Multi - stage Development Characteristics and Geomorphic Evolution Process of the Xijitan Super Large Landslide in the Guide Basin, Upper Reaches of Yellow River
Objectives : The Guide basin lies in the upper reaches of Yellow River that located at the northeastern margin of the Tibetan Plateau, where is one of the most serious area of geohazards in China. In the region, there are many typical super large scale landslides clue to their large volume, serious harm and complex mechanism. In this paper, the author studied the Xijitan super large scale landslide located at the middle part of the Guide Basin, the evolution process of the landslide are analyzed. Methods : In this paper, the ~(14)C dating is the main method to measure when the landslide took place. The dating sample was collected from silty sand layer of the Yellow River terrace, for the time when the silty sand deposition finished can be regarded as the second stage landslide occurred. The test was taken by the Beta analytic laboratory of the U. S. A. Results : The ~(14)C dating result is 5420 40 a BP, which is approximate to other results, got by different dating methods, such as TL,ESR and OSL. Conclusions : The development processes of the landslide can be divided into four stages and the development mechanism of each stage of the landslide was analyzed as follows : (1) the first stage was triggered by the enhanced of erosion of the Yellow River due to the uplift of the basin since Holocene. (2) The second stage occurred about 5000a BP that belongs to the Holocene Optimum, so this stage induced by the climate change. (3) The third stage was due to historical earthquake that occurred at 1872 AD. (4) The fourth stage was triggered by rainfall and modern human engineering activities. Finally, the impact of the landslide to the Yellow River valley and the Guide Basin geomorphic evolution process was discussed.