HR: 10:44h
AN: OS42A-02    [Abstracts]
TI: Rock dissolution, soils, and riverine solute fluxes to the world's oceans
AU: * Brantley, S
EM: brantley@eesi.psu.edu
AF: Penn State University, 2217 Earth & Engineering Science Building, University Park, PA 16802, United States
AB: Seawater chemistry responds to changes in terrestrial weathering over time in response to the forcing functions of tectonism, climate, and anthropogenic activity. Many researchers have attempted to read the effects of weathering solute fluxes in sediments in the rock record. For example, the Sr isotope record in marine limestones has been interpreted with respect to continental weathering fluxes. In contrast, our ability to predict such fluxes forward in time is limited because of difficulties in calculating weathering fluxes and the rates of formation of soils on weathering or eroding bedrock. Weathering solute fluxes are recorded in many areas as chemical and textural profiles imprinted on regolith. These profiles, when observed on noneroding regolith, propagate downward as the regolith pile thickens with time. Such a profile can be described as a quasi-stationary state. If the rate of erosion of such regolith is increased larger than the weathering advance rate, the regolith thickness must decrease with time. For such a condition, the regolith eventually disappears unless some process accelerates the weathering advance rate. However, during weathering, as regolith thins, the rate of weathering advance increases because porefluid chemistry becomes more corrosive. Thus, the rates of erosion and weathering advance can be coupled through porefluid chemistry, maintaining regolith thickness at steady state values. Solute fluxes and regolith profiles can be predicted for simplified lithologies under these assumptions. The weathering advance rate is not, however, observed to be the same when calculated at the watershed, soil profile, and hand specimen scales. Several phenomena contribute to this observation. Approaches will be described to understand the prediction and modeling of weathering advance rates across scales as well as the controls on weathering solute fluxes to the world's oceans.
DE: 0330 Geochemical cycles (1030)
DE: 0412 Biogeochemical kinetics and reaction modeling (0414, 0793, 1615, 4805, 4912)
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly