Uranium isotopes distinguish two geochemically distinct stages during the later Cambrian SPICE event.
Uranium isotopes distinguish two geochemically distinct stages during the later Cambrian SPICE event.
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DOI：
10.1016/j.epsl.2014.05.043
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发表时间：
2014-09-01
影响因子：
5.3
通讯作者：
Bizzarro M
中科院分区：
文献类型：
--
作者：
Dahl TW;Boyle RA;Canfield DE;Connelly JN;Gill BC;Lenton TM;Bizzarro M
缺氧海洋带在早古生代海洋（542-400 Ma）中很常见，并通过连接全球海洋磷再循环、初级生产和有机碳埋藏的反馈与大气pO 2存在潜在联系。碳酸盐岩中的铀（U）同位素追踪海洋缺氧的程度，而碳（C）和硫（S）同位素追踪有机碳和黄铁矿硫（大气氧的主要长期来源）的埋藏。综合起来，这些代理因此揭示了海洋缺氧和氧气释放到大气中超过百万年的时间尺度的比较动态。在这里，我们报告高精度的铀同位素数据在晚寒武世“SPICE”事件期间沉积的海洋碳酸盐岩，在约。499 Ma，记录了一个定义明确的-0.18 ‰负δ 238 U偏移，发生在SPICE事件的正δ 13 C和δ 34 S偏移的开始，但峰值（和尾部）在他们之前。动态模拟表明，U水库的不同响应不能仅仅归因于停留时间或水库大小的差异-这表明两个化学性质不同的海洋状态发生在SPICE事件。第一个海洋阶段涉及到全球性的纯沃茨扩张，引发了U埋葬的高峰，并与一个著名的三叶虫灭绝事件一起达到顶峰。在第二阶段，广泛的洋地黄减弱，导致U去除尾巴，但增强有机碳和黄铁矿埋藏继续，符合证据表明，在海洋中严重的硫酸盐枯竭。我们讨论的情况下，如何间隔升高的黄铁矿和有机碳埋藏可以持续没有广泛的euxinia在水柱（非硫化物缺氧和/或更多的含氧海洋状态的可能性）。无论哪种方式，SPICE事件包括两个不同的阶段，升高的有机碳和黄铁矿埋藏维持高营养通量的海洋，并可能维持内部海洋地球化学反馈。
Anoxic marine zones were common in early Paleozoic oceans (542–400 Ma), and present a potential link to atmospheric pO2 via feedbacks linking global marine phosphorous recycling, primary production and organic carbon burial. Uranium (U) isotopes in carbonate rocks track the extent of ocean anoxia, whereas carbon (C) and sulfur (S) isotopes track the burial of organic carbon and pyrite sulfur (primary long-term sources of atmospheric oxygen). In combination, these proxies therefore reveal the comparative dynamics of ocean anoxia and oxygen liberation to the atmosphere over million-year time scales. Here we report high-precision uranium isotopic data in marine carbonates deposited during the Late Cambrian ‘SPICE’ event, at ca. 499 Ma, documenting a well-defined −0.18‰ negative δ238U excursion that occurs at the onset of the SPICE event’s positive δ13C and δ34S excursions, but peaks (and tails off) before them. Dynamic modelling shows that the different response of the U reservoir cannot be attributed solely to differences in residence times or reservoir sizes - suggesting that two chemically distinct ocean states occurred within the SPICE event. The first ocean stage involved a global expansion of euxinic waters, triggering the spike in U burial, and peaking in conjunction with a well-known trilobite extinction event. During the second stage widespread euxinia waned, causing U removal to tail off, but enhanced organic carbon and pyrite burial continued, coinciding with evidence for severe sulfate depletion in the oceans. We discuss scenarios for how an interval of elevated pyrite and organic carbon burial could have been sustained without widespread euxinia in the water column (both non-sulfidic anoxia and/or a more oxygenated ocean state are possibilities). Either way, the SPICE event encompasses two different stages of elevated organic carbon and pyrite burial maintained by high nutrient fluxes to the ocean, and potentially sustained by internal marine geochemical feedbacks.
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影响因子：
5
作者：
BERNER, RA;RAISWELL, R
通讯作者：
RAISWELL, R
影响因子：
5.8
作者：
Bopp, Charles John, IV;Lundstrom, Craig C.;Glessner, Justin J. G.
通讯作者：
Glessner, Justin J. G.
DOI：
10.1073/pnas.1219198110
发表时间：
2013-03-19
影响因子：
11.1
作者：
Bargar, John R.;Williams, Kenneth H.;Bernier-Latmani, Rizlan
通讯作者：
Bernier-Latmani, Rizlan
影响因子：
2.9
作者：
BERRY, WBN;WILDE, P
通讯作者：
WILDE, P
影响因子：
2.1
作者：
Aller, RC;Blair, NE
通讯作者：
Blair, NE