Rapid onset of ocean anoxia shown by high U and low Mo isotope compositions of sapropel S1
Rapid onset of ocean anoxia shown by high U and low Mo isotope compositions of sapropel S1
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DOI：
10.7185/geochemlet.2027
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发表时间：
2020-09
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影响因子：
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通讯作者：
M. B. Andersen;A. Matthews;M. Bar-Matthews;D. Vance
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作者：
M. B. Andersen;A. Matthews;M. Bar-Matthews;D. Vance
土井：10.7185/geochemlet.2027全新世腐泥S1的自生铀同位素组成（δUauth= 0.10至0.52 ‰; ODP岩芯967，2550 mbsl）明显高于与沉积物铀吸收的迁移-孔隙水扩散模型相关的拟议上限（0.2 ‰）。结果表明，这些高δUauth值是兼容的快速初始减缓的温盐翻转和缺氧水柱的发展。这些条件将有利于U吸收在沉积物-水界面上的有机物丰富的絮体层。高的δUauth值与低的δMoauth值（0.02至-0.88 ‰）相关，解释为反映了由硫代钼酸盐-水溶液平衡控制的弱富氧条件。S1数据与来自同一岩芯的末次间冰期腐泥S5的已发表数据形成明显对比，后者显示出与有限的富氧盆地相一致的δUauth和δMoauth特征，这是由于温盐环流的逐渐减缓。S1的铀-钼同位素数据与一系列已发表的古环境相似。因此，腐泥被证明是有用的模板解开生产力和深水更新时间在古代设置之间的相互作用。收到2019年12月20日|2020年7月14日接受|发布2九月2020
doi: 10.7185/geochemlet.2027 Authigenic uranium isotope compositions of Holocene sapropel S1 (δUauth=þ 0.10 to þ0.52 ‰; ODP core 967, 2550 mbsl) are significantly higher than the proposed upper boundary (þ0.2 ‰) associated with the transport-porewater diffusion model for sediment uranium uptake. It is shown that these high δUauth values are compatible with rapid initial slowdown of thermohaline overturning and the development of an anoxic water column. These conditions would favour U uptake in an organic-rich floccule layer overlying the sediment-water interface. The high δUauth values correlate with low δMoauth values (þ0.02 to −0.88‰), interpreted to reflect weakly euxinic conditions controlled by thiomolybdate–molybdate solution equilibria. The S1 data contrast markedly with published data from last interglacial sapropel S5 from the same core, which show δUauth and δMoauth characteristics compatible with a restricted euxinic basin due to progressive slowdown in the thermohaline circulation. The U-Mo isotope data for S1 are similar to a range of published palaeosettings. Sapropels are therefore shown to be useful templates for the unravelling of the interplay between productivity and deep water renewal times in ancient settings. Received 20 December 2019 | Accepted 14 July 2020 | Published 2 September 2020