The early Quaternary North Sea Basin

Abstract

The onset of the Quaternary (2.58 Ma) corresponds to significant paleo-environmental events, such as the intensification and southward extension of Northern Hemisphere glaciation. In the North Sea Basin a significant late Cenozoic succession has been identified as a high-resolution archive of paleo-environmental changes during the Pliocene and Pleistocene. However, the identification of the base of the Quaternary has been a long-standing issue owing to lack of stratigraphic calibration. This study incorporates continuous, regional 3D seismic data with high-quality chronostratigraphic markers to map the base-Quaternary surface at high resolution across the entire North Sea. Depth conversion, backstripping, seismic geomorphology and sedimentation rate calculations are integrated to analyse the paleogeographical evolution of the North Sea Basin and its infill of c. 83 × 10 3 km 3 of northward prograding marine to deltaic sediments. The basin is 600 km long from SSE to NNW and largely localized above residual topography of the Mesozoic graben system. During the earliest Quaternary (2.58 -2.35 Ma) paleo-water depths were c. 300 ± 50 m and solid sedimentation rates (calculated from 0% porosity) c. 32 km 3 ka −1 . The base-Quaternary provides an important marker for further studies of the changing environment of the Quaternary of NW Europe as well as resource and shallow geohazard analysis.Supplementary material: A base Quaternary two-way travel time structure map is available at https://doi.org/10.6084/m9. figshare.c.3900343

Upslope‐climbing shelf‐edge clinoforms and the stepwise evolution of the northern European glaciation (lower Pleistocene Eridanos Delta system, U.K. North Sea): When sediment supply overwhelms accommodation

“…2.5 Ma = Paleoenvironmental Interval 3 of Kuhlmann et al, ; Rea et al, ). The climate deterioration increased the Eridanos sediment flux, with Gelasian sedimentation rates of ≥ 30 km 3 /kyr (Lamb et al, ). At this time, although ice caps might have been already in place on the northern British and Scandinavian land masses and inner shelves (e.g.…”

“…1.71 Ma), associated with a marine flooding. The end of the Eridanos system in the study area was likely due to glaciation‐driven physiographic changes in the Baltic hinterland (Bijlsma, ) and/or to delta auto‐retreat (sensu Muto, Steel, & Swenson, ) or avulsion (Lamb et al, ). A major changeover in sediment source area and marine progradation direction takes place around the “middle Calabarian” times (from after 1.6–1.7 Ma to as late as 1.0–0.7 Ma, a time span which is broadly equivalent to our Sequence IV) (Ottesen et al, ): from Fennoscandian source and east‐to‐west progradation (Eridanos River System) to Dutch‐German‐southern English source and south‐to‐north progradation (Rhine‐Meuse‐Thames River System) (e.g.…”

“…A major changeover in sediment source area and marine progradation direction takes place around the “middle Calabarian” times (from after 1.6–1.7 Ma to as late as 1.0–0.7 Ma, a time span which is broadly equivalent to our Sequence IV) (Ottesen et al, ): from Fennoscandian source and east‐to‐west progradation (Eridanos River System) to Dutch‐German‐southern English source and south‐to‐north progradation (Rhine‐Meuse‐Thames River System) (e.g. Lamb et al, ; Ottesen et al, ). It is possible that our MRS4 embodies this changeover in the study area, with marine sediment continuing to be deposited further north, out of the plane of our seismic lines.…”

“…We argue that the very high Eridanos sediment supply in the earliest Calabrian played an important role in the onset of the outbuilding of upslope‐climbing shelf‐edge scale clinoforms in the study area (Figure ). The high sediment supply owed to the Eburonian climate deterioration and low sea level stand, with the subsequent establishment of a lowstand delta (Lamb et al, ). Normally, a basinward shallowing depositional foundation would typically result in delta‐lobe avulsion or change to axial along‐basin sediment routing, but the lack of accommodation elsewhere forced the delta to prograde onto the basinward shallowing slope.…”

“…Elbe, Weser, Rhine, Thames) (Huuse, ; Knox et al, ; Kuhlmann & Wong, ; Overeem et al, ; Ottesen et al, ). The lower Pleistocene part of the Eridanos clinothem displays a maximum thickness of 600 m in a north‐northwest trending depocentre in the western CG (Figure ), and unconformably overlaps older rocks over the basin flanks (Lamb et al, ; Ottesen et al, ).…”