第八届青年地学论坛

Widespread relict surfaces surrounded by transient landscapes which archived the past tectonic uplift are well preserved in the Tibetan Plateau. In the northeastern Tibetan Plateau (NETP), a ubiquitous migrating river knickpoint and erosion wave in the upper Yellow River has been encroaching into the relict landscape from the margin of the plateau. However, the mechanism and the dynamic process of this migrating knickpoint are still not well understood. Here, we use the shear stress incision model in conjunction with numerical landscape simulations to study the dynamic evolution of a ubiquitous knickpoint at similar heights in the upper Yellow River catchment. The results show that since around 1.2 Ma, decreasing fault activity and the reduced uplift rate of the Jishi Mountain at the margin of the NETP gave rise to this transient wave of river erosion. This erosion wave has been migrating into the uplands and encroaching step-by-step into the relict surfaces on the plateau at a rate of ~500 km/Ma. The hard basement could also have modulated the migration of river knickpoint, along with the decreasing of fault activity at the margin of the Tibetan Plateau. This dynamic process might have led to a long lag between the fluvial incision and tectonics on the uplifted plateau.

relict landscape, migrating knickpoint, transient erosion wave, low-relief surfaces, northeastern Tibetan Plateau, Yellow River