A Pre-elsterian Grounded Ice-sheet in the Central North Sea

Dedicated “Glaciations past, present and future: impact on resource exploration and development” A previously unrecorded pre-Elsterian grounded ice-sheet has been identified in Quadrant 22 of the Central North Sea by reference to extensive fields of glacio-tectonic imbricate thrust stacks. Exploration 3D and HR2D seismic data have been used to map the extents of tectonised sedimentary packages lying just above the Bruhnes-Matuyama boundary in the Aberdeen Ground Fm. A lower tectonised sequence displays large scale deformation structures with vertical relief of tens or hundreds of metres, while an upper sequence has a more penetrating deformation fabric extending several km further to the south. Deformed fabrics indicate ice-movement towards the south or southwest and the transition to an undeformed fabric indicates the southerly extent of ice advance or an ice-grounding line. The deformed package is overlain by an undeformed sequence, top of which is partially represented by an erosion surface. The Elsterian erosion surface lies up to 65ms TWT above the top of the glacial sequences, placing the ice-sheet in the early Middle Pleistocene. The evidence presented demonstrates the extent to which our current understanding of North Sea glacial history is only partially complete.