Asselian

The Asselian is in Earth's history, the lowest stratigraphic stage of the Permian or the Cisuralium. The level ranges in absolute terms ( geochronological ) of about 298.9 million years to about 295.5 million years. The Asselian following the Gzhelium, the top step of the Carboniferous, and is detached from the Sakmarium.

Naming and history

The stage was in 1954 from the earlier broader Sakmar stage ( Sakmarium ) separated and named by VE Ruzhencev. The Asselian is named after the river Assel in the southern Ural mountains (Kazakhstan).

Definition and GSSP

The beginning of the Asselian ( and Cisuraliums ) is defined by the first appearance of the conodont species Streptognathodus isolatus. The end of the stage is reached postfusus with the first appearance of the conodont species Streptognathodus. The set by the IUGS ​​globally valid type locality ( GSSP = Global Stratotype Section and Point) is located in the valley of Aidaralash, near the town of Aktobe (Russian Aktjubinsk ) in the southern Urals (Kazakhstan).

Subdivision

The Asselian can be divided into five conodont biozones:

  • Streptognathodus barskovi zone
  • Streptognathodus postfusus zone
  • Streptognathodus fusus zone
  • Streptognathodus constrictus zone
  • Streptognathodus isolatus zone
Mya (unit) Changhsingian Wuchiapingian Capitanian Wordian Roadian Cisuralian Kungurian Artinskian Sakmarian Gzhelian History of the Earth
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