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词汇 Late Ordovician epoch
分类 英语词汇 英语翻译词典
释义

Late Ordovician epoch

英语百科

Ordovician

External mold of Ordovician bivalve showing that the original aragonite shell dissolved on the sea floor, leaving a cemented mold for biological encrustation (Waynesville Formation of Franklin County, Indiana).
A diorama depicting Ordovician flora and fauna.
Nautiloids like Orthoceras were among the largest predators in the Ordovician.
Fossiliferous limestone slab from the Liberty Formation (Upper Ordovician) of Caesar Creek State Park near Waynesville, Ohio.

The Ordovician (pronunciation: /ɔːrdəˈvɪʃən/) is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 485.4 and 443.8 million years ago. 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. While recognition of the distinct Ordovician period was slow in the United Kingdom, other areas of the world accepted it quickly. It received international sanction in 1960, when it was adopted as an official period of the Paleozoic Era by the International Geological Congress.

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