Sediment particle size distribution and its environmental significance in Lake Erhai, Yunnan Province

A closed or semi-closed plateau lake, whose sediment records can provide us with plenty of fine and high resolution information, is a sensitive indicator of climatic and environmental changes. During the reconstruction of various short-time-scale climatic and environmental changes, the geochemical records in plateau-lake sediments are superior to other natural files. Based on fine dissection of the vertical profile of sediment particle sizes, this paper reveals the quasi-periodical changes of sediment particle sizes, which indicates the quasi-periodical fluctuations of the regional climate. A synthetic analysis of multiple indexes shows that sediment particle size is a more sensitive and more effective index of climatic and environmental changes than other geochemical indexes. High content of >20 μm sediment particles and low content of 2 - 10 μm sediment particles indicate a warm-dry climate and conversely a cold-humid climate, and their ratio can be used as an effective index of climatic changes. The basic climate succession in the region of Lake Erhai is characterized as being alternatively warm-dry and cold-humid and it has been developing into a warm-dry climate as a whole. There exist at least 2 time-scale quasi-periodical fluctuations of the regional climate in Lake Erhai. At present, the region of Lake Erhai is at the end of the warm-dry period and at the beginning of a cold-humid period, so the temperature will go down and the water level will rise.