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 erected^1,2, 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.