Comparative petrography and organic geochemistry of different types of organic matter occurring in the Outer Carpathians rocks

Abstract

The characterization of organic matter (OM) in sedimentary rocks is important in many types of biological, geological and environmental research. The integrated use of microscopy and geochemistry, as here, is particularly useful in any attempt to define the origin and evolution of OM in sedimentary basins. The organic petrography and geochemistry different types of allogenic and authigenic OM from the Polish Outer Carpathian (POC) rocks were studied in present study to compare their genetic type, thermal maturity, depositional environment and post-sedimentation processes. Special attention was paid to redeposited coal clasts occurrences. The used techniques show differences in organic matter type originating from various sources. The organic petrography analysis shows that redeposited coal clasts (CC) and terrigenous organic matter (TOM) are composed predominantly of woody material (the gas-prone Type-III kerogen). Similar results were obtained during the Rock-Eval pyrolysis. Moreover, the GC-MS analysis of extracts indicated the additional source of OM, namely planktonic organic matter (POM) with oil-prone kerogen Type-I or II. This OM is in some cases high thermally mature and could potentially has allochthonous origin. The n-alkane, saturated and aromatic biomarker data revealed deposition of this POM in anoxic deltaic or close-shore sedimentary environments whereas the redeposited coal clasts were probably originally deposited in coal swamps as were the Upper Silesian bituminous coals.