Genese des Nordseeraumes im Quartär

Abstract

In spite of alterations due to transgressions, Pleistocene forms are still discernible in the North Sea area. In this study, explanation of their genesis is based on a reconstruction of the ice‑sheds of different dimen­sions and the dynamic elements of the glaciations. In the Scandinavian area, important ice‑sheds were besides the Scandinavian main ice‑shed the Hordaland, Utsira, Dalarna and Småland ice‑sheds. Greatly independent differential glacier streams with different drift characteristics and morphodynamic power were the Oslo, Boknfjord, Hardanger, Katte­gat and Belt Sea glacier streams. In the British area, east of the main ice‑shed formed by the Pennines, the Southern Uplands and the North­west Highlands, the Cheviot Hills and Grampian Mountains formed secondary ice‑sheds separating ice flow into East English, Southeast Scottish and Northeast Scottish glacier streams.

Every cold period of the Pleistocene started with an early advance of the Oslo glacier stream. Later, the Oslo stream was forced to the west by the Kattegat stream and subsequently by the Belt Sea glacier stream. The Dogger Bank (like the Jutland and the Turbot Bank) formed in the morphodynamically active confluence zone of the Oslo and Kattegat glacier streams during the Saale glacial. Only on the west flanks of Dogger Bank did the East English glacier stream continue to accumulate huge push moraines until Weichselian time. The areal fluctuations of the Scandinavian ice sheet were considerably greater than those in the British area. South of Dogger Bank ice‑dammed lakes formed, the extension and levels of which have been reconstructed. These lakes drained to the north, where deep erosional channels formed in the diffluence zones of the glacier streams. During earlier Pleistocene, the Scandinavian and British ice sheets collided, but since the Warthe stage of the Saale cold period the central parts of the North Sea have remained free of ice. The reason for this was the divertive effect on the glacier streams exerted by the Norwegian trough, which had deepened because of glacial erosion and subsidence.

Shore processes during transgressions shaped marine benches and cliffs. The north slope of Dogger Bank is a vast cliff, in places deformed through mass movements.