Cambrian–Ordovician extinction event

Marine extinction intensity during the Phanerozoic

%

Millions of years ago

(H)

K–Pg

Tr–J

P–Tr

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 "Big Five" extinction events are clickable hyperlinks; see Extinction event for more details. (source and image info)

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 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