Research On The Formation Mechanism Of Danxia Landform In Jianmenguan Area

Danxia Landform is a kind of the red clastic rock landform,which is characterized by red cliff,the combination of Landforms types mainly include the shape of the castle,the shape of the wall or the shape of the pillars.In the southern and northern regions of China,the Danxia Landform covers 28 provinces.This paper studies these disciplines as theoretical basis mainly,including sedimentology,structural geology,geomorphology and lithofacies paleogeography,etc.In the early cretaceous period,formation exposed Jianmenguan closed area is research scope,and taking the early Cretaceous stratigraphic outcrop area of Jianmenguan as the main research area,It is mainly based on the formation mechanism of Danxia Landform,the forming process of Danxia Landform,geological structure background and the features of sedimentary facies,and then began in-depth analysis and research on paper,so can draw the following conclusion:(1)The tectonic uplift movement is the strongest in the eastern margin of the qinghai-tibet plateau.Due to its humid climate and abundant surface runoff,the area has become a more majestic red cliff.Environmental factors occupy the main position in the formation of geomorphology,and the differences environmental conditions make the Danxia Landform show different morphological features.The slope surface features of Danxia Landform are more prominent in comparison,so the combination of landform types is more complicated.According to the combination characteristics of Danxia Landform,it can be divided into two categories:basic form and combination form,the classification of geomorphic type can also be carried out from geological structure,material basis and development stage of Danxia Landform.In numerous geomorphic area,sword door closed region has four basic types of Danxia Landforms.(2)Jianmenguan area is famous for the unique bluff landforms of circumvallation consisting mainly of massive conglomerate,or pebbled sandstone.Since the strong influence of orogenic movement.Thrust Zone,this area began to ascend and is intensively denuded.In the main exogenic geological process,such as the river incision and the gravity collapse,many systemic and unusual Danxia Landform are formed in this area.The landforms is characterized by upright-shaped peaks,mesa,stone wall,cave and vertical cave and so on.During the Cretaceous period,this area firstly experienced massif subsidence to become a foreland basin,then having thick Cretaceous red sediments accumulated on it.In the supervened tectonics,this area experienced an uplifting process,which made the thick Cretaceous sediments into a mountain with high altitude.After undergoing the processes of vertical joint development,weathering,denudation and transportation,as well as evidently differential weathering and denudationinfluenced by lithology and structure between sandstone and conglomerate,the grand Danxia Landforms formed.The different planation surface reflect the dominated uplifting processes during the neotectonics.And Jianmenguan geomorphic sites have being developed into national-level scenic areas.However,in-depth theoretical research still lacks on genesis of the landforms,especially on the research results based on the affiliation of geological structures and lithology with the development of the Danxia Landform.So,based on the recent studies of the genesis through on-the-spot investigation and analysis of its lithology,conformation,this project has a very high scientific research value in inqure into the processes of uplift of tibetan plateau and Longmen shan thrust-nappe structures and evolution of structural geomorphic features,it has very important scientific significance in reveal the relationship between sedimentary processes and structural landforms evolution of northwest of Sichuan Basin.(3)The formation mechanism of Danxia Landform is the result of inter-action of different forces,including the internal power system and the external power system.In the process of the formation of Danxia Landform,the geological tectonic movement is an important force in earth,it also plays an irreplaceable role.The external dynamic effects mainly include erosion action of running water,dissolution of water,weathering and gravity collapse.In red bed basin uplifting period,Danxia Landform began to development,through the comprehensive influence of the function of a variety of external forces,including the distance between the variable width and the depth of the valleys increase,so the rock will change along the rock joint surface,breaking the sparkling will collapse because of gravity,and rock,the phenomenon of the back,so the top of the mountain area will gradually narrowed,and form butte or pillars,In the process of shaping of Danxia Landform form,it occupies the dominant position,its form of expression of water erosion,down the side of water erosion,water erosion,precipitation,surface runoff and underground runoff erosion of rock surface,and make the rock surface changes,At the foot of the slope,the denudation of the water is mainly aimed at the soluble substance.Under the action of the cutting or lateral erosion of the water,the gravity effect is mainly in the position of the empty valley.The lateral erosion of the water makes the part of the slope in a suspended state,thus causing the rock formation to produce the phenomenon of gravity collapse along the structural plane or the joint surface of unloading.At the same time,the depth of the groove of the steep slope is increased,and the overlying rock mass also produces the phenomenon of gravity collapse,which will eventually form the steep cliff face of different landforms.The weathering effect of geomorphology is mainly the physical weathering,while in some areas,the weathering effect is mainly chemical and biological weathering.