Heat flow evolution, subsidence and erosion in Upper Silesian Coal Basin, Czech Republic

The deep boreholes in the Upper Silesian Coal Basin provide a valuable material to evaluate thermal maturity of the present Carboniferous units. 17 boreholes were used for evaluating expected paleothicknesses of the missing units and the maximum temperatures reached via 1D modelling. The models consider the geological evolution concepts accepted for the region. The reliability of the final thermal models was calibrated with vitrinite reflectance data. Vitrinite reflectance varies between 0.46 and 2.32% Rr indicating thermally early mature to over mature organic matter for the Ostrava Fm. and Karviná Fm. The coal rank increases from the east to the west. Based on the data from RockEval pyrolysis all samples from the Ostrava and Karviná Fms. belong to type III kerogen. The RE results show that the source potential of the Carboniferous sediments was not spent in full as part of the Variscan tectogen. Burial and thermal history on the Czech side of the Upper Silesian Coal Basin was reconstructed. The set of several 1D simulations proved that the thickness of the missing Palaeozoic molasses association is 2500 to 3400 m in the foreland and 1800 to 2000 m for the platform. The maximum burial is expected at the end of the Westphalian. The consequent sedimentation of the Carpathian Foredeep and nappe thrusting did not change the Palaeozoic thermal maturity pattern within the tested area of the USCB.