Paleogene - Neogene

During the late Danian-Selandian Laramide phase, open-marine carbonate deposition of the Late Cretaceous and earliest Paleocene was replaced by clastic sediment infill of the Southern North Sea Basin. The Laramide phase, associated with domal uplift and subsidence of Mesozoic grabens, led to a break in sedimentation and reworking of Upper Cretaceous carbonates into marls. Consequently, Paleogene marine deposits are condensed in most areas. Late Paleocene to earliest Eocene uplift of basin margins caused major sand influxes into marginal marine environments with restricted circulation. In the North Sea area, global Paleogene warming culminated in near-tropical conditions and associated biota. Under maximum temperature conditions and differential subsidence, deltaic and submarine-fan sand deposition continued into the early Eocene. Cenozoic sediment input changed from the northwest during the Eocene, through northeastern sources in the Oligocene and Miocene, to dominantly southeastern and southern sources during the Pliocene and Pleistocene. The Paleocene Eocene transition was interrupted by major volcanism, resulting in widespread ash layer deposition from volcanoes on the Greenland-Scotland ridge. From the middle Eocene onwards, regional sub sidence interrupted by uplift phases led to transgression/regression patterns at the basins margins. In the North Sea Basin, a major discontinuity formed due to the Pyrenean inversion phase that occurred just before Antarctic ice cap growth and global cooling at the onset of the Oligocene. From late Eocene to Mid Miocene, the basin experienced warmer and cooler phases, developing a rich, mostly endemic North Sea marine biota. In the early Oligocene, much of the Southern North Sea Basin drowned, and outer-neritic marine clays of the Rupel Formation (Boom Member) were deposited. During the late Oligocene through Pliocene, shallow marine sedimentation was balanced by subsidence resulting in monotonous sequences of marine clays and silts. During the Miocene Climate Optimum, peat formation was widespread at the southern margin of the North Sea Basin, followed by large-scale fluvial-deltaic deposition with local peatbogs as the climate cooled in the Late Miocene. The Upper Pliocene and Lower Pleistocene deposits are dominated by marine silty and sandy clays with ice-rafted debris, marking the first strong Northern Hemisphere glaciations, grading into shallow marine and fluvial sands towards the margins. These are overlain by predominantly sandy Pleistocene fluvial deposits. This chapter is structured around the varying tectonic and climatic factors that determined the structures of the North Sea Basin and its heterogeneous Paleogene-Neogene basin fill.