蒙古高原南戈壁湖泊沉积记录的全新世气候变化研究

Lake sedimentary record of Mongolian plateau is extremely sensitive to the response of climate change. In recent years, the published conclusions about reconstructed Holocene climate change of lake sedimentary records are not coordinated one with others. The project choose Orog Nuur lake in Mongolian south gobi as research object, selecting and measuring the dating of plant residual body by drilling lake rock and AMS C-14 age, combined with OSL dating to construct high resolution time series of lake evolution. At the time, reconstructing the process of lake fluctuation in Holocene by OSL dating lakeside sediments at the edge of lake is contribute to infer the arid and humid change of climate. Analyzing environmental indicators of rock cores and other substitutive index is used to reconstruct accurate environment evolution history. To understand the relationship between lake evolution and monsoon (west wind) and driving mechanism, we will conduct regional comparison.

蒙古高原的湖泊沉积记录对气候变化的响应极为敏感。然而，目前已经发表的大量湖泊沉积记录重建的全新世气候变化的结论相互不一致。本项目选择处于蒙古国南戈壁的Orog Nuur湖为研究对象，钻取湖泊岩芯，从中挑选植物残体等测年材料，通过AMS C-14年代测定，结合岩芯的OSL定年，建立高分辨率的湖泊演化时间序列；开展湖泊周缘系列湖滨沉积物的OSL定年，反演全新世古湖面波动过程，推断气候变化的干湿状况。对岩芯开展环境指标分析，结合其他代用指标分析，重建高分辨率的气候环境演化历史；通过区域比对，理解湖泊演化过程与季（西）风盛衰的关系，认识其机理机制。

1) 通过Orog Nuuer周缘湖滨相沉积物的OSL测年结果显示，在全新世的7.1-6.3 ka和5.5-4.1 ka时段形成海拔高程1240-1236 m和1234-1230 m的湖岸阶地，比现代湖面高23-19 m和17-13 m，面积分别达到900 km2和256 km2。在中全新世受东亚夏季风增强的影响，其界限北移，降水量增加，蒙古南戈壁地区出现湿润气候。该结果与蒙古高原南部中全新世高湖面和多雨期相对应。但是明显有别于蒙古高原中全新干旱气候环境的观点，也与季风穿时性导致的蒙古高原早全新世湿润气候等结论不吻合。.2）在MIS3的34.6-31.8 ka、42.1-36.1 ka、46.6-44.6 ka及MIS5的95.7-79.8 ka也形成更高的湖岸阶地，标志着大湖期出现。与蒙古高原南部沙漠地区出现的MIS5e阶段高湖面一致。.3）在干旱区湖面波动剧烈，既存在高湖面，也出现低湖面甚至湖泊干涸现象，导致湖泊沉积记录缺失，使湖泊岩芯不能完整的记录气候环境变化信息，应值得注意。