采用粒级-标准偏差法对新疆罗布泊新湖湖心区KY01孔0~8 m沉积物提取了对环境变化敏感的两个粒级组分:3.5~6.2 mum(组分1)、20.7~63.4 mum(组分2)和一个相对不敏感组分:8.9~14.3 mum(组分3)。结合湖泊沉积物粒度一般分布规律、黄土和现代降尘等大气悬浮颗粒物沉降特点,推测3个粒度组分分别指示钻孔所在位置与湖心的相对距离、区域沙尘活动强度和非沙尘活动的粉尘输入强度。根据粒级敏感组分2和AMS~(14)C测年数据重建了该区近4.5万年以来的沙尘活动历史。在过去的4.5万年,罗布泊地区沙尘活动增强主要出现在44.7~44.5、44.2~44.0、41.4~38.8、38.4~37.4、36.4~36.1、34.8~34.5、33.5~32.9、 32.5~32.2、31.9~31.5、29.9~29.5、25.6~12.3和8.9~7.8 cal ka BP期间,这些时间段多数对应于以格陵兰NGRIP冰心delta~(18)O记录所代表的北半球气候变化冷阶段或冷事件,说明该区沙尘活动的强弱与全球降温事件所引发的冷干气候密切相关。
英文摘要:
Core KY01 was recovered from the center of the New Lake district in the Lop Nur, northwestern China for paleoclimatic reconstruction. Two environmental sensitive grain-size components, 3.5 - 6.2 mum (component 1),20.7 - 63.4 mum (component 2),and one less sensitive grain-size component, 8.9 - 14.3 mum (component 3) of its sediments at the depth of 0 - 8 m were identified by the mathematical method of grain-size classes vs. standard deviation values. The three components are sensitive to the relative distance between the core KY01 and the middle of the Lop Nur, sensitive to the regional dust activities, and sensitive to the ordinary dust input intensity, respectively. Combined with the sensitive grain-size component 2 and five AMS~(14)C ages, a 45000-year dust activity history in Lop Nur area was reconstructed. The study shows that strong dust periods appeared at 44.7 - 44.5 cal ka BP, 44.2 - 44.0 cal ka BP, 41.4 - 38.8 cal ka BP, 38.4 - 37.4 cal ka BP, 36.4- 36.1 cal ka BP, 34.8 - 34.5 cal ka BP, 33.5 - 32.9 cal ka BP, 32.5 - 32.2 cal ka BP, 31.9-31.5 cal ka BP, 29.9 - 29.5 cal ka BP, 25.6 - 12.3 cal ka BP, and 8.9 - 7.8 cal ka BP. These periods are consistent well with the cold events or cold episodes of the Northern Hemisphere that were reflected by the oxygen isotope record of the NGRIP ice core, etc. It shows that the dust activities in the Lop Nur area are closely related to cold dry climate triggered by global cooling events.