长江第一弯成因及形成时代探讨

长江第一弯成因及形成时代关系到金沙江—长江水系的形成演化、西南纵向岭谷地理环 境演化、青藏高原隆升对周边环境的影响等重大科学问题, 故近百年来一直为学术界所关注。本 文通过综合考察、地貌和沉积物等的综合分析认为: 长江第一弯是在金沙江水系未曾溯源连通至 三江口段之前的古金沙江与古冲江河、水洛河的汇流口。长江在三江口袭夺了水洛河, 导致水洛 河倒流, 古金沙江与三江口下的长江贯通, 才形成真正的金沙江—长江水系。根据玉龙山强烈隆 起时间、周边层状地貌发育年代、中国水系大局形成等进行推断, 长江第一弯形成时代为中更新 世以来, 说明昆黄运动为本区构造地貌—水系发育的重大转型事件。

The Inquiry on Genesis and Formation Times of The First Bend of Yangtze River

The genesis and formation times of the first bend of Yangtze River are closely relative to such major issues as: the evolution of the formation of Jinsha River- Yangtze River drainage pattern and geographical environment of the Longitudinal Range - gorge Region (LRGR) in southwest China and the effect of Tibet Plateau uplift on peripheral environment. It has been focal points to be discussed and drawn attention from researchers for approximately a hundred years. The causes of the first bend of Yangtze River are summed up into two different viewpoints: river capture and non- river capture. Through comprehensive survey and synthesis analysis about the landforms and sediments, it is considered that the first bend of Yangtze River is a junction of paleo- Shulou river, paleo- Chongjing river and paleo- Jinsha River before Jinsha river′s headward erosion of three river junction. Jinsha River has captured Shuilou River in three river junction, forced Shuilou River to flow to backwards. The linkage of Jinsha River from paleo- Jinsha River to three river junction forms the genuine Jinsha River water system. Based on the ages of Yulong snow mountain uplift and circumjacent stratiform landforms develop as well as the formation of drainage system of China, we primarily infer that the first bend of Yangtze River has been formed since Middle Pleistocene. Kunlun Movement is a transformational event to trigger the evolvement of landforms and drainages.