The geological architecture and development of the Holmsland Barrier and Ringkøbing Fjord area, Danish North Sea Coast

Abstract

The Holmsland Barrier is a 35 km long transgressive coastal barrier located on the Danish North Sea coast, separating the highly dynamic North Sea from the large lagoon Ringkøbing Fjord. In this paper we present new geological and geophysical data from various surveys, including a ground-penetrating radar (GPR) study, several marine shallow-seismic high-resolution surveys, and onshore and marine borehole data. The GPR data has revealed both the large-scale architecture of a part of the barrier as well as small-scale internal structures. From this we conclude that the barrier primarily is built up of sequences of washover deposits, locally interspersed with eolian deposits. The data have been combined in order to construct an evolutionary model of this barrier system. Finally, a large and coherent complex of pre-Quaternary deposits is found at or close to the seabed offshore. This complex also underlies the northern part of the Holmsland Barrier, and is believed to control the position of the present shoreline, as well as its seaward convexity.