Givetium

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system series step ≈ age ( mya )
higher higher higher younger
Devon Upper Devonian Family 358.9
⬍
372.2
Frasnium 372.2
⬍
382.7
Middle Devon Givetium 382.7
⬍
387.7
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 givetium is a chronostratigraphic stage of the Devonian in the history of the earth . It forms the upper level of the Middle Devonian series, thus follows the Eifelium . The Givetium began geochronologically around 387.7 million years ago and lasted until around 382.7 million years. The Givetium is followed by the Frasnium , the lower tier of the Upper Devonian.

Naming and history

The stage is named after the French community of Givet in the French Ardennes . The name and level was proposed by Jean Baptiste Julien d'Omalius d'Halloy in 1839 .

Definition and GSSP

The lower limit of the level is defined as GSSP ("Global Stratotype Section and Point" = "Grenzstratotype-Punkt in einer Grenzstratotyp-Profil") by the base of the bank 123 in the profile Jebel Mech Irdane near Tafilalt ( Anti-Atlas , Morocco ). The boundary definition corresponds in the profile with the first appearance of the conodont Polygnathus hemiansatus and is slightly above the first appearance of the goniatite genus Maenioceras . The upper limit is defined by the GSSP of the frasnium . It is characterized by the first appearance of the conodont Ancyrodella rotundiloba in sediments of the neritic facies and the first appearance of the conodont Polygnathus asymmetricus in those of the open marine, pelagic facies and can therefore also be transferred to other profiles.

Breakdown

The givetium is subdivided into five conodont biozones:

Sedimentation conditions in Central Europe during the Givetian

Crinoid limestone from the Givetium with fossilized stalk limbs ( trochites ) from Laudonomphalus regularis (location: Ferques , Département Pas-de-Calais )

In the course of the Middle Devonian, the sedimentation conditions changed on the edge of Laurussia , the Old Red continent. The predominantly sandy , silty and marl-like sediments of the Eifelium with their high proportion of terrigenous detritus document the erosion of the Old Red continent. During the Givetium, they were replaced by lime deposits from reefs , which were increasingly able to form in the warm seas and which now appear in the mass limestone . There are also z. B. In the Sauerland so-called Flinze , these are black slate sediments that have formed in deeper still water.

literature

  • Felix M. Gradstein, James G. Ogg and Alan G. Smith: A Geologic Time Scale 2004 . Cambridge University Press, 2004 ISBN 978-0-521-78673-7 .
  • Otto Heinrich Walliser , Pierre Bultynck, Karsten Weddige , R. Thomas Becker and Michael R. House: Definition of the Eifelian-Givetian Stage Boundary. Episodes, 18 (3): 107-115, Beijing 1995 PDF

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