The Cambrian–Ordovician extinction event occurred approximately 488 million years ago (m.y.a.). This early Phanerozoic Eon extinction event eliminated many brachiopods and conodonts, and severely reduced the number of trilobite species.
It was preceded by the less-documented (but probably worse) End-Botomian extinction event around 517 million years ago and the Dresbachian extinction event about 502 million years ago.
The Cambrian–Ordovician event ended the Cambrian Period, and led into the Ordovician Period in the Paleozoic Era.
Theories
- Glaciation
- Depletion of oxygen in marine waters
- Flood basalt event (Kalkarindji large igneous province, Australia) [1]
Controversy
Soft-body fossils with morphology characteristic of the Cambrian have been uncovered in Morocco, dated 20 million years post-extinction. The paper suggests that Cambrian species persisted into the mid-Paleozoic and that the Cambrian-Ordovician extinction is instead the result of a gap in the stratigraphic record, with organic remains preserved where conditions were agreeable.[2]
See also
- End-Botomian extinction event, circa 517 m.y.a.
- Dresbachian extinction event, circa 502 m.y.a.
- Geologic time scale
- Furongian, Late or Upper Cambrian period
- Early Ordovician period
Further reading
- Gradstein, Felix, James Ogg, and Alan Smith, eds., 2004. A Geologic Time Scale 2004 (Cambridge University Press).
- Hallam, Anthony and Paul B. Wignall, 1997. Mass extinctions and their aftermath (Oxford University Press).
- Webby, Barry D. and Mary L. Droser, eds., 2004. The Great Ordovician Biodiversification Event (Columbia University Press).
References
- ^ Kravchinsky, V. A. (2012). Paleozoic large igneous provinces of Northern Eurasia: Correlation with mass extinction events. Global and Planetary Change, 86, 31-36.
- ^ Roy, P. V.; et al. "Ordovician faunas of Burgess Shale type". Nature (465): 215–218.
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External links
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