Remarks on thermal maturity level in the subsurface of the Upper Silesian Coal Basin

Abstract

The thermal maturity data presented by BROCHWICZ-LEWIŃSKI & al. (1986) from the subsurface of the Upper Silesian Coal Basin, southern Poland are discussed. The supposed low maturity level (60-70°C) in Cambrian rocks, based on acritarch color, is inconsistent with the maturity trends inferred by other indices of organic metamorphism (coal rank, vitrinite reflectance, conodont CAI), most probably because of decolorization of acritarchs due to secondary oxidation. The broad spectrum of maturity data (BEŁKA 1993 and KOTAS & al. 1983) shows that the Cambrian in the southern part of Upper Silesia must be slightly supramature. The validity of particular organic maturation indices is briefly outlined.