青藏高原北缘哈拉湖近800年来湖泊沉积及其环境意义  

ENVIRONMENTAL CHANGES DURING THE PAST 800 YEARS RECORDED IN LAKE SEDIMENTS FROM HALA LAKE ON THE NORTHERN TIBETAN PLATEAU

作　　者：曹洁[1] 张家武[2] 张成君[2] 陈发虎[2] 

机构地区：[1]山东省气候中心,济南250031 [2]兰州大学西部环境教育部重点实验室中德干旱环境联合研究中心,兰州730000

出　　处：《第四纪研究》2007年第1期100-107,共8页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:40301050);国家自然科学基金人才项目创新研究群体科学基金项目(批准号:40421101)资助

摘　　要：文章以青藏高原北缘高山祁连山湖泊———哈拉湖作为研究对象,利用放射性核素210Pb和137Cs测年资料,通过对此高海拔湖泊沉积碳酸盐氧碳同位素、碳酸盐含量、总有机碳含量、磁化率等环境代用指标的分析,揭示了这一地区近800年来的气候环境变化过程。分析表明哈拉湖记录的气候环境变化经历了3个阶段:1206～1700A.D.环境较为寒冷、湿润,并有持续变湿的趋势;1700～1920A.D.环境由冷湿的状况趋向温暖干旱,1771年之后,环境保持相对稳定;1920～2002A.D.是自1206年以来最为温暖干旱的阶段。Being surrounded with high mountains, the Hala Lake, is a large salty lake with an altitude of 4078m in the north of the Tibetan Plateau. Due to little human impacts on the lake drainage, the Hala Lake, as a typical inland closed lake located on the Chinese monsoon transition line, can provide sensitive information on the past climatic and natural environmental changes. Plateau area has been reported to be more sensitive in response to global change than the area at lower altitudes. Here we present the result of a short core retrieved form the Hala Lake in the north of Tibetan Plateau. The short core HALA -3B -02, 75cm long, was taken with a weight sampler at water depth of 19.3m in the north-west of Hala Lake （38°20′44. 8＂N, 97°26′34. 3＂E） in July, 2002. Sediment samples from the sediment core drilled at the high-altitude Hala Lake were analyzed for a range of palaeoenvironmental indicators, which include stable isotope of oxygen and carbon of carbonates （δ^13C ＆ δ^18O）, total organic carbon content, carbonate content as well as magnetic susceptibility. Chronology of the sediment core was determined using ^210 Pb and ^137Cs. However, the ^137Cs dating result shows that the cumulating peak of the year of 1954 is hardly distinguishable due to disintegration with time. In addition, because of its diffusion and transference features, ^137Cs cumulating peak is considered improper for dating. Hala Lake chronology was thus established on dating series from ^210Pb CRS model and linear extrapolating based on bottom deposit rates. Average deposit rate of the profile under 21.5 cm （ corresponding to the year of 1900） is 0. 187cm/a, while that above 21.5cm suddenly rises to 0. 199cm/a, which is possibly relevant to more and more intense human activities since the 20^th century. The lithology of the profile from bottom to 21.5cm appears to be comparatively conformed, hereby corresponding deposit rate is supposed to be 0. 187cm/a. The earliest time was thus extrapolated to be 796 years before 2002

关 键 词：哈拉湖 湖泊沉积 碳酸盐氧碳同位素 环境变化 

分 类 号：P597[天文地球—地球化学]