Mulde event

{{short description|Anoxic event causing mass extinctions during the Silurian period}}

{{Silurian graphical timeline}}

The Mulde event was an anoxic event, and marked the second of three{{ref|otherEvents|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{{what|date=April 2020}} in geochemical isotopes. Its onset is synchronous with the deposition of the Fröjel Formation in Gotland.{{cite journal

|author1=Samtleben, C. |author2=Munnecke, A. |author3=Bickert, T. | year = 2000

| title = 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

| journal = Facies

| volume = 43

| issue = 1

| pages = 1–38

| doi = 10.1007/BF02536983

|bibcode=2000Faci...43....1S |s2cid=130640332 }} Perceived extinction in the conodont fauna, however, likely represent a change in the depositional environment of sedimentary sequences rather than a genuine biological extinction.{{cite journal|doi=10.1111/pala.12326|title=Harnessing stratigraphic bias at the section scale: Conodont diversity in the Homerian (Silurian) of the Midland Platform, England|journal=Palaeontology|year=2017|last1=Jarochowska|first1=Emilia|last2=Ray|first2=David C|last3=Röstel|first3=Philipp|last4=Worton|first4=Graham|last5=Munnecke|first5=Axel|volume=61|pages=57–76|s2cid=135200300 |doi-access=free}}

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.{{Cite journal | doi = 10.1016/j.chemgeo.2021.120256 |issn=0009-2541 | title = Asynchronous δ13Ccarb and δ13Corg records during the onset of the Mulde (Silurian) positive carbon isotope excursion from the Altajme core, Gotland, Sweden | year = 2021 | last1 = Biebesheimer | first1 = Ellie J. | last2 = Cramer | first2 = Bradley D. | last3 = Calner | first3 = Mikael | last4 = Barnett | first4 = Bruce A. | last5 = Oborny | first5 = Stephan C. | last6 = Bancroft | first6 = Alyssa M. | journal = Chemical Geology |volume=576 | page = 120256 |bibcode=2021ChGeo.57620256B |s2cid=234817512 }}