Volcanic ash deposits of early Eocene age from the Rockall Trough

Abstract

The stratigraphy of the Rockall Trough (Fig. 1) has proved difficult to elucidate because a mantle of Recent sediments usually prevents piston corers and dredges from sampling older accumulations. Although a seismic stratigraphy has been erected1,2, considerable uncertainty surrounds the history of sedimentation and, consequently, the petroleum potential of the region. The upper 500–1,000 m of the succession are clearly Cenozoic deposits whose distribution has been strongly influenced by movements of Norwegian Sea overflow water1. Deeper in the section, major current-controlled accumulations are absent, a feature observed elsewhere in the Atlantic1. In view of the paucity of samples from these older deposits3, we report here the recovery of sediments that were laid down in the northern Rockall Trough before polar waters radically changed the depositional regime. The sediments record a period of explosive volcanicity during the early Eocene in the vicinity of the Wyville–Thomson Ridge.