Abstract: The analysis of Early-Middle Jurassic structural and lithofacies in Kashi sag shows that the Lower-Middle Jurassic strata developed respectively in two sedimentary systems, namely Kuzigongsu-Keziletao strike-slipping pull-apart faulted-depression and piedmont faulted-depression. Both of the sedimentary systems resulted in the different features of lithology, lithofacies, sedimentary thickness and distribution. The system of strike-slipping pull-apart faulted-depression of great thickness of Jurassic is controlled by the Talaso-Ferghana fault, with high-quality source rocks made up of coal-bearing strata and deep-semideep lake mudstone. The system of piedmont faulted-depression with relative thinner thickness of Jurassic possesses good source rocks formed by locally distributed coalmeasure strata in south Tianshan mountain and west Kunlun mountain. The oil and gas derived from the Lower-Middle Jurassic source rocks reach the key moments for hydrocarbon accumulation at end of Paleogene and Pliocene, respectively. It is concluded that the petroleum exploration in view of the Jurassic petroleum system should focus on the structural positions where the later structural transformation is relatively weak, or on the secondary oil-gas accumulation.

Key words: Tarim basin, Kashi sag, Jurassic, sedimentary environment, oil-gas accumulation