Multiple sulfur isotopes (32S, 33S, 34S, and 36S) measured on pyrites from the Penglaitan section, the Global Stratotype Section and Point (GSSP) for the Guadalupian-Lopingian Series boundary, and from the auxiliary Tieqiao section in South China show a sulfur isotope signal of negative and positive δ34S with negative Δ33S. We suggest that these data indicate mixing of 34S-enriched and 34S-depleted sulfur in the sediments, which may have been driven by shoaling of sulfidic waters. Similar isotopic data of negative δ34S with negative Δ33S were also observed from the EF section in the Delaware Basin of west Texas (USA). The consistency of the minor sulfur isotopic anomalies from both South China and west Texas suggests a causal link between widespread shoaling of sulfidic waters and the end-Guadalupian mass extinction.

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