Multiple S-isotopic evidence for episodic shoaling of anoxic water during Late Permian mass extinction

Global fossil data show that profound biodiversity loss preceded the final catastrophe that killed nearly 90% marine species on a global scale at the end of the Permian. Many hypotheses have been proposed to explain this extinction and yet still remain greatly debated. Here, we report analyses of all four sulphur isotopes (32S, 33S, 34S and 36S) for pyrites in sedimentary rocks from the Meishan section in South China. We observe a sulphur isotope signal (negative δ34S with negative Δ33S) that may have resulted from limitation of sulphate supply, which may be linked to a near shutdown of bioturbation during shoaling of anoxic water. These results indicate that episodic shoaling of anoxic water may have contributed to the profound biodiversity crisis before the final catastrophe. Our data suggest a prolonged deterioration of oceanic environments during the Late Permian mass extinction. A final catastrophe killed 90% of marine species at the end of the Permian period, but significant biodiversity loss preceded this event. In this study, sulphur isotope evidence suggests that incursion of anoxic water into shallow regions may have contributed to biodiversity loss.