1. Fluvial entrenchment and integration of the Sanmen Gorge, the Lower Yellow River.
- Author
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Hu, ZhenBo, Li, MengHao, Dong, ZiJuan, Guo, LianYong, Bridgland, David, Pan, BaoTian, Li, XiaoHua, and Liu, XiaoFeng
- Subjects
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GORGES , *RIVERS , *CLIMATE change , *RIVER sediments , *FLUVIAL geomorphology , *HEAVY minerals - Abstract
Strategic studies of gravel deposits, in particular using heavy-mineral analyses, have thrown light on the important unresolved question as to the timing of the initiation of the Yellow River drainage through the Sanmen Gorge, which linked the headwaters of that system in the Fenwei Basin and further upstream with the North China Plain and the Pacific Ocean in the east. Survey of the Sanmen Gorge reach revealed previously unrecognized gravel levels: a higher fifth terrace (T5) and a gravel that formed on a high-level planation surface that is preserved on the flanks of the gorge, below the Xiaoshan upland. This high-level gravel differs markedly from the Yellow River terraces, with a lack of material from the upstream catchment, and would appear to represent a small fluvial catchment that developed in the area during the formation of the planation surface, before the Sanmen Gorge was excavated. Comparison was also made with basin-fill gravels from the endorheic fluvio-lacustrine system that existed immediately upstream of the gorge, and was captured by the Yellow River when the latter was cut, and with the modern bedload gravel of the Yellow River in this reach. The former contains significant quantities of unstable hornblende, which implies more local derivation for the endorheic system, whereas the modern bedload resembles the terrace gravels in showing compositional maturity and long-distance transport from upstream within the catchment. The work reinforces a minimum age of 1.2 Ma for the formation of the Sanmen Gorge. • The gravel layer accumulated on the planation surface along the eastern front of the Xiaoshan represents a local river. • The local river sediments are different from the typical Yellow River gravels and the upper Sanmen Formation. • The Sanmen paleolake within the Fenwei basin was finally disrupted by the westward capture of this local river. • The Sanmen Gorge was excavated by the local river through the Xiaoshan separating the Fenwei basin and North China Plain. • The Yellow River integration may be attributed to the remarkable climatic fluctuation starting in the Mid-Pleistocene. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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