Seismic stratigraphy of the southern Rockall Basin: a comparison between wide-angle seismic and normal incidence reflection data

Abstract

A wide-angle reflection/refraction profile from the RAPIDS 3 (Rockall and Porcupine Irish Deep Seismic) experiment is compared to a coincident high-quality normal incidence reflection line, both of which traverse the southern part of the Rockall Basin on the Atlantic continental margin, offshore Ireland. The positions and geometries of the independently-derived layers show a generally close comparison between the two data sets. The normal incidence seismic reflection data show a greater degree of detail on seismic facies while the wide-angle seismic profile displays greater penetration of the entire sedimentary succession and of the crust. The wide-angle geometries and the normal incidence seismic stratigraphy provide complementary data that help constrain the geology and evolution of the lightly explored Rockall region. A seismic stratigraphy is presented, based on correlation between the wide-angle and normal incidence data, shallow seismic site surveys, shallow borehole cores and tectonostratigraphic studies. Within the central part of the Rockall Basin, the sedimentary layers are generally flat-lying and have a maximum thickness of 7 km. The succession is interpreted as Jurassic to Recent in age. Some of the layers are confined to the basin whilst others extend onto the Rockall and Porcupine highs. Marginal basins at the western (Conall Basin) and eastern (Macdara Basin) edges of the Rockall Basin contain up to 4 km of pre-Tertiary sedimentary rocks, some possibly as old as Permo-Triassic.