Carbon isotopic evidence for chemocline upward excursions during the end-Permian event
Carbon isotopic evidence for chemocline upward excursions during the end-Permian event
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DOI：
10.1016/j.palaeo.2006.11.010
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发表时间：
2007-05
期刊：
影响因子：
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通讯作者：
A. Riccardi;L. Kump;M. Arthur;S. D’Hondt
中科院分区：
文献类型：
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作者：
A. Riccardi;L. Kump;M. Arthur;S. D’Hondt
在二叠纪末生物大灭绝期间，海洋无机碳同位素组成（δ 13 Ccarb）的负移已被用作几种不同灭绝机制的证据。有机质δ 13 C的变化及其与δ 13 Ccarb之间的差异（Δ 13 C =δ 13 Ccarb − δ 13 Corg）在少数地点得到了检验，但存在相互矛盾的解释。我们研究的变化，有机和无机的碳同位素在二叠-三叠系界线在两个海洋部分从中国南方（梅山和上思），并比较这些数据从其他以前发表的部分。通过这些分析，我们证明了在整个古特提斯洋的灭绝事件期间，Δ 13 C发生了减少。下降的程度和强度因地点而异，平均负移1.5 ‰。关于这种转变的原因存在几种可能性，包括西伯利亚火山活动，陆地/海洋有机碳输入系统的变化，或通过环境变化（如广泛的海洋缺氧/euxinia）带来的占主导地位的海洋生物群的变化。在事件视界上的许多剖面上观察到的Δ 13 C的减少在这里被解释为代表了从藻类/蓝细菌到海洋陆架环境中较少分离的光养硫细菌的转变，这是由于化学跃层的向上偏移造成的。这些化学跃层向上的偏移将释放富氧水到透光层，允许光养硫细菌茁壮成长。有限的可用生物标志物数据与该解释一致。
A negative shift in marine inorganic carbon-isotope composition (δ13Ccarb) during the end-Permian mass extinction has been used as evidence for several different extinction mechanisms. Changes to the δ13C of organic matter and the difference between it and δ13Ccarb(Δ13C=δ13Ccarb− δ13Corg) have been examined at few locations, with conflicting interpretations. We examine the changes to both organic and inorganic carbon isotopes across the Permian–Triassic boundary at two marine sections from South China (Meishan and Shangsi) and compare these to data from other previously published sections. Through these analyses, we demonstrate that a decrease in Δ13C occurred during the extinction event throughout the Paleo-Tethys ocean. The extent and intensity of the decrease varies by location averaging a negative shift of ∼ 5‰. Several possibilities as to the cause of this shift exist including Siberian trap volcanism, a change in the terrestrial/marine organic carbon input to the system, or a change in the dominant marine biota brought about through environmental changes (such as widespread ocean anoxia/euxinia). The decrease in Δ13C observed at many of these sections across the event horizon is here interpreted to represent a shift from algae/cyanobacteria to less fractionating phototrophic sulfur bacteria in marine shelf environments resulting from upward excursions of the chemocline. These chemocline upward excursions would release euxinic water to the photic zone allowing phototrophic sulfur bacteria to thrive. The limited available biomarker data are consistent with this interpretation.