MGPV EARLY GEOLOGIC CAREER AWARD LECTURE: ARE LITHIUM ISOTOPES GOOD TRACERS OF CONTINENTAL WEATHERING?
Here we presented coupled Li and Sr isotope data in marine carbonates to understand how ocean biogeochemical cycles may impacted most severe mass extinction in Earth history – End-Permian mass extinction. Previous studies have argued that increasing continental weathering was linked to End-Permian mass extinction. However, we observed the lithium isotopic composition of seawater remained constant until a sharp decrease, before the End-Permian Mass Extinction (~ 252 Ma). This massive drop cannot be explained by conventional idea like changing continental weathering rate based on our mass balance modeling. Rather, increased reverse weathering in the ocean was probably responsible for the quick drawdown and extremely low Li isotopic values in the End-Permian to early Triassic ocean. Importantly, this rapid increase in reverse weathering, and its associated changes in ocean chemistry, such as ocean acidification, might have contributed to the End-Permian mass extinction and a protracted biotic recovery in the Early Triassic.