Calcium isotope evidence of Late Permian-Upper Triassic ocean acidification from Kamura, Japan

The end-Permian mass extinction (EPE; ca. 251.9 Ma) is the largest biological disaster in the Phanerozoic and has been hypothesized to be caused by ocean acidification due to large amount of CO₂ (>10,000 Pg C) emitted through Siberian Traps volcanism. The marine ecosystem, however, did not recover until several million years after the EPE. The continued deterioration of the environment is suggested to be responsible for the delayed recovery of life. To understand the causes and consequence of the end-Permian extinction event, we performed detailed geochemical analysis (δ^44/40Ca, δ¹³C, ^87/86Sr and trace elements) on carbonate from the Kamura section in Japan. The Kamura section analyzed spans the Uppermost Permian and Upper Triassic, deposited as shallow water successions in a seamount in the central Panthalassic ocean. The age framework of the Kamura section was determined based on conodont zonation and carbonate carbon isotope stratigraphy. Both δ^44/40Ca and δ¹³C_carb exhibit negative excursions across the PTB, exhibiting closely coupled relationship. We suggest that CO₂-driven global ocean acidification best explains the coincidence of the negative excursions in both δ^44/40Ca and δ¹³C_carb. During the Middle and Late Triassic, strong coupling between δ^44/40Ca_carb and δ¹³C_carb is collapsed, suggesting a recovery to normal marine pH. ⁸⁷Sr/⁸⁶Sr suggest the Siberian Trap volcanism played a significant role on the δ^44/40Ca records during the Early Triassic.