晚上新世以来南海北部上部水体结构变化及东亚季风演化

VARIATIONS IN UPPER OCEAN STRUCTURE IN THE SOUTH CHINA SEA AND THE EVOLUTION OF THE EAST ASIAN MONSOONS SINCE LATE PLIOCENE

文章通过对南海大洋钻探 1 1 4 6站有孔虫组合及其壳体氧、碳同位素的研究 ,探讨了南海北部上部水体结构对晚上新世 (3.2～ 2 .0MaB .P .)北极冰盖的形成、扩大的响应。浮游有孔虫混合层和温跃层属种相对百分含量的变化 ,Globigerinoidessacculifer,Pulleniatinaobliquiloculata和Cibicidoideswuellerstorfi种间碳同位素的差值 ,以及底栖有孔虫内生种含量的变化表明 :3.2～ 2 .0MaB .P .期间南海北部混合层、温跃层浮游有孔虫属种的百分含量主要受表层海水温度、生产力变化的控制 ;2 .7MaB .P .前后该区表层海水混合程度、生产力增加 ,上部海水垂直交换增强 ,反映了南海北部上部水体结构变化对北极冰盖的形成、扩张 。

Foraminiferal assemblages and oxygen and carbon isotopic records from ODP core 1146, located at the northern continental slope of the South China Sea, were used to study the response of the upper water column structure to the Late Pliocene (from 3.2 to 2.0MaB.P.) climatic changes. Variations in the relative abundance of planktonic foraminiferal assemblages, isotopic differences among Globigerinoides sacculifer, Pulleniatina obliquiloculata and Cibicidoides wuellerstorfi , and abundance of beneath foraminiferal infaunal species show that the abundances of mixed layer species (G. ruber and G. sacculifer groups, D. altispira, G. bulloides, G. rubescens, and G. glutinata ) and thermocline dwellers (G. menardii and Neogloboquadrina groups, G. margaritae, P. obliquiloculata, G. calida, G. eaquilateralis, and S. dehiscens) of planktonic foraminifera were controlled by sea surface temperature and primary productivity. After 2.7MaB.P., the abundance of mixed layer species decreased, while the high productivity species and Δδ 13 C among mixed layer, thermocline, and deep water species increased. These changes indicate that mixed layer depth, primary productivity and vertical exchange were enhanced, accompanied by the strengthening of the East Asian winter monsoon, which in turn is associated with the progressive intensification of glaciation in the Northern Hemisphere.