太湖东部平原平望孔全新世环境演变地层记录

通过对太湖东部平原平望钻孔的年代、有孔虫和孢粉分析,探讨了该区域全新世植被变化与环境特征。结果显示全新世(11.5 kaBP)以来,太湖东部平原未受到广泛海侵的影响,主要是以淡水湖泊-沼泽沉积为主。该区域在4 kaBP以后,才有大面积的水稻种植。11.0—9.1 kaBP,以常绿-落叶阔叶林为主,花粉浓度较小,木本植物和水生湿生植物花粉含量增加,整体环境温凉偏干,但湿度逐渐增大,指示东亚季风逐渐加强。9.1—5.8 kaBP,花粉浓度最大,木本植物花粉含量略有减小,草本植物含量明显增加,主要是水生、湿生花粉的含量增加明显,平均达到32%,藻类含量为整个钻孔最大,其中在8—7 kaBP前后常绿类花粉含量较大,水生湿生花粉、淡水藻类的含量达到整个剖面最大,推测此时区域湿度最大,东亚夏季风最为强盛。5.8—1.3 kaBP常绿阔叶林百分比含量增加,落叶阔叶花粉含量减少,陆生草本植物的含量增加,水生湿生草本的含量减小,主要以常绿-落叶阔叶林为主,环境较前一带略干,东亚夏季风减弱。

ENVIRONMENTAL EVOLUTION OF EASTERN TAIHU PLAIN DURING THE HOLOCENE ACHIEVED BY PINGWANG CORE

The paper showed the vegetation and environmental change in the Pingwang area of eastern Taihu Plain during the Holocene, using pollen, foraminifera and AMS14C dating. The eastern Taihu Plain was not affected by the transgression during the Holocene (11.5-0 kaBP), and the area was mainly dominated by fresh water lakes-marshes. Pollen data showed that the area was mainly dominated by evergreen - deciduous forest and the climate was cool and dry during the period of 11.0 ka-10.4 kaBP. Pollen concentration was minimum in I zone, and the tree pollen percentage reached the lowest, and herbaceous plants were 65.8% on average which contain a lot of terrestrial herbs. Pollen concentration increased, and the tree content changed little during the period of 10.4 ka-9.1 kaBP. Aquatic pollen content and algae content increased, showing the increasing temperature and precipitation. 9.1 ka-5.8 kaBP pollen concentration was the largest during the Holocene, and evergreen broad-leaved forest vegetation was the main forest. Aquatic pollen increased sharply to 32%. The content of freshwater algae was the largest during the Holocene, which indicates the most humid and most powerful East Asian monsoon, especially for the period of 8-7 kaBP in Taihu Lake Plain. The evergreen components increased, and the deciduous broad component reduced during the period of 5.8 ka-1.3 kaBP. Terrestrial herb increased to a high level, while aquatic herbaceous decreased and concentration of algae reduced, indicating the dry and cool climate, and the intensity of monsoon gradually reduced.