藏北长江源地区河流地貌特征及其对新构造运动的响应

对藏北长江源地区河谷地貌和新构造变形调查发现,该区具有平行式水系格局,河谷地貌以形态不同的窄谷和宽谷为特点,新近纪以来该区主要经历了早期挤压和晚期伸展构造演化过程,产生了褶皱-逆冲、走滑剪切、正断层和地堑构造3种构造变形样式。长江源区河谷地貌的形成演化明显受新构造运动的影响,新构造运动不仅控制了河谷地貌形态与水系格局,而且影响了河流阶地分布以及洪(冲)积扇的形态、结构。长江源地区主要水系至少自全新世以来是沿新构造运动产生的不同性质断裂构造溯源侵蚀发育而成。

Morphological features of river valleys in the source region of the Yangtze River, northern Tibet, and their response to neotectonic movement

Field investigations of the geomorphology of river valleys and neotectonic deformations in the source region of the Yangtze River, northern Tibet, show that the region is characterized by a parallel type drainage pattern and wide and narrow valleys of different shapes. Since the Neogene, the region mainly has undergone a tectonic evolution from compression in the early stage and extension in the late stage, thus forming three tectonic deformation styles, i.e.: folds-thrusts and strike-slip shear in the early stage and normal faults and grabens in the late stage. Neotectonic movement has not only controlled the geomorphological features of the river valleys and drainage pattern but also affected the distribution of the river terraces and shape and structure of diluvial (alluvial) fans. The main drainage system in the source region of the Yangtze River formed at least by headward erosion a-long the faults of different natures generated by neotectonic movement during the Holocene.