Editing Carboniferous (section)

=== Stratigraphy ===
Stages can be defined globally or regionally. For global stratigraphic correlation, the ICS ratify global stages based on a [[Global Boundary Stratotype Section and Point]] (GSSP) from a single [[Geological formation|formation]] (a [[stratotype]]) identifying the lower boundary of the stage. Only the boundaries of the Carboniferous System and three of the stage bases are defined by global stratotype sections and points because of the complexity of the geology.<ref name="Lucas-2022">{{Cite journal |last1=Lucas |first1=Spencer G. |last2=Schneider |first2=Joerg W. |last3=Nikolaeva |first3=Svetlana |last4=Wang |first4=Xiangdong |date=2022 |title=The Carboniferous timescale: an introduction |url=https://www.lyellcollection.org/doi/10.1144/SP512-2021-160 |journal=Geological Society, London, Special Publications |language=en |volume=512 |issue=1 |pages=1–17 |doi=10.1144/SP512-2021-160 |bibcode=2022GSLSP.512....1L |s2cid=245208581 |issn=0305-8719}}</ref><ref name="Davydov-2012" /> The ICS subdivisions from youngest to oldest are as follows:<ref name="Cohen-2013">Cohen, K.M., Finney, S.C., Gibbard, P.L. & Fan, J.-X. (2013; updated) [https://stratigraphy.org/ICSchart/ChronostratChart2020-03.pdf The ICS International Chronostratigraphic Chart]. Episodes 36: 199–204.</ref>
{|
|Series/epoch
|
|Stage/age
|Lower boundary
|-
| colspan="2" style="background-color: {{period color|Permian}};" |[[Permian]]
| style="background-color: {{period color|Asselian}};" |[[Asselian]]
|298.9 ±0.15 Ma
|-
| rowspan="4" style="background-color: {{period color|Pennsylvanian}};" |[[Pennsylvanian (geology)|Pennsylvanian]]
| rowspan="2" style="background-color: {{period color|Upper Pennsylvanian}};" |Upper
| style="background-color: {{period color|Gzhelian}};" |[[Gzhelian]]
|303.7 ±0.1 Ma
|-
| style="background-color: {{period color|Kasimovian}};" |[[Kasimovian]]
|307.0 ±0.1 Ma
|-
| style="background-color: {{period color|Middle Pennsylvanian}};" |Middle
| style="background-color: {{period color|Moscovian}};" |[[Moscovian (Carboniferous)|Moscovian]]
|315.2 ±0.2 Ma
|-
| style="background-color: {{period color|Lower Pennsylvanian}};" |Lower
| style="background-color: {{period color|Bashkirian}};" |[[Bashkirian]]
|323.2 ±0.4 Ma
|-
| rowspan="3" style="background-color: {{period color|Mississippian}};" |[[Mississippian (geology)|Mississippian]]
| style="background-color: {{period color|Upper Mississippian}};" |Upper
| style="background-color: {{period color|Serpukhovian}};" |[[Serpukhovian]]
|330.9 ±0.2 Ma
|-
| style="background-color: {{period color|Middle Mississippian}};" |Middle
| style="background-color: {{period color|Visean}};" |[[Visean]]
|346.7 ±0.4 Ma
|-
| style="background-color: {{period color|Lower Mississippian}};" |Lower
| style="background-color: {{period color|Tournaisian}};" |[[Tournaisian]]
|358.9 ±0.4 Ma
|}

==== Mississippian ====
The Mississippian was proposed by [[Alexander Winchell]] in 1870 named after the extensive exposure of lower Carboniferous [[limestone]] in the upper [[Mississippi River]] valley.<ref name="Stanley-2015" /> During the Mississippian, there was a marine connection between the [[Paleo-Tethys Ocean|Paleo-Tethys]] and [[Panthalassa]] through the [[Rheic Ocean]] resulting in the near worldwide distribution of marine faunas and so allowing widespread correlations using marine [[biostratigraphy]].<ref name="Lucas-2022" /><ref name="Davydov-2012" /> However, there are few Mississippian [[volcanic rock]]s, and so obtaining [[Radiometric dating|radiometric dates]] is difficult.<ref name="Lucas-2022" />

The Tournaisian Stage is named after the Belgian city of [[Tournai]]. It was introduced in scientific literature by Belgian geologist [[André Dumont (geologist)|André Dumont]] in 1832. The GSSP for the base of the Carboniferous System, Mississippian Subsystem and Tournaisian Stage is located at the [[La Serre]] section in [[Montagne Noire]], southern France. It is defined by the first appearance of the [[conodont]] ''[[Siphonodella|Siphonodella sulcata]]'' within the evolutionary lineage from ''[[Siphonodella|Siphonodella praesulcata]]'' to ''Siphonodella sulcata''. This was ratified by the ICS in 1990. However, in 2006 further study revealed the presence of ''Siphonodella sulcata'' below the boundary, and the presence of ''Siphonodella'' ''praesulcata'' and ''Siphonodella sulcata'' together above a local [[unconformity]]. This means the evolution of one species to the other, the definition of the boundary, is not seen at the La Serre site making precise correlation difficult.<ref name="Davydov-2012" /><ref name="Stratigraphy.org">{{Cite web |title=International Commission on Stratigraphy |url=https://stratigraphy.org/gssps/visean |access-date=2023-11-12 |website=stratigraphy.org}}</ref>[[File:Carboniferous regional subdivisions.png|thumb|upright=2|Chart of regional subdivisions of the Carboniferous Period]]The Viséan Stage was introduced by André Dumont in 1832 and is named after the city of [[Visé]], [[Liège Province]], Belgium. In 1967, the base of the Visean was officially defined as the first black limestone in the Leffe [[facies]] at the Bastion Section in the [[Dinant|Dinant Basin]]. These changes are now thought to be ecologically driven rather than caused by evolutionary change, and so this has not been used as the location for the GSSP. Instead, the GSSP for the base of the Visean is located in Bed 83 of the sequence of dark grey [[limestone]]s and [[shale]]s at the [[Peng Chong|Pengchong]] section, [[Guangxi]], southern China. It is defined by the first appearance of the [[Fusulinida|fusulinid]] ''Eoparastaffella simplex'' in the evolutionary lineage ''Eoparastaffella ovalis – Eoparastaffella simplex'' and was ratified in 2009.<ref name="Davydov-2012" />

The Serpukhovian Stage was proposed in 1890 by Russian stratigrapher [[Sergei Nikitin (geologist)|Sergei Nikitin]]. It is named after the city of [[Serpukhov]], near Moscow and currently lacks a defined GSSP. The Visean-Serpukhovian boundary coincides with a major period of glaciation. The resulting sea level fall and climatic changes led to the loss of connections between marine basins and [[endemism]] of marine fauna across the Russian margin. This means changes in [[Biome|biota]] are environmental rather than evolutionary making wider correlation difficult.<ref name="Davydov-2012" /> Work is underway in the [[Ural Mountains|Urals]] and Nashui, [[Guizhou]] Province, southwestern China for a suitable site for the GSSP with the proposed definition for the base of the Serpukhovian as the first appearance of conodont ''[[Lochriea|Lochriea ziegleri]].''<ref name="Stratigraphy.org" />

==== 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>