The Gzhelian ( ) is an age in the ICS geologic time scale or a stage in the stratigraphic column. It is the youngest stage of the Pennsylvanian, the youngest subsystem of the Carboniferous. The Gzhelian lasted from to Ma.; 2004: A Geologic Time Scale 2004, Cambridge University Press It follows the Kasimovian age/stage and is followed by the Asselian age/stage, the oldest subdivision of the Permian system.
The Gzhelian is more or less coeval with the Stephanian Stage of the regional stratigraphy of Europe.
Name and definition The Gzhelian is named after the Russian village of Gzhel (), nearby Ramenskoye, not far from Moscow. The name and type locality were defined by Sergei Nikitin (1851–1909) in 1890.
The base of the Gzhelian is at the first appearance of the Fusulinida genera Daixina, Jigulites and Rugosofusulina, or at the first appearance of the conodont Streptognathodus zethus. The top of the stage (the base of the Permian system) is at the first appearance of the conodont Streptognathodus isolatus within the Streptognathus "wabaunsensis" chronocline. higher in the reference profile, the Fusulinida species Sphaeroschwagerina vulgaris aktjubensis appears.
Currently, a golden spike for the base of the Gzhelian Stage has not been allocated. A candidate is a section along the Ussolka river (a tributary of the Belaya river) at the edge of the hamlet of Krasnoussolsky, about southeast of Ufa and northeast of Sterlitamak (in Bashkortostan).; 2006: Usolka section (southern Urals, Russia): a potential candidate for GSSP to define the base of the Gzhelian Stage in the global chronostratigraphic scale Geologija 49(2): pp 205–217,
Biozones The Gzhelian Stage is subdivided into five biozones, based on the conodont genus Streptognathodus: Streptognathodus wabaunsensis and Streptognathodus bellus Zone Streptognathodus simplex Zone Streptognathodus virgilicus Zone Streptognathodus vitali Zone Streptognathodus simulator Zone
References
External links Carboniferous timescale at the website of the Norwegian network of offshore records of geology and stratigraphy Gzhelian, GeoWhen Database