View source for End-Botomian mass extinction

{{Short description|Two extinction intervals that occurred during Stages 4 and 5 of the Cambrian Period}}
{{annotated image/Extinction
|annotations=
{{Annotation|35|62|Botomian}}
|caption=Apparent extinction intensity, i.e. the fraction of [[genus|genera]] going extinct at any given time, as reconstructed from the [[fossil record]].  (Graph not meant to include recent epoch of [[Holocene extinction event]])}}

The '''end-Botomian mass extinction event''', also known as the '''late early Cambrian extinctions''', refer to two extinction intervals that occurred during Stages 4 and 5 of the [[Cambrian|Cambrian Period]], approximately 513 to 509 million years ago. Estimates for the decline in global diversity over these events range from 50% of marine genera<ref name=":0">{{Cite journal|last1=Zhuravlev|first1=Andrey Yu.|last2=Wood|first2=Rachel A.|date=1996|title=Anoxia as the cause of the mid-Early Cambrian (Botomian) extinction event|url=https://pubs.geoscienceworld.org/geology/article/24/4/311-314/206497|journal=[[Geology (journal)|Geology]]|language=en|volume=24|issue=4|pages=311|doi=10.1130/0091-7613(1996)024<0311:aatcot>2.3.co;2|issn=0091-7613|url-access=subscription}}</ref> up to 80%.<ref>{{Cite journal |last=Signor |first=Philip W. |date=1992 |title=Taxonomic diversity and faunal turnover in the Early Cambrian: Did the most severe mass extinction of the Phanerozoic occur in the Botomian stage? |journal=The Paleontological Society Special Publications |language=en |volume=6 |pages=272 |doi=10.1017/S2475262200008327 |issn=2475-2622 |doi-access=free}}</ref> Among the organisms affected by this event were the [[small shelly fossils]], [[Archaeocyatha|archaeocyathids]] (an extinct group of sponges), [[Trilobite|trilobites]], [[Brachiopod|brachiopods]], [[Hyolitha|hyoliths]], and [[Mollusca|mollusks]].<ref name=":0" /><ref>{{Cite journal|last=Zhuravlev|first=Andrey Yu.|date=1996|title=Reef {{sic|nolink=y|ecosytem}} recovery after the Early Cambrian extinction|journal=Geological Society, London, Special Publications|language=en|volume=102|issue=1|pages=79–96|doi=10.1144/GSL.SP.1996.001.01.06|s2cid=130774496 |issn=0305-8719}}</ref><ref name="Porter2004HalkieriidsMidCambrianAustralia">{{cite journal |author=Porter, S.M. |date=May 2004 |title=Halkieriids in Middle Cambrian Phosphatic Limestones from Australia |url=https://dx.doi.org/10.1666/0022-3360%282004%29078%3C0574%3AHIMCPL%3E2.0.CO%3B2 |journal=[[Journal of Paleontology]] |volume=78 |issue=3 |pages=574–590 |citeseerx=10.1.1.573.6134 |doi=10.1666/0022-3360(2004)078<0574:HIMCPL>2.0.CO;2 |s2cid=131557288 |access-date=2008-08-01}}</ref><ref>{{Cite journal |last=Debrenne |first=Françoise |date=1991 |title=Extinction of the Archaeocyatha |journal=[[Historical Biology]] |language=en |volume=5 |issue=2–4 |pages=95–106 |doi=10.1080/10292389109380393 |issn=0891-2963 |url=https://www.tandfonline.com/doi/abs/10.1080/10292389109380393#:~:text=Archaeocyaths%20are%20a%20group%20of,pattern%20of%20extinction%20is%20proposed. |access-date=18 April 2023|url-access=subscription }}</ref>

