Cambrian–Ordovician extinction event

The Cambrian–Ordovician extinction event occurred approximately 543 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.

Marine extinction intensity during Phanerozoic

%

Millions of years ago

(H)

K–Pg

Tr–J

P–Tr

Cap

Late D

O–S

The blue graph shows the apparent percentage (not the absolute number) of marine animal genera becoming extinct during any given time interval. It does not represent all marine species, just those that are readily fossilized. The labels of the traditional "Big Five" extinction events and the more recently recognised Capitanian mass extinction event are clickable links; see Extinction event for more details. (source and image info)

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)

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).

External links

• Early Ordovician Climate
• Speculated Causes For the Cambrian Extinction