The velocity structure of the sediments in the southern Rockall Basin: results from new wide-angle seismic modelling

Abstract

Travel-time modelling of first and second arrivals have been used to produce P-wave velocity models of the sedimentary structure on three new wide-angle reflection/refraction profiles from the Irish sector of the Rockall Basin. The models indicate a sedimentary succession that is typically 4.5 km thick and reaches a maximum thickness of 7 km. The sediments are typically horizontal within the basin centre but display significant structural complexities towards the margins where sediment depocentres and large fault blocks are interpreted. Up to seven layers with velocities ranging from 1.8 to 5.2 km s −1 have been resolved within which three distinct seismic packages have been identified. An upper package, interpreted as Oligocene and Neogene in age, is approximately 1.5 km thick and confined within the Rockall Basin pinching out onto the basin margins. This overlies a structurally complex middle package, ca. 1.5 km thick, confined predominantly within the basinal areas which is interpreted as being of Cretaceous to Early Tertiary age. A regionally extensive lower package, up to 4 km thick, is interpreted as being of probable Late Palaeozoic to Jurassic age. The new data provide a much clearer picture than was hitherto available of the entire sedimentary succession in the basins that underlie the Rockall Trough. They show a significant variability in thickness of the various sedimentary layers, and in particular illustrate a marked topographic irregularity at the base of the sedimentary succession.