北京ZK3钻孔孢粉记录及第四纪古气候变化响应

Sporopollen Records of ZK3 Drilling in Beijing and the Response to the Quaternary Paleoclimate

摘要: 本文选取北京平原沙河凹陷内ZK3钻孔作为研究对象，在建立钻孔第四系格架的基础上，通过孢粉分析重建了北京地区第四纪以来植被演化历史，并以此表征古气候特征。本区早更新世划分出4个孢粉组合带，其中，组合带1反映了以蒿属为主的草原环境，气候冷干；组合带2同样反映了以蒿属为主的草原环境，在某些时段出现水生植物含量高值、蕨类孢子与藻类占优势，反映了植被的波动和湖泊的多次扩张；组合带3反映了以蒿属为主的草原植被环境，气候较上一个阶段稍暖。同时，在某些层位出现水生植物花粉含量高值，反映了气候与植被的波动和湖泊的2次扩张；组合带4以出现柏科花粉浓度升高的特征，表明这一阶段由草原演化为以柏科为建群种的疏林草原环境，气候变得较为冷湿；中更新世划分为组合带5，反映了以蒿属为主的草原环境，气候冷干；晚更新世以来划分为组合带6，反映了以菊科蒿属、藜科为主的草原环境，气候冷干，湖泊多次扩张。本次研究结果与前人研究成果较为吻合。同时，组合带4带所反映的本区早中更新世之交发生的明显的气候变迁在整个中国大陆该时期发生的气候转型均有较好的类比性。

Abstract: In order to further study the Paleoclimate characteristics, ZK3 was selected as the drilling. With building the framework and sporopollen analysis, the history of vegetation evolution since the Quaternary in Beijing is reconstructed. There are four pollen assemblage zones in the Early Pleistocene. The results reflect the grassland environment dominated by Artemisia, cold and dry climate in Assemblage zone 1. The result of assemblage zone 2 is the same as assemblage zone 2, and at some point there is a high level of aquatic plants, and fern spores and algae are dominant, reflecting vegetation fluctuations and multiple expansions of lakes. Artemisia grassland vegetation environment is still dominated in assemblage zone 3 and the climate is slightly warmer than the previous stage. High levels of pollen content in aquatic plants reflect changes in climate and vegetation and the second expansion of lakes as well. The increasing concentration of Cupressaceae pollen in assemblage zone 4 shows that the environment evolved from grassland to Cupressaceae-based savanna and the climate became cooler and more humid. The assemblage zone 5 is the Artemisia-based grassland in the Middle Pleistocene and the climate was cold and dry. The characteristics of assemblage zone 6 reflect that the environment is Asterceae and Chenopodiaceae grassland, the climate is cold and dry, multiple expansion of lakes. The results of this study are in good agreement with those of previous studies. At the same time, the obvious climate change occurred in the Early and Middle Pleistocene of the region, which is reflected by the band 4, has a good analogy in the climate change in the whole of China.