Pliocene-Pleistocene evolution of the lower Yellow River in eastern North China: Constraints on the age of the Sanmen Gorge connection

Abstract

The Yellow River, the second longest river in China, originates in the northeastern Tibetan Plateau, flows in a contorted square-bend-shaped path through the Loess Plateau, then enters the Fenwei Graben before discharging through the Sanmen Gorge onto the North China Plain. Prior to its connection through the Sanmen Gorge, which cuts through the drainage divide of the Hua and Taihang mountain belt, the Yellow River had been partly impounded as a large lake filling the Fenwei Graben. To help decipher the Pliocene-Pleistocene history of the development of the lower reaches of the Yellow River, we analyzed the sedimentary histories of the Fenhe sub-basin in the northeast part of the Fenwei Graben and of fluvial-lacustrine sediments in the Huangdigou (HDG) section, which is now exposed at the upstream entrance to the current Sanmen Gorge. The Fenhe sub-basin changed from lacustrine/peat deposition to fluvial gravels at ~2.5 Ma. We suggest that this sedimentary facies change indicates the establishment of a significant outflow of the former Fenwei Graben Lake through the deepening Sanmen Gorge. The continuing lowering of base-level in the Fenwei Graben, which culminated in the direct flow of the Yellow River through the Sanmen Gorge and/or fluvial inland regressive erosion, also led to headward erosion of a new paleo-Fenhe River that cut through the Fenhe sub-basin. Tectonic activity and climate shifts may have contributed to the change to the modern path of the Yellow River. • The Fenhe sub-basin changed from lacustrine/peat deposits to fluvial gravels at ~2.5 Ma. • The detrital material deposited in the Sanmenxia isthmus was mainly from local sources at ~2.5 Ma. • Tectonic activity and climate shifts may have contributed to the change to the modern path of the Yellow River.