Ìgbà Ọ̀rdòfísíà

Ìgbà Ọ̀rdòfísíà 488.3–443.7 ẹgbẹgbẹ̀rún ọdun sẹ́yìn PreЄ Є O S D C P T J K Pg N
Mean atmospheric O2 content over period duration	ca. 13.5 Vol % (68 % of modern level)
Mean atmospheric CO2 content over period duration	ca. 4200 ppm (15 times pre-industrial level)
Mean surface temperature over period duration	ca. 16 °C (2 °C above modern level)
Sea level (above present day)	180m; rising to 220m in Caradoc and falling sharply to 140m in end-Ordovician glaciations

The Ordovician (pronounced /ɔrdəˈvɪʃən/) is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago (ICS, 2004, chart). It follows the Cambrian Period and is followed by the Silurian Period. The Ordovician, named after the Celtic tribe of the Ordovices, was defined by Charles Lapworth in 1879 to resolve a dispute between followers of Adam Sedgwick and Roderick Murchison, who were placing the same rock beds in northern Wales into the Cambrian and Silurian periods respectively. Lapworth, recognizing that the fossil fauna in the disputed strata were different from those of either the Cambrian or the Silurian periods, realized that they should be placed in a period of their own.

Itokasi

Preceded by Proterozoic Eon	542 Ma - Phanerozoic Eon - Present
	542 Ma - Paleozoic Era - 251 Ma						251 Ma - Mesozoic Era - 65 Ma			65 Ma - Cenozoic Era - Present
	Kámbríà	Ọ̀rdòfísíà	Sílúríà	Dẹfoníà	Eléèédú	Pẹ́rmíà	Tríásíkì	Jùrásíkì	Ẹlẹ́fun	Ìbíniàtijọ́	Ìbíniọ̀tun	Quaternary