The Periglacial Subsurface Topography of the West Coast of Jutland, Denmark

Abstract

This article concentrates on the format ion and nature of the former periglacial topography of the subsurface of the continental shelf of the coastal zone of west Jutland, with particular reference to examples on the island of Rømø. The North European Wadden Sea area, one of the largest expanses of tidal flats in the world, is geomorphologically dynamic and the relationship between erosion and deposition is rather simple to explain. For example, the formation of barrier islands is due to the gently sloping offshore shelf upon which tidal surges create beach ridges which are then sculptured by storms, wind, longshore currents and tides. Behind the barrier islands, lagoons form. Tidal waters enter the lagoons through inlets. This special seascape modifies the way in which storm waves affect the coastline. The tides here create both flood and ebb deltas. Nevertheless, to understand the origin and geomorphogenesis of the current landscape of west Rømø, it is necessary to consider the following points: (1) The size and speed of sea-level fluctuations in the southern North Sea since the last glaciation (Weichselian). (2) The tidal conditions of the different post-glacial phases. (3) Former and existing climatic fluctuations. This also includes the consideration of the frequency of storms severe enough to produce temporary sea-level depths in excess of 1.5m in a region where the sea is normally very shallow. (4) The nature of the materials that are eroded and deposited; type, size, origin, quantity, and (5) The former channel networks: The variety of channel-forming processes is highlighted because of the occurrence of channels on both glaciated and non-glaciated continental shelves. A detailed understanding of channel stratigraphy, morphology and infill processes is therefore necessary and has to be related to the broader regional palaeo-environmental setting.