Petrography and geochemistry of the Permian-Triassic boundary interval, Yangou section, South China: Implications for early Griesbachian seawater δ13CDIC gradient with depth

The two most negative δ13C values in claystones of Beds 21-3 and 35 are probably related to meteoric diagenesis. Above and/or below the meteorically influenced beds, the dolomite and calcite have uniformly positive δ13C values. The primary carbon isotopic compositions are probably preserved in the early Griesbachian carbonate from the platform Yangou section, which could probably be related to the poor formation of the outermost Fe-rich HCD cortex. Compared to the slope carbonate from the Meishan section, the platform carbonate from the Yangou section has lower primary δ13Ccarb values. It is estimated that the δ13CDIC gradient with depth between Yangou and Meishan is less than the previously suggested. The results highlight the need for evaluation of local δ13Ccarb as record of δ13CDIC in paleoseawater, and carry important implications for understanding the Permian-Triassic carbonate successions throughout the world.