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The hydrocarbon potential and sedimentary environment of the Miocene siliceous formation in Tsugaru and Akita basins, northern Japan, based on the sedimentological and geochemical analyses
https://doi.org/10.20569/00005646
https://doi.org/10.20569/00005646b9f5614f-373d-4aaf-96aa-c2e41a68445e
| 名前 / ファイル | ライセンス | アクション |
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内容要旨及び審査結果要旨 (204.7 kB)
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本文 (8.5 MB)
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| Item type | 学位論文 / Thesis or Dissertation(1) | |||||
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| 公開日 | 2021-04-27 | |||||
| タイトル | ||||||
| タイトル | The hydrocarbon potential and sedimentary environment of the Miocene siliceous formation in Tsugaru and Akita basins, northern Japan, based on the sedimentological and geochemical analyses | |||||
| 言語 | ||||||
| 言語 | eng | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_db06 | |||||
| 資源タイプ | doctoral thesis | |||||
| ID登録 | ||||||
| ID登録 | 10.20569/00005646 | |||||
| ID登録タイプ | JaLC | |||||
| アクセス権 | ||||||
| アクセス権 | open access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_abf2 | |||||
| 別タイトル | ||||||
| その他のタイトル | 堆積学的および地球化学的分析に基づく津軽・秋田堆積盆地の中新統珪質泥岩層の石油根源岩ポテンシャルと堆積環境 | |||||
| 作成者 |
Martizzi, Paolo
× Martizzi, Paolo |
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| 内容記述（抄録） | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | The area extending from Hokkaido to the northwestern side of Honshu island in Japan is where most of the Japanese oil and gas fields occur. Several present and past studies focused on the Middle-Late Miocene siliceous sedimentary formations of Akita and Aomori Prefectures, which are considered the most prospective horizons for hydrocarbons generation. These formations occur in several locations of Akita and Aomori Prefectures and provide an excellent geological record of the Miocene paleoenvironmental evolution in the Japan Sea. However, in many areas of the Akita and Aomori Prefectures, petroleum potential and paleoenvironmental studies have not yet been performed, and minimal subsurface data are available. This study introduces new data about the hydrocarbon potential and the paleoenvironment of the Japan Sea in the Middle-Late Miocene through the sedimentological and geochemical analysis of the Miocene sedimentary succession of Tsugaru Basin (southwestern Aomori Prefecture) and the Middle-Late Miocene Onnagawa and Iwaya Formations (central Akita Prefecture). Rock-Eval pyrolysis analysis performed on the core and outcrop samples of the studied formations indicates that the Odoji Formation in Aomori and the Onnagawa and Iwaya Formations in Akita are characterized by a fair/good organic richness. However, these formations are immature for the generation and expulsion of hydrocarbons. According to several wells data in the Akita Prefecture, the Onnagawa Formation and its equivalents are mature for oil in various locations of the region. The main factors that determined the maturation of potential source rocks were the burial depth and the geothermal gradient anomalies determined by the intrusion of igneous bodies in the Onnagawa Formation. On the other hand, according to the wells data in the Aomori Prefecture, the increase of burial depth did not influence the thermal maturity significantly. At the current state, mature horizons for the oil generation are still not located. Paleoenvironmental reconstruction of depositional conditions of the Miocene formations of Akita and Aomori Prefectures was inferred from the lithofacies and geochemical composition of sediments. Major oxides revealed that the composition of Middle-Late Miocene formations is dominated by SiO2 and variable percentages of detrital oxides such as Al2O3 and K2O. The detrital oxides content is low in the lower and central parts of the Onnagawa and Odoji Formations, while it tends to increase at the top of these formations and in the Late Miocene formations (ex. Akaishi Formation). Major oxides interpretation indicates that the detrital fraction originated from a felsic source, located in a continental area. This result suggests that the detrital fraction derived from the erosion of continental rocks in the Asian continent or the land areas on the east margin of the northwestern Honshu basin. These interpretations suggest that the detrital fraction was related to the variation of the monsoon activity in the Asian continent during the Middle-Late Miocene and the variation of riverine supply from northeastern Honshu. The generally positive correlation between the TOC and the detrital oxides suggests that the dilution of organic matter by detritus contributed to the preservation of TOC. The high concentration of the biogenic SiO2 in the formations from both Akita and Aomori regions indicates high primary productivity in the surface waters of the Japan Sea. The intense productivity delivered considerable amounts of phytoplankton organic matter in the water column. The TOC shows a slightly negative correlation with the biogenic SiO2, possibly indicating that the intense production of biogenic SiO2 generated a biogenic dilution process that impacted the TOC content. The lithofacies and framboidal pyrite size variations indicated that paleo-oxygenation of bottom waters varied throughout the Akita and Aomori regions. The massive samples with large-size framboidal pyrite of all the formations were probably deposited in oxic/dysoxic bottom waters. On the other hand, the laminated samples with small-size framboidal pyrite of the Onnagawa Formation were deposited in anoxic bottom waters. However, no consistent difference in the TOC of massive and laminated facies, suggests that the paleo-redox conditions had a low influence in the TOC preservation in the studied formations. The only evident case of oxic degradation is represented by the Akaishi Formation in which the TOC is markedly low. Combining the data of this and previous studies, it was possible to hypothesize the paleoenvironmental setting of Akita and Aomori regions in the Middle-Late Miocene. Both regions were characterized by a detrital input from the Asian monsoon and the riverine supply, and by the widespread activity of phytoplankton on the sea surface. An intense process of upwelling stimulated by the cold surface water and the wind energy brought nutrient elements in the sea surface, favoring the surface water bio-productivity. The different paleo-oxygenation conditions in the bottom water were determined by the mixing between north Pacific OMZ and the Japan Sea waters. The OMZ waters probably did not reach the Tsugaru Basin and the Gotanzawa areas, suggesting that the paleo-depth of these basins was shallow. On the other hand, the intermittent inflow of the OMZ waters in the Ajigasawa and Sugisawa areas determined the deposition of both massive and laminated sediments. The inflow of the OMZ was regulated by the variations of the sea-level. |
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| 著者版フラグ | ||||||
| 出版タイプ | VoR | |||||
| 出版タイプResource | http://purl.org/coar/version/c_970fb48d4fbd8a85 | |||||
| 書誌情報 | 発行日 2020-09-25 | |||||
| 出版者 | ||||||
| 出版者 | 秋田大学 | |||||
| 学位名 | ||||||
| 学位名 | 博士（理学） | |||||
| 学位授与機関 | ||||||
| 学位授与機関識別子Scheme | kakenhi | |||||
| 学位授与機関識別子 | 11401 | |||||
| 学位授与機関名 | 秋田大学 | |||||
| 学位授与年月日 | ||||||
| 学位授与年月日 | 2020-09-25 | |||||
| 学位授与番号 | ||||||
| 学位授与番号 | 甲第1355号 | |||||
