关键词: 西藏, 普莫雍错, 介形类, 湖面波动, 环境变化, 古气候

Abstract: 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 are mainly influenced by lake water depth, pH, temperature and photosynthetically active radiation (PAR). Water depth is the most important environmental variable to dominate ostracods 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.

Key words: Tibet, Pumayum Co, ostracod, lake level, environmental change, paleoclimate