内蒙古东乌珠穆沁旗乌拉盖高毕湖泊沉积记录的5万年来环境演变

Environmental changes during the past 50000 years recorded by Lake Wulagaigaobi sediment,Dongwuzhumuqinqi,Inner Mongolia

中国北方季风边缘区的湖泊对环境的反应很敏感,乌拉盖高毕是位于内蒙古高原东北部的一个已干涸的内陆封闭湖泊.研究剖面总厚度为405 cm,根据取得的9个AMS14C及光释光测年数据,建立了51.9 ka BP以来的年代序列.结合岩性的变化、粒度组分分析、粒度参数(标准偏差、偏度、峰度等)及Rb/Sr比值特征进行了详细的分析,恢复了乌拉盖高毕湖泊沉积记录的5万年来的环境演化过程.将0～405 cm的剖面划分为4个较大的气候阶段:51.9-44.1 ka BP(405～343 cm),气候为干冷期,各环境指标显示为滨湖沉积,湖泊水位较低;44.1-28.5 ka BP(343～130 cm),气候为温湿期,湖泊逐渐扩张,湖泊水位升高;28.5-11.38 ka BP(130～35 cm),气候转冷,湖面萎缩,并在盛冰期出现砂楔,该阶段后期湖泊干涸;11.38 ka BP至今(35～0 cm),气温回升.

Lakes located in the monsoon marginal zone in North China are sensitive to climate change. Lake Wulagaigaobi is an enclosed lake in Inner Mongolia of China, which is in the semiarid and sub-humid ecotone on the northeast margin of the Inner Mon- golia Plateau. In this paper, a sediment profile of 405 cm deep was chose. The measured data of the sediment in AMS^14C and OSL age revealed that the sediment profile was deposited since 51.9 ka BP. Combined with chronological data and the analyses of sedi- mentary characteristics, including grain-size distribution, grain-size frequency, grain-size parameters, and trace elements, the evo- lutionary process and features of the lake environment were reconstructed during the past 50000 years. Results showed that there were four climate periods ： 51.9 - 44.1 ka BP （405 - 343 cm）, cold and dry period, a lower lake-level;44. 1 - 28.5 ka BP （ 343 - 130 cm）, warm and wet period, the lake-level fluctuated ;28.5 - 11.38 ka BP （ 130 - 35 cm）, cold and dry period ; 11.38 ka BP- today （35 -0 cm）, warm and wet period.