Stephanian (stage)
The Stephanian is a stage in the regional stratigraphy of northwest Europe with an age between roughly 307.5 and 299 Ma (million years ago). It is a subdivision of the Carboniferous system or period and the regional Silesian series. The uppermost units of the Coal Measures of England and Wales are probably of Stephanian age, though the larger part of this formation is referred to the earlier Westphalian. The stage derives its name from the city of Saint-Étienne for its coal mining basin in eastern central France (which itself derives from associations with Saint Stephen) where strata of this age occur. In the official geologic timescale of the ICS, the Stephanian is placed within the Pennsylvanian epoch (323-299 Ma). The (regionally defined) Stephanian stage corresponds to the (internationally used) Kasimovian and Gzhelian stages. References appear in scientific literature to a Stephanian epoch or Stephanian series reflecting the stage's earlier status. Sediments younger than the Stephanian are sometimes termed the Autunian, a regional stage which includes the Carboniferous-Permian boundary. Stratigraphy From youngest to oldest, the proposed substages of the Stephanian are: Stephanian C Stephanian B "Saberian" [correlation uncertain] Barruelian (Stephanian A) Cantabrian Base of the Stephanian The Westphalian-Stephanian boundary is controversial