为进一步探究定南大湖湖沼晚冰期以来的水文特征及气候变化,对研究区K02钻孔的粒度特征进行了详细的分析,采用粒级标准偏差法和主成分分析法对348个沉积样品提取了对环境变化比较敏感的三个粒级组分:0.6~7.1 mum(组分1),20~44.8 mum(组分2)和89.3~447.7 mum(组分3)。结合湖泊沉积物粒度一般分布规律,并根据敏感组分2和~(14)C测年数据探讨了该区域近16 ka B.P.以来的气候变化。结果表明在过去的16 000年里,大湖地区的水文及气候变化可以分为4个阶段:1)在16.0~11.5 ka B.P.期间,气候总体偏冷干,敏感组分含量增降比较明显,能较好的对应老、中、新仙女木事件和B/A暖期;2)11.5~6.0 ka B.P.期间,大湖地区进入了湿润的全新世适宜期,敏感组分总体含量偏低;3)6.0~3.8 ka B.P.期间,敏感粒度组分含量迅速升高且波动较大,大湖湖沼地区进入一个相对干冷的时期;4)3.8 ka B.P.至今为第四阶段,敏感粒度组分含量总体偏低,考虑到人为干扰因素,暂不做详细讨论。通过对大湖地区水文状况的研究发现,大湖湖沼地区自晚冰期以来气候变化很不稳定。与格陵兰GISP 2冰芯、董哥洞D4石笋及其K02钻孔其他指标的记录对比可以发现,敏感组分2对仙女木、9.5 ka、8.2 ka等冷事件的记录更加明显,也说明了大湖地区的气候变化具有全球性,这种气候变化可能与太阳活动有关。
英文摘要:
The content and distribution of Dahu swamp Core granularity extracted from Mastersizer 2000 were analyzed based on standard deviation change. Three environmental sensitive grain-size components:0.6-7.1 mum (C1), 20-44.8 mum (C2) and 89.3-447.7 mum (C3) of its sediments at the depth of 348 cm were identified by the mathematical method of grain-size classes and standard deviation values. Combined with the distribution characteristic of sediment and the results of radiocarbon dating, we select C2 as an index to establish a sequence of 16 000 years of climate change in the Dahu swamp Core. During the period of 16.0-11.5 ka B.P., sensitive component of the overall content is low, the climate and environment of the studied area was relatively dry. During the period of 11.5-6.0 ka B.P., sensitive component of the overall content is low and the climate is wet. During the period of 6.0-3.8 ka B.P., the climate became dry, and sensitive grain-size group content increased. From 3.8 ka B.P. to now, the content of sensitive particle fraction is generally low. Considering the anthropogenic interference factors, this paper does not discuss in detail. The study found that the climate was very unstable through reconstructing the paleoclimate of Dahu lake-swamp area since the Late Glacial. In addition, we can draw a conclusion that climate change of Dahu lake-swamp is global by contrast to the GISP2 ice core climate records and D4 stalagmite in Dongge cave. And we find that the climate change in the study area may be related to solar activity.