Ordovician dating

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Fish, the world’s first true vertebrates, continued to evolve, and those with jaws may have first appeared late in the period. The Ordovician Period started at a major extinction event called the Cambrian–Ordovician extinction events about 485.4 ± 1.9 Mya (million years ago), and lasted for about 44.6 million years.It ended with the Ordovician–Silurian extinction event, about 443.4 ± 1.5 Mya (ICS, 2004) that wiped out 60% of marine genera.It received international sanction in 1906, when it was adopted as an official period of the Paleozoic era by the International Geological Congress. 2006) have suggested a ten-second gamma ray burst could have been responsible, destroying the ozone layer and exposing terrestrial and marine surface-dwelling life to radiation; most scientists continue to agree that extinction events are complex events with multiple causes.

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It ended with a major extinction event 443.5 mya that wiped out 60% of marine genera.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.The Ordovician period is the second of the six (seven in North America) periods of the Paleozoic era.The Ordovician follows the Cambrian period and is followed by the Silurian period.Ordovician rocks contained abundant life and contain major oil and gas reservoirs in some regions.

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