No abstract

The Paleocene-Eocene Thermal Maximum (PETM; ~55.9 Ma) was a geologically rapid warming period associated with carbon release, which caused a marked increase in the hydrological cycle. Here, we use lithium (Li) isotopes to assess the global change in weathering regime, a critical carbon drawdown mechanism, across the PETM. We find a negative Li isotope excursion of ~3‰ in both global seawater (marine carbonates) and in local weathering inputs (detrital shales). This is consistent with a very large delivery of clays to the oceans or a shift in the weathering regime toward higher physical erosion rates and sediment fluxes. Our seawater records are best explained by increases in global erosion rates of ~2× to 3× over 100 ka, combined with model-derived weathering increases of 50 to 60% compared to prewarming values. Such increases in weathering and erosion would have supported enhanced carbon burial, as both carbonate and organic carbon, thereby stabilizing climate.

17The Ganges river system is responsible for the transportation of a large flux of 18 dissolved materials derived from Himalayan weathering to the oceans. Silicate 19 weathering-driven cooling resulting from uplift of the Himalayas has been 20 proposed to be a key player in Cenozoic climate variation. This study has 21analysed Li isotope (δ 7 Li) ratios from over 50 Ganges river waters and 22 sediments, in order to trace silicate weathering processes. Sediments have δ 7 Li of 23 ~0‰, identical to bulk continental crust, however suspended sediment depth 24 profiles do not display variations associated with grain size that have been 25