A NEW EVALUATION OF PALAEO-HEAT FLOWS AND ERODED THICKNESSES FOR THE CARBONIFEROUS RUHR BASIN, WESTERN GERMANY

Palaeo-heat flows and thicknesses of eroded Carboniferous overburden i n the coal-bearing Ruhr basin (western Germany) were estimated using o ne-dimensional basin modelling techniques. Thermal and burial historie s for 11 localities were calibrated by comparing measured and calculat ed vitrinite reflectance data, based on the assumption of pre-tectonic maturation. In contrast to former studies, the kinetic EASY%R(o) appr oach was applied for the calculation of vitrinite reflectance. Lopatin 's TTI algorithm was used in addition for one well in order to demonst rate the impact of the selection of the algorithm for vitrinite reflec tance calculation on the simulation results. Simulated palaeo-heat flo ws for the time of maximum burial (most probably in the Stephanian) ra nge from 64 to 83 mW/m2 and decrease towards the south. These heat flo ws are lower than values computed during earlier studies, but are stil l relatively high in comparison to recent foreland basins. The regiona l distribution of palaeo-heat flows indicates that the crust beneath t he Ruhr basin was relatively thin and thickened towards the south at t he end of the Carboniferous. After the Stephanian, 2200-3500 m of Carb oniferous overburden were eroded. An observed southward increase in er oded thicknesses is caused by an uplift of the area studied, which dec reased towards the north, at the end of the Variscan folding. Large th icknesses of deposited (and later eroded) Carboniferous sediments have to be postulated to explain the maturity data even along the present southern margin of the Ruhr basin. This indicates that the late Carbon iferous sediments originally extended far to the south. Geological arg uments suggest that the deposition of Carboniferous sediments in the e ntire Ruhr basin continued until the Stephanian.