Preliminary interpretation of paleomagnetic and magnetic property data from drill holes USW G-1, G-2, GU-3, G-3, and VH-1 and surface localities in the vicinity of Yucca Mountain, Nye County, Nevada
Measurements of magnetic properties and paleomagnetic directions have been made on thousands of samples of Miocene age volcanics from drill core and surface localities in and around Yucca Mountain at the Nevada Test Site. The directional data have firmly established paleomagnetic polarities for the various members of the Paintbrush and Crater Flat Tuffs, and for the Tuffaceous Beds of Calico Hills. In addition, the Lithic Ridge Tuff is found to have a highly unusual paleomagnetic direction (southwest and nearly horizontal). Changes in inclination of remanence with depth in the Tuffaceous Beds of Calico Hills indicate that this unit was emplaced over a substantial period of time relative to secular variation of the geomagnetic field, and that the relatively thin sequence of tuffs of this unit encountered at the USW G-1 locality correlates roughly with the basal 125 m of the much thicker sequence penetrated in drill hole USW G-2. Four widespread units, the Tiva Canyon and Topopah Spring Members of the Paintbrush Tuff and the Bullfrog and Tram Members of the Crater Flat Tuff, are identified as potential sources of significant magnetic anomalies by measurements of remanent intensity and susceptibility. The measurements also demonstrate large variations in remanent intensity and susceptibility within individual ash-flow sheets. In some cases these variations are closely related to geologically recognizable breaks in ash-flow tuff deposition. These variations provide the possibility of using magnetic field logs not only to locate major stratigraphic contacts but also to map subunits within the major ash-flow sheets. 16 references, 24 figures, 21 tables.
- Research Organization:
- US Geological Survey, Denver, CO (United States)
- DOE Contract Number:
- AI08-78ET44802
- OSTI ID:
- 59223
- Report Number(s):
- USGS-OFR-85-49; ON: DE85009129
- Resource Relation:
- Other Information: PBD: 1984
- Country of Publication:
- United States
- Language:
- English
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