地貌参数方法在小尺度地貌研究中的应用--以北天山独山子背斜为例

THE APPLICATION OF GEOMORPHIC INDEXES IN SMALL-SCALE GEOMORPHOLOGY:A CASE STUDY IN DUSHANZI ANTICLINE IN THE NORTHERN CHINESE TIAN SHAN FORELAND

地貌参数是定量地貌研究的重要方法,旨在从地表形态中提取构造运动及地表侵蚀等信息。近年来,空间对地观测技术的发展使得高精度地形数据的获取更加便捷,利用这些数据提取小尺度地貌中蕴含的更精细的地质信息成为定量地貌学研究的重要内容。文中以北天山独山子背斜为研究对象,探究地貌参数在小尺度地貌研究中的适用性及其所反映的背斜构造地貌特征。研究基于ALOS卫星12.5m分辨率的地形数据,计算了独山子背斜区的HI指数、ksn和起伏度,并对参数的适用性和含义进行讨论。结果表明:1)独山子背斜自倾伏端向核部呈现由河流逐渐深切向地势逐渐消减的连续变化,背斜核部相对倾伏端抬升速率更高、侵蚀量更大、地貌演化阶段更靠后。地貌参数的计算结果与背斜的地质特征相符,说明地貌参数方法在小尺度地貌研究中是行之有效的。2)在小尺度地貌的定量研究中,计算HI指数时在确保数据有效的前提下应尽量选择更低级别的汇水盆地参与计算,以提高计算结果的分辨率。计算ksn时需要剔除小流域无效数据并保证剩余数据具有足够的密度,以确保该参数能作为抬升速率评价指标。计算起伏度时在确保采样窗口满足统计误差要求和研究需求的前提下,应尽量选择更小的窗口进行计算以提高结果的分辨率。使用更高分辨率的地形数据有助于提高以上参数计算结果的分辨率和准确度。

Landform is the shape of the earth’s surface,which is the combined influence of tectonic movement and surface erosion.Geomorphic indexes are the quantitative methods applied in geomorphology,aiming to extract the tectonic and erosion information from the surface morphology.Since the 1950s,the HI(Hypsometric Integral)had been used to quantitatively characterize the three-dimensional volume residual rate of drainage basins after erosion and to estimate the geomorphic evolution stage,and the relief had been used to evaluate the erosion response of regional tectonic uplift.Since the 1970s,with the construction of the stream power incision model,the ksn(Steepness)based on the model has been widely used to estimate the distribution of uplift rate,and it has become an important branch of geomorphology to obtain the information contained in the landform by using geomorphic indexes.The quality of terrain data affects the research level of geomorphology.In the early stage of geomorphic research,field survey is the main method to carry out quantitative statistics of geomorphic units within a certain range.With the development of satellite remote sensing technology,DEM data are widely used in large-scale structural geomorphic research,such as the study of geomorphic parameters of orogenic belts.In recent years,with the further development of space exploration technology,a large number of high-quality DEM data have been produced.Based on these data,whether the geomorphic indexes methods which have been widely used in large-scale geomorphology research could be applied to small-scale geomorphology to extract more precise structural and geomorphic information has become an important issue of quantitative geomorphology research.In this paper,Dushanzi anticline in northern Chinese Tianshan foreland is taken as the research object to explore the application of geomorphic indexes methods to the study of small-scale geomorphology.Dushanzi anticline is a propagation fold formed in the foreland of Tian Shan Mountains as a result of the India-Eurasia collision and is still active since the Holocene.The geological outcrop of the Dushanzi anticline is about 90 km2.There are river channels which are well preserved on the anticline,providing an ideal area for the calculation of geomorphic indexes.Consequently,the area is an ideal place for the study of the application of geomorphic indexes methods in the small-scale geomorphology.Based on the 12.5 m spatial resolution DEM from ALOS(Advanced Land Observing Satellite),we calculated the HI,ksnand relief of the study area to explore their applicability to the study of smallscale geomorphology and then the geomorphic parameters are comprehensively analysed to discuss the structural and geomorphic information of anticline.The results indicate that:1)In the quantitative study of small-scale geomorphology,the lower level drainage basins should be used to generate the HI on the premise of the accuracy of the data to improve the resolution of the HI results.Invalid data of small drainage basins should be eliminated in the process of calculating ksnto ensure its accuracy although the density of the data will decrease.The smaller window should be used to calculate the relief on the premise of ensuring statistical error and research demand to improve the resolution of results.The higher resolution of DEM is helpful to improve the resolution and accuracy of the above indexes.2)The results of geomorphic indexes indicate that the core of the anticline has higher uplift rate,larger erosion amount,smaller volume residual rate,and later stage of geomorphic evolution compared with the inclined end of the anticline and a continuous change of landform from intense down-cutting to topographic relaxation could be observed from the core to the inclined end of the anticline.The calculation results of geomorphic indexes are consistent with the geological facts of Dushanzi anticline,which shows that the geomorphic indexes methods are effective in the study of small-scale geomorphology.