A seismic stratigraphic analysis of Lower Pleistocene deposits in the western Danish sector of the North Sea

Abstract

The Lower Pleistocene is well preserved in the centre of the North Sea, in contrast to the onshore sedimentary record in Denmark. In the Central Trough area the base of the Quaternary is deeper than 1000 m, and regional subsidence appears to have been uniform throughout the Early and early Middle Pleistocene. Seismic stratigraphic analysis allows subdivision of the Lower Pleistocene depositional succession in the western Danish sector into seven subunits. The seismic reflectors bounding these subunits can be correlated with seismic third-order sequence boundaries identified and mapped in the Late Tertiary and Pleistocene succession in adjacent British and German sectors. The subunits recognized in the Danish area may equal these sequences. Structure contour maps for five of the boundaries and isopach maps for three of these subunits show the position of the depocentres in the area. The main Pleistocene depocentre coincides with the axis of the central North Sea Basin. In the Early Pleistocene (Tiglian), local depocentres were also present outside this area. The sediments represented by the seismic sequences in the Dutch, British and German sectors can be related to the depositional basin of a river system draining the northwest-European continent. In addition, climatically induced changes in depositional conditions in the area have affected the sedimentation pattern.