Multi-proxy investigation of silicate weathering
IPGP - Îlot Cuvier
University Southern California
Silicate rock weathering is a key process that produces soils, delivers nutrients to the ocean, and consumes atmospheric CO2, thereby modulating Earth’s climate. An increase in uplift rates and the resulting rise in erosion and weathering has therefore been invoked as the mechanism potentially responsible for long-term cooling over the past ~60 million years. To test this hypothesis, a robust reconstruction of weathering is needed, which requires geochemical proxies that are primarily sensitive to weathering processes and reliably recorded in marine sediments. Studies utilizing a single proxy typically yield ambiguous results due to the interplay of multiple fractionating processes in the terrestrial and the marine environments. I will talk about using germanium to silicon ratios (Ge/Si) and stable Ge isotopes (?74Ge) to complement lithium stable isotopes (?7Li) in an effort to reconstruct weathering intensity over the Cenozoic. I will show data from watersheds in the Andes, Amazon, and Costa Rica, as well as seawater, hydrothermal fluids, and marine sediments.