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首页> 外文期刊>Paleoceanography >Authigenic uranium in foraminiferal coatings: A proxy for ocean redox chemistry
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Authigenic uranium in foraminiferal coatings: A proxy for ocean redox chemistry

机译：有孔虫涂层中的自生铀：海洋氧化还原化学的代表

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摘要

The rate of uranium accumulation in oceanic sediments from seawater is controlled by bottom water oxygen concentrations and organic carbon fluxes-two parameters that are linked to deep ocean storage of CO _2. To investigate glacial-interglacial changes in what is known as authigenic U, we have developed a rapid method for its determination as a simple addition to a procedure for foraminiferal trace element analysis. Foraminiferal calcite acts as a low U substrate (U/Ca < 15 nmol/mol) upon which authigenic U accumulates in reducing sediments. We measured a downcore record of foraminiferal U/Ca from ODP Site 1090 in the South Atlantic and found that U/Ca ratios increase by 70-320 nmol/mol during glacial intervals. There is a significant correlation between U/Ca records of benthic and planktonic foraminiferal species and between U/Ca and bulk sediment authigenic U. These results indicate that elevated U/Ca ratios are attributable to the accumulation of authigenic U coatings in sediments. Foraminiferal Mn/Ca ratios were lower during the glacial intervals, suggesting that the observed U accumulation on the shells is not directly linked to U incorporation into secondary manganese phases. Thus, foraminiferal U/Ca ratios may provide useful information on past changes in sediment redox conditions.
机译：海水中铀在海洋沉积物中的蓄积速率受底部氧气浓度和有机碳通量控制，这两个参数与深海CO _2储存有关。为了调查所谓的自生U中的冰间变化，我们开发了一种快速测定方法，作为有孔虫微量元素分析程序的简单补充。有孔虫方解石充当低U底物（U / Ca <15 nmol / mol），在该底物上，自生U积累在减少沉积物中。我们测量了南大西洋ODP站点1090的有孔虫U / Ca的下限记录，发现在冰川间隔期间U / Ca比值增加了70-320 nmol / mol。底栖和浮游有孔虫物种的U / Ca记录与U / Ca和大量沉积物自生U之间存在显着相关性。这些结果表明，U / Ca比率升高归因于沉积物中自生U涂层的积累。在冰川期，有孔虫的Mn / Ca比值较低，这表明观察到的铀在壳上的蓄积与铀掺入次生锰相并不直接相关。因此，有孔虫的U / Ca比值可以提供有关沉积物氧化还原条件过去变化的有用信息。

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