Drill hole USW G-1 was drilled at Yucca Mountain, Nevada Test Site, Nevada, as part of the ongoing exploration program for the Nevada Nuclear Waste Storage Investigations. Contract geophysical well logs run at USW G-1 show only limited stratigraphic correlations, but correlate reasonably well with the welding of the ash-flow and ash-fall tuffs. Rocks in the upper part of the section have highly variable physical properties, but are more uniform and predictably lower in the section.

Open-File Report↗

USGS1980

A vertical seismic profiling experiment to determine depth and dip of the Paleozoic surface at drill hole U10bd, Nevada Test Site, Nevada

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Open-File Report↗

USGS1979

Preliminary geologic and geophysical data of the UE25a-3 exploratory drill hole, Nevada Test Site, Nevada

The UE25a-3 drill hole, located in the Calico Hills area, southwestern part of the Nevada Test Site, was drilled as part of an effort to evaluate the Calico Hills area as a possible nuclear waste repository site. The purpose of the drill hole was to verify the existence of an intrusive crystalline body in the subsurface and to determine the stratigraphy, structure, and nature of fractures of the cored rocks. Cored samples were obtained for mineral, chemical, and material property analyses. Continuous cores were taken from 30.5 m (100ft) to total depth of 771.2 m (2,530.1 ft) of units J and I{?) (Late Mississippian age) of the Eleana Formation. The drill hole penetrated 416.1 m (1 ,365ft) of argillite, and 304.5 m (999ft) of thermally altered argillite of unit J, and 50.6 m (166ft) of marble of unit I(?). No crystalline rocks were intersected by the drill hole. Numerous high-angle faults and brecciated zones were intersected by the drill hole. The units cored were intensely fractured with fracture analysis of the core consisting of frequency of fractures, dips of fractures, open and closed (sealed) fractures and types of fracture sealing or coating material. Twenty-four hundred and thirty fractures, representing approximately 30 percent of the fractures present, indicate an average fracture frequency of 13.2 fractures per meter, predominantly high-angle dips with 66 percent of the fractures closed. Fractures in the argillite interval are sealed or coated predominantly with kaolinite, nacrite, and dickite. Calcite, chlorite, and magnetite are present in fractures in the altered argillite interval. Fractures in the marble interval are sealed or coated with calcite, dolomite, and ferruginous clay. The core index indicates that the lower half of the drilled interval is more competent than the upper half. Borehole geophysical logs were run by the Birdwell Division of Seismograph Service Corporation for geologic correlations and lithologic characterizations. The logs include: caliper, density, resistivity, spontaneous potential, Vibroseis, 3-D velocity, neutron, and gamma-ray logs. Lithologic boundaries and structures correlate to responses in the logs.

Nevada↗

USGS1979

Preliminary report on the geology and geophysics of drill hole UE25a-1, Yucca Mountain, Nevada Test Site

A subsurface geologic study in connection with the Nevada Nuclear Waste Storage Investigations has furnished detailed stratigraphic and structural information about tuffs underlying northeastern Yucca Mountain on the Nevada Test Site. Drill hole UE25a-1 penetrated thick sequences of nonwelded to densely welded ash-flow and bedded tuffs of Tertiary age. Stratigraphic units that were identified from the drill-hole data include the Tiva Canyon and Topopah Spring Members of the Paintbrush Tuff, tuffaceous beds of Calico Hills, and the Prow Pass and Bullfrog Members of the Crater Flat Tuff. Structural analysis of the core indicated densely welded zones to be highly fractured. Many fractures show near-vertical inclinations and are commonly coated with secondary silica, manganese and iron oxides, and calcite. Five fault zones were recognized, most of which occurred in the Topopah Spring Member. Shear fractures commonly show oblique-slip movement and some suggest a sizable component of lateral compression. Graphic logs are included that show the correlation of lithology, structural properties, and geophysical logs. Many rock units have characteristic log responses but highly fractured zones, occurring principally in the Tiva Canyon and Topopah Spring Members, restricted log coverage to the lower half of the drill hole.

Open-File Report↗