中文摘要：

本次研究通过对黄河上游10处古滑坡采用OSL和14C两种方法测年,总结归纳了6种间接取样测年的思路,即①滑坡体上覆黄土底部、②滑坡体下伏阶地黄土顶部、③滑体内部高温剪切结构面、④堰塞湖湖相层底部、⑤错落式滑坡流水相物质底部和⑥滑坡下伏物质顶部有机碳.通过分析研究发现区内特大型滑坡具有明显的群发分期特性,分别为5万年左右、3万年左右、1.0～0.8万年左右和0.5万年左右.

英文摘要：

116 super-large landslides have been developed within lO000km2 in upper reaches of Yellow River.This area is located in the transitional zone between Qinghai-Tibet Plateau and Loess Plateau,and the water cut is intense.At evolution phase of lake basins,fault depression appeared to various lake basins under the background condition in which plateau uplifts owing to the squeezing.This has provided rich material conditions for formation of super large landslide.At the formation and evolution phases of rivers,intense tectonic uplift reduced the erosion basis,which resulted in strong undercutting for Yellow River and its tributary streams.This has provided necessary topographic conditions like emptiness and high-steep slopes for formation of super large landslide.Favorable formation lithology,high-steep river valley,and coupling between endogenie process and exogenic process have offered a beneficial landform,climate and geological conditions for development of landslide in the area.Thus super large landslide has been developed in high density on both banks of the river valley.The ideal situation of phase characteristics is to date each landslide in the research area,but this is obviously impractical.Therefore,we selected 10 typical landslides and dated them via 14C and OSL methods.6 dating ideas of indirect sampling were summarized：1） at the bottom of loess on the landslide mass; 2） at the top of loess under the landslide mass;3） on high temperature shear structural plane within the landslide mass; 4） at the bottom of barrier lake lacustrine facies layer; 5） at the bottom of fluvial substance of cross landslide; 6） organic carbon at the top of substance under the landslide,super large landslides in the research area were divided into 4 obvious group occurrence phases：about 50 thousand years ago,about 30 thousand years ago,about 10～8 thousand years ago,and about 5 thousand years ago.