COMBINING ABSOLUTE DATING OF ALLUVIAL FANS WITH SOIL CHARACTERISTICS TO INVESTIGATE SPATIAL AND TEMPORAL VARIABILITY OF SLIP ALONG THE CENTRAL GARLOCK FAULT – PILOT KNOB VALLEY, CALIFORNIA

RITTASE, William, Geology, University of Kansas, Lawrence, KS 66045, MCDONALD, Eric, Division of Earth & Ecosystem Sciences, Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512, WALKER, J. Douglas, Geology, University of Kansas, 1475 Jayhawk Blvd, 120 Lindley Hall, Lawrence, KS 66045, KIRBY, Eric, Department of Geosciences, Penn State University, University Park, PA 16802, GOSSE, John, Earth Sciences, Dalhousie Univ, Halifax, NS B3J 3J5 and SPENCER, Joel Q.G., Geology, Kansas State University, 108 Thompson Hall, Manhattan, KS 66506-3201, jdwalker@ku.edu

Use of terrestrial cosmogenic nuclide (TCN) and optically stimulated luminescence (OSL) dating, combined with detailed soil profile development indices (PDI) in arid alluvial settings can be useful for neotectonic studies. In this report, we examine both late Quaternary strike-slip offsets related to the Garlock fault and uplift in response to north-south shortening across the Garlock fault.

In Pilot Knob Valley, regional age control is provided by 5 ¹⁰Be depth profiles, 3 OSL samples and 3 soil PDI sites. Our TCN ages vary between 100+ and ca. 20 ka. and, combined with displacements estimated from LiDAR and field surveys, allow us to quantify active deformation rates. In addition, ongoing development of a regional chronofunction of soil development allows extrapolation of regional fan chronology. Although OSL samples are forthcoming, these are expected to provide an important check of ages estimated from soil PDIs and may provide slightly older ages from deposits within the fan.

Together, our TCN, OSL and PDI data will help test for the presence of (1) along-strike variations in uplift rate, and/or (2) temporal variations in uplift and strike-slip rates. At one site along the southern Slate Range, a shutter ridge developed in a ca. 30 ka. alluvial fan has blocked drainage across the fault. Soil characteristics of an alluvial deposit truncated by the shutter ridge suggest that 40 – 50 m of slip has accrued in the past 3-4 ky. OSL samples will test this age, but at present, our results suggest that slip along the central Garlock fault has been markedly variable during the Holocene.

Session No. 220

T137. Developing Chronologies for Tectonic Geomorphic Studies

Tuesday, 2 November 2010: 1:30 PM-5:30 PM

Hall E (Colorado Convention Center)

Geological Society of America Abstracts with Programs. Vol. 42, No. 5, p.522

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