Mulde event

Silurian graphical timeline
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−444 — – −442 — – −440 — – −438 — – −436 — – −434 — – −432 — – −430 — – −428 — – −426 — – −424 — – −422 — – −420 — – −418 —	Paleozoic Ordovician Silurian Devonian Llandovery Wenlock Ludlow Přídolí Rhuddanian Aeronian Telychian Sheinwoodian Homerian Gorstian Ludfordian	← Lau event ← Mulde event^[1] ← Ireviken event^[2]
Subdivision of the Silurian according to the ICS, as of 2021.^[3] Vertical axis scale: millions of years ago.

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]

Notes

^1 The Ireviken, Mulde, and Lau events were all closely followed by isotopic excursions.

References

1. Jeppsson, L.; Calner, M. (2007). "The Silurian Mulde Event and a scenario for secundo—secundo events". Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 93 (02): 135–154. doi:10.1017/S0263593300000377.
2. Munnecke, A.; Samtleben, C.; Bickert, T. (2003). "The Ireviken Event in the lower Silurian of Gotland, Sweden-relation to similar Palaeozoic and Proterozoic events". Palaeogeography, Palaeoclimatology, Palaeoecology. 195 (1): 99–124. doi:10.1016/S0031-0182(03)00304-3.
3. "Chart/Time Scale". www.stratigraphy.org. International Commission on Stratigraphy.
4. Samtleben, C.; Munnecke, A.; Bickert, T. (2000). "Development of facies and C/O-isotopes in transects through the Ludlow of Gotland: Evidence for global and local influences on a shallow-marine environment". Facies. 43 (1): 1–38. doi:10.1007/BF02536983. S2CID 130640332.
5. Jarochowska, Emilia; Ray, David C; Röstel, Philipp; Worton, Graham; Munnecke, Axel (2017). "Harnessing stratigraphic bias at the section scale: Conodont diversity in the Homerian (Silurian) of the Midland Platform, England". Palaeontology. 61: 57–76. doi:10.1111/pala.12326. S2CID 135200300.
6. Biebesheimer, Ellie J.; Cramer, Bradley D.; Calner, Mikael; Barnett, Bruce A.; Oborny, Stephan C.; Bancroft, Alyssa M. (2021). "Asynchronous δ13Ccarb and δ13Corg records during the onset of the Mulde (Silurian) positive carbon isotope excursion from the Altajme core, Gotland, Sweden". Chemical Geology. 576: 120256. Bibcode:2021ChGeo.576l0256B. doi:10.1016/j.chemgeo.2021.120256. ISSN 0009-2541. S2CID 234817512.