永胜金沙江寨子村古滑坡和古堰塞湖的发现

The Ancient Iandslide and Dammed Lake Found in the Jinsha River near Zhaizicun,Yongsheng,Yunnan,China

在滇西北地区永胜南部金沙江的右岸,发现了总方量为2.5×108 m3的超大型古滑坡。滑坡后缘及两侧断壁为近直立的石灰岩峭壁,高5～30 m。滑床发育有规模不一的冲沟,覆盖有发育植被的坡积物、倒石堆和巨石。该滑坡曾造成过严重的堵江事件,在金沙江左岸仍然可以看到垄岗状残留滑坡坝,坝体方量约180×104 m3,滑坡坝和坝体后侧基岩界限清晰,两者之间岩性区别较大。滑坡堵江事件在上游形成了沿江连续分布长度约46 km的古堰塞湖沉积,沉积物主要由粉土、粉质粘土及粉细砂构成,偶夹卵石层,以水平层理为主,粉细砂层中见有小型交错层理,湖相沉积特征显著,而沉积物的树枝状平面分布进一步证实其形成于堰塞湖环境。

In the southern Yongsheng,the right bank of the Jinsha River and found that the total amount of square 2.5 × 108 m3 of large ancient landslide,Northwest Yunnan.The main and minor scarp that is limestone cliffs with a height of 5~30 m.In the sliding bed development of varying scale gullies,and covered by the slope sediments with vegetation,talus and separate giant rock.The landslide once dammed Jinsha river,and on the left bank can still see the raised residue landslide dam,and the dam is about 180 × 104 m3.There have a clear boundaries between the landslide dam and rear bedrock,the lithology is also a great difference between them.The events of landslides blocked river formed a continuous distribution ancient lake deposits along the length of 46 km in the upstream.sediments composed by the silt,silty clay and fine sand,occasionally with gravel layer.Sediments mainly horizontal bedding.Fine-sandy,ripple cross-laminated and cross-stratified beds show the existence of bottom currents in the landslide-dammed lake.The surface sediment distribution of dendritic further confirmed its formation in the lake environment.