基于地貌计量指标分析的钱塘江流域地貌演化特征

摘要

地貌过程的定量化表达已成为构造地貌学研究中的一种趋势.基于ASTER GDEM数据,运用GIS空间分析技术,本文获得了钱塘江流域87个子流域的地貌参数,包括面积-高程积分(HI)、面积-高程积分曲线(HC)、坡度、流域不对称度(AF)、流域盆地形状指数(Bs)等.进一步结合流域内地层特征与自然地理背景,探讨了钱塘江流域地貌演化阶段以及流域内主要断裂(江山-绍兴断裂、球川-萧山断裂和马金-乌镇断裂)的相对活动性.结果表明:1)HI值在小尺度范围内主要反映岩性差异,在大的空间尺度下则可能主要与构造活动性有关;2)相对于HI指数,AF和Bs更有助于揭示构造活动性的空间差异;3)基于AF、Bs、坡度、HI等的分析,认为江山-绍兴断裂和球川-萧山断裂北段的活动性要弱于南段,而马金-乌镇断裂南、北段构造活动性差异不显著;4)多种地貌计量指标的分析结果(HI=0.217、| AF-501 =4.27、Bs=0.77)均显示钱塘江流域处于地貌演化的老年阶段.%The Qiantang River drainage basin is located in Eastern China,which crosses the tectonic units of Jiangnan (including Jiangnan uprise platform and northwest Zhejiang) and Huanan subzones.There are three main northeast-trending faults developed in the Qiantang River drainage basin,i.e.,Jiangshan-Shaoxing Fault (F1),Qiuchuan-Xiaoshan Fault (F2),and Majin-Wuzhen Fault (F3).In recent years,geomorphic indexes are more and more used to quantitatively express geomorphic process in the study of tectonic geomorphology.In order to evaluate tectonic activity and characterize geomorphic evolution of the Qiantang River drainage basin,this work extracted several geomorphic indexes,including Hypsometric Integral (HI),area elevation integral integral curve (HC),slope,drainage basin asymmetry (AF),and drainage basin shape (Bs) from 87 sub-basins of the the Qiantang River drainage basin based on the ASTER GDEM data and the spatial analysis technique of GIS.Together with the lithology characteristics and the physical geography background,the development stage of the Qiantang River drainage basin and the tectonic activity of the three major faults developed in the basin were discussed.The main results are as following:(1) In the case of the area threshold less than 9km2,the HI value in the area covered by the volcanic rock with strong anti-erosion ability is usually high,whereas in the area with the shale and sandstone that is erodible,the HI value is relatively low.In the larger spatial scale,the HI value may be mainly related to tectonic activity.It opens out the spatial and area dependence of the HI.(2) The mean HI values of sub-basins which cross the three faults (F1,F2,and F3) developed in the Qiantang drainage basin are 0.2221,0.2328,and 0.2722 respectively,the results indicate that the activity of the three faults descends from northeast to southwest.(3) The calculated results for AF and Bs value illustrate that the two values range from 0.11 ～42.57 and 0.36～6.86 respectively of sub-basins in Qiantang River drainage basin.Compared to the HI index,AF and Bs are more helpful to reveal the spatial difference of tectonic activity.(4) Based on the analysis of HI,AF,Bs,and slope gradient,it shows that the northern segments of Jiangshan-Shaoxing Fault and the Qiuchuan-Xiaoshan Fault are weaker than the southern segments in the activity,while the difference in the activity between the southern and northern segments of the Majin-Wuzhen Fault is not significant.(5) From the results of geomorphic indexes (HI =0.217,|AF-50 | =4.27,Bs =0.77,the concave hypsometric curve),it can be concluded that the geomorphic evolution of Qiantang River drainage may be in the stage of old age.