Boreskov

PP‐60HOPANES IN LOWER AND MIDDLE CAMBRIAN CARBONACEOUS ROCKSIN THE EASTERN SIBERIAN PLATFORMParfenova T.M.Trofimuk Institute of Petroleum Geology and Geophysics SB RAS,Prosp. Akad. Koptyuga 3, Novosibirsk, 630090, Russia; parfenovatm@ipgg.nsc.ruHighly carbonaceous sediments of the Lower and Middle Cambrian Kuonamka complexdeposits were accumulated in a pericontinental open shelf separated from theepicontinental salt‐bearing system by barrier reefs [Kontorovich, Savitsky, 1970]. TheKuonamka complex deposits include the Kuonamka, Inikan, Shumnaya, Sekten and SinyayaFormations. These formations are distributed in the northern and eastern Siberian platform.The biomarkers of the Kuonamka and Sinyaya Formations were studied [Kashirtsev, 2004;Kontorovich et al., 2005; Parfenova et al., 2004; Parfenova et al., 2010 and others].This investigation deals with the three collections of carbonaceous rocks from threesections of the Kuonamka, Inikan, and Sinyaya Formations. Saturate hydrocarbons (HCs) ofbitumen have been examined by gas chromatography‐mass spectrometry methods. The goalof study is to analyze homologs of hopane series. These hydrocarbons are biomarkers ofbacterial and cyanobacterial organisms [Peters, Moldowan, 1993 and others].Bisnorhopanes (C 27 (Ts, Tm)), norhopanes (C 29 ), C 30 hopane (C 30 ) and homohopanes(C 31 ‐C 35 ) have been identified in the fractions of hydrocarbons in all samples (Fig. 1). Usually,the С 29 /С 30 ratio is less than 1 in bitumens of Cambrian OM in the Siberian platform.However, the concentration of С 29 norhopane is higher than that of С 30 hopane in organicmatter (OM) of the Inikan Formation (Fig. 1b). Relatively high amounts of 28,30–bisnorhopane (C 28 ) were detected in samples of the Sinyaya Formation (Fig. 1c). Thus, threetypes of distributions of homologs of hopanes occur in the examined collections. Perhaps,the diversity of hopane distributions is connected with the biochemistry of initialprokaryotes of the Kuonamka, Inikan, and Sinyaya marine basins. This information may beused to reconstruct the Cambrian microbiocoenosis and the evaluation of prokaryote bybiochemical parameters (by variations of the content and distribution of biomarkers).The С 35 /С 34 ratio is less than 1 in HCs fractions of the Kuonamka and Inikan Formations.The concentration of С 35 homohopanes is higher than that of С 3 4 homohopanes in HCs ofthe Inikan and Sinyaya Formations. These results suggest that the redox conditions varied inthe marine basin of the Lower and Middle Cambrian.238