Quaternary evolution of the Jinshan Gorge and Yellow River: Insight from numerical modelling and terrace correlation

Abstract The evolution of the Jinshan Gorge in the middle reaches of the Yellow River in China has long been a topic of debate. Previous studies have primarily focused on the connection between the Sanmen Gorge and Jinshan Gorge, attributing this connection to the Yellow River's carving through the pre‐Cenozoic bedrock areas of the Sanmen Basin. However, the patterns of knickpoint propagation along the river, influenced by tectonic upheaval and base‐level changes, have yet to be explored, despite their potential to understand fluvial system and canyon evolution. In this study, we address this issue by employing forward and inverse numerical modelling of longitudinal profiles of the Jinshan Gorge of the Yellow River and its tributaries and correlating the river terraces in this reach. We investigated 18 terrace profiles to explore their formation processes. The results demonstrated that the steepness index ( K sn ) values and the incision rates of tributaries increase downstream, aligning with the relationship between knickpoint elevation and proximity to the Hancheng Fault. The knickpoint propagation appears to be related to the tectonic activities of the Hancheng Fault before 130 ka and then was influenced by climatic change, resulting in the development of five‐stage knickpoints (named Kp1, Kp2, Kp3, Kp4 and Kp5 from old to young) that correlate with the formation of terraces in the downstream area. We calculated the formation ages of Kps 1–4 to be 1.59 ± 0.06, 0.94 ± 0.11, 0.57 ± 0.31 and 0.22 ± 0.14 Ma, respectively. Kps 1, 2 and 4 correspond to the formation of the Yellow River terraces with the ages of 1.24, 1.12 and 0.24 Ma, which were reported previously. The formation of the oldest knickpoint can be correlated to the establishment of the modern course of the Yellow River in this region, which is deduced to be ~1.59 Ma.