Silurian graphical timeline | ||||||||
−444 — – −442 — – −440 — – −438 — – −436 — – −434 — – −432 — – −430 — – −428 — – −426 — – −424 — – −422 — – −420 — – −418 — |
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Subdivision of the Silurian according to the ICS, as of 2023. [3] Vertical axis scale: Millions of years ago | ||||||||
The Mulde event was an anoxic event, [4] and marked the second of three 1 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 Fröjel 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]
^1 The Ireviken, Mulde, and Lau events were all closely followed by isotopic excursions.