The Forming Factor Analysis for the First Bend of Yangtse River

摘要

About cause of formation of the first bend of Yangtse River is always a chicken-and-egg scenario since 1920s. However, two theories for the cause of formation of the first bend are popular, which are the river piracy theory and the tectonic adaptation theory. In fact, the formation of the first bend of Yangtze River is well related to the water system development. With the uplift of Qinghai-Tibet Plateau, also the southward flowing water systems. In early Quaternary, it formed many depression basins as well as inland lake and river water systems. The episode C which happened in Qinghai-Tibet Plateau resulted in the headward erosion in the middle and lower reaches of Yangtse River which cut through the ancient lakes within the region and formed the present outflow structure of water systems. These geological and geomorphologic evidences argue that the middle and lower reaches of Yangtse River captured the originally southward flowing Shuiluo River below Hutiao Gorge and made the ancient Shuiluo River flow reversely. Uplift of Shuanlong mountain, south of the first bend, made the originally southward flowing Jinsha River and the ancient Chongjiang River flowed into the Yangtze River through the ancient channel of Shuiluo River, and formed the present water system of Jinsha river. So the first bend of Yangtse River is the river junction of the ancient Jinsha River, Chongjiang River and Shuiluo River, not a bend of pirate river, either a river bend caused by tectonics.