A Study On Characteristics And Influencing Factors Of The Development Of Red Bed Landform Based On Gis In Qilian Mountain Area

The red bed landform is an erosion landform developed on the red bed,some of which has high scientific research value and ornamental value.Danxia landform is one of the special types of red bed landform.Qilian mountain area is located in the northeast edge of the Qinghai Tibet Plateau,with strong tectonic movement,large red bed area,and unique red bed landform in arid area,which provides an ideal place for us to study the characteristics and development of red bed landform.In this paper,the red bed landform which developed since Mesozoic in Qilian mountain area is taken as the research object.By means of GIS,this paper analyzes the characteristics of red bed landform in the study area from three aspects: classification of landform type,statistics of gully direction,and statistics of slope and aspect.Based on the reflection of hypsometric integral to the development of landform,this paper quantitatively discusses the influence of lithology,fault density and water system density on the development of red bed landform.The main conclusions are as follows:(1)The red bed landform in Qilian mountain area is mainly distributed in the middle altitude areas and middle-high altitude areas,mainly tablelands and hills.The two types that account for the highest proportion of the red bed landform are middlehigh altitude tablelands and high and middle-high altitude hills.(2)In the study area,the direction of gullies in the red bed has a distribution advantage near the NNE direction.The total length of the valley near the NNE direction is about 40% longer than that in the case of uniform distribution.This may be caused by the topography of the study area.(3)The red bed in the study area is mostly distributed in the area with a slope of 0 °~ 30 °,and is evenly distributed in the slope direction,indicating that the red bed landform is generally gentle,and the red bed with high slope is mostly located near the fault zone.(4)In this paper,the area elevation integral is used to quantify the difference of red bed geomorphology between Zhonggou Formation and Xiagou Formation in Zhangye area.It is found that the hypsometric integral of Xiagou Formation with relatively hard lithology is larger,and the landform is mostly represented by steep cliffs and canyons,while the hypsometric integral of Zhonggou Formation with relatively weak lithology is smaller,and the landform is mostly represented by hills.(5)According to Pearson correlation coefficient,it is found that there is a negative correlation between fault density and the development of red bed landform.In the area with small fault density,the red bed landform tends to be old stage;in the area with large fault density,the red bed landform tends to be young stage.And it indicates that neotectonics are conducive to the transformation of red bed landform into young stage.(6)According to the Pearson correlation coefficient,it is obtained that there is a positive correlation between drainage density and the development of the red bed landform.In the area with large drainage density,the red bed landform tends to the old stage;in the area with small drainage density,the red bed landform tends to the young stage.And it is suggested that the development of drainage is conducive to the transformation of red bed landform into old stage.