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 and has not been formally defined. The early part of the Stephanian is difficult to recognize in much of Europe, due to sediment
hiatuses or a transition from coal to unfossiliferous
red beds. This issue is most apparent in the Lorraine-
Saar-Nahe Basin of France and Germany, where a long hiatus occupies several million years between the Westphalian D and Stephanian A substages. Several workarounds have been proposed, but many bring forward their own problems. Many sources air on the side of caution and position the start of the Stephanian at the end of the hiatus. By that time, Kasimovian-type plant species are well-established, suggesting that part of the Westphalian D is Kasimovian in age. Other studies disagree with this approach, instead defining the Westphalian-Stephanian boundary at a major transition of plant faunas prior to the hiatus. Northwest Spain seems to offer a potential solution to the debate, since the regions of
Asturias and
Cantabria offer undisrupted and fossil-rich sediments which appear to fill in the gap between Westphalian D and Stephanian A. Most Carboniferous stratigraphers accept the utility of this interval, which has been named as the "Cantabrian" substage, the earliest substage of the Stephanian. Kasimovian-type plants first appear just above the base of the Cantabrian, arguing that the base of the Stephanian is slightly older than the start of the Kasimovian (around 307 Ma). ==References==