Formation of the Yellow River, inferred from loess–palaeosol sequence in Mangshan and lacustrine sediments in Sanmen Gorge, China

Abstract

The formation of the Yellow River was a significant geological and hydrological event in the history of landscape evolution in northern China, resulting from interactions between various Earth System processes. Earlier concepts about the ages of the river's formation are quite controversial. This paper investigates the age of the Samen Gorge, the last gorge along the course of Yellow River before it reaches the sea. The main research materials presented here are: (a) 172.1-m-thick loess–palaeosol sequence in Mangshan located in the south side of the Yellow River, (b) Lacustrine sediments of the former Sanmen Lake. The chronology is based on the stratigraphical correlations with the well-dated loess–palaeosol sequence in Luochuan of central Loess Plateau, palaeomagnetism and optically stimulated luminescence (OSL) and thermoluminescence (TL) datings. An abrupt increase in the rate of sedimentation is recognized in the stratigraphical layers L 2 and above of the Mangshan sequence. The loess unit L 1 and palaeosol unit S 1 of Mangshan are much thicker than those of other sections in Loess Plateau as well, indicating a new and unique source only for the Mangshan region. The aeolian deposition of the loess is found to have started at ca. 150 ka in the bottom of the former large lake west of the Sanmen Gorge and suggests desiccation of the former Sanmen lake. At this point in time, the Yellow River could bring large amount of fluvial sediment east of the Sanmen Gorge after the gorge was downcut. The fluvial sediment is suggested to be the new source of loess identified in the Mangshan sequence. Therefore, it is concluded that the downcutting of the Sanmen Gorge started at ca. 150 ka and indicates the full development of the Yellow River.