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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Glacial-interglacial variations in the neodymium isotope composition of seawater in the Bay of Bengal recorded by planktonic foraminifera
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Glacial-interglacial variations in the neodymium isotope composition of seawater in the Bay of Bengal recorded by planktonic foraminifera

机译：浮游有孔虫记录的孟加拉湾海水钕同位素组成的冰间变化

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This study presents neodymium isotope and elemental data for cleaned planktonic foraminifera from ODP site 758 in the southernmost reaches of the Bay of Bengal in the north-east Indian Ocean. Cleaning experiments using oxidative- reductive techniques suggest that diagenetic Fe-Mn oxyhydroxide coatings can be effectively removed, and that the measured Nd isotope composition reflects the composition of seawater from which the foraminiferal calcium carbonate was precipitated. Modern core-top Pulleniatina obliquiloculata and Globorotalia menardii give ε_(Nd) values of -10.12 ± 0.16 and -10.28 ± 0.16, respectively, indistinguishable from recent direct measurements of surface seawater in this area. A high-resolution Nd isotope record obtained from G. menardii for the past 150 kyr shows systematic variations (Δε_(Nd) ≈ 3) on glacial-interglacial timescales. The timing of those variations shows a remarkable correspondence with the global oxygen isotope record, which suggests a process controlling the Nd isotope composition that responds in phase with global climate cycles. Palaeoclimate reconstruction indicates that during the last glacial maximum changes in monsoon circulation resulted in a reduction in rainfall over the Indian subcontinent, and a decrease in the flux of river water delivered to the Bay of Bengal. Thus, changes in the riverine input of Nd, a change in either flux or composition, most likely caused the isotope variations, although changes in dust source or local ocean circulation may have also played a role. These results clearly establish a link between climate change and variations in radiogenic isotopes in the oceans, and illustrate the potential of Nd isotopes in foraminifera for high-resolution palaeoceanographic reconstruction.
机译：这项研究提供了印度洋东北部孟加拉湾最南端ODP站点758上清洁浮游有孔虫的钕同位素和元素数据。使用氧化还原技术进行的清洁实验表明，可以有效地去除成岩的Fe-Mn羟基氧化物涂层，并且测得的Nd同位素组成反映了有孔虫碳酸钙从中沉淀出来的海水组成。现代核心顶上的Pleneniatina obliquiloculata和Genborotalia menardii的ε_（Nd）值分别为-10.12±0.16和-10.28±0.16，这与该地区最近对地表海水的直接测量没有区别。从Menardii上获得的高分辨率Nd同位素记录，记录了过去150年的时间，其冰川间时间尺度显示出系统的变化（Δε_（Nd）≈3）。这些变化的时间表明与全球氧同位素记录有着显着的对应关系，这表明控制Nd同位素组成的过程与全球气候周期同相响应。古气候重建表明，在最后一次冰川期，季风环流的最大变化导致印度次大陆的降雨减少，而输送至孟加拉湾的河水流量减少。因此，尽管粉尘源或局部海洋环流的变化也可能起了作用，但是河流中Nd的输入变化，通量或成分的变化很可能导致了同位素的变化。这些结果清楚地建立了气候变化与海洋放射性同位素变化之间的联系，并说明了有孔虫中Nd同位素在高分辨率古海洋学重建中的潜力。

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