关键词: 粒度特征, 古环境, 青土湖

Abstract: The enclosed Qingtu Lake lies in the environment-sensitive zone in Minqin County of Gansu Province, China, and the grainsize characteristics of its sediments indicate the variations of precipitation, hydrodynamics and the lake level changes. The grain size characteristics of Qingtu Lake sediment, part of palaeoterminal lake of Shiyang River, are analyzed in this paper, including grain size distribution, grain size parameters. Based on the analysis of the characteristics of the grain-size frequency curves of the lake sediments, some possible major depositions like fluvial deposition, wind deposition, low-lake deposition and lake deposition are discussed. The results indicate the palaoterminal lake of Shiyang River had erperienced four warm period and four dry period since 11 000 a BP. In brief, the evolution of lakes in Eastern Hexi Corridor is characterized by sedimentary continuity and faster sedimentary rate, which not only can indicate the paleoenvironmental and climate change in Holocence, but also provide natural background of the soil regeneration and desertification.

Key words: grainsize characteristic, paloenvironment, Qingtu Lake