Environmental Information Inferred from Environmentally Sensitive Grain-size Component Records in Wulungu Lake, Xinjiang

Key words: 
• lake sediments /
• grain size /
• sensitive component /
• environmental significance /
• Wulungu Lake

Abstract: Analysis of a sediment core from Wulungu Lake of Xinjiang was carried out by using environmental proxy of grain-size. Combining with ²¹⁰Pb and ¹³⁷Cs dating, the characteristics and environmental significance of sensitive grain-size components of Wulungu Lake sediments were studied in Wulungu Lake region. The results showed that the sediment core mainly consisted of clay and fine-silty, however, grain-size displayed a sudden shift before and after 1970 AD:the coarse particle fraction (>16 μm) was significantly increased. The grain size characteristics of the sediments also changed significantly during 1830-1842 AD and in about 1910 AD. The analysis of grain-size frequency distribution curves of the sediment core indicated that the transportation medium or transporting force had changed significantly during corresponding periods. Based on this result, environmentally sensitive grain-size component C2 (7-25 μm) was extracted by the variations of the grain-size standard deviation. Based on correlation analysis between sensitive grain-size component and meteorological data, the environmental significance of sensitive grain-size component C2 was explicated. The results indicated that the content of sensitive grain-size component C2 was related to the regional spring and summer average temperature and winter snowfall, and reflected the intensity of the snow meltwater into the lake. The significant increase of the content of component C2 during 1830~1842 AD and in about 1910 AD thus reflect the increased water inflow and higher lake level. The significant change of grain size characteristics of the sediments during 1960s-70s was related to human activity.