Ordovician dating

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Life continued to flourish during the Ordovician as it did in the earlier Cambrian period, although the end of the period was marked by the Ordovician–Silurian extinction event.Invertebrates, namely molluscs and arthropods, dominated the oceans.While recognition of the distinct Ordovician period was slow in the United Kingdom, other areas of the world accepted it quickly.

The corresponding rocks of the Ordovician System are referred to as coming from the Lower, Middle, or Upper part of the column.It ended with a major extinction event 443.5 million years ago that wiped out 60% of marine genera.The dates cited are recent radiometric dates and vary slightly from those used in other sources.The Ordovician spans 41.2 million years from the end of the Cambrian Period 485.4 million years ago (Mya) to the start of the Silurian Period 443.8 Mya.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.

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