Stratigraphic and volcano-tectonic relations of Crater Flat Tuff and some older volcanic units, Nye County, Nevada
The Crater Flat Tuff is herein revised to include a newly recognized lowest unit, the Tram Member, exposed at scattered localities in the southwest Nevada Test Site region, and in several drill holes in the Yucca Mountain area. The overlying Bullfrog and Prow Pass Members are well exposed at the type locality of the formation near the southeast edge of Crater Flat, just north of US Highway 95. In previous work, the Tram Member was thought to be the Bullfrog Member, and therefore was shown as Bullfrog or as undifferentiated Crater Flat Tuff on published maps. The revised Crater Flat Tuff is statigraphically below the Topopah Spring Member of the Paintbrush Tuff and above the Grouse Canyon Member of the Belted Range Tuff and is approximately 13.6 m.y. old. Drill holes on Yucca Mountain and near Fortymile Wash penetrate all three members of the Crater Flat as well as an underlying quartz-poor unit. Although the rocks are poorly exposed, geophysical and geologic evidence to date suggests that (1) the source of the Crater Flat Tuff is a caldera complex in the Crater Flat area between Yucca Mountain and Bare Mountain, and (2) there are at least two cauldrons within this complex - one probably associated with eruption of the Tram, the other with the Bullfrog and Prow Pass Members. The complex is named the Crater Flat-Prospector Pass caldera complex. The northern part of the Yucca Mountain area is suggested as the general location of the source of pre-Crater Flat tuffs, but a caldera related to the Lithic Ridge Tuff has not been specifically identified. 23 refs., 18 figs., 1 tab.
- Research Organization:
- Geological Survey, Reston, VA (United States)
- DOE Contract Number:
- AI08-78ET44802
- OSTI ID:
- 60073
- Report Number(s):
- USGS-PP-1323; ON: DE86015043
- Resource Relation:
- Other Information: PBD: 1986
- Country of Publication:
- United States
- Language:
- English
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