HR: 1340h
AN: H43C-0379    [Abstracts]
TI: Balancing Physical Erosion and Chemical Weathering In and Out of the Steady State
AU: * Waldbauer, J R
EM: jwal@mit.edu
AF: MIT/WHOI Joint Program in Chemical Oceanography, 77 Massachusetts Ave, Cambridge, MA 02139 United States
AU: Chamberlain, C
EM: chamb@pangea.stanford.edu
AF: Geological and Environmental Sciences, Stanford University, Building 320, Stanford, CA 94305 United States
AB: Establishing the nature of a steady state for the earth's surface and criteria for a landscape to be considered to be in such a state presents conceptual and practical challenges. Reconciliation of model predictions of weathering rates with geochemical and geomorphologic data brings this problem to the fore. We present an analytical weathering model that emphasizes the roles of tectonic uplift and weathering profile development in setting the balance between physical and chemical alteration. Ultimately, these are the processes that determine the supply rate of fresh weatherable material to the surface. To facilitate comparisons across tectonic regimes, the model is parameterized in terms of an `effective surface age'. This parameter describes a time scale on which weathering processes can occur in a given environment, and further allows examination of the bounds of steady-state conditions under varying circumstances. Our modeling suggests that physical erosion and chemical weathering, while broadly correlated, do not obey a uniform relationship over the whole spectrum of tectonic environments. Power-law behavior holds over a certain range, but towards extremes of both high uplift and ancient, stable cratons, other descriptions are more appropriate. Non-steady-state events, including slope failures, glaciations, isostatic adjustments and tectonic reorganization, will perturb or overprint the steady-state signal on a variety of temporal and spatial scales.
DE: 1886 Weathering (1625)
DE: 1045 Low-temperature geochemistry
DE: 1625 Geomorphology and weathering (1824, 1886)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting