黄河上游松坝峡特大型滑坡堰塞湖及地貌效应研究

Study on the large-scale landslide dammed lake of Songba gorge and its geomorphological effect of the upper reaches of Yellow River

青藏高原贵德盆地东部的松坝峡峡谷区分布有多处特大型和巨型岩质古滑坡,其滑动后曾堵塞黄河干流形成巨大堰塞湖。文章在野外调查、样品测试和高分影像解译的基础上,分析了松坝峡特大型和巨型滑坡的空间特征、滑坡堰塞湖地貌形态及湖泊溃决后的环境效应,主要取得了以下认识:(1)贵德盆地东部晚更新世以来至少发育了7处特大型-巨型古滑坡,其中松坝峡左岸和右岸滑坡发生后堵塞黄河形成面积达150 km^2的古滑坡堰塞湖;(2)该堰塞湖湖相纹泥层厚约14 m,湖相层底部和顶部14C年代分别为4 030+/-30 BP和1 090+/-30 BP,指示堰塞湖持续了约3 000 a;(3)贵德盆地东部晚更新世以来地貌演化时间顺序:松坝峡左右岸滑坡发生→堰塞湖形成→古洪积扇发育→堰塞湖溃决→革匝滑坡发生→古河道摆动和近百年泥石流扇发育。

There are several large scale and ancient landslides in the Songba Gorge area in the eastern part of the Guide basin NE TP,which blocked the Yellow River to form a huge dammed lake. On the basis of field investigation, sample test and high-resolution image interpretation, this paper analyzes the spatial characteristics of the landslides,geomorphology of dammed lake and the environmental effect after the lake outburst. The main achievements are as follows：（ 1） At least seven super large scale landslides have been developed since the Late Pleistocene in the eastern part of the Guiyang Basin,and the landslide on the left bank and the right bank of Songba Gorge have blocked the Yellow River and formed a big dammed lake with an area of 150 km^2.（ 2） The thickenss of lacustrine lake layers are about 14 m and the bottom of the lake layer and the top depositional ages are 4 030 ＋/-30 BP and 1 090 ＋/-30 BP by AMS14C,indicating that the barrier lake lasted for about 3 000 years.（ 3） There are very closely relationships between the landslides,debris flows and the river course fluctuations,often the landslides blocked and buried rivers and changed the normal process of YR.（ 4） The order of geomorphic evolution since the Late Pleistocene in the eastern Guide Basin： Songbaxia gorge landslides → dammed lake → ancient alluvial fans → dammed lake outburst → Gezalandslide →ancient river swing and debris flows hazard forming.