HR: 12:05h
AN: T32C-08    [Abstracts]
TI: Tectonic Control of Chemical Weathering and CO₂ Drawdown in a Steady State Landscape
AU: * Hren, M T
EM: hren@stanford.edu
AF: Stanford University, Geological and Environmental Sciences Bldg. 320 Lomita Mall Room 118, Stanford, CA 94305 United States
AU: Hilley, G
EM: hilley@pangea.stanford.edu
AF: Stanford University, Geological and Environmental Sciences Bldg. 320 Lomita Mall Room 118, Stanford, CA 94305 United States
AU: Chamberlain, C
EM: chamb@pangea.stanford.edu
AF: Stanford University, Geological and Environmental Sciences Bldg. 320 Lomita Mall Room 118, Stanford, CA 94305 United States
AB: We present a combined steady-state chemical weathering model and field-based study that examines the effects of soil depth and uplift rate on chemical weathering rates across a climate/tectonic uplift gradient. This work demonstrates the importance of rock uplift on chemical weathering relative to the effects of precipitation and temperature and shows that climatically focused erosion acts as a driver of silicate weathering, providing a direct link between climate, tectonics, and CO₂ drawdown. Our model is applied to the Skykomish river basin in the central Washington Cascades. This drainage basin was selected because previous work (Reiners et al. 2003) has shown that long-term erosion rates in the central Cascades are strongly coupled with modern mean annual precipitation patterns suggesting long-term climatically focused erosion in a steady-state topography. Our analysis of cation fluxes from thirteen catchments within this basin show that silicate weathering is strongly dependent on the rate of supply of easily weathered material and the depth of the zone of weathering. As such, the central Washington Cascades are primarily supply-limited, where weathering-derived Si fluxes are directly related to the rate of rock advection into the zone of active weathering. These data show that chemical weathering is strongly linked to areas of high exhumation, such that CO₂ drawdown is approximately 1.5 times higher in areas of rapid exhumation when compared to areas of low exhumation.
DE: 1039 Alteration and weathering processes (3617)
DE: 1815 Erosion
DE: 1824 Geomorphology: general (1625)
DE: 1886 Weathering (0790, 1625)
DE: 8107 Continental neotectonics (8002)
SC: Tectonophysics [T]
MN: Fall Meeting 2005