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The Mulde event was an anoxic event,[4] and marked the second of three1 relatively minor mass extinctions (the Ireviken, Mulde, and Lau events) during the Silurian period. It coincided with a global drop in sea level, and is closely followed by an excursion[clarification needed] in geochemical isotopes. Its onset is synchronous with the deposition of the Fröel Formation in Gotland.[4] Perceived extinction in the conodont fauna, however, likely represent a change in the depositional environment of sedimentary sequences rather than a genuine biological extinction.[5]
Higher resolution δ13C isotope analysis identifies differences in the organic and carbonate carbon isotope curves (Δ13C), allowing the inference of a sustained drop in CO2 levels coincident with the extinction once sedimentological data are taken into account.[6]