Sedimentology, organic geochemistry, and petroleum potential of Jurassic coal measures: Tarim, Junggar, and Turpan Basins, northwest China

Lower and Middle Jurassic coal-bearing strata occur widely throughout central Asia and are well developed in northwestern China. Examination of these strata along 13 transects across basin margin outcrop belts indicates that they are entirely nonmarine meandering fluvial deposits with local development of braided fluvial and lacustrine deltaic facies. Laboratory analyses of coals and organic-rich shales show a dominance of terrestrial, higher plant components. Jurassic source rock extracts are characterized by odd-over-even normal alkane distributions, high pristane/phytane and a high hopane/sterane ratios, dominance of C₂₉ sterane homologs, local abundance of diterpenoid compounds, and low abundance of tricyclic terpanes. Geochemical correlation with four petroleums from the Junggar, Tarim, and Turpan basins strongly suggests that the Jurassic coaly deposits and their lacustrine equivalents downdip are petroleum source rocks. -from Authors