南海西沙海槽近120ka以来的浮游有孔虫特征及其古气候意义

PLANKTONIC FORAMINIFERA IN THE XISHA TROUGH OF THE SOUTH CHINA SEA DURING THE LAST 120 KA AND THEIR PALEOCLIMATIC IMPLICATIONS

对南海西沙海槽83PC柱状样浮游有孔虫进行了定量分析鉴定和氧碳同位素测试，结合碳酸盐含量及AMS14C测年，并采用古生态转换函数FP—12E计算了表层海水古温度，揭示了该海区近120ka以来的古环境气候特征。浮游有孔虫分析显示冰期丰度低而间冰期丰度高，暖水种的百分含量随冰期一间冰期旋回而变化，温凉水种MIS5期以来百分含量逐渐降低。转换函数计算结果表明，冬季温度的变化范围为21．3～26．4℃，夏季温度的变化范围为28．2～29．5℃，季节温差为2．7～6．9℃。与南海南部转换函数古温度对比表明，MIs2-MIS5期南海南部和北部的温差较明显，反映北半球冰盖扩张和东亚季风强盛，冰期时南海南北的温差梯度进一步增大，指示冰期时冬季风增强。研究区在末次冰期以来出现短期气候快速变冷的新仙女木事件和多次Heinrich事件，说明全球性气候变化事件在南海也有沉积记录。

Planktonic foraminifera from the core 83PC in the Xisha Trough of the northern South China Sea （SCS） have been quantitatively analyzed. The microfaunal analytical results, combined with oxygen and carbon isotopes, carbonate content and AMS14C dating data, are used in this paper to reveal paleoceano- graphic characteristics of the study area during the last ~120 ka. The distribution of planktonic foraminif- era shows that the abundance decreased in glacial periods, warm water species were sensitive to tempera- ture changes, and the percentages of cool water species have decreased gradually since MIS5. Sea surface paleotemperature （SST） was estimated via transfer function FP-12E. The calculation results suggest that the winter SST ranged from 21.3 to 26.4℃, the summer SST from 28.2 to 29.5℃, and the SST seasonal- ity from 2.7 to 6.9~C. By comparison with the results from the southern SCS, the SST differences were evident from MIS2 to MISS, which probably resulted from the growth of the Northern Hemisphere ice sheet and the strong East Asian Monsoon, the higher SST differences in glacial periods indicated enhanced winter monsoon. Several obvious short-term SST descending events, including the Younger Dryas and Heinrich events, have been recognized since the last glaciation, suggesting the sedimentary records in re- sponse to the global climatic changes in the SCS.