Sulfur isotope evidence for transient marine-shelf oxidation during the Ediacaran Shuram Excursion

The Ediacaran Shuram Excursion (SE) was a major negative δ13Ccarb excursion (to −12‰) thought to reflect significant atmospheric-oceanic oxidation, although direct evidence is limited. Here, we model changes in seawater sulfate concentrations ([SO42−]sw) during the SE by using paired S-isotope data of cogenetic sedimentary pyrite and carbonate-associated sulfate from the Ediacaran Doushantuo Formation (South China), making independent calculations for inner-shelf and upper-slope sections. Our results show a significant increase of [SO42−]sw toward the peak of the SE and a large proximal-to-distal gradient across the Yangtze Platform. Our findings provide direct evidence for transient oxidation of marine-shelf water masses during the SE, providing insights into Ediacaran oceanic oxygenation, the origin of the SE, and contemporaneous bioevolutionary events.