Biomarker oil-to-source rock correlation in the Western Carpathians and their foreland, Czech Republic

Biomarker analyses indicate that at least two petroleum systems operate in the Vienna basin, Carpathian thrust belt and the European foreland plate in Moravia - one associated with Jurassic and the other with Palaeogene organ ic-rich rocks. Four oils from the sub-Carpathian foreland plate and one sam ple from the Vienna basin were analysed and geochemically compared to extra cts from Jurassic and Palaeogene source rocks. Two oils from the subthrust foreland plate (Lubna-18 and Dolni Lomna-1) are genetically related based o n similar geochemical compositions. These oils show high oleanane and 24-no rdiacholestane ratios, age-related biomarker ratios that are consistent wit h an origin from Palaeogene organic-rich rocks. These rocks are inferred to be either the Menilitic shales of the Carpathian thrust belt or autochthon ous Palaeogene deposits buried below the thrust belt. Two other oils from t he subthrust plate (Zdanice-7 and Damborice-16) correlate geochemically wit h extracts from Jurassic source rocks in the Sedlec-1 and Nemcicky-1 wells. Like the oil extracts, these oils lack oleanane and show low 24-nordiachol estane ratios, supporting an origin from Jurassic organic-rich marls. The o il sample from the Vienna basin (Tynec-34) appears to be a mixture of the t wo oil groups.