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Co-occurrence of charcoal, polycyclic aromatic hydrocarbons and terrestrial biomarkers in an early Permian swamp to lagoonal depositional system, Paraná Basin, Rio Grande do Sul, Brazil
International Journal of Coal Geology ( IF 5.6 ) Pub Date : 2020-10-01 , DOI: 10.1016/j.coal.2020.103590
Rafał Kubik , Leszek Marynowski , Dieter Uhl , André Jasper

Abstract The Permian period had the most oxygen-rich atmosphere in Earth's history. With the presence of large amounts of fuel from vegetation, there was therefore a high probability of igniting fires during this time. This study presents the geochemical characterization of charcoal-bearing Asselian sediments, represented by terrestrial to lagoonal facies, collected from the Quiteria and Curva do Belvedere outcrops, Parana Basin, Rio Grande do Sul in Brazil. Lower Permian sedimentary rock organic extracts were studied using gas chromatography–mass spectrometry, to determine their molecular composition. Associations were found between biomarkers of unburned terrestrial gymnosperm plants and organic matter (OM) of pyrolytic origin. The predominance of odd-carbon n-alkanes with a high molecular weight (C25–C31), indicates an origin from higher plants. The same pattern was observed for high molecular weight even-carbon n-carboxylic acids, but was less distinctive. Between other polar compounds, aromatic carboxylic acids, and aldehydes associated with decomposition of lignin, were found as important polar fraction constituents. Aromatic carboxylic acids were also the main components of a copper oxide (CuO) oxidation experiment, which imply preservation of lignin remnants in OM-rich sedimentary rocks. Other higher plant biomarkers were represented by cadalene, simonellite, retene and perylene. Aromatic hydrocarbon series such as alkylnaphthalenes and alkylphenanthrenes are very common in the OM-rich mudstones, and rare or absent in alluvial fan or lagoon deposits, which may be associated with secondary processes like water washing and OM oxidation. Unsubstituted polycyclic aromatic hydrocarbons (PAH), common in pyrolytic processes, were widespread in the investigated material. The PAHs with the highest concentrations in the rock samples were benzo[e]pyrene, benzo[b]fluoranthene, chrysene/triphenylene, fluoranthene and pyrene. Less abundant but almost always present were phenanthrene, benzo[a]pyrene, benzo[a]anthracene, anthracene and 13H-indeno[1,2-e]pyrene. The temperatures and types of wildfires were assessed based on total unsubstituted PAH concentrations and fusinite reflectance measurements. The estimated temperatures were around 400–500 °C, which correspond to surface fires. These findings suggest that wildfires occurred more commonly during dry seasons when the swamps were periodically desiccated.

中文翻译:

巴西南里奥格兰德州巴拉那盆地早期二叠纪沼泽至泻湖沉积系统中木炭、多环芳烃和陆地生物标志物的共存

摘要 二叠纪是地球历史上含氧量最高的大气层。由于存在大量来自植被的燃料,因此在此期间发生火灾的可能性很高。本研究展示了含木炭的 Asselian 沉积物的地球化学特征,以陆地到泻湖相为代表,收集自巴西南里奥格兰德州巴拉那盆地的 Quiteria 和 Curva do Belvedere 露头。使用气相色谱-质谱法研究了下二叠统沉积岩有机提取物,以确定它们的分子组成。在未燃烧的陆生裸子植物的生物标志物与热解来源的有机物 (OM) 之间发现了关联。具有高分子量(C25-C31)的奇数碳正构烷烃占优势,表示来自高等植物。对于高分子量偶碳 n-羧酸也观察到相同的模式,但不太明显。在其他极性化合物之间,芳香族羧酸和与木质素分解相关的醛被发现是重要的极性部分成分。芳香族羧酸也是氧化铜 (CuO) 氧化实验的主要成分,这意味着木质素残留物在富含 OM 的沉积岩中得以保存。其他高等植物生物标志物以卡达林、硅锰矿、维甲酸和苝为代表。烷基萘、烷基菲等芳烃系列在富含有机质的泥岩中很常见,而在冲积扇或泻湖沉积物中很少或不存在,这可能与水洗和有机质氧化等二次过程有关。未取代的多环芳烃 (PAH) 在热解过程中很常见,在所研究的材料中很普遍。岩石样品中浓度最高的多环芳烃是苯并[e]芘、苯并[b]荧蒽、屈/苯并苯、荧蒽和芘。含量较少但几乎总是存在的是菲、苯并[a]芘、苯并[a]蒽、蒽和13H-茚并[1,2-e]芘。野火的温度和类型是根据未取代的多环芳烃总浓度和辉石反射率测量值来评估的。估计温度约为 400–500 °C,对应于地表火灾。这些发现表明,当沼泽周期性地干燥时,在旱季更容易发生野火。在调查材料中广泛存在。岩石样品中浓度最高的多环芳烃是苯并[e]芘、苯并[b]荧蒽、屈/苯并苯、荧蒽和芘。含量较少但几乎总是存在的是菲、苯并[a]芘、苯并[a]蒽、蒽和13H-茚并[1,2-e]芘。野火的温度和类型是根据未取代的多环芳烃总浓度和辉石反射率测量值来评估的。估计温度约为 400–500 °C,对应于地表火灾。这些发现表明,当沼泽周期性地干燥时,在旱季更容易发生野火。在调查材料中广泛存在。岩石样品中浓度最高的多环芳烃是苯并[e]芘、苯并[b]荧蒽、屈/苯并苯、荧蒽和芘。含量较少但几乎总是存在的是菲、苯并[a]芘、苯并[a]蒽、蒽和13H-茚并[1,2-e]芘。野火的温度和类型是根据未取代的多环芳烃总浓度和辉石反射率测量值来评估的。估计温度约为 400–500 °C,对应于地表火灾。这些发现表明,当沼泽周期性地干燥时,在旱季更容易发生野火。荧蒽和芘。含量较少但几乎总是存在的是菲、苯并[a]芘、苯并[a]蒽、蒽和13H-茚并[1,2-e]芘。野火的温度和类型是根据未取代的多环芳烃总浓度和辉石反射率测量值来评估的。估计温度约为 400–500 °C,对应于地表火灾。这些发现表明,当沼泽周期性地干燥时,在旱季更容易发生野火。荧蒽和芘。含量较少但几乎总是存在的是菲、苯并[a]芘、苯并[a]蒽、蒽和13H-茚并[1,2-e]芘。野火的温度和类型是根据未取代的多环芳烃总浓度和辉石反射率测量值来评估的。估计温度约为 400–500 °C,对应于地表火灾。这些发现表明,当沼泽周期性地干燥时,在旱季更容易发生野火。这对应于表面火灾。这些发现表明,当沼泽周期性地干燥时,在旱季更容易发生野火。这对应于表面火灾。这些发现表明,当沼泽周期性地干燥时,在旱季更容易发生野火。
更新日期:2020-10-01
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