The Sedimentary Characteristics And Tectonic Significance Of Xiyu Conglomerate Of Late Pliocene To Early Pleistocene In Northeastern Pamir,Xinjiang

The Xiyu conglomerate is of key significance for the study of the late Cenozoic tectonic deformation in the Tarim basin and its surrounding areas,and its sedimentation responds to the event such as the uplift of Qinghai-Tibet plateau and the Cenozoic tectonic deformation in the Tarim basin and its surrounding areas,and it can also serve as an important reference for the division of tectonic active periods in the northeastern margin of Pamir.On the basis of predecessors'research,our geological sections and routes,statistics of the composition of conglomerate,gravel's size,roundness,sorting,and palaeocurrent direction in Xiyu and Artush formation,Akto region,were counted.At the same time,the study results of the paleocurrent directions and sedimentary facies of Wuqia group,Artush formation and Xiyu formation show that the paleo-topography in the northeast margin of Pamir has undergone a great change.MPT activity was relatively stable in the sedimentary period of Wuqia group,increased in the sedimentary period of Atush formation,and intensified in the sedimentary period of Xiyu formation.The study on the contact relationship amoung the main stratas and the structural characteristics of the main faults in the study area shows that since the middle Pleistocene,MPT has ceased to be active,the Xiyu conglomerate deposition has ended,and the continuous northward pushing process of the pamir tectonic junction is mainly controlled by the right-lateral strike-slip fault near s-n strike in the northeast margin of pamir.The deformation of Xiyu conglomerate was mainly controlled by Uper fault?WPF?,Kurgan fault?KGF?and the branch faults of Kashgar-Yecheng transform system?KYTS?.The ¹⁴C age of the Holocene diluvial sediments obtained near Akcharema village is 330³50 a BP,and the OSL age of the Holocene residual slope sediments obtained at the northwest side of Tashmirik township is 500⁴00 a BP,both of which are cut by WPF,indicating that WPF is still active after 330 a BP,further deforming the Xiyu conglomerate and subsequent sedimentary strata.