青藏高原全新世环境变化的兹格塘错元素地球化学沉积记录

Holocene Environmental Change Record Derived from Elements in the Sediment Core of Zigetang Lake,Tibetan Plateau

兹格塘错是位于藏北高原腹地的一个封闭型湖泊,流域内没有现代冰川和永久积雪存在,其湖泊的水量平衡主要是大气降水和蒸发之间的平衡,因此其湖泊的变化过程可直接反映区域的气候变化。为了探讨该区域全新世的气候与环境变化过程,在其湖泊中心水深30m处钻取了一支深727cm的沉积岩芯,对沉积岩芯进行了元素地球化学分析,利用主成分分析得出影响沉积物化学组成的三个主要因子,主要受控于流域侵蚀因子和径流因子,区域背景作用因子所占比重很小。结合Mg/Ca的变化,其结果反映了全新世期间湖泊水体退缩与扩张,水质的浓缩与淡化的过程,揭示了兹格塘错流域气候的干湿变化,呈现暖干/冷湿气候组合模式;元素地球化学所反映出的湖面波动与环境变化得到了其他资料较好的支持,同时又显示了区域的差异性。

The unique geographic environment of Tibetan Plateau leads to sensitive responses of lake depositing to climatic changes. Located in the hinterland of North Tibetan Plateau, Zigetang Lake is an enclosed lake with bad climate and little great evaporation precipitation, the regional environment has always been faintly disturbed by human beings, with and no glacier in the catchment, the main supply of water comes from surface runoff, and factors of water balance are simple. Thus Zigetang Lake is ideal for study on the climatic evolution of Tibetan Plateau. A 727 cm long core （ZGT02） was obtained at water depth of 30 m in the west of Zigetang Lake, and its AMS age covers the whole Holocene. Geochemic analysis shown that element content in the sediment change with the depth, three important factors were identified using factor analysis method, which control chemical composition of sedi- ments, such as catchment erosion, diagenetic modification and endogenic calcium carbonate precipiration. Further more research combined with Mg/Ca, the evolution history of the regional climate and environment is evaluated, and it is revealed that the basic climate succession in the region of Zigetang Lake is warm dry and cold humid alternatively, the lake level fluctuate frequently during the Holoence, including the following high lake levels periods, i.e. （1）10-9.7cal. kaB. P.,（2）9.3-9.0cal. kaB. P. ,（3）6.0-5.6 cal. kaB. P. ,（4）4.0-3.8 cal. ka B. P. , （5） 3.1 - 2.7 cal. ka B. P. , （6） 0.6 - 0.2 cal. ka B. P.. These environmental changes and the variations of the lake level reflected by the geochemic of Zigetang Lake sediments are well supported by other research results, at the same time, there are different as the different area.