Late Cenozoic evolution of the northern North Sea and North Sea Fan: A seismic sequence stratigraphic analysis

Abstract

The Late Cenozoic outbuilding in the northern North Sea and southeastern Norwegian Sea demonstrates strong relationship between uplift, erosion, subsidence, variations in relative sea level, basin infill, glacial dynamics and climate. The study is made to get better understanding of the Plio-Pleistocene outbuilding in reference to glacial-interglacial or/and stadial-interstadial cyclicity, variation in accommodation space, as function of basin subsidence, glacioeustacy, and glacial dynamics and sedimentation. A total of 31 sequences, along with the SS-A to SS-D sequences in the Norwegian Channel, were observed, and are interpreted mainly to represent glacial-interglacial cycles. In terms of seismic stratigraphical geometry and architecture three distinct depositional regimes have been observed in present study and have been named as megasequence I, megasequence II and NSF megasequence. Megasequence I contains steep prograding clinothems. The prograding clinothems are built by glacially derived sediments sourced from the uplifted southwestern mainland Norway. Megasequence II was formed in the Norwegian Channel by fast flowing ice streams gouging the sediment around the coast of southern Norway. The flat successions, overlying a near-margin 1.1 Ma erosion surface, consist of till, glacial marine and marine sediments. The megasequence NSF (North Sea Fan) consists of prograding wedges that developed by the fast flowing ice streams in the Norwegian Channel. The continued aggradation in the channel subsequently gave rise to progradation of the North Sea Fan. An effort was made to correlate sequences that have been found in the Norwegian Channel with those that have been identified in the North Sea Fan. The environment of deposition for the sequences has been determined using seismic facies. Furthermore, four main seismic facies has been has been identified that equate glacigenic debris flows, glaciomarine sediments, slide debrites and hemipelagic/contourite sediments. The recorded 31 glacigenic sequences have been correlated with glacial records form the mid-Norwegian continental shelf, from deep-sea sediments and from Iceland. The correlations confirm that the number of glaciations that impacted the depositional history of the Norwegian shelf well may be in the order of 30.