Floian

The Floian is the second stage of the Ordovician geologic period. It succeeds the Tremadocian with which it forms the Lower Ordovician epoch. It precedes the Dapingian stage of the Middle Ordovician. The Floian extended from 477.7 to 470 million years ago. The lower boundary is defined as the first appearance of the graptolite species Tetragraptus approximatus.[1]

Epochs in the Ordovician

-485 —

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-480 —

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-475 —

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-470 —

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-465 —

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-460 —

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-455 —

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-450 —

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-445 —

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Cambrian

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Silurian

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Epochs of the Ordovician Period.
Axis scale: millions of years ago.

Naming and history

The Floian stage is named after Flo, a village in Västergötland, southern Sweden. The name "Floan" was proposed in 2004, but the International Commission on Stratigraphy adapted Floian as the official name of the stage.[2]

GSSP

The GSSP of the Floian is the Diabasbrottet Quarry (58.3589°N 12.5024°E / 58.3589; 12.5024) which is an outcrop of a shale-dominated stratigraphic succession. The lower boundary of the Floian is defined as the first appearance of Tetragraptus approximatus which is above the base of the Tøyen Shale.[2] Radiometric dating has set the Tremadocian-Floian boundary at 477.7million years ago.[1]

Palaeontology

Agnathans

Agnathans of the Floian
Taxa	Presence	Location	Description	Images
Arandaspis	Tremadocian-Floian	Alice Springs, Australia

Molluscs

Cephalopods

Cephalopods of the Tremadocian
Taxa	Presence	Location	Description	Images
Proterovaginoceras	Tremadocian-Darriwilian

References

"GSSP Table - Paleozoic Era". Geologic TimeScale Foundation. Retrieved 24 November 2012.
Bergström, Stig M.; Anita Löfgren; Jörg Maletz (2004). "The GSSP of the Second (Upper) Stage of the Lower Ordovician Series: Diabasbrottet at Hunneberg, Province of Västergötland, Southwestern Sweden" (PDF). Episodes. 27 (4): 265–272. Retrieved 20 September 2012.

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[GSSP_Table_-_Paleozoic_Era-1] "GSSP Table - Paleozoic Era". Geologic TimeScale Foundation. Retrieved 24 November 2012.

[Bergström_2004-2] Bergström, Stig M.; Anita Löfgren; Jörg Maletz (2004). "The GSSP of the Second (Upper) Stage of the Lower Ordovician Series: Diabasbrottet at Hunneberg, Province of Västergötland, Southwestern Sweden" (PDF). Episodes. 27 (4): 265–272. Retrieved 20 September 2012.