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The distribution of “molecular fossils” (bio-markers) of steroid compounds in extracts from some spe-cific geologic age in the Tarim Basin have been analyzed andare used as the fingerprints for the oil-source rock correla-tion. Having been affected by maturation, migration, phasefractionation and biodegradation, not any molecular fossilsrelated to source and environment can be used as the finger-prints for oil-source rock correlation. Some special bio-markers widely existed in the extracts from Cambrian andOrdovician rocks in the Tarim Basin and showed obviousdifference in each stratum, including dinosteranes (C_(30)),4-methyl-24-ethyl-cholestanes (C_(30)) and their aromatizedsteroids, C24-norcholestanes and C_(28) steranes originated fromdinoflagellates and diatom. Few oils such as the heavy oildrilled in the Cambrian reservoir from Tadong 2 well (TD2)correlated well with the extracts from the Cambrian. Theamazing similarity of the relative contents of these com-pounds between the marine oils produced in Tazhong andTabei uplifts and the extracts from the Upper Ordoviciansuggests that the Middle-Upper Ordovician is the very likelymain source for the marine oils.
The distribution of “molecular fossils” (bio-markers) of steroid compounds in extracts from some spe-cific geologic age in the Tarim Basin have been analyzed and used as the fingerprints for the oil-source rock correla- tion. Having been affected by maturation, migration, phase fractionation and biodegradation, not any molecular fossilsrelated to source and environment can be used as the finger-prints for oil-source rock correlation. Some special bio-markers widely existed in the extracts from Cambrian and Ordovician rocks in the Tarim Basin and showed obvious difference in each stratum, including dinosteranes (C_ (30)), 4-methyl-24-ethyl- cholestanes (C_ (30)) and their aromatizedsteroids, C24- norcholestanes and C_ (28) steranes originated from dinoflagellates and diatom. Few oils such as the heavy oildrilled in the Cambrian reservoir from Tadong 2 well (TD2) correlated well with the extracts from the Cambrian. Theamazing similarity of the relative contents of these com-pounds between the m arine oils produced in Tazhong and Tabei uplifts and the extracts from the Upper Ordoviciansuggests that the Middle-Upper Ordovician is the very likely main source for the marine oils.