A DISCUSSION ON THE PROBLEM OF RIVER-CAPTURING OF THE JINSHAJIANG RIVER IN NORTHWEST YUNNAN
He Haosheng He Kezhao Zhu Xiangmin Zhu Zhaoyu
The argument on the river-capturing of the Jinshajiang river, i. e, the upper Yangtze River, in northwestern Yunnan Province has proceeded for decades. In 1981-1987, a series of detail research works on geomorphology, Quaternary sed iments and geologic structure were done in Jinshajiang valley between Wuzhu and Reshuitang and the valley from Hongwen to Jianchuan-the "desert Jinshaji ang Valley". Base on a large amount of first-hand data, following conclusions were reached. 1.In the Jinshajiang valley seven continuous terraces have been found in the upper, middle and lower Shigu and Hongwen village, which indicate that the Jinshajiang River has never altered its course since early Pleistocen; 2. In the valley between Hongwen and Jianchuan, the "three erosion terraces of old Jinshajiang" are now proved |o be the fault steps of the same planation surface formed in the end of Pliocene, The composition of alluvialand pluvial gravels inside the valley is rigorously confined to the rock exposed around, which is sharply different from that in Jinshajiang valley. The "Jiuhe conglomerate". which was regarded as old Jinshajiang deposit is acturally only widely spreaded Eocene molasse deposit. 3. So, the Hongwen-Jianchuan valley can not be deemed as the old Jinshaji ang River valley but a fault valley controlled by the Jianchuan Fault Zone, where there are several fault basins and lakes in it.