越南岸外上升流区45万年来上层海水变化的颗石藻证据

对位于南海西部越南岸外的MD05-2901柱状样45万年以来深海沉积样品进行了颗石藻分析,通过Florisphaera profunda百分含量讨论了营养跃层深度变化的趋势,并利用Beaufort等的经验公式计算了初级生产力。结果表明,45万年以来越南岸外上升流区海水营养跃层深度和初级生产力都经历了4个比较明显的变化阶段。频谱分析表明该区F.profunda百分含量和初级生产力都受到岁差和半岁差周期的控制。与南海南部ODP1143站研究资料对比表明,两地区上层海水变化趋势基本一致,都受到东亚夏季风和地球轨道岁差和半岁差周期的驱动。

COCCOLITH EVIDENCE FOR VARIATIONS IN UPPER OCEAN WATER IN UPWELLING AREA OFF THE COAST OF VIETNAM FOR THE PAST 450 000 YEARS

Florisphaera profunda is one of the lower euphotic zone species of coccolithophores. Using its percentage we can reconstruct the variations in the upper ocean water such as the depth of nutricline and the primary productivity. Coccolith analysis has been carried out for the past 450 ka sediment from core MD05-2901 off the Vietnam coast in the western South China Sea. The results show that the depth of nutricline and primary productivity of surface water have experienced significant changes. The spectral analysis indicates that the percentage of F. profunda is influenced by low latitude process such as precession and half-precession. Comparison of F. profuuda percentage and primary productivity between the present core and ODP Site 1143 of the southern South China Sea indicates that the two sites have a similar trend in the upper ocean water change since 450 ka which are controlled by changes of Asian monsoon and orbital forcing.