Stratigraphy of upper Visean carbonate platform rocks in the Carlow area, southeast Ireland

The stratigraphy of the upper Visean (Asbian to Brigantian) carbonate succession in southeast Ireland is revised on the basis of seven quarry and two borehole sections. Six lithological units have been distinguished, two units (units 1 and 2) in the upper Asbian Ballyadams Formation, and four units (units 4 to 6) in the Brigantian Clogrenan Formation (both formations are dated precisely using foraminiferans, calcareous algae and rugose corals). The boundary between the Ballyadams and Clogrenan formations is redefined 19 m below the horizon proposed by the Geological Survey of Ireland, and thus, lithological characteristics of both formations are redescribed. The upper part of the Ballyadams Formation is characterized by well-developed large-scale cyclicity, with common subaerial exposure surfaces. Fine- to medium-grained thin-bedded limestones with thin shales occur in the lower part of cycles, passing up into medium-grained pale grey massive limestones in the upper part. The Clogrenan Formation is composed mainly of medium- to coarse-grained thick limestone beds with variable presence of shales; but no large-scale cyclicity. There is a decrease in the number of subaerial exposure surfaces towards the top of the formation and common chert nodules; macrofauna occurs mostly concentrated in bands. The six units recognized in the Carlow area are comparable with other units described for the same time interval (Asbian-Brigantian) from south and southwest Ireland, demonstrating the existence of a stable platform for most parts of southern Ireland, controlled principally by glacioeustatics. Copyright (C) 2004 John Wiley Sons, Ltd.