黄河上游贵德盆地席芨滩巨型滑坡发育特征及地貌演化

Multi- stage Development Characteristics and Geomorphic Evolution Process of the Xijitan Super Large Landslide in the Guide Basin,Upper Reaches of Yellow River

黄河上游贵德盆地位于青藏高原东北缘,是我国地质灾害最发育的地区之一,该地区的巨型滑坡因其方量大、危害严重、机制复杂等特点在全球范围内都具有典型性和代表性。本文以贵德盆地黄河左岸的席芨滩巨型滑坡为研究对象,通过资料收集、野外精细调查、遥感影像解译和测年数据,分析了该巨型滑坡的发育期次和诱发因素,认为滑坡发育主要经历了4个阶段:1全新世早期温度升高引发冰雪融水增多导致黄河侵蚀作用加强而引发的Ⅰ期滑坡;2由全新世适宜期暖湿气候条件下降水触发的Ⅱ期滑坡;3由1872年历史地震诱发的Ⅲ期滑坡;4由降雨和近年来人类工程活动引发的Ⅳ期滑坡。文章最后讨论了席芨滩巨型滑坡对贵德盆地黄河河谷地貌演化过程的影响。

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 due 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,the14 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： The14 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 about5000 a 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.