The use of foraminifera as a record of the past neodymium isotope composition of seawater
The use of foraminifera as a record of the past neodymium isotope composition of seawater
复制标题
利用有孔虫作为过去海水钕同位素组成的记录
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
N. Slowey
中科院分区：
文献类型：
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作者：
D. Vance;A. Scrivner;Patricia Beney;M. Staubwasser;G. Henderson;N. Slowey
[1]我们提出了新的同位素数据，沉积浮游有孔虫，以及潜在的水柱和沉积源的钕（Nd），这证实有孔虫的同位素组成是相同的表层海水和非常不同的深水和沉积钕。沉积有孔虫记录地表海水Nd的同位素特征的忠实性很难解释，因为它们的Nd/Ca比值变化很大，通常是沉积有孔虫的比值，通常比直接掺入方解石结构的比值高得多。我们提出了进一步的数据表明，在浮游生物拖有孔虫，范围可能是由氧化还原条件控制的水柱中的Nd/Ca比类似的大范围。清洗实验表明，在共同与早期的工作，大量的钕释放清洗与肼和二亚乙基三胺五乙酸，但在每个步骤中释放的钕是表面起源。虽然需要进一步的详细研究，以核实表面同位素签名的确切位置和有孔虫Nd同位素系统学的关键控制，这些新的数据将使用浮游有孔虫作为记录地表水Nd同位素比值，从而在过去的Nd从大陆通过风化和侵蚀的海洋供应的变化，在一个合理的可靠的基础。
[1] We present new isotopic data for sedimentary planktonic foraminifera, as well as for potential water column and sedimentary sources of neodymium (Nd), which confirm that the isotopic composition of the foraminifera is the same as surface seawater and very different from deep water and sedimentary Nd. The faithfulness with which sedimentary foraminifera record the isotopic signature of surface seawater Nd is difficult to explain given their variable and high Nd/Ca ratios, ratios that are often sedimentary foraminifera, ratios that are often much higher than is plausible for direct incorporation within the calcite structure. We present further data that demonstrate a similarly large range in Nd/Ca ratios in plankton tow foraminifera, a range that may be controlled by redox conditions in the water column. Cleaning experiments reveal, in common with earlier work, that large amounts of Nd are released by cleaning with both hydrazine and diethylene triamine penta-acetic acid, but that the Nd released at each step is of surface origin. While further detailed studies are required to verify the exact location of the surface isotopic signature and the key controls on foraminiferal Nd isotope systematics, these new data place the use of planktonic foraminifera as recorders of surface water Nd isotope ratios, and thus of variations in the past supply of Nd to the oceans from the continents via weathering and erosion, on a reasonably sure footing.