The discovery of debris flow sediments in the middle-upper Xiyu Formation of Lower Pleistocene on the northern margin of West Kunlun Mountains and its significance

Dozens of layers of debris flow were discovered in Qiaha,Sangzhu and Kekeya areas on the northern margin of West Kunlun Mountains. Density measurements show that they are mainly clayey debris flows. Typical combinations of sedimentary facies are AC,AA1C,DAA1BC,AA1BC,AA1B and A1BC,suggesting that the sedimentary facies of debris flow evolved from top to edge of the alluvial fan,and the age of debris flow sediments is early-middle Early Pleistocene through comparison. The discovery of debris flow sedimentation in middle -upper Xiyu Formation on the northern margin of Tibetan Plateau provides important new information on tectonic background,geomorphic conditions and climate characteristics for analyzing sedimentation age of Xiyu Formation in the north margin of West Kunlun Mountains and also supplies new evidence for the uplift of Tibetan Plateau ant its geological disaster effects,thus putting forward warning for the prevention and treatment of debris flow disaster.