Biomarkers in Source-Rock and Solid Bitumen in Epirus, Western Greece. Implications for Oil-Source Correlations

The Epirus region in Western Greece demonstrates important hydrocarbon potential indicated by widespread oil-seeping, which proves that all elements and processes of a petroleum system are present and active. This study compares biomarker signatures of biodegraded solid bitumen samples from 3 sites [Petousi, Elataria and Vassiliko (the last two SB yet unreported)], with those from source rock samples obtained from two of the most promising oil-prone source rocks outcropping in Epirus i.e., the Pantokrator Shale and the Toarcian Lower Posidonia Shale, aiming to assess oil affinities. Petousi and Elataria solid bitumens were both found filling joints within the sediments of the Toarcian Lower Posidonia Shale Fm, whereas Vassiliko solid bitumen was obtained from Triassic collapse-breccias. The results suggest that the solid bitumen in Elataria Lower Posidonia Shale exhibits geochemical similarity to the Lower Posidonia Shale source rock. Petousi solid bitumen although found in Lower Posidonia Shale source rock has likely derived form the adjacent Pantokrator Shale of Pantokrator bituminous limestones. Vassiliko solid bitumen likely originate from a source matching Pantokrator Shale geochemical characteristics. Moreover, bitumen yields of these source rocks indicate that Pantokrator Shale generation potential well exceeds that of the Lower Posidonia Shale.