Mesozoic Structural Characteristics And Evolution In Hangjinqi Block,Northern Ordos Basin

Hangjinqi Block in the northern part of Ordos Basin is located in the western part of the North China plate.It is located in the three major tectonic regions and is affected by the interaction of several orogenic belts and subduction zones.It is a good material for the study of the evolution of sedimentary basin.Meanwhile,the seemingly gentle and continuous stratigraphic characteristics of Hangjinqi Block allow researchers to neglect its possible complex formation process,which needs to be finely defined.On the basis of previous studies,this paper describes the Mesozoic tectonic evolution process in Hangjinqi Block,and discusses its formation mechanism through field geological survey and data analysis and a variety of research methods.The results show that the Mesozoic deposits in the Hangjinqi Block are gentle.The Hangjinqi Block experienced two tectonic periods in the Mesozoic era.The first stage was the Triassic.During the period,the sediments were gentle and continuous,and the strata distributed evenly.In the second period,the Jurassic-Cretaceous period,the region experienced a number of subsidence and uplift,and the range of uplift varies in different periods.The range of denudation of the 5 unconformable surfaces in the study area is different from the intensity of the uplift.The uplift and erosion of the Yanchang Formation is more intense,and the formation of 300-500 m thick is generally eroded.The northern area of the Yanan Formation is in contact with the upper floating stratum,and the erosion amount in the south is 0-146 meters,and the formation of the Zhiluo Formation is affected by the activation thrusting of the Hangjinqi fault zone.The erosion amount of the upper disk in the southern Boerjianghaizi faults of the study area is more than 200 meters.The Anding Formation varies from 50 to 700 m eastward from west to East,and the erosion of Zhidan Group is affected by three eye wells,and the amount of erosion from west to East is increasing gradually,and the maximum of the northeast region is more than 900 meters.The formation of Mesozoic tectonics in the study area has been influenced by many aspects,including the closure of the northern Xingmeng-Okhotsk ocean,the extrusion of the southern Qinling-Dabie orogenic belt,the extrusion of the Qilian orogenic belt in the southwest and the Northwest Alashan block,and the subduction of the eastern Pacific plate to the North China plate.