Late Tertiary detachment faults in the Bullfrog Hills, southwestern Nevada

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6462800

Maldonado, F

A complex structural terrane containing two detachment faults and numerous high-angle and listric normal faults is exposed in the Bullfrog Hills. Metamorphosed late Precambrian rocks are exposed in a central structural culmination which has previously been interpreted as a metamorphic core complex. The lower detachment fault separates that core complex from an overlying incomplete succession of highly faulted lower and middle Paleozoic rocks. The faulted Paleozoic rocks are truncated above by a major upper detachment fault. A succession of faulted Miocene volcanic rocks of ash-flow tuffs, volcaniclastic rocks, and rhyolite, latite, dacite, and basalt lava flows overlies the upper detachment fault. The volcanic succession dips at moderate to high angles into the upper detachment fault and is truncated by it. Internally, the volcanic succession is repeated in blocks bounded by normal faults that terminate against or flatten to merge with the upper detachment fault. The geometry of the normal faults and repetition and dip direction of the volcanic rock succession suggest that extension above at least the upper detachment fault was relatively WNW and ESE. Muscovite and biotite from the metamorphic core have been dated radiometrically (K-Ar method) by other investigators as 11.2 and 10.5 Ma respectively. Extension across the complex, however, is likely younger because an ash-flow tuff, dated radiometrically (sanidine, K-Ar method) by R. W. Kistler (USGS) from an adjacent area as 7.5 Ma old, is involved in the detachment faulting.

• Research Organization: Geological Survey, Denver, CO (USA)
• OSTI ID: 6462800
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580100* -- Geology & Hydrology-- (-1989)
AGE ESTIMATION
BIOTITE
CENOZOIC ERA
FEDERAL REGION IX
GEOLOGIC AGES
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GEOLOGY
GEOMETRY
ISOTOPE DATING
MATHEMATICS
METAMORPHIC ROCKS
MICA
MINERALS
MUSCOVITE
NEVADA
NORTH AMERICA
ORIENTATION
PRECAMBRIAN ERA
ROCKS
SILICATE MINERALS
STRATIGRAPHY
TERTIARY PERIOD
TUFF
USA