西菲律宾海190 ka以来钙质超微化石的氧碳同位素记录

对西菲律宾海Ph05-5柱状样190ka以来钙质超微化石进行了氧碳同位素分析.研究结果表明, 钙质超微化石δ18O值在末次间冰期(MIS 5e) 和全新世明显低于末次冰期(MIS5d~2) 和倒数第二次冰期(MIS6).超微化石δ18O值与浮游和底栖有孔虫δ18O值都呈明显的正相关关系, 但超微化石δ18O平均值比浮游有孔虫Globigerinoides rubber δ18O平均值高0.431×10-3, 比Neogloboquadrina dutertrei δ18O平均值低0.410×10-3, 而这三者又远远低于底栖有孔虫Cibicides wullerstorfi的δ18O平均值.超微化石δ13C值变化阶段性特征明显, 并与该孔超微化石绝对丰度变化趋势极为相似, 二者共同反映出西菲律宾海大约从190ka到110ka的MIS6和大约MIS 5e期, 表层海水初级生产力相当稳定且显著低于其他各时期; 大约从MIS5d期开始表层初级生产力显著上升, 初级生产力的这一高值一致持续到约25ka左右的末次冰期; 在25ka以来的MIS1、2期, 表层初级生产力有所下降, 但仍高于190ka到110ka的MIS6和MIS 5e期. 

Oxygen and Carbon Isotope Records of Calcareous Nannofossils from the West Philippine Sea during the Last 190 ka

The piston core Ph05-5 recovered from the West Philippine Sea (16.049 3°N, 124.344 8°E, water depth 3 382 m) was used to study the δ18O and δ13C variations of calcareous nannofossils.The δ18O values of calcareous nannofossils were obviously lower in Holocene and the last interglaciation than those in the last and the penultimate glaciation.During the last 190 ka the nannofossil δ18O values were positively correlated with those of planktonic and benthic foraminifera from the same core.But the average δ18O value of nannofossils was 0.431×10-3, higher than that of planktonic foraminifera Globigerinoides rubber, and was 0.410×10-3, lower than that of planktonic foraminifera Neogloboquad rina dutertrei.All the above three average δ18O values were much lower than those of benthic foraminifera Cibicides wullerstorfi.The change of nannofossil δ13C values showed similar trends with the absolute abundance of calcareous nannofossils in core Ph05-5, which also indicates the primary productivity variations in the West Philippine Sea.The primary productivity stayed at a stable but relatively low level at MIS 6 and MIS 5e.There was an abrupt rise at the beginning of MIS 5d for the primary productivity which retained high value until 25 ka BP.The primary productivity showed a slight decline during MIS 2 and MIS 1, but still higher than that of MIS 6 and MIS 5e.