HR: 0800h
AN: H51C-1158    [Abstracts]
TI: The Effects of Hyperaridity on Soil Production and Transport on Hillslopes: Adapting Geomorphic Models in the Atacama Desert, Chile
AU: * Owen, J
EM: jowen@nature.berkeley.edu
AF: University of California-Berkeley, Department of Environmental Science, Policy, and Management, Division of Ecosystem Sciences, 151 Hilgard Hall-3110, Berkeley, CA 94720-3110
AU: Dietrich, W
EM: bill@eps.berkeley.edu
AF: University of California-Berkeley, Department of Earth and Planetary Sciences, 307 McCone Hall, Berkeley, CA 94720-4767
AU: Yoo, K
EM: kyoo@nature.berkeley.edu
AF: University of California-Berkeley, Department of Environmental Science, Policy, and Management, Division of Ecosystem Sciences, 151 Hilgard Hall-3110, Berkeley, CA 94720-3110
AU: Amundson, R
EM: earthy@nature.berkeley.edu
AF: University of California-Berkeley, Department of Environmental Science, Policy, and Management, Division of Ecosystem Sciences, 151 Hilgard Hall-3110, Berkeley, CA 94720-3110
AU: Nishiizumi, K
EM: kuni@ssl.berkeley.edu
AF: University of California-Berkeley, Space Sciences Lab, 7 Gauss Way, Berkeley, CA 94720-7450
AB: On most soil-mantled hillslopes, slope-dependent sediment transport is primarily driven by biological processes and, at steady-state, the eroded soil is replaced by production from the underlying saprolite. We are investigating how soil production, weathering, and transport change as precipitation and biological activity decrease to near zero values in order to better understand soil and geomorphic processes in hyperarid deserts and on Mars. We are studying convex hillslopes in the Atacama Desert, Chile along a precipitation gradient (~55 mm to ~2 mm yr$^{-1}$). All sites have similar bedrock, elevation, and temperature, and are surrounded by fluvial sediments of Pliocene age (based on $^{10}$Be and $^{26}$Al exposure ages and Ar-Ar dating of volcanic ash). Our field observations suggest that as precipitation declines to near zero, biologically driven sediment transport ceases and atmospheric deposition may replace saprolite erosion as the dominant mode of soil production. Here we report our initial results for the rates of saprolite erosion and surface gravel transport on these hillslopes. We also present a hillslope soil mass balance model for the Atacama Desert, based on work by Heimsath, Dietrich, and others, that it explicitly includes atmospheric deposition and chemical processes as controls on hillslope soil thickness.
DE: 1824 Geomorphology (1625)
DE: 1886 Weathering (1625)
DE: 1625 Geomorphology and weathering (1824, 1886)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting