Biogeochemical Weathering Controls on Soil Formation and Landscape Development

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AbstractBiogeochemical weathering controls on soil formation and landscape development.The soil production rate is defined as the rate at which bedrock, in this study chemically weathered granodiorite, converts to a mobile layer (soil, defined by loss of granitic texture). Previous studies have established the form of the inverse relationship between soil production rates and soil thickness. However, these studies have not compared erosion to solute losses during landscape lowering, or incorporated detailed consideration of the biogeochemical weathering processes that must precede, and generally follow, soil formation. In this project, conservation of mass equations will be solved using geochemical tracer results and existing cosmogenic dating information to determine long-term mass transfers due to erosion and solute loss during landscape development on the Bemboka Granodiorite in SE Australia. Variation in solute versus erosional fluxes with soil thickness and landscape position will be evaluated, and possible relationships between the solute loss rates (prior to soil formation), soil thickness, and microbial processes in the weathered granite will be examined. The analysis will also yield values for long-term erosion and solute losses for most elements per unit area of land surface per unit time. This investigation extends prior geomorphological approaches to incorporate biogeochemical as well as biophysical weathering contributions to soil formation and landscape evolution. Broader impacts of the research will stem from new insights into factors controlling rates of soil formation, improved understanding of the processes by which landscapes respond to perturbation, and the quantification of long-term sediment and solute fluxes to the oceans.