| 东南季风区及青藏高原东部湖泊沉积研究与古环境重建 |
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| 引用本文： | 王苏民,吉磊,薛滨,羊向东.东南季风区及青藏高原东部湖泊沉积研究与古环境重建[J].第四纪研究,1995,15(3):243-248. |
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| 作者姓名： | 王苏民 吉磊 薛滨 羊向东 |
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| 作者单位： | 中国科学院南京地理与湖泊研究所湖泊沉积与环境开放研究实验室 |
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| 摘 要： | 本文根据青藏高原东部若尔盖盆地ＲＨ孔的全面分析，讨论了青藏高原８２．６万年以来的长期气候变化，共划分为２３个阶段。基本特征为冷期持续时间要远远超过暖期，内部结构相对比较稳定，而暖期的内部次级波动要频繁得多。通过呼伦湖和固城湖岩芯研究，重建晚冰期以来的气候变化历史，新仙女木事件及全新世几次降温事件在两个湖泊中均有反映。统计了中国东部２７个湖泊湖面波动资料，讨论了季风区环境变化的穿时性。
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| 关 键 词： | 青藏高原 季风区 环境变化穿时性 新仙女木事件 |
LAKE SEDIMENT RESEARCH AND PALEOENVIRONMENT RECONSTRUCTION OF SOUTHEAST MONSOON REGION AND EASTERN QINGHAI-XIZANG PLATEAU |
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| Institution: | Lake Sediment cud Environment Laboratory, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciencct, Nanjing |
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| Abstract: | In recent years the study of lake sediments has developed extensively and intensively in China in order to respond to the study of the past global changes. Much attention has been paid especially to lake sediments in the Qinghai-Xizang Plateau and the arid/semi-arid region and the monsoon region of China. In this paper we study lake sediments in the Ruoergai basin, the Hulun Lake and the Gucheng Lake, which are located in the Qinghai-Xizang Plateau and the arid/semi-arid region and the monsoon region of China, respectively, and use data of lake level changes of 27 lakes in Central China to approach some problems of environmental changes.Using many means, we analyzed rock cores from a borehole 120.46m deep in the Ruoergai basin. From 14C AMS dating and paleomagnetic stratigraphic study,the chronology sequence for this borehole was constructed. The age of its bottom core is 826 000a B.P. analyzing environmental proxies such as spore-pollen, ostrocode,diatom, TOC, fossil pigment, hydrogen indices, the 813C and 818O of organic matter and inorganic carbonate, the carbonate content and authigenic minerals, we inferred the nutrient state, primary productivity, salinity, water depth, water temperature and the rainfall condition around the lake where the studied sediments were deposited. Meanwhile, 23 stages has been distinguished in this core, and they can be basically with those stages based on deep sea sl8O. It can be seen from information provided by this borehole that in the past 80 000 a the duration of cold stages (even stages) was much longer than lasting by warm stages (odd stages)in eastern Qinghai-Xizang Plateau, and that the number of climate fluctuation incold stage was relatively less than the number in warm stage. The more obviouswarm climate was at stages 23, 21, 13 and sa when peat was accumulated, showinga higher productivity. These stages are also characterized by peaks in TOC and HI,increasing woody plant pollen, more negative δ13Corg values (-26.9 to -27.9 % ) and more negative δ13C and δ18O values of inorganic carbonate. These characteristics show that TOC originated from C3 plant was increasing, rain was plentiful, lake water was being freshened, and CO2 from plant decom.Position was involving in carbonate deposition.The more obvious cold climate was at stages 18, 16,8,6 and 2, which was characterizedby finer sediments, the high 'content of carbonate, minor rainfall, sparse vegetation,lower productivity and a certain extent salinizition. Compared sediments from thisborehole with glacial moraille and morphological features in the western side of theRuoergai basin, we believe that stages 18-16 (0.719-0.525 Ma B.P.), stages 86 (0.289-0.133 Ma B.P.) and stages 4-2(0.067-0.011 Ma B.P.) respond to thedevelopment stages of last three glacier ages.The Hulun Lake is located in the semi-arid climate-sensitive zone and theGucheng Lake is located in the prevailing monsoon area. Through studying andcomparing sediments in the two lake, environmental changes since the beginning ofthe last glacial age were reconstructed. During Late Glaciation the climate wasinstable both in the monsoon area and in the semi-arid area. But owing to difference in rainfall, the monsoon area was different in association of temperature andmoisture from the semi-arid area, especially in the Allerod period (12 000 a B.P.)and the Younger Dryas period (11 000 aB.P.).Fluctuation data of lake level of 27 lakes in Central and East China since12 000 a B.P. were analyzed to approach relationshilps among summer monsoon rainfall, temperature changes and lake level fluctuations. From 12 000 a B.P. thehigher lake.level in Southwest China was related to india monsoon. The emergencetime for the higher lake level in East China was early on the north and late onthe south. Analyses of fluctuation data of these lakes also reveal the diachronityof climatic events in the monsoon area |
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