Thermal maturity of organic matter within Carboniferous clastic rocks in the Drogomyśl IG-1 drill hole (the Upper Silesian Coal Basin, Poland)

Abstract

The aim of the study was to determine the thermal maturity level of organic matter on the basis of reflectance measurements performed on vitrinite from Carboniferous sandstones, mudstones and claystones in the Drogomyśl IG-1 drill hole in the Upper Silesian Coal Basin, Poland. Random reflectance Rr of vitrinite in the sandstones varies between 0.72% and 1.28%, while in the fine-grained rocks between 0.77 and 1.31%, which corresponds to paleotemperature of 110 to 180oC. Calculated geothermic paleogradients varies between 60oC/km and 63oC/km which leads to the conclusion that minimum thickness of the sedimentary overburden eroded from the surface of Carboniferous beds was from 4800 to 5000m. However, taking into consideration only geothermic paleogradients (70o - 100oC/km), calculated for the layers occurring below the depth of 1500m, the thickness of the eroded overburden should be from 5600 to 8000m.