Evolution characteristics of Ordos Basin in sedimentary period of Chang 10-Chang 8 member of Yanchang Formation

By analyzing the stratigraphic development characteristics, clastic filling structure and sedimentary facies distribution of the Chang 10-Chang 8 sedimentary period of the Yanchang Formation in the Ordos Basin, combined with petrological and geochemical analysis, it is proposed that affected by the Qinling orogeny, Ordos Basin strongly subsided, transformed from platform to basin, and climate shifted sharply at the Chang 10-Chang 8 sedimentary period: ① It is cheared that significant subsidence occurred during the sedimentary period of the Chang 10, and the subsidence center is located in Huanxian-Zhenyuan-Zhenning area, the southwestern basin, with significant asymmetry rapidly filled by thick coarse clastic. Chang 9 and Chang 8 member are stable deposits dominated by climate in a stable tectonic environment, with relatively fine sediment. ② It is proposed that the Chang 10 subsidence ended the stable platform during the late Paleozoic and began the evolution of inland basin. The platform-basin transformation and basin evolution under the influence of orogenic tectonic activities have left traces in the maturity of clastic sediments and the characteristics of detrital protoliths. ③The sedimentary period of Chang 10 member ended the long-term arid and hot climate since the Late Permian, and began the transition to semi-arid and semi-humid, and to warm and humid climate. ④ The Chang 10-Chang 8 members constitute a subsidence-filling cycle of lower Yanchang Formation, about 1000~1550 m thick in the subsidence center. This study furthers the understanding of the formation and evolution of the Ordos Basin.