Frasnian

The Frasnian (usually called in the German language only Frasnian ) is in the Earth's lower chronostratigraphic stage of the Late Devonian ( Devonian). The stage took geochronological from about 382.7 million to about 372.2 million years. The Frasnian following the Givetian and is detached from the Famennian.

Naming and history

The Frasnian is named after the Belgian town Frasnes- lez- Couvin (municipality Couvin ) in the Ardennes. Stage and name were proposed in 1862 by Jean Baptiste Julien d' Omalius d' Halloy.

Definition and GSSP

The base of the Frasnian was placed at the first appearance of the conodont species Ancyrodella rotundiloba, which is also the base of the Lower Polygnathus asymmetricus - conodont zone. The end of the stage is marked by the end of the Kellwasser events, a major extinction event in the Upper Devonian ( with type locality in the resin). As the reference profile ( GSSP = Global Stratotype Section and Point) the profile of the Col du Puech de la Suque, Saint- Nazaire -de- Ladarez, Hérault, Montagne Noire, France has been set.

Subdivision

The Frasnian is divided into seven conodont biozones:

  • Palmatolepis linguiformis zone
  • Palmatolepis rhenana zone
  • Palmatolepis jamiae zone
  • Palmatolepis hassi zone
  • Palmatolepis punctata Zone
  • Palmatolepis transitans zone
  • Palmatolepis falsiovalis zone
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