青海湖江西沟黄土记录的环境演变

THE ENVIRONMENTAL CHANGE RECORDED IN JIANGXIGOU LOESS SECTIONS IN QINGHAI LAKE REGION

青海湖地区是全球变化研究的热点区域,对全球气候环境变化极其敏感。末次冰消期是青海湖地区风成沉积物发生广泛堆积的时期,也是青海湖地区气候环境发生重要变革时期。通过对青海湖江西沟JXG1和JXG2黄土剖面的研究,重建了末次冰消期以来的环境演变记录。结果指示:(1)13～11.5kaBP,剖面主要发育砂质黄土,青海湖区总体环境从冷干向相对温暖湿润的凉干环境过渡;(2)11.5～5kaBP左右,剖面主要发育古土壤层,特别是9～5kaBP时期,水热组合匹配达到最佳,气候呈现暖湿状态;(3)5kaBP以来,干湿冷暖交替,尘暴频繁,植被盖度降低,气候进入相对不稳定状态。江西沟黄土剖面记录与青海湖湖泊钻孔和黑马河黄土剖面记录的气候变化过程具有一致性,红度指标是记录环境演变的敏感指标。末次冰消期以来该区黄土沉积主要受控于北半球高纬度夏季太阳辐射驱动的冰量变化,西风带扮演了北大西洋和青藏高原东北部"冷空气传输机"的角色。

The Qinghai Lake area is a hot spot in global change studies,due to its sensitivity to global warming.During the last deglaciation,aeolian deposits were widely distributed in the region,with drastic environmental and climatic changes.In this paper,we studied two loess sections（JXG1and JXG2） near the Jiangxigou town to the south of Qinghai Lake,upon which we reconstructed the regional environmental changes since the last deglaciation.The results show that ：（1） During 13～11.5kaBP,the paleolclimate was cold and dry there.Aeolian deposition prevailed and sandy loess formed.In general,the region was changing from a cold and dry to a cool and humid environment;（2） During 11.5～5kaBP,pedogenesis was relatively strong.Maximum moisture levels occurred during the period of 9～5kaBP,and in general,the paleoclimate was warm and wet;（3） After 5kaBP,climate often alternated,dust storm occurred frequently,vegetation coverage decreased,and the climate entered a relatively unstable stage.The environmental changes of the Jiangxigou Loess section are comparable with those revealed by the boreholes in the Qinghai Lake and the Heimahe loess section.The redness of the Jiangxigou loess section is a sensitive index to environmental change.The loess deposition since the last deglaciation in Qinghai Lake area was mainly controlled by the ice volume of the northern hemisphere,which was driven by the summer solar irradiation at the high latitude.The Westerlies played the role as a cold-air conveyer between the North Atlantic and the northeastern Tibetan Plateau.