Frasnian

The Frasnian is one of two faunal stages in the Late Devonian period. It lasted from 382.7 million years ago to 372.2 million years ago. It was preceded by the Givetian stage and followed by the Famennian stage.

System/
Period		 Series/
Epoch		 Stage/
Age		 Age (Ma)
Carboniferous Mississippian Tournaisian younger
Devonian Upper/
Late		 Famennian 358.9 372.2
Frasnian 372.2 382.7
Middle Givetian 382.7 387.7
Eifelian 387.7 393.3
Lower/
Early		 Emsian 393.3 407.6
Pragian 407.6 410.8
Lochkovian 410.8 419.2
Silurian Pridoli no faunal stages defined older
Subdivision of the Devonian system
according to the ICS, as of 2017.[1]

Major reef-building was under way during the Frasnian stage, particularly in western Canada and Australia. On land, the first forests were taking shape. In North America, the Antler and Taconic orogenies peaked, which were contemporary with the Bretonic phase of the Variscan orogeny in Europe.

The Frasnian coincides with the second half of the "charcoal gap" in the fossil record, a time when atmospheric oxygen levels were below 13 percent, the minimum necessary to sustain wildfires.[2]

North American subdivisions of the Frasnian include

Name and definition

The Frasnian stage was proposed in 1879 by French geologist Jules Gosselet and was accepted for the lower stage of the Upper Devonian by the Subcommission on Devonian Stratigraphy in 1981.[3] It is named after the village of Frasnes-lez-Couvin in Belgium.[4]

Frasnian life

Fish

Cartilaginous fish
Cartilaginous fish of the Frasnian
Taxa Presence Location Description Images
Stethacanthus

Placoderms
Placoderms of the Frasnian
Taxa Presence Location Description Images
Bruntonichthys Gogo Reef Formation, Australia
Groenlandaspis

Sarcopterygians
Actinistia
Actinistians of the Frasnian
Taxa Presence Location Description Images
Diplocercides Bergisch-Gladbach, Germany A basal actinistian
Miguashaia Escuminac Formation, Quebec A basal actinistian
Tetrapodomorphs
Tetrapodomorphs of the Frasnian
Taxa Presence Location Description Images
Elginerpeton Scat Craig, Scotland
Elpistostege Escuminac Formation, Quebec, Canada
Metaxygnathus New South Wales, Australia
Obruchevichthys Ogre Formation, Latvia
Panderichthys Early Frasnian Mikhailovskii Mine, Zheleznogorsk, Russia
Tiktaalik Fram Formation, Nunavut, Canada

References
  1. http://www.stratigraphy.org/index.php/ics-chart-timescale
  2. McGhee, George R. Jr. (12 November 2013). When the Invasion of Land Failed: The Legacy of the Devonian Extinctions. Columbia University Press. pp. 110–11. ISBN 978-0-231-16057-5. Retrieved 21 April 2015.
  3. Coen-Aubert, Marie; Boulvain, Frédéric (2006). "Frasnian". Geologica Belgica. 9 (1–2): 19–25. Retrieved 10 March 2013.
  4. "Frasnian mudmounds from Belgium". University of Liège. Retrieved 2011-02-25.


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