HR: 0800h
AN: H51C-1143    [Abstracts]
TI: Drainage Basin Erosion Rates Along the Death Valley Fault Zone, California From In-Situ Cosmogenic $^{14}$C in Alluvial Sediment: Preliminary Results
AU: * Frankel, K L
EM: kfrankel@usc.edu
AF: Department of Earth Sciences University of Southern California, 3651 Trousdale Parkway ZHS 117, Los Angeles, CA 90089 United States
AU: Pigati, J S
EM: pigati@geo.arizona.edu
AF: Department of Geosciences University of Arizona, Gould-Simpson Building #77 1040 E 4th St., Tucson, AZ 85721 United States
AU: Hoeft, J S
EM: hoeft@usc.edu
AF: Department of Earth Sciences University of Southern California, 3651 Trousdale Parkway ZHS 117, Los Angeles, CA 90089 United States
AU: Lifton, N A
EM: lifton@geo.arizona.edu
AF: Department of Geosciences University of Arizona, Gould-Simpson Building #77 1040 E 4th St., Tucson, AZ 85721 United States
AU: Dolan, J F
EM: dolan@usc.edu
AF: Department of Earth Sciences University of Southern California, 3651 Trousdale Parkway ZHS 117, Los Angeles, CA 90089 United States
AB: Catchment-wide erosion rates and drainage basin evolution are poorly understood processes in arid and hyper-arid climates. We collected samples from two small catchments in Death Valley, CA to determine basin-wide erosion rates using in-situ cosmogenic $^{14}$C to help understand drainage development in a hyper-arid setting. Death Valley is a tectonically active pull-apart system with a normal fault-bounded basin in the center and strike-slip faults to the north and south. On average, the area receives $<$ 5 cm of precipitation per year. Two basins were sampled from different parts of the fault zone; one along the normal fault-bounded segment in the Black Mountains and one from the southern strike-slip segment in the Owlshead Mountains. Topography along the dip-slip segment of the fault zone in the Black Mountains is youthful with steep, high relief catchments, triangular facets, and young fault scarps at the base of the range. Drainage basins in the Black Mountains have high ratios of basin excavated volume to planimetric area and high first-order stream gradients. Additionally, basins formed along the normal fault-bounded segment typically have large, 10-20 m high knickpoints and highly convex channel profiles. In contrast, the Owlshead Mountains are relatively low relief, and appear to be in a state of topographic decay. Samples were collected above and below a $\sim$20 m high knickpoint in the Badwater catchment, above and below a smaller (5 m high) knickzone in the Owlshead Mountains, and at the mouths of both catchments. In-situ $^{14}$C can be used to determine erosion rates in rapidly denuding areas that are integrated over a period of several thousand years. We are particularly interested in post-last glacial maximum erosion rates, which could be a function of climate change and the drying up of glacial Lake Manly, relative base-level fall resulting from recent movement on the fault zone, or a combination of both. Previous studies have shown that climate change since the last glacial maximum appears to have had little or no effect on erosion rates in eastern California. Because of this, drainage basin erosion rates may express a link between ground-rupturing earthquake activity on the Death Valley fault zone and denudation. The catchment-wide erosion rates may also help characterize fault zone segmentation, in conjunction with paleoseismologic, slip rate, and topographic metrics data.
DE: 8107 Continental neotectonics
DE: 8109 Continental tectonics--extensional (0905)
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1035 Geochronology
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting