HR: 14:25h
AN: V13F-04 INVITED    [Abstracts]
TI: Weathering Rates Across Natural Landscape Gradients, Measured Using Cosmogenic Radionuclides
AU: * Kirchner, J W
EM: kirchner@berkeley.edu
AF: Dept. of Earth and Planetary Science, University of California, Berkeley, CA 94720-4767, United States
AU: * Kirchner, J W
EM: kirchner@berkeley.edu
AF: Swiss Federal Institute for Forest, Snow, and Landscape Research (WSL), Zuercherstrasse 111, Birmensdorf, CH-8903, Switzerland
AU: Ferrier, K L
EM: ferrier@eps.berkeley.edu
AF: Dept. of Earth and Planetary Science, University of California, Berkeley, CA 94720-4767, United States
AU: Ferrier, K L
EM: ferrier@eps.berkeley.edu
AF: Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA 94550, United States
AU: Riebe, C S
EM: csriebe@gmail.com
AF: Dept. of Earth and Planetary Science, University of California, Berkeley, CA 94720-4767, United States
AU: Finkel, R C
EM: finkel1@llnl.gov
AF: Dept. of Earth and Planetary Science, University of California, Berkeley, CA 94720-4767, United States
AU: Finkel, R C
EM: finkel1@llnl.gov
AF: Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA 94550, United States
AB: Landscape gradients provide "natural laboratories" for studying how weathering rates respond to environmental conditions. Over the past several years, we have developed methods for measuring long-term (1,000's to 10,000's of years) chemical weathering rates in actively eroding terrain, using measurements of cosmogenic ¹⁰Be and the elemental composition of regolith and its parent rock. These methods are applicable to a wide range of field situations, thus facilitating comparative studies of weathering rates and processes. We have used these methods to measure rates of physical erosion and chemical weathering across three elevation transects, spanning up to 1500m in altitude, and across a network of over 40 field sites spanning large gradients in climate and tectonic forcing. Comparisons among these sites show that chemical weathering rates respond to variations in temperature and precipitation, and that they are also strongly coupled to rates of physical erosion. Rates of physical erosion, in turn, respond to variations in hillslope gradients, tectonic forcing, and lithology. Physical erosion rates are also highly episodic, as demonstrated by comparing cosmogenic nuclide measurements with direct measurements of erosion rates over decadal timescales. The view that emerges is of a highly dynamic system in which chemical weathering and physical erosion are coupled to climatic and tectonic forcing, and to each other.
DE: 1886 Weathering (0790, 1625)
DE: 3617 Alteration and weathering processes (1039)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting