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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Sulfur record of rising and falling marine oxygen and sulfate levels during the Lomagundi event
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Sulfur record of rising and falling marine oxygen and sulfate levels during the Lomagundi event

机译：Lomagundi事件期间海洋氧气和硫酸盐含量上升和下降的硫记录

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Carbonates from approximately 2.3-2.1 billion years ago show markedly positive δ~(13)C values commonly reaching and sometimes exceeding +10‰. Traditional interpretation of these positive δ~(13)C values favors greatly enhanced organic carbon burial on a global scale, although other researchers have invoked widespread metha-nogenesis within the sediments. To resolve between these competing models and, more generally, among the mechanisms behind Earth's most dramatic carbon isotope event, we obtained coupled stable isotope data for carbonate carbon and carbonate-associated sulfate (CAS). CAS from the Lomagundi interval shows a narrow range of δ~(34)S values and concentrations much like those of Phaner-ozoic and modern marine carbonate rocks. The δ~(34)S values are a close match to those of coeval sulfate evaporites and likely reflect seawater composition. These observations are inconsistent with the idea of diagenetic carbonate formation in the methanic zone. Toward the end of the carbon isotope excursion there is an increase in the δ~(34)S values of CAS. We propose that these trends in C and S isotope values track the isotopic evolution of seawater sulfate and reflect an increase in pyrite burial and a crash in the marine sulfate reservoir during ocean deoxygenation in the waning stages of the positive carbon isotope excursion.
机译：大约2.3-21亿年前的碳酸盐显示出明显的正δ〜（13）C值，通常达到甚至超过+ 10‰。对这些正δ〜（13）C值的传统解释有利于在全球范围内大大增强有机碳埋藏，尽管其他研究人员已经在沉积物中调用了广泛的成生作用。为了在这些竞争模型之间以及更普遍的是在地球上最剧烈的碳同位素事件背后的机制之间进行解析，我们获得了碳酸盐碳和碳酸盐相关硫酸盐（CAS）的耦合稳定同位素数据。 Lomagundi区间的CAS显示出的δ〜（34）S值和浓度范围很窄，非常类似于Phaner新生代和现代海相碳酸盐岩。 δ〜（34）S值与同期硫酸盐蒸发物的值非常匹配，可能反映了海水的成分。这些观察结果与甲烷区中成岩碳酸盐形成的观点不一致。在碳同位素偏移接近尾声时，CAS的δ〜（34）S值增加。我们建议这些C和S同位素值趋势跟踪海水硫酸盐的同位素演化，并反映在正碳同位素偏移逐渐减弱的阶段，在海洋脱氧过程中黄铁矿埋藏的增加和海洋硫酸盐储层的崩溃。

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