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 (δ¹³C_org) were obtained from 36 samples from section Am-2. The δ¹³C_org 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 δ¹³C_org 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 δ¹³C_org increases at the PTB in Panthalassa may reflect less algal and bacterial blooming in pelagic Panthalassa compared to the shallow-water Paleotethys.