Quantitative geomorphological constraints on the landform evolution of the current active boundary of the northeastern Tibetan Plateau

Abstract

The Hexi Corridor lies along the northeastern margin of the Tibetan Plateau forming its northern boundary. The late Cenozoic tectonic and landscape evolution of this area are key to understanding the growth of the Tibetan Plateau. We investigate the river profile morphology of 36 drainage areas located on the southern flanks of the Heli Shan, which is the outermost range of the Hexi Corridor. Here, bedrock channels are segmented by steep downstream channels and upper segments with lower gradients. A synthesis of tectonics, climate, lithology, and river reorganization indicates that this area has experienced accelerated tectonic uplift. We constrain the response times for knickpoint evolution based on a knickpoint celerity model and reconstruct paleo-channel profiles. Combined with onset ages for the growth of the Qilian Shan (10 Ma) and Yumu Shan (4 Ma), we propose that the Hexi Corridor and Heli Shan were affected by the outward growth of the Tibetan Plateau at 0.6–2.1 Ma ago.