Print this page3d Seismic Megasurvey Geomorphology of the Southern North Sea: Tunnel Valley Records and Associated Ice-Sheet Dynamics
Julien Moreau1, Mads Huuse1, Philip L. Gibbard2, and Andrea Moscariello3
1Geology and Petroleum Geology, University of Aberdeen, Aberdeen, United Kingdom
2The Quaternary Palaeoenvironments, Group Department of Geography, University of Cambridge, Cambridge, United Kingdom
3Department of Geotechnology, Faculty of Civil Engineering and Geosciences, Delft, Netherlands
The presence of super-continents at high latitudes has triggered major glaciation events through geologic time. Some depositional systems associated with these glacial events are involved in petroleum systems. The architecture and nature of those depositional systems from regional to reservoir scale is not obvious and remain very difficult to constrain. Tunnel valleys are important glacial features implicated in some oil fields. They are considered to be formed by overpressured meltwater beneath ice sheets and can be up to 100km long, 2-3km wide and 600m deep. The genesis, flow dynamic and infilling facies of tunnel valleys are very controversial. The North Sea Basin and surrounding area are known for their record of tunnel valleys during the Pleistocene. Those valleys appear to be the best analogy to published reservoir systems comprising tunnel valleys in the Palaeozoic.
The main problem of former analogies is the scale in time and space of the analog considered. Exposures of Pleistocene tunnel valleys infill are sparse and restricted to quarries, excavations, and coastal cliffs. So, the onshore lithological data are limited to present day surface mapping and groundwater boreholes. 2D and 3D seismic analysis were also restricted to small areas compared to oil exploration- or ice sheet-scale. The present study of the 3D seismic megasurvey of the Southern North Sea gives the first opportunity to compare at equivalent scale ancient and recent glacial system encompassing tunnel valleys. New data about the former ice-sheet of the North Sea in term of ice dynamic and sub- to proglacial sedimentation are extracted. Those data permit to inset tunnel valley formation and infill into a framework usable for petroleum exploration in the ancient rock record. This new approach is facilitating a better understanding of recent and past ice-sheet dynamics and related records.
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