黄河、长江的形成演化及贯通时间

On the Chronology of the Yellow Rivers and the Yangtze Rivers

黄河、长江的形成演化是在新生代以来统一构造-气候-地貌体系中发生的重大地貌事件。印度板块与亚洲大陆碰撞和太平洋板块向亚洲大陆之下俯冲,造成了中国大陆地势从东高西低变为西高东低,和随之的东亚季风形成、强化,导致黄河、长江水系形成。中更新世以来的构造运动,导致青藏高原东缘山地的加速隆升,进入了冰冻圈,季节性冰川融水加大了河川径流,为两大河流的贯通奠定了水动力基础。末次间冰期的气候突然变暖,不但导致冰冻圈融水补给的河川径流陡增,可能给了长江、黄河贯通最后一击,而且加速了三峡一带碳酸盐岩地下化学溶蚀,促进地下河发育和瞿塘峡地表河袭夺的完成。黄河、长江在末次间冰期期间彻底贯通,现今的水系格局形成。黄河三门峡的贯通时间为0.125 Ma左右,长江三峡可能在0.30～0.12 Ma期间完成贯通。

The formation date and evolution of the Yellow Rivers and the Yangtze Rivers is an important geomorphological event in a united tectonics-climate-geomorphology system in Cenozoic era in China as well as in the world.Owing to collision between the Indian and Asian plates,and simultaneous subduction of the Pacific plate under Asia plate,the geomorphology in China mainland had involved from“east high,west low”to“west high,east low”during Cenozoic era.Consequently,the Eastern Asia monsoon was introduced and enhanced.The hydrological systems of the Yellow Rivers and the Yangtze Rivers were formed mostly due to the joint changes of regional terrains and the formation of the Eastern Asia monsoon.In the early Quaternary,there were fresh lakes sprinkled at the regions where the Yellow River would be and then it was gradually channelized with the disappearances of these lakes.Due to the problems of dating,provenance tracing and incomplete sedimentary records,the date of formation and channelization of the Yangtze River was highly controversial.The tectonic activities since middle Pleistocene induced an accelerating uplifting of mountains in the eastern margin of the Tibet Plateau and resulted in those mountains to be exposed to the cryosphere.Increasing runoff due to glacier melting was the hydrodynamic basis for the channelization of the two rivers.During the Last Interglacial period,fast warming up not only resulted in the rapid rise of runoff in rivers by glacier melting,but also promoted chemical corrosion of carbonate rocks in the Three Gorges.The chemical corrosion expedited the growth of underground streams and complement of the river-capture process in the Qutanxia Gorge.It is our understanding that the complete channelization and formation of the two rivers with the current hydrological patterns were finally finished during the Last Interglacial period.The formation of the Sanmengxia Gorge occurring at the age of the Sanmen lake s disappearance in the Yellow River was about 0.125 Ma,while the transformation of the Three Gorges from complex underground rivers to a surface river in the Qutang Gorge of the Yangtze River was finished during the period of 0.30-0.12 Ma.