Induan

The indusium (sometimes also Induum, Induium, Indus - stage) is in Earth's history, the first or lowest chronostratigraphic stage of the Lower Triassic and the Triassic so ever. The stage begins geochronological ago 252.2 million and ends in front of about 251 200 000 years and thus lasted about 1.5 million years. It replaces the Changhsingium, the top step of the Permian; the indusium follows the Olenekian. Regionally there is still divided into the Lower School Griesbachium and Dienerium. The indusium was formerly with the Olenekian a part of the Scythian stage ( Skythium ), which is not an officially recognized international level, however, more and only regionally used (for example in the Alps).

Naming and history

The original type locality lies in the Salt Range ( Punjab ), on the upper reaches of the river Indus, which flows mainly through Pakistan; of which the name is derived. The name was suggested by Kiparisova and Popov in 1956. The internationally recognized GSSP, however, lies in the district of Changxing in Zhejiang Province in China.

Definition and GSSP

The beginning of the stage is defined by the first appearance of the conodont species Hindeodus parvus and the end of the negative carbon anomaly after the peak of the Late Permian mass extinction. The first appearance of ammonite species Meekoceras gracilitatis marks the end of the stage.

Subdivision

Despite the presumably very short absolute duration of the stage, the indusium can in boreal area in five, are subdivided in the Tethyan region in four ammonite zones.