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 and species: Orthoceras regulare
Name meaning: “straight horn”
Classification: Order: Orthocerida – Family: Orthoceratidae
Location: Baltic States
Time: Middle Ordovician
Genus: Cameroceras sp.
Name meaning: “chambered horn”
Classification: Order: Endocerida – Family: Endoceratidae
Location: Laurentia, Baltica, and Siberia
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 and species: Orthoceras regulare
Name meaning: “straight horn”
Classification: Order: Orthocerida – Family: Orthoceratidae
Location: Baltic States
Time: Middle Ordovician
Genus: Cameroceras sp.
Name meaning: “chambered horn”
Classification: Order: Endocerida – Family: Endoceratidae
Location: Laurentia, Baltica, and Siberia
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

Genus: Cameroceras sp.
Name meaning: “chambered horn”
Classification: Order: Endocerida – Family: Endoceratidae
Location: Laurentia, Baltica, and Siberia
Time: Middle Ordovician

Floian Age/Stage

Early Ordovician: 477.7 to 470.0 million years ago

The Floian Stage is the second stage of the Ordovician Period and marks the last stage of the early Ordovician. The Floian is named after Flo, a village in Vastergotland, southern Sweden. The name Floan was first purposed in 2004, but the International Commision on Stratigraphy adapted Floian as the official name of the stage.

Tremadocian Age/Stage

Early Ordovician: 485.4 to 477.7 million years ago

The Tremadocian Stage was named in 1846 by Adam Sedgwick and is named after the village of Tremadoc in Wales. The Tremadocian is the first stage of the lower or early Ordovician period.

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