HR: 13:40h
AN: H52D-01    [PDF]
TI: Chemical Weathering in Steady State Orogens
AU: * Chamberlain, C P
EM: chamb@pangea.stanford.edu
AF: Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305 United States
AB: We present an analytical model for steady-state chemical weathering with an emphasis on the effect of uplift on the total rate of weathering is a depth profile. This one-dimensional model accounts for chemical weathering of the various constituent minerals and the total release of cations from the weathering profile as material moves from the bottom of a weathering zone to the surface at constant velocity. This model is parameterized in terms of "effective surface age", which is defined as the amount of time it takes for rock to move from the lower boundary of the weathering profile to the surface. The parameters that determine the effective surface age, the weathering depth and uplift velocity, are variables that are measurable and are generally uniform over large areas of the earth's surface. Thus, the effective surface age is a useful parameter to compare chemical weathering rates in different tectonic regimes. Comparison of model results with data sets from granitic catchments throughout the world show that in general our model reproduces the observed trends in chemical weathering. The following results come from this analysis: 1) Chemical weathering rates are closely linked with tectonism. The chemical weathering rate declines sharply with increasing effective surface age, dropping by more than an order of magnitude between active collisional orogens to temperate cratons; 2) Chemical weathering rates vary in a predictable and systematic fashion within a steady-state orogen. Coupling the one-dimensional model with calculated vertical velocities for a steady-state orogen shows that high weathering rates occur in areas of high uplift, the Inboard region, and lower weathering rates occur in the areas of low uplift of the Outboard region.
DE: 1035 Geochronology
DE: 1040 Isotopic composition/chemistry
DE: 1625 Geomorphology and weathering (1824, 1886)
SC: Hydrology [H]
MN: 2003 Fall Meeting