Dynamic changes in depositional patterns and glaciotectonic deformations revealed by high-resolution 3D seismic data in the Northern North Sea.

During the Last Glacial Maximum (LGM), the British-Irish ice sheet is known to have been coalescent with the Fennoscandian ice sheet. Some models indicate that this might have been rather short-lived, whereas other reconstructions indicate an early and long-lasting coalescence of the ice sheets which, together reached the Northern North Sea continental shelf edge around 27,000 years ago. To date, the lack of empirical data, in the form of boreholes or high and ultra-high resolution seismic data has hindered efforts to validate the reconstructions and identify ice flow directions, drainage patterns, and chronology. Little is also known about the nature of the deglaciation and unzipping of the two ice sheets which would have likely comprised multiple ice re-advances, stillstands, and retreats as well as an unknown duration of ice grounding which, based on experience, will result in complex and heterogeneous stratigraphy, vertically and horizontally In this study, a unique 3D seismic dataset with bin spacing of 3.125m x 3.125m and a frequency range of ~10-160Hz will be used to reconstruct the depositional history and sequence of events in the shallow subsurface(~ 200m below sea bed) including but not limited to processes responsible for tunnel valley formation and infill, large scale glaciotectonic deformation or postglacial deposition. This will be juxtaposed against known paraglacial reconstructions to propose preliminary timing of events. Implications for offshore infrastructure projects will be subsequently discussed in the context of ground conditions identified over the site.