Sedimentary environment evolutionary characteristics of Longjie silt layer in the middle reaches of the Jinsha River, Yunnan

The Longjie silt layer consists of a series of silt, silty clay and clay lacustrine sediments which are grayish black, grayish yellow and grayish white in color. This silt layer is distributed along the valley of the Jinsha River from Sanduizi of Panzhihua City to Baimakou of Wuding County, and is well developed in the Longjie basin in Yunnan Province. The Longjie drill hole intersects the stratatigraphic thickness of 101.18m, which includes 92.96m Longjie silt layer. Its sedimentation occurred about 150~30ka BP, as shown by the analysis of magnetostratigraphy and OSL dating. Through the study of sedimentary variation characteristics, this paper deals with the formation process of Longjie silt layer, the relative regional neotectonics movement stage and its influence on the development of the Jinsha River.