- Country of Publication:
- United States
- Language:
- English
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