早第四纪西太平洋底栖有孔虫群与大洋深层水环流演化的关系

EVOLUTION OF EARLY PLEISTOCENE DEEP WATER CIRCULATION IN WESTERN PACIFIC:EVIDENCE FROM BENTHIC FORAMINIFERA

选取赤道西太平洋ODP 807站位(3°36.42′N,156°37.49′E,水深2 803.8m,岩心长822.9m)26.27～43.02mbsf层段中的底栖有孔虫进行研究,以便了解早更新世2.5～1.6Ma BP时期古生产力和深水环流的变化。结果显示,这一时期底栖有孔虫堆积速率(BFAR)、表生种和内生种比值(E/I)、Uvigerina spp.百分含量和有机碳百分含量(TOC%)等替代指标反映了西太平洋古生产力总体上呈现冰期高、间冰期低的特点,而其中Bulimina alazanensis的丰度变化则相反,反映了该种有可能更适合温暖、低营养的底层水环境。2.5～1.6 MaBP时期底栖有孔虫在丰度上以Uvigerina spp.为主,指示了早更新世西太平洋深层水受北部水团的控制更强。

Benthic foraminifera picked out from the interval of 43.02-26.27 mbsf （meters below seafloor） of ODP 807（（°36.42′N,156°37.49′E,,water depth 2 803.8 re,length 822.9 re）on the Ontong-Java Plateau, western Pacific was studied for understanding the changes in paleoproductivity and its relation with deep water circulation during the period of 2.5 -1.6 MaBP. The benthic foraminifera accumulation rate （BFAR）, Epifaunal/Infaunal ratio （E/I）, percentage of Uvigerina spp. and total organic carbon （TOC~） were used as the proxies of paleoproductivity in this study. Results show that the change in paleoproduc- tivity was generaly high in glacials but low in interglacials during the period of 2.5 ~ 1.6 MaBP. , except Bulimina alazanensis, of which the paleopruductivity was low in glacials but high in interglacials. It may suggest that B. alazanensis, opposite to the others, preferred a warmer environment with lower nutrients. The benthic foraminiferal fauna was dominated by Uvigerina spp. in the samples, indicating that the west- ern Pacific deep water was under the control of the North Pacific Deep Water Mass during Early Pleisto- cene.