Petroleum surface oil seeps from a Palaeoproterozoic petrified giant oilfield

• Published in: Terra Nova
• Main Authors: Melezhik, V.A., Fallick, A.E., Filippov, M., Lepland, A., Rychanchik, D.V., Deines, Y.E., Medvedev, P.V., Romashkin, A.E., Strauss, H.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Wiley-Blackwell Publishing Ltd. 2009
• Subjects: QE Geology; GE Environmental Sciences; Onega; Fennoscandia
• Online Access: https://eprints.gla.ac.uk/5303/; https://doi.org/10.1111/j.1365-3121.2009.00864.x

Early Palaeoproterozoic rocks from the Onega Basin in Russian Fennoscandia contain evidence for substantial accumulation and preservation of organic matter (up to 75 wt% total organic carbon) with an estimated original petroleum potential comparable to a modern supergiant oilfield. The basin contains a uniquely preserved petrified oilfield including evidence of oil traps and oil migration pathways. Here, we report the discovery of the surface expression of a migration pathway, along which petroleum was flowing from the sub-surface. This surface oil seep, the first occurrence ever reported from the Palaeoproterozoic, appears as original bitumen clasts redeposited in Palaeoproterozoic lacustrine turbidites. The δ 13 C org of clastic pyrobitumen ranges between −35.4 and −36.0‰ (n = 14), which is within the range of interbed- and vein-trapped fossil oil (−46 and −24‰), suggesting similar source. Biogenic organic matter, whose isotopic composition was modified during thermal maturation, is the likely source for the migrated hydrocarbon.