Petroleum surface oil seeps from a Palaeoproterozoic petrified giant oilfield |
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| Authors: | Victor A. Melezhik Anthony E. Fallick Michail M. Filippov Aivo Lepland Dmitry V. Rychanchik Yuliya E. Deines Pavel V. Medvedev Alexander E. Romashkin Harald Strauss |
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| Affiliation: | Geological Survey of Norway, Leiv Eirikssons vey 39, N-4791, Trondheim, Norway;;Centre for Geobiology, University of Bergen, P.O.BOX 7803, N-5020, Bergen, Norway;;Scottish Universities Environmental Research Centre, East Kilbride, Glasgow G75 0QF, Scotland;;Institute of Geology of Karelian Science Centre, Russian Academy of Sciences, Pushkinskaja 11, 185610, Petrozavodsk, Russia;;Geologisch-Paläontologisches Institut, Westfälische Wilhelms-Universität Münster, 48149 Münster, Germany |
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| Abstract: | 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 δ13Corg 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. |
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