Developmental characteristics and geological significance of the bentonite in the Upper Ordovician Wufeng – Lower Silurian Longmaxi Formation in eastern Sichuan Basin, SW China
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摘要
Based on the Qiliao section of the Upper Ordovician Wufeng Formation – Lower Silurian Longmaxi Formation in Shizhu, Chongqing city, the development characteristics of bentonite in eastern Sichuan Basin was examined systematically, and its geological significance and scientific value were analyzed. The main understandings are as follows:(1) Six bentonite dense layers were found in the Qiliao section, mainly occurring in 6 graptolitic belts of the Katian, Rhuddanian and Aeronian. Most of the bentonite dense layers showed obvious increase in clay, peak response of GR curve, and indistinct relationship between volcanic ash and total organic carbon(TOC).(2) The bentonite dense layers of Longmaxi Formation were widely distributed in eastern Sichuan Basin and its periphery, and generally showed GR peak, which can be an important reference interface for dividing the bottom boundary of the Coronograptus cyphus belt and the top boundary of the Rhuddanian in eastern Sichuan Basin and western Hubei province.(3) Taking the bentonite dense layers as the stratification basis of the Rhuddanian and Aeronian, it was determined that the sediment thickness of the Rhuddanian in the eastern Sichuan depression was generally 10–40 m, but only the upper part of the Coronograptus cyphus belt was deposited in the hinderland of Yichang Uplift, and the sedimentary thickness was only 3–7 m.(4) In the hinderland of the Yichang Uplift, at least five and a half graptolitic belts were missing in Wufeng Formation – Rhuddanian, and the deposition time of Rhuddanian was less than 0.4 Ma.(5) The bentonite dense layers were important sedimentary responses to the strong deflection of the Yangtze basin at the turn of the Ordovician–Silurian, which suggested that four tectonic activity periods existed in the eastern Sichuan depression, including the early stage of the depression, the middle-late stage of the depression, the early stage of the foreland flexure and the development stage of the foreland flexure. The high-quality shale was mainly developed from the early stage to the middle-late stage in the depression.
Based on the Qiliao section of the Upper Ordovician Wufeng Formation – Lower Silurian Longmaxi Formation in Shizhu, Chongqing city, the development characteristics of bentonite in eastern Sichuan Basin was examined systematically, and its geological significance and scientific value were analyzed. The main understandings are as follows:(1) Six bentonite dense layers were found in the Qiliao section, mainly occurring in 6 graptolitic belts of the Katian, Rhuddanian and Aeronian. Most of the bentonite dense layers showed obvious increase in clay, peak response of GR curve, and indistinct relationship between volcanic ash and total organic carbon(TOC).(2) The bentonite dense layers of Longmaxi Formation were widely distributed in eastern Sichuan Basin and its periphery, and generally showed GR peak, which can be an important reference interface for dividing the bottom boundary of the Coronograptus cyphus belt and the top boundary of the Rhuddanian in eastern Sichuan Basin and western Hubei province.(3) Taking the bentonite dense layers as the stratification basis of the Rhuddanian and Aeronian, it was determined that the sediment thickness of the Rhuddanian in the eastern Sichuan depression was generally 10–40 m, but only the upper part of the Coronograptus cyphus belt was deposited in the hinderland of Yichang Uplift, and the sedimentary thickness was only 3–7 m.(4) In the hinderland of the Yichang Uplift, at least five and a half graptolitic belts were missing in Wufeng Formation – Rhuddanian, and the deposition time of Rhuddanian was less than 0.4 Ma.(5) The bentonite dense layers were important sedimentary responses to the strong deflection of the Yangtze basin at the turn of the Ordovician–Silurian, which suggested that four tectonic activity periods existed in the eastern Sichuan depression, including the early stage of the depression, the middle-late stage of the depression, the early stage of the foreland flexure and the development stage of the foreland flexure. The high-quality shale was mainly developed from the early stage to the middle-late stage in the depression.
Based on the Qiliao section of the Upper Ordovician Wufeng Formation – Lower Silurian Longmaxi Formation in Shizhu, Chongqing city, the development characteristics of bentonite in eastern Sichuan Basin was examined systematically, and its geological significance and scientific value were analyzed. The main understandings are as follows:(1) Six bentonite dense layers were found in the Qiliao section, mainly occurring in 6 graptolitic belts of the Katian, Rhuddanian and Aeronian. Most of the bentonite dense layers showed obvious increase in clay, peak response of GR curve, and indistinct relationship between volcanic ash and total organic carbon(TOC).(2) The bentonite dense layers of Longmaxi Formation were widely distributed in eastern Sichuan Basin and its periphery, and generally showed GR peak, which can be an important reference interface for dividing the bottom boundary of the Coronograptus cyphus belt and the top boundary of the Rhuddanian in eastern Sichuan Basin and western Hubei province.(3) Taking the bentonite dense layers as the stratification basis of the Rhuddanian and Aeronian, it was determined that the sediment thickness of the Rhuddanian in the eastern Sichuan depression was generally 10–40 m, but only the upper part of the Coronograptus cyphus belt was deposited in the hinderland of Yichang Uplift, and the sedimentary thickness was only 3–7 m.(4) In the hinderland of the Yichang Uplift, at least five and a half graptolitic belts were missing in Wufeng Formation – Rhuddanian, and the deposition time of Rhuddanian was less than 0.4 Ma.(5) The bentonite dense layers were important sedimentary responses to the strong deflection of the Yangtze basin at the turn of the Ordovician–Silurian, which suggested that four tectonic activity periods existed in the eastern Sichuan depression, including the early stage of the depression, the middle-late stage of the depression, the early stage of the foreland flexure and the development stage of the foreland flexure. The high-quality shale was mainly developed from the early stage to the middle-late stage in the depression.
