Geomorphic constraints on Middle Yangtze River reversal in eastern Sichuan Basin, China

The Yangtze, the longest river in Asia, was hypothesized to be assembled through a series of Cenozoic capture events, such as the reversal of Middle Yangtze River and the capture of Upper Yangtze River, but the history remains largely unknown. Here, we present new geomorphic observations in the structural context of the eastern Sichuan Basin, namely the Eastern Sichuan fold belt, and identify an important drainage divide along the “midline” of this arc-shape fold belt. Based on longitudinal profile analysis, we find that the river capture events more likely occurred in the syncline valleys of low-relief landscape. Our results yield a new perspective on Middle Yangtze River reversal, and we propose that the “midline” drainage divide, rather than the Three Gorges, was the starting site of Middle Yangtze River reversal. In this manner, the reversal could have been accomplished by a sequence of river reversal over range-parallel segments in syncline valleys with less impact on the pre-existing drainage system in eastern Sichuan Basin.

► We present new geomorphic observations for Yangtze River reversal. ► We identify a drainage divide along the “midline” of Eastern Sichuan fold belt. ► This drainage divide would have been the starting site of Yangtze River reversal. ► River capture events more likely occurred in the syncline valleys of low relief.