| Continued uplift of Tibetan Plateau result in strong erosion of large rivers and valley deep cutting in the southwest of China. Induced by earthquake or heavy rainfalls, slope usually tends to localized necking with collapse or landslide and forms dam which blocks a river channel. If the barrier dam formed by collapse or landslide can keep stable for long-term, its upstream barrier lake would accumulate lake deposits in a certain scale. According to statistics, there have formed 65 landslide dams on the Jinsha River and its tributary situated in southeastern Tibetan Plateau since 1973(the barrier dams formed during "5.12" Wenchuan earthquake are not included). The Zhaizicun landslide that happened about 26 million years ago has restrained the complete barrier-lake deposits and residue landslide dam till now. And owing to the huge scale of Zhaizicun landslide, to some degree, the evolution of regional geomorphology and the change of geological environment are affected.The landslide of Zhaizicun is located in Jinsha River Bridge downstream 1.0 km of the highway S220 near Jinjiang Street, where is in the right-bank of Jinsha river between Zhaizicun and Daludi in Taoyuan town, Yongsheng county Yunnan Province, and is about 42 km away from Binchuan county, about 57 km away from Yongsheng county.In this paper, on the basis of field geological survey, collecting and analyzing the geological data, taking the Zhaizicun landslide as the research object, the engineering geological characteristics of barrier-lake deposits and residue landslide dam in Zhaizicun are described, and genetic mechanism of Zhaizicun landslide is discussed. According to comprehensive analysis of the characteristics of lake deposits and ESR date of landslide and lake deposits, it is discussed that how the formation of barrier-lake affect the evolution of geomorphology and the relation of Zhaizicun landslide and the uplift of Tibetan Plateau.Zhaizicun landslide is a super large ancient landslide with the volume of 2.5 billion m3. The trailing of landslide and both sides of broken walls are nearly vertical limestone cliffs. The landslide has caused sever river blocking ever, and up to now, in the left-bank of Jinsha River the residue landslide dam can be seen and the Zhaizicun is situated in the dam. The river blocking formed a continuous distribution ancient barrier lake deposits with the length of 30 km along the river in upstream. The lake deposits are dominated by horizontal bedding, small cross bedding is occasion, and the lacustrine deposits feature is significant, the distributed characteristics confirm that the barrier lake environment of deposits formation is the typical Xigeda stratum. An ancient and strong activity Chenghai fault zone nearly NS drills through the whole ancient landslide in Zhaizicun, the fault is dominated by left-slip eastward movement with vertical displacement, and its complex activities destroy the continuity of geologic body and accelerate the rock fragmentation degree. The erosion of Jinsha River and the activities of fault zone both control the evolution of right-bank landscape. Based on the fact that the Zhaizicun landslide scale, lithologic features, instability trend and its formation mechanism are restrained by geological structure of neat field region, it can be concluded that the earthquake which induced by Chenghai fault activities is the main factor leading to Zhaizicun landslide. |
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