Boreskov

PP‐20MID‐CHAIN BRANCHED MONOMETHYLALKANES IN THE UPPER PROTEROZOICAND CAMBRIAN OF SIBERIAN PLATFORMKontorovich A.E. 1 , Kashirtsev V.A. 1 , Nagovitsin K.E. 1 , Sobolev P.N. 2 ,Sukhoruchko V.I. 2 , Timoshina I.D. 11 Institute of Petroleum Geology and Geophysics SB RAS, Prosp. Akad. Koptyuga 3,Novosibirsk, 630090, Russia; fax: 8(383)3332301; e‐mail: TimoshinaID@ipgg.nsc.ru2 Siberian Research Institute of Geology, Geophysics, and Mineral Raw MaterialsKrasnii prosp. 67, Novosibirsk, 630091, Russia; fax: (383)2214539;e‐mail: geochim@sniiggims.ruMid‐chain branched alkanes or 12‐, 13‐monomethylalkanes (12‐, 13‐mmas) present inhigh concentrations (up to 18% of the total alkanes) in Upper Proterozoic oils of the SiberianPlatform and Oman [1‐4 and others], as well as in the Neoproterozoic dispersed organicmatter from Oman [3] and the East European Platform [5] represent well the biochemistryof lipids from the Precambrian specific biota (eukaryotes?) dominating some ecologicalniches. Until recently, the 12‐, 13‐mmas were unknown from the Upper Proterozoicdispersed organic matter of the Siberian Platform.165