Neodymium isotopes in benthic foraminifera from the South Atlantic@en

Records of the past neodymium (Nd) isotope composition of the deep ocean can resolve ambiguities in the interpretation of other tracers. We present the first Nd isotope data for sedimentary benthic foraminifera. Comparison of the epsilon-Nd of core-top foraminifera from a depth transect on the Cape Basin side of the Walvis Ridge to published seawater data, and to the modern dissolved SiO2- epsilon-Nd trend of the deep Atlantic, suggests that benthic foraminifera represent a reliable archive of the deep water Nd isotope composition. Neodymium isotope values of benthic foraminifera from ODP Site 1264A (Angola Basin side of the Walvis Ridge) from the last 8 Ma agree with Fe-Mn oxide coatings from the same samples and are also broadly consistent with existing fish teeth data for the deep South Atlantic, yielding confidence in the preservation of the marine Nd isotope signal in all these archives. The marine origin of the Nd in the coatings is confirmed by their marine Sr isotope values. These important results allow application of the technique to down-core samples. […]重建深海过去的钕（Nd）同位素组成，可消除其他地球化学示踪剂解译中的多解性问题。本研究首次报道了沉积底栖有孔虫的钕同位素数据。将沃尔维斯脊开普盆地一侧深度断面的表层沉积物有孔虫的εNd（epsilon-Nd）值，与已发表的海水数据以及大西洋深部现代溶解态SiO₂-εNd趋势进行对比后发现，底栖有孔虫可作为深水钕同位素组成的可靠记录载体。采自沃尔维斯脊安哥拉盆地一侧的大洋钻探计划（Ocean Drilling Program, ODP）1264A站位过去8百万年的底栖有孔虫钕同位素值，与同一样品中的铁锰氧化物包膜数据一致，同时也与南大西洋深部已发表的鱼牙数据大体吻合，这证实了所有上述记录介质均能保存海洋钕同位素信号。包膜中的钕源自海洋，这一点可通过其海洋锶同位素比值得到验证。上述重要发现为该技术应用于岩心剖面样品奠定了基础。[…]