Age constraints on pre and synextensional Tertiary strata and normal faulting in the Windermere Hills, northeast Nevada

Conference · Thu Apr 01 04:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5095871

Mueller, K J ^[1]; Cerveny, P F ^[2]; Snee, L W ^[3]; Brown, F H ^[4]

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1. Univ. of Montana, Missoula, MT (United States). Dept. of Geology
2. ARCO Oil and Gas Co., Plano, TX (United States)
3. Geological Survey, Denver, CO (United States)
4. Univ. of Utah, Salt Lake city, UT (United States). Dept. of Geology

Tertiary strata exposed in the eastern Windermere Hills and northern Pequop Mountains define the development of a widespread late eocene volcanic landscape and multiple generations of Oligocene-Miocene extensional half-grabens. 28 new [sup 40]Ar/[sup 39]Ar and fission-track age determinations and tephrachronology analyses on ash-flow and air fall tuffs suggest a complex history of extensional strain. The oldest Tertiary rocks exposed in the region consist of a diverse suite of calc alkaline volcanic rocks and volcaniclastic sediments. [sup 40]Ar/[sup 39]Ar age determinations of volcanic strata in this sequence indicate that it ranges from 39.18 [+-] .12 to 40.38 [+-] 0.6 Ma in age; strata exposed in the Deadman Creek area include 260 meters of rhyolitic ash-flow tuff, andesitic flow breccia, a rhyodacite lava flow and volcaniclastic conglomerate and sandstone. Subsequent extension is defined by the development of west-tilted, extensional half-grabens between 34.79 [+-] .18 to 39.18 [+-] .12 Ma ([sup 40]Ar/[sup 39]Ar). These basins evolved during the development of the Black Mountain fault (BMF), an east-rooted low-angle normal fault overlain by an array of synthetic tilt-blocks. Subsequent extension is defined by a poorly constrained, north-dipping normal fault of Oligocene or Miocene age. Both the BMF and the north-dipping normal fault are overprinted by two east-dipping listric normal faults which bound 1--3 km deep half-grabens filled with 11.9 [+-] 0.3 to about 15 Ma strata (zircon fission track, tephrachronology analyses and mammalian fossils). An important aspect of the thermal history of the Windermere Hills includes a middle Miocene (ca. 11--16 Ma) thermal event (200 [+-] 50 C > T > 280 C), which annealed, or partially annealed fission tracks in zircon grains in several of the extensional basins discussed above.

• OSTI ID: 5095871
• Report Number(s): CONF-9305259--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:5
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AGE ESTIMATION
ARGON 39
ARGON 40
ARGON ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CENOZOIC ERA
DEVELOPED COUNTRIES
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FISSION TRACKS
GEOLOGIC AGES
GEOLOGIC FAULTS
GEOLOGIC FORMATIONS
GEOLOGIC FRACTURES
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
IGNEOUS ROCKS
ISOTOPE DATING
ISOTOPES
LIGHT NUCLEI
MINERALS
NEVADA
NORTH AMERICA
NUCLEI
PARTICLE TRACKS
RADIOISOTOPES
ROCKS
SILICATE MINERALS
STABLE ISOTOPES
STRAINS
TERTIARY PERIOD
TUFF
USA
VOLCANIC ROCKS
YEARS LIVING RADIOISOTOPES
ZIRCON