Sedimentary and geochemical characterization of Middle–Late Miocene formations in the Neogene Tsugaru Basin, Japan by means of DTH27‐1 well sediment analysis
Sedimentary and geochemical characterization of Middle–Late Miocene formations in the Neogene Tsugaru Basin, Japan by means of DTH27‐1 well sediment analysis
复制标题
通过 DTH27-1 井沉积物分析对日本新近纪津轻盆地中-晚中新世地层进行沉积和地球化学表征
作者：
P. Martizzi;S. Chiyonobu;H. Arato
本州岛西北侧出露的中新世中晚期硅质地层被认为是碳氢化合物的潜在烃源岩。对地球物理、沉积学和地球化学特性的分析对于评估地层的源潜力以及了解决定有机质积累和保存的因素至关重要。本研究通过对 DTH27-1 井 200 米长的岩心部分进行分析，调查了位于青森县西部的津轻弧后盆地的中新世中晚期地质记录。该岩心由 Akaishi 组的硅藻质粉砂岩和 Odoji 组的硅质泥岩组成。沉积学和地球物理表征表明，赤石组的硅藻质粉砂岩大多为块状且受到生物扰动，具有较低的磁化率，并表现出中等的天然放射性。尽管Odoji组的硅质泥岩块状，但它们的磁化率极低，天然放射性也很高。来自岩石热解的地球化学数据，如总有机碳和生成潜力 (S1 + S2) 表明，在津轻地区，只有 Odoji 组可能是碳氢化合物的潜在烃源岩。另一方面，Tmax 值表明这两个地层在热学上尚未成熟，无法生成碳氢化合物。赤石组和大土路组沉积相在生物扰动程度和有机碳含量方面的差异表明了孔隙度和粒度等岩性性质的变化；此外，这种差异表明底层水的古氧化作用发生了变化，从中中新世的缺氧条件过渡到晚中新世的富氧条件。岩性和古环境因素都可能影响这两个地层的有机质丰富度。
Middle–Late Miocene age siliceous formations outcropping along the northwestern side of Honshu Island are considered prospective source rocks for hydrocarbons. An analysis of geophysical, sedimentological, and geochemical properties is essential to evaluate the formations' source potential, and to understand the factors that determined the accumulation and preservation of organic matter. This study investigates the Middle–Late Miocene geological record of the Tsugaru back‐arc basin, located in the western part of Aomori prefecture, through an analysis of a 200 m long portion of a core from the DTH27‐1 well; this core is composed of the diatomaceous siltstones of the Akaishi Formation and the siliceous mudstones of the Odoji Formation. Sedimentological and geophysical characterization showed that the Akaishi Formation's diatomaceous siltstones are mostly massive and bioturbated, have low magnetic susceptibility, and demonstrate moderate natural radioactivity. Although the Odoji Formation's siliceous mudstones are massive, they have exceedingly low magnetic susceptibility and high natural radioactivity. Geochemical data from a Rock‐Eval Pyrolysis such as total organic carbon and generative potential (S1 + S2) revealed that, in the Tsugaru area, only the Odoji Formation is a likely prospective source rock for hydrocarbons. On the other hand, Tmax values indicate that both the formations are thermally immature for generating hydrocarbons. The difference between the Akaishi and Odoji Formation in the sedimentological facies, in terms of the degree of bioturbation and the organic carbon content, indicates variations in lithological properties, such as porosity and grain size; moreover, this difference indicates a variation in the paleo‐oxygenation of bottom waters, with the transition from oxygen‐deficient conditions in the Middle Miocene to the more oxygenated conditions in the Late Miocene. Both the lithological and paleo‐environmental factors possibly influenced the organic richness in the two formations.
影响因子：
2.8
作者：
S. Kimura;N. Shikazono;Hirohiko Kashiwagi;M. Nohara
通讯作者：
S. Kimura;N. Shikazono;Hirohiko Kashiwagi;M. Nohara