A large regional structure from puzzle pieces – Gulf of Mexico structures on the western flank of the Eichsfeld-Altmark-Swell (EAS)?

We discuss the structures associated with the Eichsfeld-Altmark-Swell (EAS) in Central Germany, using observations from published cross-sections, outcrops, few boreholes and reflection seismics in a some 200 kilometres long swath in Central Germany. The EAS is well-documented as an approximately NNE-SSW-trending Permo-Triassic intrabasinal high, expressed by reduced thickness, facies changes and unconformities. It was accompanied by depocenters trending parallel to its axis, which changed in position and magnitude during geologic epochs. North of the Harz Mountains an approximately 10 km wide strip of the EAS´s western flank is strongly structured by faults of the Braunschweig-Gifhorn-Fault Zone (BGFZ). There, local thickness reductions of several hundred meters, in places culminating in complete absence of Lower and Middle Buntsandstein and apparently often associated with salt tectonics, are documented by seismics and well data, contrasting with the regional thickness reductions in the range of tens of meters typically attributed to the EAS. In Keuper time areas with large Buntsandstein hiatuses turned into depocenters. The spatial relationships of these depocenters with bordering normal faults and associated salt structures indicate that the western flank of the EAS was influenced by strong extension (up to 5 km) along low-angle normal faults detaching in Zechstein evaporites. No prominent basement offsets are observed, although they become prominent along trend of the BGFZ in the aligned westward terminations of the Flechtingen High, Harz and Thuringian Forest basement blocks. We discuss solutions for the mismatch of strong thin-skinned extension and apparently little deformed basement.