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 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 Period, approximately 513 to 509 million years ago. Estimates for the decline in global diversity over these events range from 50% of marine genera{{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|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}} up to 80%.{{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}} Among the organisms affected by this event were the small shelly fossils, archaeocyathids (an extinct group of sponges), trilobites, brachiopods, hyoliths, and mollusks.{{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}}{{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}}{{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 }}
Causes
There are several hypotheses for the causes of these extinctions. There is evidence that major changes in the carbon cycle{{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 |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 }}{{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}}{{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]{{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}} and sea level occurred during this time.{{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 }} Evidence also exists for the development of anoxia (a loss of oxygen) in some environments in the oceans.{{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 |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}}{{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}}
One hypothesis that unifies this evidence links these environmental changes to widespread volcanic eruptions caused by the emplacement of the Kalkarindji Large Igneous Province or LIP.{{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 |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}}{{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 |language=en |volume=34 |issue=6 |pages=461 |doi=10.1130/G22122.1 |issn=0091-7613}}{{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 }} 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. 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.{{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}} The precise timing between the eruptions and the extinction events remain unresolved.
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]