A GPR study of sedimentary structures within a transgressive coastal barrier along the Danish North Sea coast

The Danish North Sea coast is characterized by the presence of coastal barrier systems. One of these systems, the Holmsland Barrier, is a transgressive wave-dominated barrier. For the purpose of studying large-scale architecture in a transgressive barrier, as well as small-scale sedimentary structures, a ground penetrating radar (GPR) field experiment has been carried out. The study focuses on the identification of high-amplitude reflections of the large-scale architecture of the barrier and the recognition of small-scale structures for interpretation of coastal processes. The observed radar facies fall into two groups, both interpreted as storm washover deposits. One group, dominated by parallel to subparallel reflection, is related to the seaward horizontal stratification in the washover fans. The other group, dominated by sigmoid and oblique clinoforms, is related to delta foreset stratification, indicating that the washover fans are terminated in standing water. The observations derived from the GPR study of the Holmsland Barrier suggest that this transgressive barrier is composed almost entirely of washover deposits with local small amounts of aeolian deposits. This study has shown that the GPR method is outstanding in mapping both large-scale architecture and small-scale internal structures in a coastal barrier.