New insight into the Evolution of the Jasmund Glacitectonic Complex from Seismic Mapping of Glacial Erosion Unconformity East of Rügen (SW Baltic Sea)

Abstract

The Jasmund Glacitectonic Complex (JGC) on the island of Rügen (NE Germany) is a key area where the interplay between glaciation, erosion and tectonics can be studied. Previous reconstructions are based on land-based and outcrop studies. Here, we use 148 high-resolution multi-channel seismic reflection profiles from several cruises of the University of Hamburg with RV ALKOR as well as adjacent borehole data to decipher the offshore extent of the JGC. The seismic data image erosional channels and depressions as well as moraines, which delineate the mainly southwestward directed Weichselian glacier movement. The depth of the erosional surface at around 100 m correlates with the previously modelled décollement depth. Furthermore, these results suggest a continuation of the observed glacial features onshore, highlighting the connection between the marine and terrestrial features of the JGC. Our investigations suggest that the complex evolution of the JGC is not due to three distinct ice streams, as proposed by previous studies. Instead, our data suggest that a single southwestward ice flow, which splits northeast of Jasmund, is responsible for the three-phase evolution. During the formation of the northern and eastern subcomplexes, the Cretaceous sediments were overthrusted almost perpendicular to the ice movement. In the southern subcomplex, however, the overthrusting was caused by the lateral pressure of the ice flow passing south of Jasmund. This study provides a methodological blueprint for the study of similar glacitectonic complexes elsewhere.