Density structure of the Northeast German basin: 3D modelling along the DEKORP line BASIN96

The key for understanding the dynamics of the Northeast German basin is the knowledge of its present-day structures. Our studies are focused on the co mplex geometry and evolution of this basin by the aid of numerical models. To support this task, it was necessary to consider and integrate all availa ble geoscientific information. Based on borehole data, depth maps and on re sults of isostatic modelling we derived a 3D model of the basin structure. A smoothed map of the regional gravity field (after Grosse and Conrad, 1990 ) completed the data base. By means of 3D gravity modelling, the initial mo del structure was modified to fit in the geophysical data set. An important characteristic of the Northeast German Basin is the presence o f Upper Permian Zechstein salt. The salt domes and walls related to the pos tdepositional mobilisation of the salt layer cause pronounced negative grav ity anomalies. This effect is considered as a central problem in this study . In order to investigate possible causes of gravimetric anomalies, we stud ied the influence of different crustal depth levels. We applied a 3D gravit y stripping approach to eliminate the gravimetric effects caused by sedimen tary fill of the basin and to separate density anomalies within the sedimen tary fill from the influence of deeper levels in the crystalline crust. Com plementary, we calculated the downward continuation of the gravimetric fiel d to the basin floor and compared the outcome with the results obtained by 3D stripping. The good fit between the calculated gravity anomalies and the measured anomalies confirms the applicability of the approach. Additionall y, we interpreted the Bouguer anomalies in terms of crustal density distrib ution and discuss the model concerning its consistency with other geophysic al data considering the first results of the seismic reflection experiment DEKORP BASIN96. (C) 1999 Elsevier Science Ltd. All rights reserved.