INVESTIGATION INTO THE TECTONIC EVOLUTION OF THE PORCUPINE BANK, OFFSHORE IRISH ATLANTIC MARGIN, USING NEW SEISMIC REFLECTION AND GRAVITY DATA

The offshore Irish Atlantic margin and related rift basins have been intensively studied for several decades, however, the Porcupine Bank, which straddles between the well-studied Porcupine and Rockall basins, is a poorly understood region due to sparse geophysical data coverage. In this study, ten newly acquired multichannel seismic profiles extending across the western Porcupine Bank margin, integrated with gravity data, are used to investigate the crustal architecture and tectonic evolution along the margin. Considerable structural variations observed from seismic data are used to map the crustal architecture regarding rifted margin domains. In the transitional zone between continental and oceanic crust, both shallow peridotite ridges and deeper exhumed serpentinized mantle are interpreted, similar to the conjugate Iberian and Newfoundland margins, as well as further south at the Goban Spur margin. In addition to inferred variations in extension rate during poly-phased rifting episodes, the reactivation of pre-existing inherited Caledonian and Variscan structural fabrics is proposed to have influenced the variable geometries and distributions of the crustal domains along the Goban Spur-Porcupine Bank region. Rigid plate reconstructions of the Irish Atlantic and the Newfoundland margins, particularly involving the Flemish Cap, back to the early Campanian period, show asymmetric rifting and final continental breakup migrating toward the Porcupine Bank region, possibly due to oblique extension between the two margins, and/or oblique deformation on the Porcupine Bank side due to its shearing and rotation during the opening of the Porcupine Basin.