Givetian

The Givetian is in Earth's history, a chronostratigraphic stage of the Devonian. It forms the upper level of the Middle Devonian series, so following the Eifelian. The Givetian began geochronological front of about 387.7 million years ago and lasted until around 382.7 million years. On the Givetian the Frasnian, the lower stage of the Late Devonian follows.

Naming and history

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

Definition and GSSP

The lower boundary of the stage is as GSSP ("Global Stratotype Section and Point" = "border stratotype point in a boundary stratotype profile" ) defined by the base of the bank 123 in the profile Jebel Mech Irdane in Tafilalet (Anti - Atlas, Morocco). The boundary definition corresponds to the profile with the first appearance of the conodont Polygnathus hemiansatus and lies just above the Erstauftretens the Goniatitengattung Maenioceras. The upper limit is defined by the GSSP of Frasniums. It is characterized by the first appearance of the conodont Ancyrodella rotundiloba in sediments of neritic facies or by the first appearance of the conodont Polygnathus asymmetricus in those of the open - marine, pelagic facies and therefore transferable to other profiles.

Subdivision

The Givetian is divided into five conodont biozones:

  • Palmatolepis norrisi zone
  • Folding Erina disparilis zone
  • Schmidtognatus hermanni Zone
  • Polygnathus varcus zone
  • Polygnathus hemiansatus zone

Sedimentation in Central Europe during the Givetiums

During the Middle Devonian, the sedimentation changed on the edge of Laurussia, the Old Red Continent. The predominantly sandy, silty and marly sediments of the Eifeliums document with its high proportion terrigenous detritus erosion of the Old- Red- continent. In its place we calcification by reefs that were allowed to form increasingly in the warm seas and now come to light in the Massenkalken during Givetiums. Alongside these, eg in the so-called Sauerland Flinze that are black shale sediments that have formed in deeper Still water.

Mya (unit) Carboniferous Famennian History of the Earth Antiatlas Sandstone Corallian Limestone
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