末次冰期以来冲绳海槽北部古气候变化的孢粉记录

通过分析冲绳海槽北部CSH1柱状样的孢粉组合,重建了海槽区邻近岛屿末次冰期以来的植被和气候变化史.将所测岩心的孢粉记录从下到上分为三期:Ⅰ期为热带山地针叶林的繁盛期,松属及亚热带高山的常绿针叶林含量较高,气候干燥温暖;Ⅱ期为旱生草本植物繁盛期,蒿属大量出现,气候干冷;Ⅲ期为常绿阔叶、落叶阔叶林及蕨类植物繁盛期,常绿阔叶及落叶阔叶林成分增加,蕨类孢子达到极高值,草本植物含量剧减,气候温暖潮湿.将一些主要科属花粉的百分含量曲线与格陵兰冰心GISP2δ18O曲线进行了对比分析,发现各花粉百分含量曲线分别在距今4.1~4.6,11.7~13.0,15.4,23.2,29.4,47.4ka显示出了一系列明显的次级波动,这些次级波动与格陵兰冰心δ18O曲线所记录的4ka左右的降温事件、新仙女木(Younger Dryas)事件和Heinrich事件H1,H2,H3和H5在时代上相吻合.尽管格陵兰及北大西洋地区的气候变化影响冲绳海槽地区的途径和载体尚不清楚,但北半球高纬度的气候变化所引发的东亚季风强度在数百年或千年尺度的波动可能是其主要的机制.

The paleoclimatic change since the last glaciation in the north of Okinawa Trough based on the spore-pollen records

On the basis of spore-pollen assemblage analysis in the piston core CSH.collected in the northern Okinawa Trough,the history of vegetation and climatic variation on islands nearby the Okinawa Trough during the Last Glaciation was reconstructed.The shape of spore-pollen curves makes it possible to subdivide the succession into different time inter vals.PeriodⅠis the prosperous period of torpic serra coniferous forest,when pinus and semitropical alpine aiphyllus coniferous forest flourished.The derived spore-pollen assem blage suggests that the paleoclimate during that period is arid and warm.PeriodⅡis a prosperous period of xerolphitic herbage,when Artemisia plants prosper,which suggests the climate is xeric and large-scale marine regression may have occurred.Period Ⅲ is the prosperous period for everg reen latifoliate forest,the decilious broadleaved forest increases,the relative abundance of ferns spore reaches the maximum while herbs decreases rapidly,which suggests it is warm and humid.Atotal of six cooling events were identified based on the curves of some especial pollens,these cold events occurred at 4.1~4.6,11.7~13.0,15.4,23.2,29.4 and 47.4 ka BP respectively and showed good correlation with the coldest stadials of Dansgaard-Oeschgercy cles documented in the record of δ18O from the Greenland GRIP ice core,which correspond to the Younger Dry as event and the four Heinrich events H1,H2,H3 and H5.