Timescale for the Kasimovian Stage


 
 The Kasimovian Stage is the lower stage of the Upper Pennsylvanian Subsystem, in which a series of considerable biotic- and abiotic events have happened and changed the earth. The Variscan orogeny and the Late Paleozoic Glaciation are two major events that caused geographical isolation of marine faunas and difficulties for a global correlation of biostratigraphy. Regional timescales of the Kasimovian across major continents are reviewed here. A global correlation of the Kasimovian is tentatively established based on a detailed review of major fossil groups such as conodonts, fusulines, and some macrofossils. The index taxon for the base of the Kasimovian Stage has not been selected. The following conodont species,
 Swadelina subexcelsa
 ,
 Idiognathodus heckeli
 ,
 I
 .
 turbatus
 , and
 I
 .
 sagittalis
 , have a high potential. Among them,
 I
 .
 heckeli
 is considered the best marker for the base of the Kasimovian Stage because it can mark a bioevent in a wide geographic range and more importantly it has a clear taxonomic definition within a phylogenetic lineage. The fusuline
 Montiparus
 might be regarded as an auxiliary marker to define the base of the Kasimovian based on its wider distribution. Other proxies, i.e. isotopic dating and strontium, carbon, and oxygen isotopic stratigraphy throughout the Kasimovian, are also reviewed. The GSSP candidates for the Kasimovian Stage include the Naqing section,South China, the Usolka section,South Urals, and the Afanasievo section,Moscow Basin. The Naqing section is regarded as the most appropriate GSSP candidate in terms of its complete sedimentary succession, well-recorded conodont lineages, and well-studied bio-, chemo- and cyclo-stratigraphy.
