Unravelling the sources of carbon emissions at the onset of Oceanic Anoxic Event (OAE) 1a
Unravelling the sources of carbon emissions at the onset of Oceanic Anoxic Event (OAE) 1a
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DOI：
10.1016/j.epsl.2019.115947
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发表时间：
2020-01-15
影响因子：
5.3
通讯作者：
Monteiro, Fanny M.
中科院分区：
文献类型：
--
作者：
Adloff, Markus;Greene, Sarah E.;Monteiro, Fanny M.
早期阿普第阶海洋缺氧事件（OAE）1a代表了地球气候系统，特别是碳循环的重大扰动，海洋环境中有机物质的广泛保存以及其开始时特有的负碳同位素漂移（CIE），随后是广泛的正CIE。一个大火成岩省（LIP）的同期侵位被认为是OAE Ia（和一般的OAE）的触发因素，但这种联系和OAE发生时碳扰动的最终来源仍有争议。在这项研究中，我们同时同化的大气pCO（2）重建沿着与三角洲C-13记录从西班牙Cau部分在地球系统模型中，以获得一个新的瞬态重建的排放率和确定的主要碳排放源在负CIE间隔在OAE的开始。我们从碳源的混合物中重建了4，300 - 29，200 Pg的碳排放量。这一估计是一个下限，因为同期有机碳埋藏没有考虑在内。碳首先以缓慢的速率从C-13耗尽的储层释放（例如来自岩床侵入体的热成因和/或生物成因甲烷）。在负CIE结束时，排放率增加，碳-13含量更高，可能来自主要的火山源（如LIP）。新的锇同位素（Os-187 /Os-188）测量，从同一部分的pCO（2）重建和三角洲C-13数据，揭示了一个转移到较少的放射性成因值与地幔来源的碳排放量的变化一致，我们的模拟结果表明，贷款进一步支持我们的解释。这些结果强调，地质触发的碳排放可能推动OAE的发生。(C)2019作者由爱思唯尔公司出版。这是一篇开放获取的文章，使用CC BY许可证（http：//creativecommons.org/licenses/by/4.0/）。
The early Aptian Oceanic Anoxic Event (OAE) la represents a major perturbation of the Earth's climate system and in particular the carbon cycle, as evidenced by widespread preservation of organic matter in marine settings and a characteristic negative carbon isotopic excursion (CIE) at its onset, followed by a broad positive CIE. The contemporaneous emplacement of a large igneous province (LIP) is invoked as a trigger for OAE la (and OAEs in general), but this link and the ultimate source of the carbon perturbation at the onset of OAEs is still debated. In this study, we simultaneously assimilate an atmospheric pCO(2) reconstruction along with a delta C-13 record from the Spanish Cau section in an Earth system model to obtain a novel transient reconstruction of emission rates and identify the primary carbon-emitting sources across the negative CIE interval at the onset of OAE la. We reconstruct carbon emissions of 4,300-29,200 Pg from a mixture of carbon sources. This estimate is a lower bound, as contemporaneous organic carbon burial is not accounted for. Carbon was first released at slow rates from a C-13-depleted reservoir (e.g. thermo- and/or biogenic methane from sill intrusions). Towards the end of the negative CIE the rate of emissions increased and they became more C-13-enriched, likely from a dominantly volcanic source (e.g. LIPs). New osmium isotope (Os-187 /Os-188) measurements, from the same section as the pCO(2) reconstruction and delta C-13 data, reveal a shift to less radiogenic values coinciding with the change towards mantle-derived carbon emissions as indicated by our modelling results, lending further support to our interpretation. These results highlight that geologically triggered carbon emissions were likely driving the OAE onset. (C) 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).