3-D modelling of subsidence related processes in the northeast German Basin

A typical intracratonic basin--the Northeast German Depression--has been studied with special regard to its present thermal structure and to its early evolution. Today the basin is characterized by a positive thermal anomaly. Three dimensional modelling, in connection with a detailed structural model, indicates that the thermal anomaly can mainly be attributed to the low conductivities of the sediment filling. However, some modifications result from a variety of salt structures. Basin formation has been studied in terms of sediment accumulation and by subsidence modelling with various methods. The initial phase requires lithosphere and crustal thinning, perhaps by different amounts vertically and regionally, and if accompanied by a strong volcanism. The initial phase then is followed by long term thermal subsidence, associated with an extension of the basin and a sedimentary onlap pattern. Initial stretching rates are about 1.2.-1.3. at the basin centre and vanish at its margin. The basin, therefore, lacks a typical rifting phase. These observations will be complemented and discussed in terms of three dimensional thermal subsidence models which shed light onto the growth of the basin during its thermal evolution. The models help to explain the low stretching rates at the basin's borders. In addition, the models allow to study the thermally induced strains and stresses which can be used to deduce the possible location of fault zones and rheological properties of the crust. Finally, some problems specific to three-dimensional models will be briefly discussed.