北大巴山汉江流域地貌特征及其构造意义

Geomorphic feature and tectonic implications of the Hanjiang River basin in the northern Dabashan

北大巴山地区位于青藏高原向东扩张的前缘地带,研究该区域水系流域的构造地貌特征以及构造活动程度的空间分布,探讨研究区的新构造运动和地貌演化阶段,有助于理解该地区地貌演化对青藏高原新生代隆升的响应。同时,也能在一定程度上限定青藏高原向东扩张的范围。基于ASTER GDEM数据,提取了研究区流域的面积高程积分值(HI)及曲线(HC)、标准化河长坡降指标(SL/K)和Hack剖面、流域盆地不对称度(AF)、河谷宽高比(VF)、盆地延伸率(Re)等地貌指数,分析流域地貌特征。结果表明,研究区48个子流域中有46个面积高程积分小于0.5且积分曲线呈“S”型和下凹型,表明北大巴山地区处于地貌演化阶段的壮年-老年期。综合5种地貌指数分析,揭示研究区主要断裂都具有构造活动性,其中宁陕断裂和城口-房县断裂的构造活动性较强,安康断裂的活动性较弱。这表明青藏高原的向东扩张已经影响到了北大巴山地区的构造变形和现代地貌的演化过程。

The northern Dabashan region is located at the leading edge of the eastward expansion of the Tibetan Plateau.Studying the tectonic geomorphological characteristics and spatial differentiation in the degree of tectonic activity recorded in the fluvial systems and drainage basins of the northern Dabashan region,can help to deepen our understanding of the remote uplift effect of the Tibetan Plateau in the region and effectively limit the degree and scope of its growth towards the east.Based on the ASTER GDEM data,the drainage basins in the study area were extracted and analyzed for characteristics of the watersheds basin through the hypsometric integral(HI),standardized stream length‐gradient index(SL/K)and Hack profile,drainage basin asymmetry factor(AF),valley floor width‐to‐height ratio(VF),and the elongation ratio(Re).The results indicate that 46 of 48 sub‐catchments in the study area have HI values less than 0.5 and the hypsometric curves are S‐shaped and concave,indicating that the northern Dabashan area is in the early‐old stage of geomorphological evolution.Based on the analysis of the five geomorphic indices,the main faults in the study area are tectonically active,with the Ningshan fault and Chengkou‐Fangxian fault having stronger tectonic activity,while the Ankang fault has weaker activity.The eastward expansion of the Tibetan Plateau has already affected the northern Dabashan region,and the tectonic deformation and modern landscape pattern of the Hanjiang River basin in the northern Dabashan are controlled by the tectonic forces of the eastward expansion of the Tibetan Plateau.