热带东太平洋晚第四纪的古海洋及古气候记录

Late Quaternary Paleoceanographic and Paleoclimatic Records in the Tropical East Pacific Ocean

热带东太平洋8001柱状样晚第四纪以来放射虫标志种Buccinosphareainvaginata和Collosphaeratuberosa的研究发现,它们的初现面(FAD)出现于柱深22cm和45cm处,年龄分别为0.21Ma和0.42Ma.它们的初现面年龄与SPECMAP氧同位素记录结合为该柱建立了地层框架.该柱放射虫丰度、生源蛋白石和有机碳含量、粒度的分析显示,大约在氧同位素11、9～8.4、5～3和1期,高的放射虫总丰度、第四纪常见种丰度和始新世-渐新世种丰度大致对应于高的中值粒径和平均粒径,以及大约氧同位素5期以来增加的有机碳含量,表明此期间贸易风增强,搬运的陆源颗粒增大,北赤道洋流加强,导致上升流增强,表层水生产力提高,同时,南极底层流的活动也加强.大约在氧同位素10、8.3～6和2期,低的放射虫总丰度、第四纪常见种丰度和始新世-渐新世种丰度大致对应于减小的中值粒径和平均粒径,反映此期间贸易风减弱,搬运的陆源颗粒减小,北赤道洋流减弱,导致上升流消失,表层水生产力降低,同时,南极底层流的活动也减弱.

Radiolarians studied in Core 8001 of the northeast equatorial Pacific show that the first appearance datum （FAD） of Buccinospharea invaginata and Collosphaera tuberosa occur at depths of 22 and 45 era respectively, and their FAD ages are 0. 21 and 0. 42 Ma. The stratigraphic framework of this core is established by the combination of the two FAD ages with the SPECMAP isotopic records in deep-sea sediments. Variations of radiolarian abundance, biogenic opal, organic carbon and grain size in this core indicate that the high radiotarian abundance during the MIS 11, 9- 8.4, 5- 3 and 1, with the high abundance of Quaternary and Eocene-Oligocene species, corresponds to the high median and mean grain sizes. Organic carbon increased during the MIS 5, reflecting the enhancing trade wind, which brought on increasing grain size in conveyed terrestrial detritus. The intensive north equatorial current led to the upwelling becoming stronger and high surface productivity, together with enhanced activity in the Antarctic bottom water. The low radiolarian abundance during the MIS 10, 8. 3-6 and 2, coinciding with the low abundances of the Quaternary and Eocene-Oligocene species, corresponds to low median and mean grain sizes. This implies the weak trade wind caused the decreasing grain size of the transported terrestrial detritus and the slack north equatorial current resulted in the weak upwelling and low surface productivity, coming along the weak activity of the Antarctic bottom water.