HR: 16:00h
AN: H34A-01 INVITED     [Abstracts]
TI: The Transience Of Soil Mantled Landscapes: Quantifying Sediment Transport Processes
AU: * Heimsath, A M
EM: arjun.heimsath@dartmouth.edu
AF: Dartmouth College, Dept. of Earth Sciences, Hanover, NH 03755 United States
AU: Furbish, D J
EM: david.j.furbish@vanderbilt.edu
AF: Vanderbilt University, Dept. of Earth and Environmental Sciences, Nashville, TN 37235 United States
AU: Dietrich, W E
EM: bill@seismo.berkeley.edu
AF: University of California, Dept. of Earth and Planetary Sciences, Berkeley, CA 94720 United States
AB: Soil-covered upland landscapes are common for much of the habitable world, and our understanding of their evolution as a function of different climatic, tectonic, and geologic regimes is important across a wide range of disciplines. Erosion laws direct quantitative study of the processes shaping Earth's surface and form the basis of landscape evolution modeling, but are based on limited field data. Here we use in situ produced cosmogenic 10-Be and 26-Al concentrations from granitic saprolite to quantify an exponential decline in soil production with increasing soil thickness for a new field site in Point Reyes, California. Non-uniform soil thicknesses across the hillslopes suggest that transient soil storage is occurring. Results are similar to soil production functions from two different, previously studied field sites, and are used with extensive measurements of soil thickness to quantify depth-integrated sediment transport flux. Plots of calculated sediment fluxes against the product of soil depth and hillslope gradient provide the first field-based evidence that soil transport is a nonlinear, depth-dependent function. Data from all sites suggest that the widely used linear "diffusion" equation is only appropriate for shallow gradient, convex-up regions, while the depth-dependent transport law is more broadly applicable. We use these field-quantified transport relationships to show how soil-mantled landscapes might respond to changes in climatic or tectonic forcing.
DE: 1815 Erosion
DE: 1826 Geomorphology: hillslope (1625)
DE: 1862 Sediment transport (4558)
DE: 1865 Soils (0486)
SC: Hydrology [H]
MN: Fall Meeting 2005