Detailed investigation of the Asse salt structure (Subhercynian Basin) based on new 3D seismic data

The Asse salt structure is a salt-cored anticline with steep, locally overthrusted flanks located in the Subhercynian Basin. It is an excellent example of salt structures in the North German Basin containing a wedge-shaped intrusion of Upper Permian into Upper Triassic salt (‘salt wedge’). The Asse is also known as a location for the disposal of low- and intermediate-level radioactive waste emplaced in the former salt mine Asse II during the 1970s. Detailed knowledge of the tectonic structures is indispensable for planning new retrieval infrastructure and for long-term safety analysis. The Asse salt structure has been thoroughly explored for over 100 years by surface geological mapping, 2D seismic and drilling. Ongoing exploration provides further insights into the salt structures and strengthens our understanding of its evolution.

A new 3D seismic data set (2019-2020) provides new insights into the details of this salt structure. Here we present first results of the seismic interpretation revealing substantial changes in the structural style opposing previous geological models. It can be shown that the sub-horizontal northern flank terminates at the base of the southern flank implying a north-ward instead of a south-ward directed overthrusting. Small-scale faults crossing the crest were previously interpreted as transpressional faults developed during the Late Cretaceous inversion. Ongoing kinematic modeling suggests that these faults originated as steeply dipping pre-Cretaceous normal faults that were overprinted during flank-rotation. These implications as well as observations of thickness variations and unconformities in Mesozoic layers will help to reconstruct the evolution of the Asse salt structure.