Reconstruction of Cenozoic original basin and its structural destruction in Hejing area, Xinjiang province

The North Hejing basin located in the north of the Hejing area now is a piggyback basin. Gravels components from the Cenozoic strata are mainly composed of metamorphic rocks and sedimentary rocks with little magmatic rocks. The low maturity of sandstones are characterized by low contents of quartz, feldspar and large amount of rock debris. From Oligocene-Miocene Masagaite Formation to Pliocene- Pleistocene Anjiran Formation, the maturity of the debris decreases. The paleocurrent direction of Cenozoic strata in the internal and around basin was from north to south, which indicates the southern Tianshan Mountain was the source region of Cenozoic strata. Until Pleistocene Epoch, there is no individual piggyback basin in the northern Yanqi Basin. Because of the lateral spreading process of the Tianshan Mountain caused southward thrust wedge belt in the Northern Hejing area. And the northern thrust uplifted the middle-Devonian upon the Anjiaran Formation, while central thrust fault uplifted the middle-Devonian and the granite, formed present topographical feature on the ground. In addition, southern thrust fault caused a series of folds in the Anjiran Formation characterized by steep dip angle in the south section and gently angle in the north. During the Cenozoic, the age of deformation event is older in the northern area than southern in Hejing district. Furthermore, the deformation in the western area is stronger than eastern and the shorten ratio related to structural activities is larger too.