C. N. Waters, 2011. "Fastnet, Celtic Sea and St George’s Channel", A Revised Correlation of Carboniferous Rocks in the British Isles, C. N. Waters, I. D. Somerville, N. S. Jones, C. J. Cleal, J. D. Collinson, R. A. Waters, B. M. Besly, M. T. Dean, M. H. Stephenson, J. R. Davies, E. C. Freshney, D. I. Jackson, W. I. Mitchell, J. H. Powell, W. J. Barclay, M. A. E. Browne, B. E. Leveridge, S. L. Long, D. McLean
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This offshore area broadly comprises two ENE-trending Mesozoic and Tertiary grabens. The northern graben comprises the Fastnet, North Celtic Sea and St George’s Channel basins, separated from the South Celtic Sea and Bristol Channel basins by the Pembrokeshire Ridge-Labadie Bank (Fig. 50). The graben appears to represent the reactivation of Caledonian structures, for example, the southern margin of the St George’s Channel Basin was controlled by reactivation of the onshore Bala Fault System (Naylor 2001). The North Celtic Sea Basin locally developed in the hanging wall of a low-angle southerly dipping fault, which may represent the reactivation of the Variscan Front during Mesozoic extension (Gibbs 1987). However, traditionally, the Variscan Front has been taken as a poorly delineated feature extending across southern Ireland, north of the Munster Basin.
Hydrocarbon exploration has revealed intermittent presence of Carboniferous strata of Tournaisian to Westphalian age, although the distribution of these strata is still poorly constrained. The Devono-Carboniferous South Munster Basin, evident onshore in southern Ireland (Chapter 23), extends at least 50 km south of the coastline (Higgs 1983). The platform developed to the south of the South Munster Basin has been proved within the Fastnet Basin and Goban Spur (Fig. 50; Sevastopulo & Wyse Jackson 2009). The presence of limestone within St George’s Channel suggests that this part of the Leinster-Wales Massif was drowned by Visean times (Sevastopulo & Wyse Jackson 2009).