AN APPROACH TO RECONSTRUCT THE EARLY HOLOCENE TIDALCONDITIONS IN THE INNER GERMAN BIGHT, NORTH SEA

摘要

Results of an investigation aimed at the reconstruction of tidal conditions in the earlyrnHolocene, to improve the understanding of the long-term (Holocene) geomorphologicalrnevolution in a coastal area, are summarised in this paper. The domain of investigation is thernDithmarschen on the German North Sea coast. The main objective was to simulate tidalrnconditions for an early Holocene morphological stage of the area, in the context of therndifferences between the coastal configuration an generated features in the past and today. Thernmorphology from an early stage of the Holocene transgression (about 7000 BP) is reconstructedrnbased on previous investigations and by considering records of mean sea level, cores andrnshallow seismic. Numerical model simulations of the tidal flow taking into account the existingrnand a reconstructed paleo-bathymetry combined with the corresponding mean sea levels wererncarried out. Results from measurements and numerical modelling for the existing conditionsrnshow a clear tidal domination and small opposite tidal asymmetries for inner and outer parts,rnsuggesting a dynamic equilibrium. Simulations considering the reconstructed paleo-bathymetryrnshow important reduction in the tidal range and overall flood domination. It might have lead torna wave dominated sediment transport in the early stages of the Holocene evolution of the area,rnthat would explain the formation of narrow coast parallel beach ridge like structures, in contrastrnwith the wide and open tidal flats found today in the area.