Offshore Western Ireland

This offshore area comprises two broadly NNE–trending Mesozoic and Tertiary basins present to the northwest of Ireland: the larger Rockall Trough occurs to the north-west of the interlinked Slyne Trough–Erris Trough–Donegal Basin (Northwest Offshore Basins). To the west of Ireland is the north-trending linked Main Porcupine–Seabight basins (Fig. 17.1). There has been little exploratory drilling in the basins, other than the Porcupine Basin (Croker & Shannon 1987), for which there are extensive seismic reflection data. Carboniferous rocks up to 3 km thick are present within the Porcupine Basin, with deposits also recorded in the Goban Spur and Northwest Offshore Basins (Naylor 2001). The Donegal Basin is considered to have initiated during the Carboniferous in response to dextral strike-slip displacement (Dobson & Whittington 1992). Geophysical data suggest the offshore extension of the Namurian Clare Basin, which may have existed as a west–east orientated Pennsylvanian basin extending beneath the Porcupine Basin. The age of the sedimentary infill of the Rockall Trough is still uncertain and may extend back to Late Palaeozoic in age, although the main phase of extension is likely to be during the Cretaceous (Naylor 2001, and references therein).