Reconstruction of Paleoenvironment of the Eocene Source Rocks in the Xihu Sag, East China Sea, Based on Major and Trace Elements and Biomarkers

HIGHLIGHTS (1) The organic and inorganic multi-indexes jointly reveal that Baoshi and Pinghu formations are freshwater-brackish water, and the salinity decreases from the Baoshi Formation to the Pinghu Formation. (2) Oxidizing conditions progressively intensified in the Xihu Sag during the Baoshi–Pinghu sedimentary period due to an overall regression. (3) Terrestrial biomarkers C27R/C29R and C19TT/C23TT, as well as the oxides of Al2O3 and TiO2, indicate a significant increase in the terrigenous input of the Pinghu Formation.