HR: 10:35h
AN: T12A-02    [Abstracts]
TI: Reconciling observations and theory of erosion rate patterns in the Olympic Mountains of Washington State
AU: * Stolar, D B
EM: dstolar@u.washington.edu
AF: University of Washington, Box 351310, Seattle, WA 98195 United States
AU: Roe, G H
EM: gerard@ess.washington.edu
AF: University of Washington, Box 351310, Seattle, WA 98195 United States
AU: Willett, S D
EM: swillett@u.washington.edu
AF: University of Washington, Box 351310, Seattle, WA 98195 United States
AB: In evaluating models of convergent orogenesis, it is crucial to fully exploit the information that thermochronometry data provide about the long-term pattern of erosion rate. An extensive suite of low-temperature thermochronometry data available for the Olympic Mountains affords an excellent opportunity to determine the information content of such data sets. Along a transect parallel to the North America-Juan de Fuca convergence vector, we invert for the erosion rate profile that best explains a suite of zircon fission track (ZFT), apatite fission track (AFT), and U/Th-He closure ages. The forward model consists of a model that predicts rock trajectories through the orogen, a model that predicts the temperature field in a deforming medium, and closure age models for the three different thermochronometers. We consider step-function erosion rate profiles consisting of a variable number of segments and minimize the weighted root-mean-square misfit of the closure ages using the controlled random search algorithm. The results of the inversions suggest that the ZFT data can only resolve the mean rate of erosion over the entire range, whereas the AFT and U/Th-He data resolve an increase in erosion rate away from the western coast towards the core of the range. This pattern is consistent with a simple model of an eroding critical wedge, which predicts that ridge-valley relief and erosion rates should increase away from the coast.
DE: 1815 Erosion
DE: 8108 Continental tectonics: compressional
DE: 8175 Tectonics and landscape evolution
SC: Tectonophysics [T]
MN: Fall Meeting 2005