岷江源地区新构造运动特征

为了深入了解岷江断裂带晚新生代以来的构造活动,以岷江源地区河谷地貌、新生代盆地、夷平面为主要研究内容,研究区内新构造运动的特征。结果表明该区河谷地貌以宽谷和窄谷的交替出现为特点,源区发育三级夷平面,新构造运动强烈,地貌差异显著。该区新近纪以来主要经历了早期(5.3 Ma)伸展断陷和中期(1.8 Ma)逆冲推覆兼左行走滑及晚期(0.13 Ma)掀斜抬升演化过程。岷江源区河谷地貌的演化严格受新构造运动的影响,构造运动控制了河谷以及第四纪断陷盆地的形态,影响了河岸两侧阶地的分布、形态与结构。本区新构造运动具有南北分带型和东西向掀斜运动的不对称性等特征。本研究为进一步研究青藏高原东缘的活动构造提供了重要的地貌证据。

Features of Neotectonic Movement in the Source Area of the Minjiang River

In order to further understand the Late Cenozoic tectonic activities of the Minjiang River fault,this paper studies the river-valley landform,Cenozoic basins and planation surface in the source area of the Minjiang River so as to explain its neotectonic movement features.The results show that the valley landform is characterized by the alternating wide and narrow valleyes.The source area developed three planation surfaces,which reflect strong neotectonic movement and significant landform differences.Since the Neogene,the regional evolution has mainly experienced the faulted depression in the early stage(5.3 Ma),the thrust system accompanied by sinistral strike-slip movement in the middle stage(1.8 Ma),and the axially tilting uplift in the late stage(0.13 Ma).The landform was obviously influenced by the neotectonic movement,which formed the Quaternary fault basin,planation surface and river terraces.Neotectonic movement in this region is characterized by the SN zonation and the EW asymmetric tilting movement.This research provides morphological evidences for further study on tectonic activities in the eastern margin of the Tibetan Plateau.