No evidence for anoxia during the Valanginian carbon isotope event—An organic-geochemical study from the Vocontian Basin, SE France
No evidence for anoxia during the Valanginian carbon isotope event—An organic-geochemical study from the Vocontian Basin, SE France
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瓦兰吉阶碳同位素事件期间没有缺氧的证据——法国东南部沃康田盆地的有机地球化学研究
DOI：
10.1016/j.gloplacha.2012.04.007
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发表时间：
2012
影响因子：
3.9
通讯作者：
Mutterlose
中科院分区：
文献类型：
--
作者：
Heimhofer;Ostertag-Henning;Gréselle;Mutterlose
Valanginian时间间隔（早白垩世）的特征是正碳同位素偏移（CIE），这是白垩纪几个突出的δ 13 C异常中的第一个。采用化学地层学和有机地球化学相结合的方法，研究了Valanginian CIE之前沉积的沉积有机质（OM）的组成和分布。这样做是为了测试该CIE是否伴随着海洋初级生产和/或OM保存的变化。生物地层学校准存款从两个半远洋部分位于法国东南部Vocontian盆地被用作沉积档案。一个新建立的高分辨率δ 13 C记录覆盖了复合序列，显示了特征的Valanginian模式，并使详细的对比与现有的碳同位素曲线从北方特提斯边缘。分析的沉积有机质的溶剂可提取部分主要由海洋来源的陆地植物材料的混合物。研究了蓝细菌（2α-甲基-藿烷）、甲藻（甲藻甾烷或4-去甲基-23，24-二甲基甾烷）和陆源植物源OM（奇数长链正构烷烃）的特异性生物标志物以及甾烷/藿烷比、C35藿烷指数和类异戊二烯植烷和姥鲛烷的变化。与研究充分的白垩纪中期海洋缺氧事件（OAE）相比，在Valanginian CIE的建立阶段，既没有显着的OM富集，也没有显着的波动，在选定的生物标志物丰度可以观察到。这表明海洋古环境条件相对稳定，底层沃茨水含氧良好。在CIE之前，总有机碳含量高达4%的四厘米厚的精细层压的深色层（称为巴兰德层）显示出与通常稳定的生物标志物模式不同的例外。沉积学和生物标志物证据支持Barrande层在含氧较少的条件下沉积。然而，它们的出现明显早于δ 13 C碳转变的开始（大约180 kyrs）。与随后的白垩纪中期CIE相反，与Valanginian CIE相关的广泛缺氧的发生不能被证实为Vocontian盆地。
The Valanginian time interval (Early Cretaceous) is characterized by a positive carbon isotope excursion (CIE) which represents the first of several prominent Cretaceous δ13C anomalies. A combined chemostratigraphic and organic-geochemical approach has been chosen to investigate the composition and distribution of sedimentary organic matter (OM) deposited before the Valanginian CIE, during its onset and plateau-phase. This was done to test whether this CIE is accompanied by changes in marine primary production and/or OM preservation. Biostratigraphically well-calibrated deposits from two hemipelagic sections located in the Vocontian Basin of SE France are used as sedimentary archives. A newly established high-resolution δ13C record covering the composite succession shows a characteristic Valanginian pattern and enables a detailed correlation with existing carbon isotope curves from the northern Tethyan margin. The analyzed solvent extractable fraction of the sedimentary OM is mainly composed of a marine origin with an admixture of land plant material. Variations in specific biomarkers for cyanobacteria (2α-methyl-hopanes), dinoflagellates (dinosterane or 4-desmethyl-23,24-dimethyl steranes) and terrigenous plant-derived OM (odd‐numbered long-chain n-alkanes) as well as the sterane/hopane ratio, the C35hopane index and the isoprenoids pristane and phytane were investigated. In contrast to the well-studied mid-Cretaceous Oceanic Anoxic Events (OAEs), neither significant OM enrichment nor prominent fluctuations in the selected biomarker abundances can be observed during the build-up phase of the Valanginian CIE. This points to relatively stable marine paleoenvironmental conditions with well-oxygenated bottom waters. Prior to the CIE, four cm-thick, finely laminated, dark layers (known as Barrande layers) with total organic carbon content reaching up to 4% show an exception from the generally stable biomarker pattern. Sedimentological and biomarker evidence support deposition under less oxygenated conditions for the Barrande layers. However, their occurrence clearly predates the onset of the positive δ13Ccarbshift (by about 180kyrs). Contrary to the subsequent mid-Cretaceous CIEs, the occurrence of widespread anoxia associated with the Valanginian CIE cannot be confirmed for the Vocontian Basin.
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DOI：
--
发表时间：
2005
期刊：
影响因子：
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作者：
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1992
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DOI：
10.1016/j.palaeo.2006.07.010
发表时间：
2007-01
期刊：
Palaeogeography, Palaeoclimatology, Palaeoecology
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DOI：
--
发表时间：
2008
期刊：
影响因子：
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作者：
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Vocontian 盆地（法国东南部）复杂的 Valanginian nannoconid 衰退的证据
影响因子：
1.9
作者：
N. Barbarin;A. Bonin;E. Mattioli;E. Pucéat;H. Cappetta;B. Gréselle;B. Pittet;E. Vennin;M. Joachimski
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