Geologic Time Scale: Ordovician Period
(485.4 to 443.8 million years ago)
The Ordovician Period is the second of six periods in the Paleozoic Era. The name is derived from the Welsh tribe of the Ordovices. Charles Lapworth named it in 1879 to reslove a dispute between followers of Adam Segwich (British geologist and Anglican proest, one of the founders of modern geology) and Roderick Murchison (Scottish geologist who served as director-general of the British Geologic Survey from 1855 until his death in 1871), who were placing the same rock beds in North Wales in the Cambrian and Silurian systems. Lapworth recognised that fossils fauna in disrupted strata (rock layers) were different than those of either the Cambrian or the Silurian systems, and placed them in a system of their own. The Ordovician recieved international approval in 1960 (forty years after Lapworth’s death) when it was adopted as an official period of the Paleozoic Era by the International Geologic Congress.
The first land plants appear in the Ordovician, while the seas were dominated by arthropods and molluscs with a a considerable increase fish (the world’s first true vertebrates).
Hirnantian Age/Stage
Late Ordovician: 445.2 to 443.8 million years ago
The Hirnantian Stage was named in 1933 by B.B. Bancroft after Cwm Hirnant south of Bala, in northerm Wales. Cwn Hirmant means the “valley of the long stream” in Welsh.
Katian Age/Stage
Late Ordovician: 453.0 to 445.2 million years ago
The Katian Stage is the second of the upper or late Ordovician Period. The name Katian is derived from Katy Lake in Atoka County, Oklahoma, United States.
Sandian Age/Stage
Late Ordovician: 458.4 to 453.0 million years ago
The Sanbian Stage was propsed in 2006 and is derived from the village Sodra Sandby in Lund Municipality, Skane County, Sweden.
Darriwilian Age/Stage
Middle Ordovician: 467.3 to 458.4 million years ago
The Darriwilian Stage is the upper stage of the middle Ordovician Period. The Darriwilian was named in 1899 by Thomas Sergeant Hall and name is derived from Darriwil, a parish in County of Grant, Victoria, Australia.
European Darriwilian Stage Middle Ordovician: 467.3 to 458.4 million years ago
Genus: Cameroceras sp.
Name meaning: “chambered horn”
Classification: Order: Endocerida – Family: Endoceratidae
Location: Laurentia, Baltica, and Siberia
Time: Middle Ordovician
Genus and species: Orthoceras regulare
Name meaning: “straight horn”
Classification: Order: Orthocerida – Family: Orthoceratidae
Location: Baltic States
Time: Middle Ordovician
North American Darriwilian Stage Middle Ordovician: 467.3 to 458.4 million years ago
Genus: Cameroceras sp.
Name meaning: “chambered horn”
Classification: Order: Endocerida – Family: Endoceratidae
Location: Laurentia, Baltica, and Siberia
Time: Middle Ordovician
Asian Darriwilian Stage Middle Ordovician: 467.3 to 458.4 million years ago
Genus: Cameroceras sp.
Name meaning: “chambered horn”
Classification: Order: Endocerida – Family: Endoceratidae
Location: Laurentia, Baltica, and Siberia
Time: Middle Ordovician
Dapingian Age/Stage
Middle Ordovician: 470.0 to 467.3 million years ago
The Dapingian Stage is the first stage of the middle Ordovician Period. The Dapingian was introduced in 2007 after Daping, a village that lies near Dapingian GSSP at Huanghuachang.
European Dapingian Stage Middle Ordovician: 470.0 to 467.3 million years ago
Genus: Cameroceras sp.
Name meaning: “chambered horn”
Classification: Order: Endocerida – Family: Endoceratidae
Location: Laurentia, Baltica, and Siberia
Time: Middle Ordovician
Genus and species: Orthoceras regulare
Name meaning: “straight horn”
Classification: Order: Orthocerida – Family: Orthoceratidae
Location: Baltic States
Time: Middle Ordovician
North American Dapingian Stage Middle Ordovician: 470.0 to 467.3 million years ago
Genus: Cameroceras sp.
Name meaning: “chambered horn”
Classification: Order: Endocerida – Family: Endoceratidae
Location: Laurentia, Baltica, and Siberia
Time: Middle Ordovician
Asian Dapingian Stage Middle Ordovician: 470.0 to 467.3 million years ago
