Knickpoint Dynamics During the Outward Growth of the Northeastern Tibetan Plateau

Abstract

Mountain-building events often initiate fluvial erosion waves that usually propagate upstream. Previous studies have delved into the erosion wave, manifested as knickpoint migration, presuming a spatially consistent uplift of plateaus. However, the expansion of plateaus can spatially result in spatially variable rock uplift rates across different regions, complicating our understanding of knickpoint dynamics. In this study, conducted at the edge of the northeastern Tibetan Plateau, we investigated the impact of plateau expansion on erosion wave processes within the upper Yellow River basin. Through river profile analyses and landscape evolution simulations, we reveal that the continuous outward expansion of the northeastern Tibetan Plateau into its periphery has induced localized uplift followed by erosion. Subsequently, an erosion wave migrated headward along the Yellow River during the Pleistocene. Observations from the Digital Elevation Model and modeling results show that this erosion wave spread within the tectonically active sub-block at the margin of the plateau, but did not continue further upstream. In contrast, modeling results suggest that erosion waves would consistently migrate upstream under conditions of spatially uniform rock uplift. Our findings highlight that spatially variable rock uplift rates, driven by the expansion of the plateau, are crucial in determining whether fluvial erosion waves migrate or remain stationary. This refined understanding of knickpoint dynamics during plateau development offers insights into the persistence of relict high-elevation and low-relief landscapes.