Organic geochemistry and geohistory of the Triassic succession of Bjørnøya, Barents Sea

The Triassic outcrops of Bjørnøya provide an important reference for regional characterization of potential hydrocarbon source rocks of this age in the southwestern Barents Sea. The organic matter in both the Urd and Skuld Formations is dominated by woody and herbaceous material, with elevated contents of algal/bacterial organic matter present in the Urd Formation. Minor amounts of oil is likely to have been generated from these shales. These rocks have been deeply buried and are at a present-day thermal maturity corresponding to vitrinite reflectance of 1.2%, i.e. full realization of the kerogenʹs oil potential. One-dimensional basin modeling suggests that these Triassic rocks have been buried to near 5 km depth and expelled oil and gas during the Late Cretaceous to Early Tertiary. Bulk geochemical data show good agreement with visual observations of bitumen staining in thin sections. This staining has a biomarker distribution characterized by a homologous series of tricyclic terpanes. GC/MS/MS analyses showed this tricyclic series to extend from C21 to C46.