Integrated 3D gravity and geological modelling in the Subhercynian Basin (Germany) – A modelling strategy for the enhanced study of the basins sedimentary and crustal setting

3D geological modelling in highly complex areas with sparse or ambiguous information is affected be conceptual uncertainty, which can be significantly reduced by the integration of gravity data. However, gravity modelling itself underlies the non-uniqueness problem, indicating that there is more than one model consistent with the observed gravity field. Therefore, cross-validation of gravity models by integration of regional geologic concepts, geometric and kinematic construction and restoration techniques helps solving this problem. In this regard, we defined an integrated modelling strategy, which starts with extracting a-priori information from geological maps, 2D seismics, borehole and gravity data, which were independently analysed and conservatively interpreted; i.e. non-unique solutions were completely avoided. Subsequently, geologic interpretations were combined with gravity data, which was analysed by use of gradient calculation and 2D-EULER deconvolution. The resulting combined dataset was validated by use of 2D cross-section balancing techniques considering bed-lengths and area consistency. The resulting serial balanced cross-sections served as solid basis for a 3D gravity modelling. Our integrated workflow was tested for the less-explored eastern part of the Subhercynian Basin (Saxony-Anhalt, Central Germany). We show that the combination of independently ambiguous data holds the potential to generate new insights into the local fault system, the topography of the crystalline basement (transition of the Mid-German Crystalline Rise and Rhenohercynian Zone) and outlines of salt structures as well as the setting of the base Cenozoic. Furthermore, modelling of long wavelength gravity anomalies provides new information on the crustal setting at the margins of the North German Basin.