An integrated study of the NE German Basin

The NE German Basin is part of the Southern Permian Basin south of the TransEuropean Suture Zone (TESZ). Here we report an attempt to integrate a variety of geological and geophysical data in order to reveal the present day deep crustal structure of the NE German Basin. Special focus is taken on detailed geological information, available reflection seismic data, wide angle refraction seismic data and gravity data. Based on this integrative approach, a concise crustal model is developed which can be subject to further evaluation. Furthermore, it is shown that the NE German Basin is an outstanding feature quite different from classical basin types. As the Moho is flat below the basin, neither a simple-shear-, nor a pure-shear-extension model can be applied. Instead, a thick high-velocity lower crustal layer is present below the basin centre. This high-velocity lower crust is also observed in the western part of the basin and can be taken as characteristic for East Avalonia. Results of gravity modelling indicate the presence of a high-density lower crust, thus supporting the wide-angle data. Furthermore, changes in crustal structure can be derived from changes in reflectivity pattern and from the gravimetric signature along the Elbe Fault System, indicating the presence of different crustal domains north and south of the fault system. An elastic plate model, where the forces applied are the sediment load, a vertical load at the southern margin accounting for the Harz Mountains and a NNE-SSW-directed compression, indicates a buckling of the crust during Late Cretaceous to Tertiary inversion. However, the correlation between the observed crustal structure and the tectonic events that have affected the area remains a subject of discussion. A Permian thermal event affected the upper mantle and the lower crust and, therefore, may have modified the 'crustal memory' with regard to Caledonian and Variscan events. Additional tectonic events affected the area during the Mesozoic. In conclusion, it remains an open question whether the high-velocity and high density lower crustal structure represents a remnant of East Avalonia, whether it is related to the formation of the Permo-Triassic basin, or is the cumulative result of a series of events during the Palaeozoic and Mesozoic.