Polycyclic aromatic hydrocarbons in the Jurassic–Cretaceous Tetori Group, central Japan
Polycyclic aromatic hydrocarbons in the Jurassic–Cretaceous Tetori Group, central Japan
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DOI：
10.1111/j.1440-1738.2010.00720.x
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发表时间：
2011-03
期刊：
影响因子：
1.5
通讯作者：
T. Hasegawa;Tsuyoshi Hibino
中科院分区：
文献类型：
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作者：
T. Hasegawa;Tsuyoshi Hibino
通过日本北陆地区的两个地质剖面，获得了鸟取群有机地球化学的初步资料，为研究其沉积环境和有机质热成熟提供了基本信息。用甲基菲指数‐1评价有机质的热成熟度。在福井县的泉段，成熟度在地层上逐渐提高。在基底附近，镜质组的等效反射率估计为2.0%。热成熟过程可以通过该剖面解释多环芳烃丰度的地层变化。然而，在Izumi剖面中部偶尔出现的日冕物质可能是由于古野火为沉积部位提供了更多的日冕物质。富山县Tateyama剖面的多环芳烃地层分布也可以用与Izumi剖面相同的情景来解释，但风化和/或其他次要因素可能部分改变了该剖面的主要信号。在这两个剖面的几乎所有样品中都观察到多环芳香族硫化合物，即使在推测为淡水古环境的样品中也是如此。最有可能的是，一些还原的硫被再氧化为单质硫，这些单质硫持续存在于沉积物中，可能有助于芳香族硫化合物的形成。因此，多环芳香族硫化合物不能为鸟取群提供将海洋环境与淡水环境分开的指标。
Primary data on the organic geochemistry of the Tetori Group provide basic information about depositional environments and thermal maturation of organic matter through two geological sections in the Hokuriku region, central Japan. The thermal maturity of organic matter was evaluated by the methylphenanthrene index‐1. The maturity progressively increases stratigraphically down through the Izumi section in Fukui Prefecture. The estimated vitrinite reflectance equivalent is 2.0% near the base. The thermal maturation process can account for stratigraphic changes in abundance of PAHs through this section. However, the occasional occurrence of coronene in the middle of the Izumi section is attributed to possible paleo‐wildfires that supplied more coronene to the depositional site. The stratigraphic distribution of PAHs through the Tateyama section, Toyama Prefecture, also can be explained by the same scenario as envisaged for the Izumi section, but weathering and/or other secondary factors may have partly modified primary signals for this section. Polycyclic aromatic sulfur compounds were observed in nearly all samples from both sections, even in samples for which a freshwater paleoenvironment is surmised. Most plausibly, some reduced sulfur was re‐oxidized to elemental sulfur, which persisted in the sediments and may have contributed to the formation of aromatic sulfur compounds. Hence, polycyclic aromatic sulfur compounds do not provide an index to separate marine environments from the freshwater settings for the Tetori Group.