Research Of The Particularity Of Danxia Landform's Development Stage In Southern China

The Geographical Cycle by William M.Davis is been widely used in the study regarding the evolution stage of Danxia landform in China.In the previous study,the development stages of the Danxia landform in southern China were often simply divided into three stages including "The Youth,The Maturity,Old Age".However,they ignored the premise of using the theory by M.Davis,that is,to meet the uniformity of lithology and stability principle of the structural factors.In view of this phenomenon,this paper presents a hypothesis:lithology and structural differences will have a certain impact on the evolution of Danxia landform.In order to verify this hypothesis,this paper first takes Jianglang Mountain in Zhejiang Province as the study object,and starts with the special geological factors such as tectonics,stratigraphy and lithology,which influenced the forming of Danxia landform.Based on research method like field investigation,literature review,identification of rock sheet,uniaxial compressive strength test of rock mass,whole rock oxide content test and so on,this study tries to explore the development mechanism of landform in Jianglang Mountain and then concludes the following understanding:1)Jianglang Mountain has multi-level stripping surface and the experience of intermittent uplift and multiple transformation of tectonics during Cenozoic,which is the tectonic setting of the forming and retention of landscape pattern---the solitary peak of " Sanpanshi”as well as the deep canyons.2)There are obvious spatial differentiation in stratigraphic lithology and sedimentary facies of Jianglang Mountain,which is the root reason for spatial zoning of landscape development in Danxia landform in the same basin.3)Fracture and joint development are the precondition to shape the landform and the basis for the occurrence of freezing and thawing effect of fissure water together with water erosion and gravity collapse,so that the canyon in Jianglang Mountain is widened.In addition,The lithological features make the Danxia landform maintain steep slope.4)The existence of volcanic clastic rocks and magmatic intrusions increases the compressive strength of strata rocks and locally changes the rate and process of landform evolution.Besides,the rocks body in Danxia landforms extend their life span due to its influence.5)Caves and grooves are formed in the weak rock formations containing more calcite cements.The lithology differenciation and the consequent Danxia karst caused by influence the development of Jianglang cave.Based on the factors influencing the landform evolution in Jianglang Mountain,further comparison is made with Danxia landforms of other parts in southern China,so we get a few macro law:1)Tectonic setting leads to the analogous molasse formation in Danxia basin.Different position in a Danxia basin affects the migration distance,particle size and roundness of sedimentary rocks,which leads to spatial differentiation of lithology and sedimentary facies as well as spatial zoning of landscape development of Danxia landform in the same basin.2)The active volcano in the Gan-Hang tectonic belt and the northern section of Wuyi Mountains during Mesozoic cause the compressive strength of Danxia landform in these areas are over 100MPa generally,which are higher than that of other areas affected by relatively small volcanism.The compressive strength of rock containing volcanic clastic rock is higher.The life span of Danxia landforms formed in different geological backgrounds is different and its development stage is not comparable.3)Negative landform is a typical feature of Danxia landform.It is a key step for Danxia landform to stand out from the red bed landforms.Fracture and joint development are the precondition to shape the landform and the basis for the occurrence of freezing and thawing effect of fissure water together with water erosion and gravity collapse.Danxia landform in southern China possessing the special phenomena including multiple tectonic uplift,analogous molasse formation,influence by volcanic activity,uneven lithology,the stratum belonging to same period but having different forms,notable gravity collapse,existing with karst phenomenon and so on,its development phase can not meet the applicability requirement of the Geographical Cycle by Davis.These phenomena demands Danxia landform to establish its own evolution model based on its particular reality.The shape of Danxia landform is mainly controlled by lithology and geological structure.If the climate impact and evolution process are to be studied with that,it is necessary to put them under the same geological background.So we can not analogize different forms generated under different conditions into one evolutionary series.Before the attempt to affirm the evolutionary stage and to find out the evolution series by contrasting present geomorphological shape,we should first clarify two questions:whether these forms are generated under the same conditions,and what causes the old form to stop moving forward so that we can still see it nowadays?...