The structural framework of the Irish Atlantic Margin

Abstract

Analysis of the results of regional mapping, integrated with new regional subcrop maps, has yielded significant regional concepts regarding the development of the frontier sedimentary basins west of Ireland. Five provinces of basement and Devono-Carboniferous rocks are mapped across the region. The nature of the basement successions, together with their inherent lineaments and structural fabrics, exerted a major influence on the location and structural segmentation of the basins and in acting as a conduit for Early Cretaceous and Early Cenozoic igneous activity. The major structures in the Porcupine region were N–S throughout its Late Palaeozoic to Cenozoic history, while those in the Slyne, Erris, Rockall and probably Hatton basins were predominantly NNE–SSW to NE–SW. The main structural controls in the Goban region were orientated ENE–WSW and NNW–SSE. The Porcupine Basin is shown to have a more pronounced N–S orientation than has hitherto been proposed. In particular, the basement core of the Porcupine High is shown to extend southwards to the Goban province, thereby isolating the basin for most of its history from the Atlantic region to the west. Separate Permo-Triassic to Jurassic basins occur on the flanks of the main, younger Rockall Basin and their location and orientation were influenced by NE–SW to ENE–WSW structural fabrics. Permo-Triassic sedimentation took place in a series of rift basins in the Porcupine, Rockall, Slyne–Erris and Goban regions. Jurassic rifting was widespread in most of the basins, commencing in Middle Jurassic time in the Slyne Basin but later (Late Jurassic) in the Porcupine and Rockall basins. Early Cretaceous sedimentation was more pronounced in the Porcupine and Rockall basins and shows less control by deep-seated structures. Late Jurassic to Early Cretaceous basin margin uplift on the flanks of the Rockall Basin in particular, is likely to explain the thin to absent nature of such strata in some of the adjacent smaller basins.