Please join us for a special B2-CZO seminar given by Mark Torres (Department of Earth Sciences, University of Southern California).
Abstract: The interaction between water and rock at Earth’s surface (i.e. chemical weathering) plays a major role in global biogeochemical cycles. As a result, determining the sensitivity of chemical weathering to tectonic forcings is key to many problems in the Earth Sciences. In this study, chemical weathering is investigated along the transition from the rapidly eroding Andes Mountains to the tectonically "quiescent" Amazon foreland floodplain in Peru. In this system, chemostatic concentration-runoff behavior is associated with the steep Andean catchments and results in higher weathering fluxes relative to the foreland floodplain sites. Analysis of the isotopic ratios of dissolved inorganic carbon, sulfur, and strontium reveals that high weathering fluxes from the Andean sites are dominantly driven by sulfide mineral oxidation and are associated with CO2 release into the ocean-atmosphere system. This correlation between tectonic uplift and sulfide-oxidation driven CO2 release, which is also seen in other global datasets, has many important implications for the geologic evolution of global biogeochemical cycles. A case study of weathering during the Cenozoic era is used to explore the effects of tectonic uplift on the coupled cycling of carbon, sulfur, and dioxygen.