(Table 1) Relative abundance of planktonic foraminifers in ODP Hole 164-997A sediments

Hole 997A was drilled during Leg 164 of the Ocean Drilling Program at a depth of 2770 m on the topographic crest of the Blake Ridge in the western Atlantic Ocean. We report here an analysis of the faunal assemblages of planktonic foraminifers in a total of 91 samples (0.39-91.89 mbsf interval) spanning the last 2.15 m.y., latest Pliocene to Holocene. The abundant species, Globigerinoides ruber, Globigerinoides sacculifer, Neogloboquadrina dutertrei, Globorotalia inflata, and Globigerinita glutinata together exceed over ~70% of the total fauna. Each species exhibits fluctuations with amplitudes of 10%-20% or more. Despite their generally low abundance, the distinct presence/absence behavior of the Globorotalia menardii group is almost synchronous with glacial-interglacial climate cycles during the upper part of Brunhes Chron.

本研究涉及的997A钻孔，系西大西洋布雷克海岭（Blake Ridge）地形脊线处的大洋钻探计划（Ocean Drilling Program）第164航次钻孔，该站位水深为2770米。本文报道了覆盖距今215万年（2.15百万年，m.y.）、年代跨度为上新世晚期至全新世的91个沉积物样品（采样层位为海底以下0.39~91.89米，meters below sea floor, mbsf）的浮游有孔虫（planktonic foraminifers）动物群组合（faunal assemblages）分析结果。本次研究识别出5种优势浮游有孔虫物种，分别为红拟抱球虫（*Globigerinoides ruber*）、袋拟抱球虫（*Globigerinoides sacculifer*）、杜氏新弯球虫（*Neogloboquadrina dutertrei*）、膨胀抱球虫（*Globorotalia inflata*）以及胶粘抱球虫（*Globigerinita glutinata*），其总丰度占浮游有孔虫总群落的70%以上。各优势物种的丰度均存在10%~20%及以上幅度的波动。尽管曼德德抱球虫群（*Globorotalia menardii group*）整体丰度较低，但其在布容正极性时（Brunhes Chron）上部地层中的出现与缺失变化，几乎与冰期-间冰期气候旋回同步。