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Giant Palaeogene Debris Flow Tongues in the United Kingdom North Sea Sector

F. Surlyk1, H. Tirsgaard2, A. Uldall2, and J. Megson2
1 University of Copenhagen, Copenhagen K, Denmark
2 Mærsk Oil and Gas, Copenhagen K, Denmark

Palaeocene deep-water sediments from the UK North Sea sector have been studied based on core facies analysis, 3D seismic profiles and horizon slicing. The combined evidence gives an unusually complete picture of the depositional system. The coarser grained facies were deposited from turbidity flows, cohesive mudflows, debris flows and concentrated sandy flows and virtually allcored debris flow deposits consists of remoulded, refolded and sheared debrites. The depositional system is an elongate NW–SE oriented tongue, more than 150 km long and between 20 and 50 km wide. It is narrowest in the middle part and flares out in the distal SE part, which is characterized by rounded lobate terminations and pressure ridges formed by the compression during the late stage of debris flow movement. Another characteristic feature comprises lineaments or striations, which are roughly parallel to the main tongue but diverge slightly downslope. A depositional model for the large debris flow dominated system is presented. It differs from most currently accepted ideas of formation of large-scale debris flow systems, which essentially comprise chaotic, line sourced, non-erosional irregular sheets.