Effect of Ancient Earthquake and Its Geological Significance of Upper Triassic Yanchang Formation in Southeast Ordos Basin

Qinling orogenic movements in Indo-sinian epoch control and impact the southern boundary nature and the sediment of the Upper Triassic Yanchang Formation in Ordos Basin.Through analysis of cores,such typical soft sedimentary deformation structures were identified from the Yanchang Formation in southeastern Ordos Basin as earthquake rimas,ladder-shaped faults,micro folds,liquefied sandstone veins,vibrational liquefaction curled deformation structures,ball-and-pillows,loop beddings,colliculus-groove structures,earthquake breccias,which reflected that there were intense and frequent earthquakes during the period in study area.On the base of the above analysis,deeply analyzing the dynamic mechanism of basin—mountain coupling action process and responses in Late Triassic Ordos Basin,and further studying on the special formation mechanism,spatial and temporal distribution of seismo-turbidites which were event deposits in detail,consequently,sedimentary model of seismo-turbidites have been established.Finally,the attribute character and active period of seismic events in Late Triassic Ordos Basin are discussed.