The Gzhelium (also Gzhel or GSEL stage) is in Earth's history the top chronostratigraphic stage of Pennsylvaniums ( Carboniferous). The stage took geochronological from about 303.7 million to about 298.9 million years. The Gzhelium 's going ahead Kasimovian, it is followed by Asselian, the lowest level of the Permian.
Naming and history
The Gzhelium is named (Russian Гжель ) at Ramenskoje not far from Moscow to the Russian village Gzhel. The name and level have been proposed in 1890 by Sergei Nikitin ( 1850-1909 ).
Definition and GSSP
The base of Gzheliums Zethus is close to the first appearance of the fusulinids genera Daixina, Jigulites and Rugosofusulina, or the Erstvorkommen the conodont species Streptognathodus. The end of the stage is the first appearance of the conodont species Streptognathodus isolatus within the Streptognathus " wabaunsensis " conodont Chrono Cline. 6 m higher in the profile appears the fusulinids Type Sphaeroschwagerina vulgaris aktjubensis. A reference profile ( GSSP = Global Stratotype Section and Point) for the base of Gzhelium has not yet been determined. Proposed is the Ussolka ( Usolka ) profile (after Ussolka, a small right-hand tributary of the Belaya ) about 120 km south-east of Ufa and about 60 km northeast of Sterlitamak on the northern edge of the settlement Krasnoussolski ( Bashkortostan, Russia).
The Gzhelium is divided into five conodont zones:
- Streptognathodus wabaunsensis / Streptognathodus bellus Zone
- Streptognathodus simplex zone
- Streptognathodus virgilicus zone
- Streptognathodus vitali - zone
- Streptognathodus simulator zone