首页> 中文期刊>气候变化研究进展 >西藏普莫雍错介形类反映的中晚全新世以来湖面波动与环境变化

西藏普莫雍错介形类反映的中晚全新世以来湖面波动与环境变化

     

摘要

西藏普莫雍错位于喜马拉雅山脉印度季风雨影区,主要由冰川融水补给.根据湖泊的等深线分布和主要补给河流的入湖路径,对采自普莫雍错1 ~ 62m水深范围的表层沉积物介形类和相关水环境参数进行了分析.结果表明,普莫雍错表层沉积物中含有7属9种介形类,其分布主要受湖泊水深、pH值、温度和光合有效辐射等环境因子的影响.介形类与水环境因子的降维对应分析、典型对应分析结果显示,水深是影响表层沉积物介形类分布的最重要的环境因子,用偏最小二乘法加权平均回归与校正模型建立的介形类-水深转换函数具有较高的精度与可靠性.利用此转换函数模型和一个72 cm长重力湖芯的介形类属种分析结果,定量重建了湖泊水深波动历史.湖面波动与湖芯的总有机碳、总无机碳、粒度等代用指标比较结果表明,普莫雍错6.0 kaBP以来的环境变化具有6.0~4.3 kaBP的温凉浅湖面期、4.3 ~ 2.0 kaBP温暖的湖面波动期及2.0 kaBP以来温暖的湖面扩张期.%The Pumayum Co is in the Indian monsoon rain shadow zone of the Tibetan Himalaya ranges. It is mainly supplied by glacial melting water, and sensitive to climatic changes. According to the lake's isobath distribution and transportation routes of the inputting rivers, we collected and analyzed ostracods of surface sediments and water indices from 1 to 62 m water depth in different areas. Our results have shown that there are 7 genera and 9 species ostracods in surface sediments of Pumayum Co. Their distributions arc mainly influenced by lake water depth, pH, temperature and photosynthetically active radiation (PAR). Water depth is the most important environmental variable to dominate oslracods distribution through the Dentrended Correspondence Analysis and Canonical Correspondence Analysis. An ostracods water depth transfer function with high precision has been built by using the weighted averaging partial least squares regression and calibration model The transfer function has been applied to analyze ostracods of a 72 cm long gravity core and a historical lake water depth sequence has been reconstructed. We have compared the lake level fluctuations with TOC, TIC, grain-size of the core sediments. The results showed that the environmental changes since 6.0 kaBP in Pumayum Co area could be divided into 3 stages: a warm-cool period with a shallow lake level from 6.0 to 4.3 kaBP, a warm period with a fluctuated lake level from 4.3 to 2.0 kaBP, and a warm period with expanding lake area from 2.0 kaBP to present.

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