[sup 40]Ar/[sup 39]Ar geochronology of Cenozoic magmatism and faulting, Yerington and northern Wassuk Range Nevada

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

OSTI ID:5342056

Dilles, J H ^[1]; Gans, P B ^[2]

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1. Oregon State Univ., Corvallis, OR (United States). Geosciences Dept.
2. Univ. of California, Santa Barbara, CA (United States). Dept. of Geological Sciences

[sup 40]Ar/[sup 39]Ar radiometric ages ([+-] sigma) refine the ages of magmatism and both normal and strike-slip faulting in the Yerington district and to the east in the northern Wassuk Range portion of the Walker Lane. The oldest rhyolite ignimbrites (28.58 [+-] 0.04 Ma (san)) underlie the Mickey Pass Tuff. Two rhyolite ignimbrites yielded 24.66 [+-] 0.02 (san) and 24.60 [+-] 0.02 (san) Ma and lie in angular unconformity upon the [approximately]26 Ma Singatse Tuff within a NW-striking fault zone in that N. Wassuk Ra., recording the earliest tectonism in the Walker Lane here. In this area, an ignimbrite from the upper part of the Hu-Pwi Rhyodacite yielded 23.09 [+-] 0.04 Ma (bi), and is cut by faults intruded by pyroxene andesites dated at 22.16 [+-] 0.27 Ma (wr). The andesite of Lincoln Flat is closely associated with tectonism throughout the Yerington-N. Wassuk area, and yielded four ages: 14.95 [+-] 0.24 (hbl), 14.08 [+-] 0.23 (hbl), 12.85 [+-] 0.33 (hbl), and 13.83 [+-] 0.17 (hbl) Ma. The 14.95 Ma-andesite is late-tectonic, whereas the 14.08 and 12.85 Ma andesites post-date early, northwest-striking vertical (strike-slip ) and normal faults in the N. Wassuk portion of the Walker Lane. In summary, tectonism initiated in the region within the Walker Lane portion of the northern Wassuk Ra. at [approximately]25 Ma, was active between 23 and 22 Ma, and in the interval prior to 14 Ma. Rapid crustal extension migrated westward to the Yerington district, where normal faulting and 30--40 W -- tilting of the upper crust initiated at 14 Ma and proceeded rapidly for the next 1--2 m.y. This period was succeeded by normal-oblique slip and strike-slip faults bounding Wassuk Group sedimentary basins in the Wassuk Ra. at [approximately]9 Ma and synchronously tilting them 10--35 W. Since [approximately]6 Ma, modern range-front normal faults and NW-striking strike-slip faults have yielded reduced rates of crustal extension and tilting.

• OSTI ID: 5342056
• 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

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