Geochemical and petrological evidence for Tertiary terrestrial and Cretaceous marine potential petroleum source rocks in the western Kamchatka coastal margin, Russia

Rock-Eval pyrolysis and microscopic analyses of Palaeogene terrestrial strata from the western Kamchatka coastal margin, Russia, indicate that good oil-prone source rocks are present in both coals and shales. Hydrogen Indices (HI) of up to 493 mg HC/g TOC are present in low maturity (0.45 %Ro vitrinite) shale samples from the Irgirninvayam River Delta region, whereas coals with 0.37-0.75 %Ro and HI of 270-310 mg HC/g TOC comprise potential oil/gas- and oil-prone source rocks in the Kvachincha Bay, Tigel coastal, and Rassoshina-Napanskaya River areas. The shales and coals with the highest petroleum potential were deposited in a freshwater paleo-setting, and consist of gelovitrinite, cutinite, suberinite, sporinite, resinite and matrix bituminite. Molecular geochemistry was also used to group genetically related oil samples and to postulate the likely petroleum systems in this area. While the preliminary data confirm the origin of two families of oils from the Palaeogene deltaic to marginal lacustrine source rocks, the chemical composition of oils in two other families suggests the possible presence of marine source rocks in not yet penetrated Upper Cretaceous-Paleocene sequences of the basin.