云南小中甸盆地湖相沉积记录的最近5 次Heinrich事件

通过对小中甸盆地厚15.3 m的湖相沉积进行系统的粒度、孢粉和地球化学元素分析，结合 ¹⁴C年代测定，发现小中甸盆地在最近40 ka 以来经历了5 次湖泊收缩事件，其形成年代可以同北大西洋的Heinrich 事件H₀-H₄逐一对比，指示西南季风不仅在其水汽源区，而且在其控制的内陆腹地对最近40ka 以来的Heinrich 事件都存在敏感的响应。与在水汽源区所表现不同的是，Heinrich 事件在内陆地区主要表现为干旱。通过与西南季风水汽源地之一的阿拉伯海深海沉积记录和格陵兰冰芯记录进一步对比发现，小中甸盆地仅对千年尺度的Heinrich 冷事件信号敏感而对D/O (Dansgaard-Oescher) 暖事件缺乏明显记录，这与阿拉伯海的响应模式有较大差异。分析周边环流形势认为，冰期青藏高原对西南季风“抽吸”作用的减弱是造成小中甸盆地D/O暖信号记录不明显的重要原因。

Last Five Heinrich Events Revealed by Lacustrine Sediments from Xiaozhongdian Basin in Yunnan Province

Xiaozhongdian Basin is located in the southeastern margin of the Qinghai-Tibet Plateau which is completely controlled by southwest monsoonal circulation. A thick continental lacustrine sedimentary sequence is preserved due to late Cenozoic fault depression and offers a unique opportunity to study the variability of the southwest monsoonal circulation in detail. Based on the analytical results of grain size, spore-pollen and geochemical elements and ¹⁴C datings from a 15.3-m-long lacustrine stratum, five lake dry and shrink events during the last 40 ka, which might be correlated to Heinrich events H₀-H₄ discovered in North Atlantic region, have been found in Xiaozhongdian Basin, suggesting that Heinrich events for the last 40 ka are strongly imprinted not only in moisture source area of southwest monsoonal circulation, but also in inland area controlled by this circulation. The Heinrich events footprint became drier in inland area, differently from that in moisture source area. However, the signals of the D/O (Dansgaard-Oescher) warm events, which are also clearly recorded in Greenland ice cores and Arabian Sea sediment cores, are ambiguous in Xiaozhongdian Basin. According to the general circulation patterns, we believe that the effect attenuation of the Qinghai-Tibet Plateau on “Pumping Action”of southwest monsoonal circulation system during the glacial periods should be responsible for this phenomenon.