The Toarcian lacustrine deposits of the Sichuan Basin (China) are represented mainly by silty marlstones and bivalve rich limestones disposed in decametric-scale thickening upwards sequences. Dense accumulations of bivalve shells are related to episodes of mass mortality under oxygen depleted conditions in the bottom waters. The geochemical detrital proxies indicate a climatic turnover during the Toarcian. The lower part of the Toarcian succession is characterized by high values of Zr/Rb and Sr/Cu that point to warm and arid conditions, whereas the upper part is characterized by low values of Zr/Rb and Sr/Cu and enhanced C-value related to relatively more humid conditions.
