3D structural modelling of Brandenburg (NE German Basin) and evaluation of the dominant controlling mechanism for the present-day thermal field

We use new data of the structural setting and the spatial distribution of thermal properties to develop a refined 3Dstructural model of the Brandenburg area, located in the Northeast German Basin (NEGB). The structural settingof the area is morphologically differentiated by a thick layer of mobilised salt (Zechstein, Upper Permian). Assalt has a considerably higher thermal conductivity than other sediments, it strongly influences heat transport andaccordingly temperature distribution in the subsurface.The crustal-scale model covers an area of about 250 km (E-W) times 210 km (N-S) and has a horizontal resolutionof 1 km. It integrates an improved representation of the salt structures and is used for detailed calculations of the3D conductive thermal field with a FE method.The modelled temperature-distribution with depth shows strong lateral variations. The lowest temperatures forconstant levels occur in the area of the southern basin margin, where a highly conductive crystalline crust comesclose to the surface. In general, the highest temperatures are predicted in the north-western part of the model,where rim syncline deposits around the salt domes cause isolating effects. The pattern of temperature distributionchanges with depth. Closely beneath the salt, the temperature distribution shows a complementary pattern to thesalt cover as cold spots reflect the cooling effect of the thick highly conductive salt structures. The predictedtemperatures at depths beneath 8 km suggest that the influence of the salt is not evident any more. Similar tothe temperature distribution, the calculated surface heat flow shows strong lateral variations. Also with depth thevariations in thermal properties due to lithology-dependent lateral heterogeneities provoke changing pattern of theheat flow.