(Table 1) Planktonic foraminifera counts and stable oxygen isotope ratios of Pacific Ocean surface sediments

Core-top samples from the eastern tropical Pacific (10°N to 20°S) were used to test whether the ratio between Globorotalia menardii cultrata and Neogloboquadrina dutertrei abundance (Rc/d) and the oxygen isotope composition (?18O) of planktonic foraminifera can be used as proxies for the latitudinal position of the Equatorial Front. Specifically, this study compares the ?18O values of eight species of planktonic foraminifera (Globigerinoides ruber sensu stricto (ss) and sensu lato (sl), Globigerinoides sacculifer, Globigerinoides triloba, Pulleniatina obliquiloculata, Neogloboquadrina dutertrei, Globorotalia menardii menardii, Globorotalia menardii cultrata and Globorotalia tumida) with the seasonal hydrography of the region, and evaluates the application of each species or combination of species for paleoceanographic reconstructions. The results are consistent with sea surface temperature and water column stratification patterns. We found that in samples north of 1°N, the Rc/d values tend to be higher and d18O values of G. ruber, G. sacculifer, G. triloba, P. obliquiloculata, N. dutertrei, and G. menardii cultrata tend to be lower than those from samples located south of 1°N. We suggest that the combined use of Rc/d and the d18O difference between G. ruber and G. tumida or between P. obliquiloculata and G. tumida are the most suitable tools for reconstructing changes in the latitudinal position of the Equatorial Front and changes in the thermal stratification of the upper water column in the eastern tropical Pacific.本研究采用东热带太平洋（10°N至20°S）的核心表层样品，验证浮游有孔虫（planktonic foraminifera）门氏圆球虫剑状亚种（Globorotalia menardii cultrata）与杜氏新方球虫（Neogloboquadrina dutertrei）的丰度比值（Rc/d）及其氧同位素组成（δ¹⁸O）能否作为赤道锋面（Equatorial Front）纬度位置的代用指标。具体而言，本研究对比了8种浮游有孔虫的δ¹⁸O值，涵盖红拟抱球虫严格型（Globigerinoides ruber sensu stricto, ss）与广义型（Globigerinoides ruber sensu lato, sl）、袋拟抱球虫（Globigerinoides sacculifer）、三叶拟抱球虫（Globigerinoides triloba）、斜室普林虫（Pulleniatina obliquiloculata）、杜氏新方球虫（Neogloboquadrina dutertrei）、门氏圆球虫指名亚种（Globorotalia menardii menardii）、门氏圆球虫剑状亚种（Globorotalia menardii cultrata）以及膨圆圆球虫（Globorotalia tumida），并将上述同位素值与该区域的季节性水文特征进行比对，同时评估各单物种或物种组合在古海洋重建（paleoceanographic reconstructions）中的应用潜力。研究结果与海表温度及水层分层模式高度一致。我们发现，在1°N以北的样品中，Rc/d值整体偏高，且红拟抱球虫、袋拟抱球虫、三叶拟抱球虫、斜室普林虫、杜氏新方球虫以及门氏圆球虫剑状亚种的δ¹⁸O值普遍低于1°N以南的样品。综上，我们认为联合使用Rc/d比值与红拟抱球虫和膨圆圆球虫的δ¹⁸O差值，或斜室普林虫与膨圆圆球虫的δ¹⁸O差值，是重建东热带太平洋赤道锋面纬度位置变化及上层水柱热分层变化的最优手段。