【摘要】 内蒙古黄旗海是位于东亚夏季风尾闾与冬季风腹地的一个封闭流域,其湖泊沉积敏感并反映了区域冬夏季风变化的历史。基于黄旗海北部湖滩上的H3剖面,在高分辨率年代序列的基础上,利用粒度特征,特别是沉积物各粒级的时间序列变化特征,探讨了古湖泊水位变化、剖面沉积环境过程与冬季风的风尘记录。研究结果表明,8.0~5.1 ka BP,气候暖湿,湖泊水量丰富,为相对稳定的深水-半深水环境,为全新世气候最适宜期,降尘微弱;但在6.7~5.5 ka BP期间存在两次明显的湖面回落,降沉剧烈的气候恶化事件,揭示了气候适宜期气候也存在短暂的不稳定性。5.1~4.0 ka BP,气候逐渐变得冷干,风力作用较强,降尘加剧,湖面波动较大;3.6~2.2 ka BP,剖面所在位置演变为浅滩沼泽相,并可能季节性暴露地表。更多还原

【Abstract】 Huangqihai,a small enclosed lake in Inner Mongolia of China,lies at the northern boundary of Eastern Asian Summer Monsoon and in the center area of Asian Winter Monsoon,thus its lacustrine sediment sensitively recorded the climate change of the above two monsoon systems.Based on the granular size character of sediment from profile H3 on the northern lacustrine bottomland 13m above the Huangqihai lake surface in 1986,the paper investigates the record of palaeolake water level,sedimentary environment evolution,and winter monsoon change.Together with the 13δ record(Shen et al,2005),the granular size character and sediment stratigraphic evidence of profile H3 suggested that(1)the lake level was at a high stage between 8.0-5.5 ka BP,which indicating that the palaeoclimate that was warm and humid for the summer monsoon was intensified,and the winter monsoon subdued,corresponding to the so-called Holocene Magathermal.However,the climate system made up of the two monsoon circulations far from the stable state for there appeared air mass dust sedimentation and low lake level events in twice during the 7.0-5.5 ka BP for abruptly-reinforced winter monsoon and fluvial effect inferred from the increased proportion of 6.25±0.25 Φ,7.25±0.25 Φ,-0.75±0.25 Φ,and-0.25±0.25 Φ size interval respectively;(2)during 5.1 ka BP～3.6 ka BP,timed to the so-called new-glacier,there appeared more and more air mass dust sedimentation and the lake level gradually decreased,which showed a cooler and drier climate for summer monsoon circulation was weakened and winter monsoon enhanced on the contrary.this kind of condition was persisted in during 3.6 ka BP～2.2 ka BP.更多还原