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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 >Highly dynamic marine redox state through the Cambrian explosion highlighted by authigenic delta U-238 records
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Highly dynamic marine redox state through the Cambrian explosion highlighted by authigenic delta U-238 records

机译：通过Authigenic Delta U-238记录突出显示的高度动态海洋氧化还原状态

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The history of oceanic oxygenation from the late Neoproterozoic to the early Cambrian is currently debated, making it difficult to gauge whether, and to what extent environmental triggers played a role in shaping the trajectory of metazoan diversification. Uranium isotope (delta U-238) records from carbonates have recently been used to argue for significant swings in the global marine redox state from the late Neoproterozoic to the early Cambrian. However, geochemical signatures in carbonates-the U isotope archive most commonly employed to argue for redox shifts-are susceptible to diagenetic alteration and may have variable offsets from seawater values. Therefore, there is an impetus to reconstruct seawater U isotopic evolution using another sedimentary archive, in order to verify that these excursions can indeed be linked to global shifts in marine redox landscape. Here we report new U isotope data from two fine-grained siliciclastic upper Ediacaran to lower Cambrian (ca. 551-515 Ma) successions in South China. We find large delta U-238 swings between -0.63 parts per thousand and +0.39 parts per thousand for calculated values of authigenic U in the siliciclastic rocks, consistent with correlative records from the carbonates. The replication of these patterns in both carbonate and siliciclastic units provides confirmatory evidence that the early Cambrian seawater was characterized by highly variable U isotope compositions. These new delta U-238 data also provide higher-resolution records of global oceanic redox conditions during Cambrian Age 3, coeval with a critical interval of the Cambrian explosion. These delta U-238 data bolster the case that the Ediacaran-Cambrian transition experienced massive swings in marine redox state, providing a dynamic environmental backdrop for and potentially even a key driver of the emergence and radiation of metazoans. (C) 2020 Elsevier B.V. All rights reserved.
机译：从新元古代末期到寒武纪早期海洋氧合的历史正在讨论，使得它难以衡量环境诱因是否以及在多大程度上塑造后生多样化的轨迹起到了一定作用。铀同位素（三角洲U-238）从碳酸盐记录最近被用来论证在全球海洋的氧化还原状态的早寒武世显著摆幅新元古代末期。然而，在地球化学签名碳酸盐-在U同位素档案最常用的争辩氧化还原转变-易受成岩蚀变，并且可以具有从海水中值变量的偏移量。因此，有一个推动使用其它沉积归档重构海水ü同位素演化，以验证这些游览活动确实可以链接到海洋的氧化还原景观的全球变化。在这里，我们报告从两个细粒度碎屑上埃迪卡拉新ü同位素数据，以降低在中国南方寒武纪（约551-515马）继承。我们发现-0.63千分之和+0.39千分之在碎屑岩自生的U计算值，从碳酸盐相关记录相符之间的大三角U-238的波动。在这两个碳酸酯和硅质碎屑单元这些图案的复制提供确证的证据表明，早期寒武纪海水的特征是高度变量U同位素组合物。寒武纪时代3，同时代与寒武纪大爆发的关键期间，这些新的增量U-238的数据也提供了全球海洋氧化还原条件更高分辨率的记录。这些增量U-238数据加强的情况下，该埃迪卡拉纪，寒武纪过渡经历了海洋的氧化还原状态下巨大的波动，提供一个动态的环境背景和后生动物的出现和辐射甚至可能一个关键驱动力。 （c）2020 Elsevier B.v.保留所有权利。

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