Evolution characteristics of Ordos Basin in sedimentary period of Chang 10-Chang 8 member of Yanchang Formation
By analyzing the stratigraphic development characteristics,elastic 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,Or-dos 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 peri-od of the Chang 10,and the subsidence center is located in Huanxian-Zhenyuan-Zhenning area,the southwest-ern 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 evo-lution 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 proto-liths.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 1 000～1 550 m thick in the subsidence center.This study furthers the understanding of the formation and evolution of the Ordos Basin.
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