Neotectonic Movement Characterictics In Southwestern Margin Of Ordos Basin

Since the late Cenozoic,the continuous collision between the Indian plate and the Eurasian plate has led to the uplift of the Qinghai-Tibet Plateau,the most important geological event in modern Asia.The uplift of the Qinghai-Tibet Plateau has a fundamental impact on the transformation of the general circulation pattern in East Asia and the reconstruction of the Late Cenozoic tectonic and geomorphological pattern in Asia.As the southwestern margin of the Ordos Basin adjacent to the Qinghai-Tibet Plateau,the impact is particularly evident.In the middle Eocene,the southwestern margin of Ordos was subjected to NWW-SEE trending tension stress due to the subduction of the Pacific plate to the Asian continent,which resulted in the faulting of the Weihe graben and the formation of the early Weihe basin.After the late Miocene,the uplift of the Qinghai-Tibet Plateau took over the long-distance effect of the westward subduction of the Pacific plate and became the southwestern margin of the Ordos basin.The dominant factor of tectonic evolution.Since Pliocene,the Qinghai-Tibet Plateau has undergone three periods of strong uplift,which resulted in the overall uplift and counterclockwise rotation of the Ordos massif,resulting in the formation of the left-lateral strike-slip fault system on the southwestern margin of the Ordos massif.In order to clarify the evolutionary history of neotectonic movement and discuss its response to the uplift of the Qinghai-Tibet Plateau,the original data of neotectonic movement in the southwestern margin of Ordos are obtained by field geological survey method and analyzed.Based on ASTER-GDEM(30m)data,the tributary channel landforms across the fault in the Qianhe River Basin are interpreted by using ARCGIS hydrological analysis and other technical means,and the elevation area is calculated.Geomorphological parameters including HI,SL and VF were used to quantitatively analyze the influence of neotectonic movement on the geomorphology.The results show that:(1)the Badu-Longwei segment of Guguan-Guzhen fault is a sinistral strike-slip fault,which has been active since the late Pleistocene;(2)the Caobi-Tianjiagou segment of Longxian-Qishan-Mazhao fault is also a sinistral strike-slip fault,which has been active frequently since the late Pleistocene,and its time limit is later than 0.01 Ma.(3)The geomorphological parameters of the Tsubi-Tianjiagou segment of the Longxian-Qishan-Mazhao fault show strong tectonic activity in the north-west end and weak tectonic activity in the south-east end,which is consistent with the geological phenomenon that the sliding rate of the north-west end of the fault is fast and the sliding rate of the south-east end is slow,reflecting that the formation of Neotectonic movement in the southwestern margin of the Ordos Basin is mainly caused by the uplift of the Qinghai-Tibet Plateau.And the extent of the impact is decreasing from west to east.