【摘要】 以南海北、西、南部3个沉积速率相对较高而且连续的沉积柱状样MD2904,MD2901和MD2897为基础,通过粒度、碳酸盐、有机地球化学和元素分析,并综合前人研究成果,对南海MIS3期进行探讨。结果显示,南海MIS3是末次冰期中的弱暖期,海水表层古温度比相邻的MIS2和MIS4期略高,但是明显比MIS1和MIS5期低。MIS3的最大特点就在于其气候的不稳定性,发生了多次气候快速变化事件。在格陵兰冰芯中记录的千年尺度快速气候变化事件(D/O事件和Heinrich事件)基本上在南海北、西、南部都有响应,具有与全球同步的特征。南海MIS3古生产力都显示出较高的特点,这与东亚季风有着密切的关系,北部主要受冬季风影响,西部和南部主要受夏季风影响。南海南部MIS3表现出比MIS5更高的古生产力和更强的夏季风强度,这一特点有待更进一步深入研究。更多还原

【Abstract】 Marine Isotope Stage 3(MIS 3,5.9～2.4kaB.P.)is an interstadial during the Last Glaciation.Many paleoclimatologists and marine geologists have paid attentions to it because it is characterized by millennial-to submillennial-scale variations,such as the Heinrich events and Dansgaard-Oeschger events.The most prominent feature of MIS 3 is the climatic instability,which is found in ice core records,loess section,lacustrine sediments,stalagmite records,and deep sea sediment cores.Three cores(MD2904,MD2901,and MD2897)from the northern,western,and southern slopes of South China Sea respectively,were studied to depict the paleoceanographic features of the South China Sea during MIS 3.Through analyses of grain size,carbonate content,organic geochemistry,and element compositions,incorporating with previous research,the paleoclimatic and paleoceanographic conditions during MIS 3 in the South China Sea were reviewed.Results indicated that MIS 3 is a relatively warm period within the Last Glaciation.SSTs during MIS 3 are slightly higher than MIS 2 and MIS 4 and significantly lower thanMIS 1 andMIS 5.SST estimated by using the Uk37 alkenone index shows that SSTs vary between 21.66℃ and 24.66℃ in the northern part of South China Sea,and decreased at 24kaB.P.,29kaB.P.,39kaB.P.,45.8kaB.P.,54kaB.P.,and 59.5kaB.P.,corresponding with Heinrich 2～6 events.SSTs in the south varied from 24.4℃ to 26.0 ℃.SSTs estimated by planktonic foraminiferal transfer function(FP-12E)shows that SSTs change from 23.0℃ to 26.5℃ during winter,from 28.5℃ to 29.7℃ during summer in the west.Millennium-scale rapid climatic events(D/O events and the Heinrich events)recorded in Greenland Ice Core have responded in the northern,western,and southern South China Sea,with global synchronization features respectively.During the later phase of MIS 3(40～30kaB.P.),the"High Temperature and Large Precipitation Event",which was first found in the Tibetan Plateau,is not distinctly displayed in the South China Sea and only shows a little stronger trend in the southern part of the South China Sea.Grain-size analysis reveals that 8～25μm size fraction in the north,30.1～43.7μm in the west,and 3～5μm in the south have obvious glacial/interglacial cycles,which may indicate the changes of sea level.Sea level of MIS 3 is higher than MIS 2 and MIS 4,but lower thanMIS 5.MIS 3 of South China Sea shows high paleoproductivity,which has close relations to East Asian monsoon.During MIS 3,winter monsoon was dominant in northern South China Sea,and summer monsoon was dominant in the west and south.Paleoproductivity of MIS 3 in the north is higher than MIS 1 and MIS 5,but lower than MIS 2 and MIS 4.In the west,paleoproductivity of MIS 3 is the highest since 150kaB.P.and changes greatly.In the south,paleoproductivity of the interglacial is higher than that of glacial.The productivity,and by inference,monsoon intensity in the southern South China Sea during MIS 3 is greater than that duringMIS 5,a feature needs further study.更多还原