The end-Permian mass extinction was the largest biotic catastrophe of the last 540 million years, resulting in the disappearance of >80% of marine species. The effects of such catastrophe were also particularly long, since a full biotic recovery only occured 4–8 million years after the extinction event. Marine paleochemistry seems essential to explain not only the triggers of the mass extinction but also the reason why the effects lasted so long.
This study focus on redox chemistry changes in the Panthalassic Ocean (which represented ∼85–90% of the global ocean area at the time) and analyses all four sulfur isotopes (32S, 33S, 34S, and 36S) for pyrite from the deep-sea sediments of western Canada and Japan, two of the only three places where Permian–Triassic boundary deep-sea sediments are known to have survived subduction in accretionary terranes or marginal uplifts.
Previous studies offered competing hypotheses, proposing extensive deepwater anoxia (“superanoxic ocean”) or suboxic deep waters in combination with spatially constrained thermocline anoxia. The data now presented suggests that shoaling of H2S-rich waters, i.e. sulfur deplection, may have been the most revelant factor driving the mass extinction and delaying the recovery of the marine ecosystem.
Sources: PNAS, Cosmos
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Title: “Redox chemistry changes in the Panthalassic Ocean linked to the end-Permian mass extinction and delayed Early Triassic biotic recovery”
Authors: Guijie Zhanga, Xiaolin Zhanga, Dongping Hua, Dandan Lia, Thomas J. Algeob, James Farquharc, Charles M. Hendersond, Liping Qina, Megan Shene, Danielle Shene, Shane D. Schoepferd, Kefan Chena, & Yanan Shena
Publisher: Proceedings of the National Academy of Sciences of the United States of America
Read it online: article page.
“The end-Permian mass extinction represents the most severe biotic crisis for the last 540 million years, and the marine ecosystem recovery from this extinction was protracted, spanning the entirety of the Early Triassic and possibly longer. Numerous studies from the low-latitude Paleotethys and high-latitude Boreal oceans have examined the possible link between ocean chemistry changes and the end-Permian mass extinction. However, redox chemistry changes in the Panthalassic Ocean, comprising ∼85–90% of the global ocean area, remain under debate. Here, we report multiple S-isotopic data of pyrite from Upper Permian–Lower Triassic deep-sea sediments of the Panthalassic Ocean, now present in outcrops of western Canada and Japan. We find a sulfur isotope signal of negative Δ33S with either positive δ34S or negative δ34S that implies mixing of sulfide sulfur with different δ34S before, during, and after the end-Permian mass extinction. The precise coincidence of the negative Δ33S anomaly with the extinction horizon in western Canada suggests that shoaling of H2S-rich waters may have driven the end-Permian mass extinction. Our data also imply episodic euxinia and oscillations between sulfidic and oxic conditions during the earliest Triassic, providing evidence of a causal link between incursion of sulfidic waters and the delayed recovery of the marine ecosystem.”
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