Editing Carboniferous (section)

==== Pennsylvanian ====
The Pennsylvanian was proposed by [[J. J. Stevenson (geologist)|J.J.Stevenson]] in 1888, named after the widespread coal-rich strata found across the state of Pennsylvania.<ref name="Stanley-2015" /> The closure of the Rheic Ocean and formation of Pangea during the Pennsylvanian, together with widespread glaciation across [[Gondwana]] led to major climate and sea level changes, which restricted marine fauna to particular geographic areas thereby reducing widespread biostratigraphic correlations.<ref name="Lucas-2022" /><ref name="Davydov-2012" /> Extensive volcanic events associated with the assembling of Pangea means more radiometric dating is possible relative to the Mississippian.<ref name="Lucas-2022" />

The Bashkirian Stage was proposed by Russian stratigrapher [[Sofia Semikhatova]] in 1934. It was named after [[Bashkiria (1917–1919)|Bashkiria]], the then Russian name of the republic of [[Bashkortostan]] in the southern Ural Mountains of Russia. The GSSP for the base of the Pennsylvanian Subsystem and Bashkirian Stage is located at [[Arrow Canyon Range|Arrow Canyon]] in [[Nevada]], US and was ratified in 1996. It is defined by the first appearance of the conodont ''[[Declinognathodus|Declinognathodus noduliferus]]''. Arrow Canyon lay in a shallow, tropical seaway which stretched from Southern California to Alaska. The boundary is within a [[Cyclothems|cyclothem]] sequence of [[Sequence stratigraphy|transgressive]] limestones and fine [[sandstone]]s, and [[Sequence stratigraphy|regressive]] [[mudstone]]s and [[breccia]]ted limestones.<ref name="Davydov-2012" />

The Moscovian Stage is named after shallow marine limestones and colourful [[clay]]s found around Moscow, Russia. It was first introduced by Sergei Nikitin in 1890. The Moscovian currently lacks a defined GSSP. The fusulinid ''Aljutovella aljutovica'' can be used to define the base of the Moscovian across the northern and eastern margins of Pangea, however, it is restricted in geographic area, which means it cannot be used for global correlations.<ref name="Davydov-2012" /> The first appearance of the conodonts ''Declinognathodus donetzianus'' or ''Idiognathoides postsulcatus'' have been proposed as a boundary marking species and potential sites in the Urals and Nashui, Guizhou Province, southwestern China are being considered.<ref name="Stratigraphy.org" />

The Kasimovian is the first stage in the Upper Pennsylvanian. It is named after the Russian city of [[Kasimov]], and was originally included as part of Nikitin's 1890 definition of the Moscovian. It was first recognised as a distinct unit by A.P. Ivanov in 1926, who named it the "''Tiguliferina''" Horizon after a type of [[brachiopod]]. The boundary of the Kasimovian covers a period of globally low sea level, which has resulted in [[Unconformity|disconformities]] within many sequences of this age. This has created difficulties in finding suitable marine fauna that can used to correlate boundaries worldwide.<ref name="Davydov-2012" /> The Kasimovian currently lacks a defined GSSP; potential sites in the southern Urals, southwest USA and Nashui, Guizhou Province, southwestern China are being considered.<ref name="Stratigraphy.org" />

The Gzhelian is named after the Russian village of [[Gzhel (selo), Moscow Oblast]], near [[Ramenskoye, Moscow Oblast|Ramenskoye]], not far from Moscow. The name and type locality were defined by Sergei Nikitin in 1890. The Gzhelian currently lacks a defined GSSP. The first appearance of the fusulinid ''Rauserites rossicus'' and ''Rauserites'' ''stuckenbergi'' can be used in the [[Boreal Sea]] and Paleo-Tethyan regions but not eastern Pangea or Panthalassa margins.<ref name="Davydov-2012" /> Potential sites in the Urals and Nashui, Guizhou Province, southwestern China for the GSSP are being considered.<ref name="Stratigraphy.org" />

The GSSP for the base of the Permian is located in the Aidaralash River valley near [[Aqtöbe]], Kazakhstan and was ratified in 1996. The beginning of the stage is defined by the first appearance of the conodont ''[[Streptognathodus|Streptognathodus postfusus]].''<ref>Davydov, V.I., Glenister, B.F., Spinosa, C., Ritter, S.M., Chernykh, V.V., Wardlaw, B.R. & Snyder, W.S. 1998. [https://www.researchgate.net/publication/237222028_Proposal_of_Aidaralash_as_Global_Stratotype_Section_and_Point_GSSP_for_base_of_the_Permian_System Proposal of Aidaralash as Global Stratotype Section and Point (GSSP) for base of the Permian System]. Episodes, 21, 11–17.</ref>