INTERIM GEOLOGICAL INVESTIGATIONS IN THE U12b.08 TUNNEL, NEVADA TEST SITE, NYE COUNTY, NEVADA
The Ul2b.08 tunnel is a part of the Ul2b tunnel system, which was driven southwestward beneath Rainier Mesa in the northern part of the Nevada Test Site. The tunnel was driven in nonwelded vitric tuff of the Survey Butte Member of the Oak Spring Formation of Miocene(?) or younger age. Vertical and minimum cover over the end of the tunnel to the surface of Rainier Mesa is about 800 feet. The tuffs in the tunnel strike northwest to northeast and dip 5 deg to 14 deg SW to NW. The principal structural features of the tuffs are a major northwest- trending fault of steep dip with a downward displacement to the southwest of mor- e than l5 feet and two west-trending synclines. The major fault exposes tuffs of the Survey Butte Member that are stratigraphically higher than any previously mapped in the tunnel system. Several other steeply drpping northwest- and northeast-trending faults of small displacement cut the tunnel. Joints are common and they trend dominantly either northeast or northwest with generally vertical to steep dips. The tuffs in this section of the Survey Butte Member are moderately well bedded to structureless fresh vitric tuffs that show cylical repetitions in sets of texture, structure, color, and ccmposition. The chemical and physical properties of the tuffs in the U12b.08 tunnel are similar to other tuffs of the Oak Spring Formation from the Nevada Test Site. (auth)
- Research Organization:
- Geological Survey, Washington, D.C.
- NSA Number:
- NSA-16-022408
- OSTI ID:
- 4837496
- Report Number(s):
- TEI-814
- Country of Publication:
- United States
- Language:
- English
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