| ON STEADY STATE IN MOUNTAIN BELTS, WITH THE OLYMPIC MOUNTAINS AS AN EXAMPLE | ||
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WILLETT, Sean D., Earth and Space Sciences, Univ of Washington, Seattle, WA 98195, swillett@u.washington.edu and BRANDON, Mark T., Department of Geology and Geophysics, Yale Univ, P.O. Box 208109, 210 Whitney Avenue, New Haven, CT 06520-8109 The dynamic system of tectonics and erosion contains important feedback mechanisms such that orogenic systems tend toward a steady state. This concept is often invoked, but the nature of the steady state is commonly not specified. We identify four types of steady state that characterize the orogenic system and illustrate these cases by using numerical-model results and natural examples. These types are (1) flux steady state, (2) topographic steady state, (3) thermal steady state, and (4) exhumational steady state: they refer to the erosional flux, the topography, the subsurface temperature field, and the spatial pattern of cooling ages, respectively. Models suggest that the topography will reach a steady mean form at the scale of an orogenic belt, but perfect topographic steady state is unlikely to be achieved at shorter length scales. Thermal steady state is a precondition for exhumational steady state and in the case of temperature-dependent deformation, topographic steady state. Exhumational steady state is characterized by reset age zones spatially nested according to closure temperature, as illustrated in natural systems from New Zealand, the Cascadia accretionary margin, and Taiwan. | ||
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Cordilleran Section - 98th Annual Meeting (May 13–15, 2002)
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| Session No. 28 Pattern and Rates of Long-term Deformation across the Washington Segment of the Cascadia Forearc High CH2M Hill Alumni Center: Ballroom 110C 1:30 PM-5:30 PM, Tuesday, May 14, 2002 | ||
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