Late Cenozoic co-evolution of tectonics, weathering and climate in the Amazon Basin: insights from neodymium and hafnium isotopes
weathering, climate, Andes, Amazon Basin Hf-Nd and Li, Geochemistry, Rare Earths Elements.
Chemical weathering plays an important role in sequestering atmospheric CO2, but its potential influence on global climate over geological time remains debated. To some extent, this uncertainty arises from the difficulty in separating the respective contribution of igneous/metamorphic and sedimentary rocks to total weathering rates during mountain erosion; two types of rocks having different impacts on the long-term carbon cycle. Here, we propose a novel approach for identifying the origin of weathered rocks on continents and their evolution through time, based on the combined analyses of geochemical and isotopic (Hf-Nd and Li) proxies on iron oxide and detrital silicate fractions in the sediment record. This new approach will be used to reconstruct, for the first time, the weathering history of the Amazon Basin for the last 20 Ma and its relationships to the Andean uplift and global climate.