1264 / 2024-09-20 21:09:12

Historical fast sedimentation rates in the Yellow River Delta linked to human-natural interplay: insights from high-resolution OSL chronology of cores

high-resolution OSL chronology, Yellow River Delta, fast aggradation, human activity

The Yellow River (YR) in the North China Plain (NCP) is now a “sky” river with river bed 10-15 meters higher than the surroundings for most part of the river channels, which requires urgent investigation. High-resolution core chronology forms the basis for understanding detailed delta development and its natural-anthropogenic response. In this project, 46 cores (60-740 m in depths) have been obtained along the river channel in the plain, and we present here high resolution luminescence ages from three cores (DYZK1, DYZK2 and DYZK3), focusing on the period of the past ~3 ka which is still poorly studied due to the scarcity of ¹⁴C dating material in silty-sandy sediments. The Bayesian age model reveals an age range of 2.66+0.18/-0.18 – 1.48+0.15/-0.16 ka, showing higher deposition rates in 2.8–2.4, 2.4–2.0, and 1.6–1.3 ka than in 2.0–1.6 ka. A comparison with collected paleoenvironmental archives highlights the interactive role of nature (river shift and flood) and human (agriculture and river control) in delta aggradation. River shifts in the NCP provided constant sediment supply for rapid deposition in ~3–1 ka, before it turned its course toward the Jiangsu Plain in the south. Higher deposition rates occurred during periods of 2.8–2.0 ka and 1.6–1.2 ka, despite reduced flood occurrence frequency then. This could be likely linked to the boosting metallurgical technology and millet agriculture, which led to extensive deforestation and increased soil erosion upstream. Periods of higher deposition rates corresponded to the dynasties of Qin-Han (2.230–2.015 ka, relative to 2023) and Sui-Tang (1.442–1.116 ka), when the highly centralized authority was capable of intensified river management, leading to the increased magnitude of bleach floods and more sediment release in each of the floods. The lower deposition rate in 2.0–1.6 ka contradicted the increasing flood occurrence rate, but well matches the decreasing soil erosion during warring periods of the Three Kingdoms, Jin and Wei Dynasties (1.803–1.442 ka) with reduction in population and agricultural activity.