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Ordovician period stages
Timechart with stages in the Ordovician period
The Ordovician period (486-443 mya) follows the Cambrian period and precedes the Silurian. It has seven stages, distributed over Early, Middle, and Late phases. These are, in turn, subdivided into a number of individual faunal episodes characterized by various index fossils.
The
Ordovician, named after a mountain range in Wales, was defined in the
late 19th century as a needed transitional period between the Cambrian
and Silurian periods, as previously defined in the 1830s and 40s by
Sedgewick and Murchison, based on geological formations and associated
fossils in Wales and elsewhere in Britain.
References
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