Frasnium

system	series	step	≈ age ( mya )
higher	higher	higher	younger
Devon	Upper Devonian	Family	358.9 ⬍ 372.2
	Upper Devonian	Frasnium	372.2 ⬍ 382.7
	Middle Devon	Givetium	382.7 ⬍ 387.7
	Middle Devon	Eifelium	387.7 ⬍ 393.3
	Lower Devon	Emsium	393.3 ⬍ 407.6
		Pragium	407.6 ⬍ 410.8
		Lochkovium	410.8 ⬍ 419.2
deeper	deeper	deeper	older

The Frasnium (usually just called Frasne in German) is the lower chronostratigraphic level of the Upper Devonian ( Devonian ) in the history of the earth . The stage lasted geochronologically from about 382.7 million to about 372.2 million years. The frasnium follows the givetium and is replaced by the famennium .

Naming and history

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

The base of the frasnium was placed on 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 event , a major extinction event in the Upper Devonian (with type locality in the Harz ). The profile at Col du Puech de la Suque, Saint-Nazaire-de-Ladarez , Département Hérault , Montagne Noire , France was set as the reference profile (GSSP = Global Stratotype Section and Point) .

The frasnium is divided into seven conodont biozones:

Felix Gradstein, Jim Ogg, Jim & Alan Smith: A Geologic timescale. Cambridge University Press 2004, ISBN 978-0-521-78673-7 .
G. Klapper, R. Feist and MR House: Decision on the Boundary Stratotype for the Middle / Upper Devonian Series Boundary. In: Episodes. 10 (2): 97-101, Beijing 1987.
G. Klapper, R. Feist, RT Becker and MR House: Definition of the Frasnian / Famennian Stage boundary. In: Episodes. 16 (4): 433-441, Beijing 1993 PDF .
Hans Murawski & Wilhelm Meyer: Geological dictionary . 10., rework. u. exp. Ed., 278 pages, Enke Verlag, Stuttgart 1998, ISBN 3-432-84100-0 .