Relative abundance of major benthic foraminiferal assembalges and total organic carbon content at IODP Site U1391 during the past 1.3 myr

R-mode cluster analysis of foraminiferal census data from the >250 μm fraction reveals six associations. Two of them are closely related to productivity. Association A is composed of miliolids and Cibicidoides pachyderma. Association B consists of Shpaeroidina bulloides, agglutinated taxa, Uvigerina peregrina parva and Lenticulina. Periods of high productivity are marked by high relative abundance of Association B, while low productivity is marked by the dominance of Association A. The faunal record indicates higher productivity during the interglacial periods and the interstadial stages, supported by the reliable productivity proxy—the total organic carbon content (TOC) of the sediments. The relative abundance of Association B is significantly correlated with ETP (a normalized and summed record of three Earth’s orbital parameters) in the ~41-kyr obliquity band, suggesting that the Earth’s obliquity is probably the primary driver of variability in ocean productivity off the Portuguese margin.对>250微米粒级组分（>250 μm fraction）的有孔虫计数数据（foraminiferal census data）开展R型聚类分析（R-mode cluster analysis），结果识别出6个有孔虫组合。其中两个组合与海洋生产力密切相关：组合A由粟孔虫类（miliolids）和厚壁卷管虫（Cibicidoides pachyderma）组成；组合B则包含Shpaeroidina bulloides、胶结质有孔虫类（agglutinated taxa）、小型异地卷泡虫（Uvigerina peregrina parva）以及透镜虫属（Lenticulina）。高生产力时期以组合B的相对丰度显著升高为标志，低生产力时期则以组合A占主导为特征。该有孔虫动物群记录显示，间冰期（interglacial periods）与间冰阶（interstadial stages）的海洋生产力更高，这一结论得到了可靠的生产力代用指标——沉积物总有机碳（total organic carbon, TOC）含量的支持。组合B的相对丰度与~41千年尺度倾斜度波段（obliquity band）内的ETP（三种地球轨道参数的归一化求和记录）呈显著相关关系，表明地球倾斜极有可能是控制葡萄牙陆缘（Portuguese margin）近海海洋生产力变化的主要驱动因素。