ALKYL STERANES AND ALKYL TRIAROMATIC STEROIDS: NEW BIOMARKERS IN PRECAMBRIAN AND CAMBRIAN OILS OF THE NEPA-BOTUOBIYAN AND ALDAN ANTECLISES ( Siberian Platform )
V.A. Kashirtsev and A.E. Kontorovich
Institute of Petroleum Geology and Geophysics, Siberian Branch of the RAS,
3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
Keywords: Oil, oil shales, biomarker molecules, alkyl steranes, triaromatic steroids, Nepa-Botuobiyan and Aldan anteclises, Siberian Platform
Pages: 812-819
Abstract
Chromato-mass-spectrometric studies of fractions of saturated and aromatic hydrocarbons from oils and oil shows of the Nepa-Botuobiyan and Aldan anteclises as well as chloroform extracts from mudstones of the Lower Cambrian Sinyaya Oil Shale Formation have revealed a series of new biomarker molecules. In oils from the Nepa-Botuobiyan anteclise, 3-alkyl steranes with 32 carbon atoms in the molecule were identified. Biological precursors of these alkyl steranes are still unknown. Such structures might have been produced from Δ2-sterenes as a result of bacterial methylation. The Cambrian oil shales and oil shows of the Aldan syneclise have abnormally high concentrations of triaromatic steroids C28. In addition, new triaromatic steroids with an alkyl chain substituent in the ring A have been identified. The identical distribution of biomarkers in the oils and oil shales casts no doubt on their genetic relationship.
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