Evidence for late movement on the Whipple detachment fault, southeastern California

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

OSTI ID:5291870

Beratan, K K ^[1]; Nielson, J E ^[2]

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1. Univ. of Pittsburgh, PA (United States). Dept. of Geology and Planetary Science
2. Geological Survey, Menlo Park, CA (United States)

Sedimentary strata of middle Miocene age contain evidence for tectonic unroofing of lower plate rocks in core of the Whipple Mountains. The unroofing probably represents an episode of major movement on the Whipple detachment fault, or related faults at about 14 Ma, a time approximately coeval with regionally-widespread basaltic volcanism that has been interpreted as late- to post-extension. The unroofing marks the inception of present-day topography, which is significantly different from earlier landscapes. Late detachment fault movement in the Whipple Mountains area is indicated by structural relations and abrupt contrasts in clast types between sedimentary units that are older and younger than about 14 Ma. Limestone in the southern Whipple Mountains that is cut by the Whipple detachment fault, contains clasts of 18.5-Ma Peach Springs Tuff. Thus, the last movements on the Whipple detachment fault must have occurred after 18.5 Ma, and involved sufficient displacement to juxtapose post-Peach Springs Tuff rocks against the lower plate. Regionally, units older than about 14 Ma contain no clasts of lower plate rocks, whereas younger strata are dominated by such rocks, including mylonites. The pre-14 Ma sections do not contain large volumes of conglomerate with clasts from upper-plate sources of Tertiary age. Therefore, rapid widespread denudation of the lower plate probably was accomplished by a distinct structural event, rather than gradually by erosion.

• OSTI ID: 5291870
• 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
CALIFORNIA
CENOZOIC ERA
DEVELOPED COUNTRIES
DISPLACEMENT RATES
GEOLOGIC AGES
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
GEOLOGY
NORTH AMERICA
QUATERNARY PERIOD
STRATA MOVEMENT
TERTIARY PERIOD
USA