3D seismic megasurvey geomorphology of the Southern North Sea: Tunnel valley records and associated ice-sheet dynamics

Analysis of offshore glacial geomorphology is becoming a popular topic since the massive release of industrial seismic data in the North Sea. As well, glaciogenic sediments are involved in several petroleum systems (Permo-Carboniferous, Ordovician rocks). These contexts leaded to the creation of the Glaciogenic Reservoir Analogue Studies Group (GRASP), an academic team founded by 6 oil companies, aiming to bring new analogue models from the glacial record of the North Sea. Part of this research is using the 3D seismic mega-merge of the southern North-Sea (PGS) to investigate the glaciogenic record of the Upper Quaternary deposits. This work results in an enhanced knowledge of the 3D geometry of glacial surfaces, encompassing the tunnel valley incisions and ice-front morphology. A thorough conversion into depth-geometries was carried out. Knowing the subglacial topographic variations permits to model the icesurface altitudes. Thus, ice thicknesses can be estimated and consequently, the loading pressure at ice-base. Finally, the model gives new constrains of the conditions during tunnel valley activity as well as new stratigraphic, palaeogeographic and paleoenvironmental data.