晚冰期以来乌伦古湖沉积物多指标高分辨率的古环境演化

A high-resolution climatic change since the Late Glacial Age inferred from multi-proxy of sediments in Ulungur Lake

对位于北疆福海县的乌伦古湖Ulungur10B孔岩芯进行分析,以AMS^(14)C测年为年代框架,结合粒度、烧失量和色度指标重建了该地区12.3 cal ka BP以来的古环境演化。结果显示:12.3~11.2 cal ka BP期间,湖泊有机质含量较高,区域有效湿度较大;11.2~7.4 cal ka BP期间,沉积物平均粒径大,有机质含量低,色度a*值、b*值偏大,区域气候冷干,湖面水位较低;7.4~4.3 cal kaBP期间,沉积物平均粒径减小,有机质含量升高,色度a*值、b*值减小,区域气候暖湿,湖泊水位较高;4.3 cal ka BP以来指标在波动中变化,反映湖泊水位在波动中变化,区域有效湿度有所降低。乌伦古湖晚冰期以来古环境演化与周边环境记录一致,气候变化模式符合中亚干旱区全新世气候变化的西风模式。

Record of Late Glacial Age environmental and climatic change in the Ulungur area, Xinjiang, China is reconstructed from a sediment core at Ulungur Lake. The proxies used mainly include sediment grain size, organic matter content and sediment color. As is known to us, the sediment grain size and organic matter content are the nor- mal proxies, and they are widely used in exploring the climate change. The experimental dates of these two proxies are from the Laboratory of West China＇ s Environmental System. The proxy of sediment color deserves to be men- tioned, as it is initially used in deep-sea sediment research, as time goes, it is developed to Chinese loess research. But the proxy of sediment color was rarely used in lake sediment research. This paper tries to explore the signifi- cance and practicability of this proxy in indicating the climate change in lake sediment. The results show that the proxy of sediment color can compare well with the other proxies, and is sensitive to the climate change. In the aspect of chronology, radiocarbon dating is conducted using AMS^14C and conventional^14C methods to date 10 samples, con- sisting of organic matter and charred material. Taking full account of the＂reservoir effect＂, this paper gets a series of relatively reliable chronological dates, which lays a foundation for the reconstructing of the past climate change of Ulungur area. Multi-proxy dates show that the effective moisture and lake level is a little higher during the late-gla- cial （12.3-11.2 cal ka BP）, which is inferred from the higher organic matter content and smaller mean grain size; During the early Holocene （11.2-7.4 cal ka BP）, the proxies have an character of large sediment grain size, low or- ganic matter content and high sediment color a＊ and b＊, which shows the climate was cold and dry, and lake level is low;During the period of 7.4-4.3 cal ka BP, the proxies indicates a warm and wet climate, and lake level is high; After 4.3 cal ka BP, the proxies are fluctuated in change, which indicates that the effective moisture and lake level are changed repeatedly. The climate change after late glacial period recorded by Ulungurl0B is not only consistent with the records of other lake records around Ulungur area, but also has a good comparability with the records of cen- tral Asia lakes. As a result, this article gets the conclusion that the climate change in the area of Ulungur lake is con- sistent with regional climate background, and obeys the＂arid Central Asian westerly mode＂.