HR: 10:20h
AN: H52B-01    [Abstracts]
TI: Distinguishing Between Lithogenic and Biogenic Processes in a Soil Chronosequence
AU: * White, A
EM: afwhite@USGS.gov
AF: U. S. Geological Survey, 345 Middlefield Rd, Menlo Park, CA 94025, United States
AU: Schulz, M S
EM: mschulz@usgs.gov
AF: U. S. Geological Survey, 345 Middlefield Rd, Menlo Park, CA 94025, United States
AU: Vivit, D V
EM: dvvivit@usgs.gov
AF: U. S. Geological Survey, 345 Middlefield Rd, Menlo Park, CA 94025, United States
AU: Bullen, T D
EM: tdbullen@usgs.gov
AF: U. S. Geological Survey, 345 Middlefield Rd, Menlo Park, CA 94025, United States
AB: It is increasingly recognized that many geochemical processes observed in soils result from a combination of chemical weathering and biological cycling. This relationship is particularly important in understanding the distribution of inorganic macronutrients which are products of chemical weathering and are used extensively in the biosphere. Approaches to differentiating between these processes are being investigated in a soil chronosequence (65 to 260 kyrs) developed on silicic sediments contained on marine terraces near Santa Cruz California. An example of what we term the lithogenic/biogenic fractionation occurs soil pore waters in which specific cation ratios such as Ca/Na, Mg/Na and Sr/Na are spatially delineated and are dependent on the extent of mineral reactions and the degree plant uptake. These fractionation are further discussed in terms of other major elements as well as Ge/Si ratios and the isotopes of Ca, Sr and Si. Results of this study indicate that important macronutrients, including K and Ca, are tightly cycled to considerable depths in the profiles which weathering-dominated elements such as Na and Si produce net exports.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0790 Weathering (1625, 1886)
DE: 0798 Modeling
DE: 1009 Geochemical modeling (3610, 8410)
DE: 1838 Infiltration
SC: Hydrology [H]
MN: 2007 Fall Meeting