Sulfur and carbon isotopic systematics of Guadalupian‐Lopingian (Permian) mid‐Panthalassa: <scp>δ³⁴S</scp> and <scp>δ¹³C</scp> profiles in accreted paleo‐atoll carbonates in Japan

<jats:title>Abstract</jats:title><jats:p>Immediately before the extinction of the end‐Guadalupian (Middle Permian; <jats:italic>ca</jats:italic> 260 Ma), a significant change to the global carbon cycle occurred in the superocean Panthalassa, as indicated by a prominent positive δ<jats:sup>13</jats:sup>C excursion called the Kamura event. However, the causes of this event and its connection to the major extinction of marine invertebrates remain unclear. To understand the mutual relationships between these changes, we analyzed the sulfur isotope ratio of the carbonate‐associated sulfate (CAS) and HCl‐insoluble residue, as well as the carbon isotope ratio of bulk organic matter, for the Middle‐Upper Permian carbonates of an accreted mid‐oceanic paleo‐atoll complex from Japan, where the Kamura event was first documented. We detected the following unique aspects of the stable carbon and sulfur isotope records. First, the extremely high δ<jats:sup>13</jats:sup>C values of carbonate (δ<jats:sup>13</jats:sup>C<jats:sub>carb</jats:sub>) over +5 ‰ during the Capitanian (late Guadalupian) were associated with large isotopic differences between carbonate and organic matter (Δ<jats:sup>13</jats:sup>C = δ<jats:sup>13</jats:sup>C<jats:sub>carb</jats:sub> − δ<jats:sup>13</jats:sup>C<jats:sub>org</jats:sub>). We infer that the Capitanian Kamura event reflected an unusually large amount of dissolved organic matter in the expanded oxygen minimum zone at mid‐depth. Second, the δ<jats:sup>34</jats:sup>S values of CAS (δ<jats:sup>34</jats:sup>S<jats:sub>CAS</jats:sub>) were inversely correlated with the δ<jats:sup>13</jats:sup>C<jats:sub>carb</jats:sub> values during the Capitanian to early Wuchiapingian (early Late Permian) interval. The Capitanian trend may have appeared under increased oceanic sulfate conditions, which were accelerated by intense volcanic outgassing. Bacterial sulfate reduction with increased sulfate concentrations in seawater may have stimulated the production of pyrite that may have incorporated iron in pre‐existing iron hydroxide/oxide. This stimulated phosphorus release, which enhanced organic matter production and resulted in high δ<jats:sup>13</jats:sup>C<jats:sub>carb</jats:sub>. Low δ<jats:sup>34</jats:sup>S<jats:sub>CAS</jats:sub> values under high sulfate concentrations were maintained and the continuous supply of sulfate cannot by explained only by the volcanic eruption of the Emeishan Trap, which has been proposed as a cause of the extinction. The Wuchiapingian δ<jats:sup>34</jats:sup>S<jats:sub>CAS</jats:sub>–δ<jats:sup>13</jats:sup>C<jats:sub>carb</jats:sub> correlation, likely related to low sulfate concentration, may have been caused by the removal of oceanic sulfate through the massive evaporite deposition.</jats:p>