Anisian
The Anisian (usually shortened in the German language to anise ) is in Earth's history, the first or lower chronostratigraphic stage of the Middle Triassic. The stage includes geochronological the period before about 247.2 to about 242 million years ago and thus lasted about 8.9 million years. The anise is preceded Olenekian; it is detached from the Ladinian.
Naming and history
The original type locality is Großreifling in Styria ( Austria ). The name is derived from Anisus, the Latin name of the river Enns. The anisische stage was introduced by Wilhelm Heinrich scales and Carl Diener in 1895, and is open there in the Reifling lineup.
Definition and GSSP
As the lower limit of the level (and thus the lower limit of the center triad ) discussed two horizons; the first appearance of the conodont species Chiosella timorensis or the base of the magnetic Ozone MT1n. The upper limit of the Anisian (and the lower limit of the Ladinian ) is defined by the first appearance of the ammonite species Eoprotrachyceras curionii and inserting the ammonite family Trachyceratidae. The boundary also coincides with the first appearance of the conodont species Neogondolella praehungarica. In December 2007, the " Subcommission on Triassic Stratigraphy " suggested a locality on Deşli Caira Mountain in Dobrogea (Romania ) as the GSSP ( Global Type locality and type profile ) ago. A ratification and final confirmation by the IUGS is expected for 2009. The GSSP of the Ladinian has already been set.
Subdivision
In Tethysbereich the stage is divided into six ammonite zones:
- Nevadites zone
- Hungarites zone
- Paraceratites zone
- Balatonites balatonicus zone
- Kocaelia zone
- Acrochordiceras zone
As a regional sub-stages the Aegeum, the Bithynium, the Pelsonium and Illyrium are mainly used in the Alpine region.