山西离石断裂南段区域河流地貌指数和阶地下切过程及其构造意义

Regional fluvial geomorphic index and terrace downcutting process in the southern section of Lishi fault in Shanxi Province and their tectonic significance

基于数字高程模型(DEM)、野外河流阶地测量和光释光(OSL)测年,对离石断裂带南段坡度、地形起伏度(RDLS)、面积高程积分(HI)和河道陡峭指数(Ksn)指标进行了提取和分析,对穿过断裂的黄河支流中垛河进行了下切速率的蒙特卡洛模拟。研究结果表明,根据河流地貌指数指示,各河流流域地貌指标均呈低值分布,河流地貌发展总体上处于发育或成熟阶段,离石断裂南段构造活动性较弱。根据中垛河河流阶地和断层的断错关系,结合阶地测年结果认为,该断裂带至少晚更新世晚期以来不活动。利用各级阶地拔河高度和年代数据,中垛河T1—T4年龄分别为(2.08±0.19)ka、(5.63±0.5)ka、(10.22±0.62)ka和(41.22±2.33)ka,42 ka以来中垛河流下切速率线性拟合的结果为0.78 mm/a,全新世以来的下切速率为1.89 mm/a,主要受气候变化影响。

Based on digital elevation model(DEM),field river terrace survey and optical stimulated luminescence dating(OSL)dating,the slope,relief degree of land surface(RDLS),hypsometric integral(HI)and channel steepness index(Ksn)of the southern section of the Lishi fault zone are extracted and analyzed.Monte Carlo simulation of the cutting rate of Zhongduo River,a tributary of the Yellow River that passes through the fault is carried out.The results show that,according to the river geomorphic index,the river geomorphic index is low,the river geomorphic development is in the developing or mature stage overall,and the structural activity of the southern section of Lishi fault is weak.According to the faulting relationship between the river terrace and the fault in Zhongduo River,combined with the terrace dating results,the fault zone is inactive at least since the Late Pleistocene.Using the height and age data of terrace tug-of-war at all levels,the ages of T1—T4 of Zhongduo River are(2.08±0.19)ka,(5.63±0.5)ka,(10.22±0.62),ka and(41.22±2.33)ka,respectively.The linear fitting result of the river cutting rate of Zhongduo River since 42 ka is 0.78 mm/a.The river cutting rate since Holocene is 1.89 mm/a,which is mainly influenced by climate change.