Cenozoic Tectonics And It's Relationship With Danxia Landform In The Northern Margin Of The Northern Tianshan Mountains

Danxia landform is an ecological resource for human survival and sustainable development,recording the changes of geological environment.The Baili Danxia landform of Tianshan Mountain is located in the north foot of the Northern Tianshan Mountain,close to the southern edge of Junggar basin,which is a typical Danxia Landform in the northwest.Danxia Geopark has been established in the local area,but there are few tourists and low popularity,and no systematic geological process research has been carried out.In this paper,The Baili Danxia landform of Tianshan Mountain is selected as the research object,and the field geological survey,remote sensing geological structure interpretation,digital elevation extraction and other methods are used to study the sedimentary characteristics,structural deformation process,and geomorphic characteristics of the study area.The causes and evolution process of Danxia landform are discussed to provide scientific basis for the rational development and protection of Danxia landform.The main conclusions are as follows:1.The red bed of Baili Danxia Landform in Tianshan is mainly composed of purple thin layer fine sandstone,siltstone with grey green sandstone of Qigu formation of upper Jurassic and red brown sand conglomerate and conglomerate of kalazar formation.2.The Qigu formation of the upper Jurassic is developed in parallel bedding,which shows the characteristics of lake facies deposition in arid climate conditions.According to the characteristics of typical sedimentary sequences,it can be further divided into shallow lake facies and lakeside facies,and the sedimentary environment is unstable,with alternate redox environment;the kalazar formation of the upper Jurassic is partially developed in cross bedding and trough bedding.The overall stratification of the rock is acceptable and the consolidation is poor,which reflects the sedimentary characteristics of alluvial fan facies.3.Three different stages of structural deformation have been determined in the region.D₁ and D₃ have little influence on the formation and evolution of Danxia landform.The main controlling factor for the development of Danxia landform is the South-North thrust in D₂ period,which is characterized by a series of fold fault zones of South-North thrust.The Jurassic in the middle part is characterized by the development of wide and gentle folds and local folds faults,while the northern part is mainly characterized by the development of monoclinic strata,which shows a large number of linear structures near East-West in remote sensing image interpretation.4.According to the density development of water system,the integral distribution of area and elevation,and the depth of surface cutting,the whole area can be divided into three zones with different structural deformation intensity.Each zone shows the corresponding laws in the aspects of uplift and subsidence,structural activity and geomorphic development.5.Comprehensive analysis shows that the upper Jurassic lithology plays a fundamental role in the evolution of Danxia landform.The monoclinic formation formed by structural control determines the shape of"gentle foot"of Danxia landform,and the linear structure in EW direction leads to the appearance of scarps,which are the controlling factors of"steep body"characteristics.