The top of the
Kasimovian stage is close to the first appearance of Streptognathodus zethus. The
golden spike for the Kasimovian stage has not yet been assigned (in 2008).
The Kasimovian is subdivided into three conodont
biozones:
Streptognathodus excelsus and Streptognathodus makhlinae Zone
The base of the
Gzhelian is at the first appearance of Streptognathodus zethus. The top of the stage (also the top base of the
Silesian and the base of the Permian system) is at the first appearance of Streptognathodus isolatus within the Streptognathus "wabaunsensis" chronocline.[2]
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
Early Permian
The base of the
Asselian stage is at the same time the base of the
Cisuralian series and the Permian system. It is defined as the place in the stratigraphic record where
fossils of the species Streptognathodus isolatus first appear. The global reference profile for the base (the
GSSP or golden spike) is located in the valley of the Aidaralash River, near
Aqtöbe in the Ural Mountains of Kazakhstan.[3] The top of the Asselian stage (the base of the
Sakmarian stage) is at the first appearance of the species Streptognathodus postfusus.
The base of the
Sakmarian stage is laid with the first appearance of Streptognathodus postfusus in the fossil record. A global reference profile for the base had in 2009 not yet been appointed. The top of the Sakmarian (the base of the Artinskian) is defined as the place in the stratigraphic record where fossils of conodont species Sweetognathus whitei and Mesogondolella bisselli first appear.
References
^Texas Pennsylvanian conodonts and their stratigraphic relations. CR Stauffer, HJ Plummer - University of Texas Bulletin, 1932
^Davydov, V.I.; Glenister, B.F.; Spinosa, C.; Ritter, S.M.; Chernykh, V.V.; Wardlaw, B.R. & Snyder, W.S.; 1998: Proposal of Aidaralash as Global Stratotype Section and Point (GSSP) for base of the Permian System, Episodes 21(1): pp 11-18,
"Archived copy"(PDF). Archived from
the original(PDF) on 2007-09-28. Retrieved 2007-09-28.{{
cite web}}: CS1 maint: archived copy as title (
link)
^The GSSP was first proposed by Davydov et al. (1998)