==Causes==
There are several hypotheses for the causes of these extinctions. There is evidence that major changes in the [[carbon cycle]]<ref>{{Cite journal|last1=Brasier |first1=M. D. |last2=Corfield |first2=R. M. |last3=Derry |first3=L. A.|last4=Rozanov |first4=A. Yu. |last5=Zhuravlev |first5=A. Yu. |date=1994 |title=Multiple δ13C excursions spanning the Cambrian explosion to the Botomian crisis in Siberia |url=https://pubs.geoscienceworld.org/geology/article/22/5/455-458/206101 |journal=[[Geology (journal)|Geology]] |language=en |volume=22 |issue=5 |pages=455 |doi=10.1130/0091-7613(1994)022<0455:mcestc>2.3.co;2 |issn=0091-7613|url-access=subscription }}</ref><ref>{{Cite journal |last1=Brasier |first1=M D |last2=Sukhov |first2=S S |date=1998 |title=The falling amplitude of carbon isotopic oscillations through the Lower to Middle Cambrian: northern Siberia data |journal=[[Canadian Journal of Earth Sciences]] |language=en |volume=35 |issue=4 |pages=353–373 |doi=10.1139/e97-122|issn=0008-4077}}</ref><ref>{{Cite journal |last1=Faggetter |first1=Luke E. |last2=Wignall |first2=Paul B. |last3=Pruss |first3=Sara B. |last4=Newton |first4=Robert J. |last5=Sun |first5=Yadong |last6=Crowley |first6=Stephen F. |date=2017 |title=Trilobite extinctions, facies changes and the ROECE carbon isotope excursion at the Cambrian Series 2–3 boundary, Great Basin, western USA |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |language=en |volume=478 |pages=53–66 |doi=10.1016/j.palaeo.2017.04.009 |url=http://eprints.whiterose.ac.uk/115157/1/Faggetter%20et%20al.%2C%202017..pdf}} Available at [https://www.researchgate.net/publication/315961877_Trilobite_extinctions_facies_changes_and_the_ROECE_carbon_isotope_excursion_at_the_Cambrian_Series_2-3_boundary_Great_Basin_western_USA ResearchGate]</ref><ref>{{Cite journal |last1=Zhu |first1=Mao-Yan |last2=Zhang |first2=Jun-Ming |last3=Li |first3=Guo-Xiang |last4=Yang |first4=Ai-Hua |date=2004 |title=Evolution of C isotopes in the Cambrian of China: implications for Cambrian subdivision and trilobite mass extinctions|journal=[[Geobios]] |language=en |volume=37 |issue=2 |pages=287–301 |doi=10.1016/j.geobios.2003.06.001}}</ref> and sea level occurred during this time.<ref name=":0" /><ref>{{Cite journal|last=Hallam |first=A |date=December 1999 |url=https://www.sciencedirect.com/science/article/abs/pii/S0012825299000550 |title=Mass extinctions and sea-level changes |journal=[[Earth-Science Reviews]] |volume=48 |issue=4 |pages=217–250 |doi=10.1016/S0012-8252(99)00055-0 |access-date=18 April 2023|url-access=subscription }}</ref> Evidence also exists for the development of [[Anoxic event|anoxia]] (a loss of oxygen) in some environments in the oceans.<ref name=":0" /><ref>{{Cite journal|last1=Hough |first1=M. L. |last2=Shields |first2=G.A. |last3=Evins |first3=L.Z. |last4=Strauss |first4=H.|last5=Henderson |first5=R.A. |last6=Mackenzie |first6=S. |date=2006 |url=https://www.researchgate.net/publication/230272533 |title=A major sulphur isotope event at c . 510 Ma: a possible anoxia-extinction-volcanism connection during the Early-Middle Cambrian transition?: Global warming as a major determining factor in biosphere evolution |journal=[[Terra Nova (journal)|Terra Nova]] |language=en |volume=18 |issue=4 |pages=257–263 |doi=10.1111/j.1365-3121.2006.00687.x |s2cid=130528056 |access-date=18 April 2023}}</ref><ref>{{Cite journal|last1=Pagès |first1=Anais |last2=Schmid |first2=Susanne |last3=Edwards |first3=Dianne |last4=Barnes |first4=Stephen |last5=He |first5=Nannan |last6=Grice |first6=Kliti |date=2016 |title=A molecular and isotopic study of palaeoenvironmental conditions through the middle Cambrian in the Georgina Basin, central Australia |journal=[[Earth and Planetary Science Letters]] |url=https://www.researchgate.net/publication/302632195 |language=en |volume=447 |pages=21–32 |doi=10.1016/j.epsl.2016.04.032 |access-date=18 April 2023}}</ref>

One hypothesis that unifies this evidence links these environmental changes to widespread volcanic eruptions caused by the emplacement of the [[Kalkarindji]] [[Large igneous province|Large Igneous Province]] or LIP.<ref name=":2">{{Cite journal |last1=Evins |first1=Lena Z. |last2=Jourdan |first2=Fred |last3=Phillips |first3=David |date=2009 |title=The Cambrian Kalkarindji Large Igneous Province: Extent and characteristics based on new 40Ar/39Ar and geochemical data |journal=[[Lithos (journal)|Lithos]] |language=en |volume=110 |issue=1–4 |pages=294–304 |doi=10.1016/j.lithos.2009.01.014 |hdl=20.500.11937/35356 |hdl-access=free}}</ref><ref name=":1">{{Cite journal|last1=Glass |first1=Linda M |last2=Phillips |first2=David |date=2006 |title=The Kalkarindji continental flood basalt province: A new Cambrian large igneous province in Australia with possible links to faunal extinctions |journal=[[Geology (journal)|Geology]] |language=en |volume=34 |issue=6 |pages=461 |doi=10.1130/G22122.1 |issn=0091-7613}}</ref><ref>{{cite journal |doi=10.1016/j.gloplacha.2012.01.007 |title=Paleozoic large igneous provinces of Northern Eurasia: Correlation with mass extinction events |date=2012 |last1=Kravchinsky |first1=Vadim A. |journal=Global and Planetary Change |volume=86-87 |pages=31–36 }}</ref> These widespread eruptions would have injected large amounts of greenhouse gases into the atmosphere causing warming of the climate and subsequent acidification and loss of oxygen in the oceans.<ref name=":2" /> Mercury anomalies have been discovered in strata corresponding to the extinction event; however, such enrichments in mercury are also found in older rocks that predate the biotic crisis.<ref>{{cite journal |last1=Faggetter |first1=Luke E. |last2=Wignall |first2=Paul B. |last3=Pruss |first3=Sara B. |last4=Jones |first4=D. S. |last5=Grasby |first5=Stephen E. |last6=Widdowson |first6=M. |last7=Newton |first7=Robert J. |date=5 April 2019 |title=Mercury chemostratigraphy across the Cambrian Series 2 – Series 3 boundary: evidence for increased volcanic activity coincident with extinction? |url=https://www.sciencedirect.com/science/article/abs/pii/S0009254119300415 |journal=[[Chemical Geology]] |volume=510 |pages=188–199 |doi=10.1016/j.chemgeo.2019.02.006 |s2cid=135233659 |access-date=18 April 2023}}</ref> The precise timing between the eruptions and the extinction events remain unresolved.<ref name=":1" />

==References==
{{reflist}}

==External links==
*[https://web.archive.org/web/20080803011232/http://www.palaeos.com/Paleozoic/Cambrian/Botomian.htm Palaeos: Botomian]

* [http://www.fossilmuseum.net/Paleobiology/Tommotian_fauna.htm Tommotian fauna] 

[[Category:Cambrian Series 2 extinctions]]
[[Category:Extinction events]]