HR: 0800h
AN: H51C-0365    [Abstracts]
TI: Characterization of Parent Material in Loess Dominated Soils
AU: * Cacy, C M
EM: cacy@colorado.edu
AF: Department of Environmental Studies INSTAAR, University of Colorado Campus Box 450, Boulder, CO 80309 United States
AU: Anderson, S P
EM: suzanne.anderson@colorado.edu
AF: Department of Geography INSTAAR, University of Colorado Campus Box 450, Boulder, CO 80309
AB: Analysis of elemental gains and losses in soils relative to unweathered parent material provides a powerful tool for calculating weathering rates. In depositional systems, such as loess, parent material may be heterogeneous over time or space. We are studying weathering of loess soils in order to assess the full impact of glaciers on silicate weathering rates. Given that chemical weathering fluxes generally are enhanced by high physical erosion rates, one might expect glaciers to have high chemical weathering fluxes, yet low temperatures keep silicate-weathering fluxes from glaciers low. Weathering of glacial erosion products where they are deposited may be more significant than at the site of erosion. Glacial loess deposited over a landscape should increase weathering fluxes from soils due to their fine grain size. In loess-derived soils, parent material (the loess deposited at the surface) may vary in composition as function of time and distance from the source. For insight into this question, the Matanuska Valley in Alaska provides an active glacial and loess depositional system. In the summer of 2005 unweathered loess was collected from a 17 meter cliff on the Matanuska river. Analysis of loess samples from different depths in this profile will illustrate changes in deposition rates and variations in mineralogy over time. Additionally, silt collected at intervals along the modern Matanuska riverbank demonstrates compositional changes in silt available for eolian transport. We will assess the influence of the variations in these samples of parent material on calculation of elemental mass gains and losses in soils. Having an understanding of parent material in loess depositional systems allows more accurate chemical weathering flux calculations.
DE: 0486 Soils/pedology (1865)
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
DE: 1886 Weathering (0790, 1625)
SC: Hydrology [H]
MN: Fall Meeting 2005