HR: 0800h
AN: ED41A-0077    [Abstracts]
TI: Three Dimensional (U-Th)/He Constraints on the Exhumation History of the Shawave- Nightingale Horst Block, Northwestern Nevada
AU: * Hall, B
EM: imaequichick@aol.com
AF: Monta Vista High School, 21840 Mcclellan Rd, Cupertino, CA 95014,
AU: Weinert, A
EM: gnirps2010@yahoo.com
AF: Rio Lindo Adventist Academy, 3200 Rio Lindo Ave, Healdsburg, CA 95448, United States
AU: Whitehill, C S
EM: cwhitehill@gmail.com
AF: Stanford University, 450 Serra Mall, bldg 320, Stanford, CA 94305,
AB: We present data from the northwestern Basin and Range Province that provide constraints on the along-strike variation in slip distribution on the Granite Springs Valley fault as well as three-dimensional constraints on the exhumation history of the Shawave-Nightingale horst block. Through the application of coupled apatite-fission track (AFT) and apatite (U-Th)/He (AHe) thermo-chronometry we have determined that an episode of rapid slip (6- 8km) on the fault and exhumation of the granitic block occurred between ~13-8Ma. Combined with data from a more southerly transect and through morphometric observations of the general topographic expression of the range, we are able to delimit that the greatest amount of slip on the fault is coincident with the Juniper Peak transect in the central Shawave Range. The overall distribution on the fault is highest near this central part of the range and is distributed asymmetrically along strike with less relief in the southern termination of the fault and the least exhumation at the very northern termination of the fault. Recent paleo-seismic investigations of the Granite Springs Valley fault document a minimum of two Holocene slip events of ~2-3m along the entire (~60km) length of the range front fault that occurred simultaneously along fault strike. These data are exciting because this is the first three-dimensional application of thermo-chronology to the problem of Basin and Range fault propagation and slip history. Our geologic data support an asymmetric slip history that is in contrast to well-documented simultaneous Quaternay rupture and implies that the fault grew asymmetrically as typically modeled for the normal fault growth but at some point in time, or at some critical fault length, the entire system of range front faults was connected and now currently slips at a constant rate along the length of the range. This holds strong implications for considering geologic vs. geodetic strain rates and for delineating seismic hazard in the region. Data presented here are, in part, a product of the diligent efforts of students, Briana Hall and Arian Weinert through their participation in the Stanford School of Earth Sciences High School Internship Program, Summer 2007 mentored by Caroline S. Whitehill.
UR: http://pangea.stanford.edu/outreach/
DE: 0805 Elementary and secondary education
DE: 1140 Thermochronology
DE: 8175 Tectonics and landscape evolution
SC: Education and Human Resources [ED]
MN: 2007 Fall Meeting