Effects of volcanic activities in Ordovician Wufeng–Silurian Longmaxi period on organic-rich shale in the Upper Yangtze area, South China
Based on the corresponding relationship between the paleoproductivity, redox conditions and volcanism within a chronostratigraphic framework, the effects of volcanic events in the Wufeng–Longmaxi period on organic abundance of shale were examined. Bentonite layers were mostly developed in the transg...
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KeAi Communications Co., Ltd.
2018-10-01
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| Series: | Petroleum Exploration and Development |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S1876380418300892 |
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| author | Lanyu WU Yongchao LU Shu JIANG Xiaofeng LIU Guisong HE |
| author_facet | Lanyu WU Yongchao LU Shu JIANG Xiaofeng LIU Guisong HE |
| author_sort | Lanyu WU |
| collection | DOAJ |
| description | Based on the corresponding relationship between the paleoproductivity, redox conditions and volcanism within a chronostratigraphic framework, the effects of volcanic events in the Wufeng–Longmaxi period on organic abundance of shale were examined. Bentonite layers were mostly developed in the transgressive systems tract 1 (TST1, Wufeng Formation) and transgressive systems tract 2 (TST2, Longmaxi Formation), and the two systems tracts corresponded to favorite shale lithofacies with high silica and total organic carbon (TOC) contents. According to the stratigraphic characteristics of bentonite rich interval, TST1 is classified as the interval with dense bentonite layers with the frequency of bentonite layer (bentonite layers/time) of more than 1.5 layers/Ma and the cumulative thickness ratio of bentonite layers (thickness of bentonite layers/thickness of shale) of more than 1%; TST2 is classified as the interval with sparse bentonite layers (frequency < 1.5 layers/Ma; cumulative thickness ratio < 1%). TST1 (dense interval) witnessed more intense and high-frequency volcanic activities than TST2 (sparse interval), so the TST1 has generally higher TOC than TST2. The intense and frequent volcanic activities had dual effects on organic-rich shale: on one hand, volcanic ash provided a sufficient supply of nutrients, which triggered high marine productivity; on the other hand, the extremely anoxic environment caused by volcanic activity enhanced the burial amount and preservation rate of organic matter. Key words: shale, organic abundance, volcanism, sequence stratigraphy, Ordovician Wufeng Formation, Silurian Longmaxi Formation, Upper Yangtze area, bentonite |
| first_indexed | 2024-12-16T17:11:31Z |
| format | Article |
| id | doaj.art-e4d0d5e45a1549c491f253d0f173ec48 |
| institution | Directory Open Access Journal |
| issn | 1876-3804 |
| language | English |
| last_indexed | 2024-12-16T17:11:31Z |
| publishDate | 2018-10-01 |
| publisher | KeAi Communications Co., Ltd. |
| record_format | Article |
| series | Petroleum Exploration and Development |
| spelling | doaj.art-e4d0d5e45a1549c491f253d0f173ec482022-12-21T22:23:24ZengKeAi Communications Co., Ltd.Petroleum Exploration and Development1876-38042018-10-01455862872Effects of volcanic activities in Ordovician Wufeng–Silurian Longmaxi period on organic-rich shale in the Upper Yangtze area, South ChinaLanyu WU0Yongchao LU1Shu JIANG2Xiaofeng LIU3Guisong HE4Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China; Corresponding authorFaculty of Earth Sciences, China University of Geosciences, Wuhan 430074, ChinaEnergy & Geosciences Institute, The University of Utah, Salt Lake City, Utah 84108, USAFaculty of Earth Sciences, China University of Geosciences, Wuhan 430074, ChinaEast China Branch of SINOPEC, Nanjing 210011, ChinaBased on the corresponding relationship between the paleoproductivity, redox conditions and volcanism within a chronostratigraphic framework, the effects of volcanic events in the Wufeng–Longmaxi period on organic abundance of shale were examined. Bentonite layers were mostly developed in the transgressive systems tract 1 (TST1, Wufeng Formation) and transgressive systems tract 2 (TST2, Longmaxi Formation), and the two systems tracts corresponded to favorite shale lithofacies with high silica and total organic carbon (TOC) contents. According to the stratigraphic characteristics of bentonite rich interval, TST1 is classified as the interval with dense bentonite layers with the frequency of bentonite layer (bentonite layers/time) of more than 1.5 layers/Ma and the cumulative thickness ratio of bentonite layers (thickness of bentonite layers/thickness of shale) of more than 1%; TST2 is classified as the interval with sparse bentonite layers (frequency < 1.5 layers/Ma; cumulative thickness ratio < 1%). TST1 (dense interval) witnessed more intense and high-frequency volcanic activities than TST2 (sparse interval), so the TST1 has generally higher TOC than TST2. The intense and frequent volcanic activities had dual effects on organic-rich shale: on one hand, volcanic ash provided a sufficient supply of nutrients, which triggered high marine productivity; on the other hand, the extremely anoxic environment caused by volcanic activity enhanced the burial amount and preservation rate of organic matter. Key words: shale, organic abundance, volcanism, sequence stratigraphy, Ordovician Wufeng Formation, Silurian Longmaxi Formation, Upper Yangtze area, bentonitehttp://www.sciencedirect.com/science/article/pii/S1876380418300892 |
| spellingShingle | Lanyu WU Yongchao LU Shu JIANG Xiaofeng LIU Guisong HE Effects of volcanic activities in Ordovician Wufeng–Silurian Longmaxi period on organic-rich shale in the Upper Yangtze area, South China Petroleum Exploration and Development |
| title | Effects of volcanic activities in Ordovician Wufeng–Silurian Longmaxi period on organic-rich shale in the Upper Yangtze area, South China |
| title_full | Effects of volcanic activities in Ordovician Wufeng–Silurian Longmaxi period on organic-rich shale in the Upper Yangtze area, South China |
| title_fullStr | Effects of volcanic activities in Ordovician Wufeng–Silurian Longmaxi period on organic-rich shale in the Upper Yangtze area, South China |
| title_full_unstemmed | Effects of volcanic activities in Ordovician Wufeng–Silurian Longmaxi period on organic-rich shale in the Upper Yangtze area, South China |
| title_short | Effects of volcanic activities in Ordovician Wufeng–Silurian Longmaxi period on organic-rich shale in the Upper Yangtze area, South China |
| title_sort | effects of volcanic activities in ordovician wufeng silurian longmaxi period on organic rich shale in the upper yangtze area south china |
| url | http://www.sciencedirect.com/science/article/pii/S1876380418300892 |
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