Molecular and petrographical evidence for lacustrine environmental and biotic change in the palaeo-Sichuan mega-lake (China) during the Toarcian Oceanic Anoxic Event

Abstract The organic-rich upper Lower Jurassic Da'anzhai Member (Ziliujing Formation) of the Sichuan Basin, China is first stratigraphically well-constrained lacustrine succession associated with Toarcian Oceanic Anoxic Event (T-OAE; c. 183 Ma). expansion palaeo-Sichuan mega-lake, probably one most extensive freshwater systems to have existed on planet, marked by large-scale organic productivity and carbon burial during T-OAE, possibly owing intensified hydrological cycling nutrient supply. New molecular biomarker petrographical analyses, combined bulk inorganic geochemical palynological data, are presented here, providing insight into aquatic productivity, land-plant biodiversity terrestrial ecosystem evolution in continental interiors T-OAE. We show that algal growth T-OAE accounted for a significant organic-matter flux lakebed mega-lake. Lacustrine water-column stratification facilitated formation dysoxic–anoxic conditions at lake bottom, favouring preservation sequestration black shales Basin. attribute mega-lake enhanced more vigorous monsoonal climate hinterland greenhouse.