Abstract
Extensive areas with low-relief surfaces that are almost flat surfaces high in the mountain ranges constitute the dominant geomorphic feature of the Three Gorges area. However, their origin remains a matter of debate, and has been interpreted previously as the result of fluvial erosion after peneplain uplift. Here, a new formation mechanism for these low-relief surface landscapes has been proposed, based on the analyses of low-relief surface distribution, swath profiles, χ mapping, river capture landform characteristics, and a numerical analytical model. The results showed that the low-relief surfaces in the Three Gorges area could be divided into higher elevation and lower elevation surfaces, distributed mainly in the highlands between the Yangtze River and Qingjiang River. The analyses also showed that the rivers on both sides of the drainage divide have not yet reached equilibrium, with actively migrating drainage divides and river basins in the process of reorganizing. It was concluded that the low-relief surfaces in the Three Gorges area did not share a common uplift history, and neither were they peneplain relicts, but rather that the effect of “area-loss feedback” caused by river capture has promoted the formation of upland low-relief surface landscapes. A future work aims to present the contribution of accurate dating of low-relief surface landscapes.
Highlights
In the 19th century, Davis [1] proposed erosion cycle and quasi-plain theories, and in conformity with these, gentle rolling surfaces perched high in rugged mountain ranges, have been considered widely to be the remains of large peneplains
Identifying the distribution of upland low-relief surfaces was an important foundation for the study of the Three Gorges region long-term geomorphic evolution
The analyses showed that the Three Gorges area has many low-relief surfaces distributed throughout, mainly on the highlands of the drainage divide between the Yangtze and Qingjiang rivers
Summary
In the 19th century, Davis [1] proposed erosion cycle and quasi-plain theories, and in conformity with these, gentle rolling surfaces perched high in rugged mountain ranges, have been considered widely to be the remains of large peneplains. Its origin, and whether it should be labeled as a planation surface remain controversial topics This shows that analysis of the upland, low-relief surface landscape formation mechanisms is important if the topographic evolution of the Three Gorges area is to be understood. Located in the subtropical monsoon climate zone, the average annual rainfall exceeds 800 mm in the Three Gorges region (Figure 1b), which causes severe ground erosion and makes deposit preservation on the low-relief surface landforms problematic. These characteristics make it difficult to obtain material suitable for dating
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