Transient fluvial incision in the Western Han River Basin: Implications for the late Cenozoic rock uplift of the Western Qinling Mountains, northeastern Tibetan Plateau

Abstract

Situated in the northeastern Tibetan Plateau, the Western Qinling Mountains have undergone foreland propagation and surface uplift due to the northeastward expansion of the Tibetan Plateau since the late Cenozoic. In this study, the differential rock uplift and fluvial incision were investigated by extracting longitudinal profiles of the 227 major tributaries of the Western Han River Basin, which are located in the hinterland of the Western Qinling Mountains. Of 227, 178 tributaries have “slope-break” knickpoints. Channel segments upstream of knickpoints with low steepness indices represent the relict low-relief landscape, while the downstream of knickpoints with higher steepness indices represents the adjusting landscape formed after the knickpoint initiation. The spatial patterns of channel steepness indices show the western part of the Western Han River Basin having a higher rock uplift rate than the eastern part. Three-stage rock uplift of the Western Qinling Mountains has been identified by the shape of the longitudinal profile of the Western Han River. The magnitude of fluvial incision in the three-stage is about ∼180 m, ∼380 m, and ∼100 m, respectively. The results of this study reveal that the tectonic uplift of northeastern Tibetan Plateau has regulated the late Cenozoic rock uplift and fluvial incision in the Western Qinling Mountains, and highlight the potential use of channel profiles as indicators for tectonic forcing.