Early-onset of rapid deposition rates of the Mangshan loess challenges the classical hypothesis of full Yellow River connection during the late Pleistocene

Abstract

Understanding the origin and evolution of the Yellow River is not only crucial for understanding the geomorphic and climatic history, but also pivotal due to its historical significance and ecological impact on China's environment. However, the timing of the full connection of the Yellow River, as a critical event in the genesis of this major river system, is still debated continuously. Among various competing hypotheses, the abrupt increase of deposition rates following paleosol 2 (S2 of Chinese loess sequence, starting at about 0.245 Ma at the late Pleistocene) of the Mangshan loess was considered as major evidence of the late Pleistocene hypothesis, which attributes this increase to a sudden connection of the Yellow River. Here we scrutinized the stratigraphy of the Mangshan loess and identified abrupt increase of deposition rates occurring significantly earlier (at layers L11, S10, S9, L8, L7, L3) than S2, undermining the late Pleistocene hypothesis of the Yellow River genesis in the perspective of time. Moreover, we attribute the abrupt deposition rates to episodic gully erosion of the Loess Plateau, a mechanism distinct from the late Pleistocene full-river connection hypothesis. Therefore, the hypothesis that the Yellow River fully connected during the late Pleistocene is mechanistically unsupported, suggesting this connection likely occurred much earlier than 0.245 Ma.