Grain-size Distribution Patterns of the Surface Sediments and Their Influential Factors in Lake Lugu

Key words: 
• Lugu Lake /
• surface sediments /
• particle sizes /
• distribution in space

Abstract: Lugu Lake is one of the typical plateau-type lakes in the transitional zone between Tibet Plateau and Yunnan-Guizhou Plateau. With relatively weak human impacts, lake Lugu is one of the most suitable lakes for palaoenvironmental study. Based on the grain-size analysis results on 70 surface (modern) sediment samples in south main lake, combined with the investigation/observation results on the surrounding natural conditions, we have analyzed the spatial distribution features of the different particle compositions and their influential factors controlling the spatial distribution of grain sizes in the Lake. The results show that the grain-size of the samples can be classified into three types, including clayey silt, sand silt and sand. Meanwhile, the grain size components in the studied area have some obvious spatial distribution patterns, for example, the grain size in the east side of the study area controlled by the rivers (Shankua River and Sanjiacun River) show a obvious tongue-shape mainly composed of clay, and with eastward and northwestward distributions, respectively. Whole in the south part of the study area, the particle distribution pattern is influenced by lake current. In the northwest, the grain-size is dominated by sand because of suspension effect. The lake current carries a lot of sediments from the north and southwest of the study area to the south of the lake and deposit there. Generally speaking, the differences between the grain size distribution patterns are mainly attributed to the lake dynamic processes and the different respond of the sediments to the climate changes. The study on lake surface sediments not only promotes the understanding of the lake dynamics and the status of material input, but also important to select suitable sites to take cores for the paleoclimate-paleoenvironmental reconstruction.