Irish Serpukhovian revisited

Abstract

In this study of Mississippian rocks in Ireland, it is now recognized, based on faunal evidence, that several upper Viséan limestone formations which were previously excluded from the Serpukhovian now belong, in part, to the lower two substages of the Serpukhovian. A reassessment of previous foraminiferal determinations, together with new foraminiferal data, has confirmed that rocks equivalent to the Tarusian and Steshevian substages are present in several sections. In the Slievenaglasha Formation and Magowna Formation (County Clare) and Deer Park Formation (County Meath), Tarusian and Steshevian foraminiferal assemblages are thus recorded. In the Clogrenan Formation (County Carlow), Carganamuck Limestone Formation (County Armagh) and Rockdale Limestone Formation (County Tyrone), Tarusian foraminiferal assemblages are recorded in the upper beds of thick limestone successions. Key foraminiferal and algal taxa characterize each assemblage, which have been correlated with equivalent Serpukhovian strata in the north of England and Scotland. A three‐stage evolution is recognized in archaediscid foraminifers: from Neoarchaediscus gregorii, followed by Neoarchaediscus postrugosus form 1, and N. postrugosus form 2, with Neoarchaediscus postrugosus form 1 used to define the base of the Serpukhovian. The recognition of Tarusian and Steshevian foraminiferal assemblages implies that areas of shallow‐water platform carbonate sedimentation in Ireland during the upper Viséan (Brigantian) persisted into the Early Serpukhovian.