A smooth negative shift of organic carbon isotope ratios at an end-Permian mass extinction horizon in central pelagic Panthalassa

The end-Permian mass extinction is associated with a global perturbation in the carbon isotopic composition of carbonates and organic matter, but such changes are not well documented from pelagic deep-sea sediments. One of the most continuous pelagic deep-sea Permian/Triassic boundary (PTB) sections, the Am-2 section, is exposed in the accretionary complexes of Japan. New data for organic carbon isotope ratios (δ13Corg) were obtained from 36 samples from section Am-2. The δ13Corg excursion curve exhibits a negative shift of 2.0‰ in the low-latitude, pelagic Panthalassic Ocean at the end of the Permian, which coincides with a radiolarian extinction. The δ13Corg values of pelagic, deep-sea Panthalassic sections and those of shallow-water sections from Panthalassic seamounts exhibit a smooth, negative shift that lacks temporary increases like those reported from Paleotethyan PTB sections. Absence of temporary δ13Corg increases at the PTB in Panthalassa may reflect less algal and bacterial blooming in pelagic Panthalassa compared to the shallow-water Paleotethys.