粒度和元素证据指示的居延海1.5kaBP来环境演化

居延海是黑河的终端湖, 在最近3 000 a来已由原来面积 800 km2逐渐萎缩而最终干涸, 同时其周边环境也发生了巨大的变化.东居延海(索果诺尔)湖相沉积的粒度和元素资料研究结果表明: 明清以前湖泊的变化主要受气候变化的影响, 温暖时期, 气候偏湿, 入湖水量增多, 湖泊面积扩大, 流域化学风化作用增强; 寒冷时期, 气候偏干, 入湖水量减小, 湖泊萎缩, 流域化学风化作用减弱.明清之后特别是近40 a来, 由于黑河上中游地区大规模的土地开发及水资源利用, 入湖水量不断减小, 甚至河流断流, 最终导致了目前居延海的干涸.

Evolution and Climate Changes of the Juyan Lake Revealed from Grain Size and Geochemistry Element Since 1 500 a BP

The Juyan Lake, located in the north of Ejin Banner of Alxa League in Inner Mongolia, is a terminal lake of the Heihe River. The water area of the lake has gradually shrunk from 800 km² and even dried up in the past 3 000 years. The environment around the lake has also changed enormously. What is the reason bringing about such enormous changes? In this paper the lake evolution and climate changes are studied by analyzing the granularity and chemical elements of the lacustrine sediments in the Juyan Lake. The following conclusions are drawn: The lake evolution was controlled mainly by climate changes before Ming and Qing Dynasties, when the warm-humid climate resulted in an increase of inflow to the lake, which made the lake area expand and the chemical weathering strengthen; whereas the cold-arid climate resulted in a decrease of inflow to lake, which corresponded to lake water level drop, lake area shrank and chemical weathering weaken. After Ming and Qing Dynasties, especially in the recent 40 years, the anthropogenic factor predominated the lake evolution process. The Heihe River continuously decreases its inflow to the lake, because of large-scale land development, finally the Juyan Lake dried up due to zero inflow.