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

Abstract：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 along the faults of different natures generated by neotectonic movement during the Holocene.