Geochemical Characteristics and Significance of Late Cretaceous Deposits in the Kuqa Depression, Xinjiang
新疆库车坳陷晚白垩世沉积的地球化学特征及意义

The Bashijiqik Formation developed in Kuqa depression is the main reservoir of the large-size Kelasu gas field in northern Tarim basin of Xinjiang. Nevertheless, its sedimentary environment is a problem of long controversy. Based on geochemical data of the Bashijiqik Formation in Kuqa depression, the authors analyzed the Late Cretaceous transgressive sediments in this depression. Combined with lots of marine calcareous nannofossils in the upper member of the Bashijiqik Formation recently discovered in the outcrop and drillhole sections and the features of sedimentary facies, it is held that the transgression must have happened in Late Cretaceous in northern Tarim basin, and that the sea water was widely distributed over the Kuqa River area. The sedimentary environment, however, was relatively closed. The paleosalinity indices indicate that the medium was salt water, and the paleoclimate was dry and of high temperature. This research has laid a foundation for the correlation of Cretaceous strata between southwestern and northern Tarim basin and hence is of great significance in the oil-gas exploration and perspective analysis.