南海北部一百万年以来的表层古生产力变化:来自ODP1144站的蛋白石记录

Paleoproductivity Variability of the Northern South China Sea during the Past 1 Ma: The Opal Record from ODP Site 1144

通过南海北部ODP 1144站蛋白石含量测定及其堆积速率的计算,并结合氧同位素记录等相关资料,获得南海北部1050ka以来高分辨率的表层古生产力变化与冰期旋回和东亚季风的关系。约900ka以来,蛋白石含量及其堆积速率较900ka以前明显增加,反映了“中更新世革命”事件之后,全球气候变冷,并导致表层生产力的提高。由于第四纪冰期旋回中的冬、夏季风的加强,加上1144站特殊的地理位置,使该站在冰期时表层生产力增加,间冰期时表层生产力降低。浮游有孔虫氧同位素记录与蛋白石含量及其堆积速率的时间序列频谱分析结果显示,三者均出现了相对应的偏心率周期、斜率周期和岁差周期,说明该站表层生产力的变化主要受地球轨道周期的驱动。

A biogenic silica analysis was performed on 857 samples at ODP Site 1144 in the northern South China Sea. The correlation of opal content and MAR with oxygen isotopic records of plankton foraminifera shows that they increased during glacial periods and decreased during interglacial. The increases of opal content and MAR after the middle Pleistocene (about 0. 9 Ma) result from the higher surface productivity, which was induced by the intensified monsoon circulation after the ' Mid ?Pleistocene Revolution' and the special situation of Site 1144. The time ?sequence spectral analyses of oxygen isotopic record, opal content and MAR reveal that the variability of the surface productivity were dominantly forced by the earth orbital cycles.