South Central Ireland

The South Central Ireland region extends from the South Munster Basin north to the southern margin of the Dublin Basin and from Wexford in the southeast to the Burren in the northwest (Fig. 22.1). The region is dominated by strata of Mississippian age, with Pennsylvanian strata preserved in boreholes in south Co. Wexford and in the upper part of the Leinster and Kanturk Coalfields. Throughout the South Central region, the Tournaisian strata present below the Waulsortian mud-bank limestones, which form a continuous thick unit of massive pale grey limestone across most of the region, is represented by the Lower Limestone Shale and Ballysteen Limestone groups (Brück 1985) of the Limerick Province (see Philcox 1984; Sevastopulo & Wyse Jackson 2001). The Lower Limestone Shale Group is related to a northward-directed marine transgressive event across the North Munster shelf. The deepening trend, which started during the deposition of the Ballysteen Limestone Group, continued with the Waulsortian facies on the distal part of a ramp. From the latest Tournaisian time and throughout the Visean there is widespread development of shallow-water marine carbonate platform sediments with only localised deeper water ramp and basinal facies (mostly in the Shannon Basin) (Somerville et al. 1992b; Strogen et al. 1996; Sevastopulo & Wyse Jackson 2001). The greatest areal extent and stratigraphic thickness (c. 2 km) of Namurian rocks occurs in the Shannon Basin, centred on counties Clare and Limerick. This basin developed as a result of extension and collapse above the position of the former Iapetus Suture and was the locus of a thick Lower Carboniferous succession in the Shannon Basin (Strogen et al. 1996). The Namurian succession was assigned to a lower Shannon Group followed by the Central Clare Group (Rider 1974), and its palaeogeographic development was summarised in Collinson et al. (1991). Westphalian strata are restricted to outliers of the Leinster, Slieve Ardagh and Kanturk coalfields (Fig. 22.1).