引文
[1]ZOU Caineng,DONG Dazhong,WANG Yuman,et al.Shale gas in China:Characteristics,challenges and prospects(I).Petroleum Exploration and Development,2015,42(6):689-701.
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[3]WANG Yuman,DONG Dazhong,LI Xinjing,et al.Stratigraphic sequence and sedimentary characteristics of Lower Silurian Longmaxi Formation in the Sichuan Basin and its peripheral areas.Natural Gas Industry,2015,35(3):12-21.
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[6]FAN Junxuan,MELCHIN M J,CHEN Xu,et al.Biostratigraphy and geography of the Ordovician-Silurian Lungmachi black shales in South China.SCIENCE CHINA Earth Sciences,2011,54(12):1854-1863.
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[9]SU Wenbo,LI Zhiming,SHI Xiaoying,et al.K-bentonites and black shales from the Wufeng-Longmaxi Formations(Early Paleozoic,South China)and Xiamaling Formation(Early Neoproterozoic,North China):Implications for tectonic processes during two important transitions.Earth Science Frontiers,2006,13(6):82-95.
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[11]XIE Shangke,WANG Zhengjiang,WANG Jian,et al.LA-ICP-MS zircon U-Pb dating of the bentonites from the uppermost part of the Ordovician Wufeng Formation in the Haoping section Taoyuan,Hunan.Sedimentary Geology and Tethyan Geology,2012,32(4):65-69.
[12]HU Yanhua,ZHOU Jibin,SONG Biao,et al.SHRIMP zircon U-Pb dating of the bentonites from the uppermost part of the Ordovician in the Wangjiawan section Yichang,Hubei,China.SCIENCE CHINA Earth Sciences,2008,51(4):493-498.
[13]WU Lanyu,LU Yongchao,JIANG Shu,et al.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,2018,45(5):806-816.
[14]SHU Yi,LU Yongchao,Ll U Zhanhong,et al.Development characteristics of bentonite in marine shale and its effect on shale reservoir quality:A case study of Wufeng Formation to Member 1 of Longmaxi Formation,Fuling area.Acta Petrolei Sinica,2017,38(12):1371-1381.
[15]LI Denghua,LI Jianzhong,HUANG Jinliang,et al.An important role of volcanic ash in the formation of shale plays and its inspiration.Natural Gas Industry,2014,34(5):56-65.
[16]QIU Zhen,JIANG Zengguang,DONG Dazhong,et al.Organic matter enrichment model of the shale in WufengLongmachi Formation of Wuxi area.Journal of China University of Mining&Technology,2017,46(5):1134-1142.
[17]MA Yongsheng,CAI Xunyu,ZHAO Peirong.China’s shale gas exploration and development:Understanding and practice.Petroleum Exploration and Development,2018,45(4):561-574.
[18]CHEN Xu,RONG Jiayu,ZHOU Zhiyi,et a1.Middle Guizhou uplift and Yichang uplift through the Ordovician and Silurian transition.Chinese Science Bulletin,2001,46(12):1052-1056.
[19]WANG Yi,FAN Junxuan,ZHANG Yuandong,et al.On the Ordovician-Silurian Depositional Hiatus at Taiyanghe,Enshi,Hubei Province.Journal of Stratigraphy,2011,35(4):361-367.
[20]WANG Yuman,CHEN Bo,LI Xinjing,et al.Sedimentary characteristics of the upwelling facies shale in Longmaxi Formation of the Lower Silurian,northeast Sichuan.Acta Petrolei Sinica,2018,39(10):1092-1102.
[21]JOMES B,MANNING D A.Comparison of geochemical indices used for the interpretation of palaeoredox conditions in ancient mudstones.Chemical Geology,1994,111(1):111-129.
[2]WANG Yuman,LI Xinjing,DONG Dazhong,et al.Main factors controlling the sedimentation of high-quality shale in Wufeng-Longmaxi Fm,Upper Yangtze region.Natural Gas Industry,2017,37(4):9-20.
[3]WANG Yuman,DONG Dazhong,LI Xinjing,et al.Stratigraphic sequence and sedimentary characteristics of Lower Silurian Longmaxi Formation in the Sichuan Basin and its peripheral areas.Natural Gas Industry,2015,35(3):12-21.
[4]WANG Yuman,DONG Dazhong,HUANG Jinliang,et al.Guanyinqiao member lithofacies of the Upper Ordovician Wufeng Formation around the Sichuan Basin and the significance to shale gas plays,SW China.Petroleum Exploration and Development,2016,43(1):42-50.
[5]WANG Yuman,LI Xinjing,CHEN Bo,et al.Distribution characteristics and geological significance of the thickest Aeronian bentonite bed in Middle-Upper Yangtze Region.Natural Gas Geoscience,2018,29(1):42-54.
[6]FAN Junxuan,MELCHIN M J,CHEN Xu,et al.Biostratigraphy and geography of the Ordovician-Silurian Lungmachi black shales in South China.SCIENCE CHINA Earth Sciences,2011,54(12):1854-1863.
[7]RONG Jiayu,CHEN Xu,WANG Yi,et al.Expansion of the Cathaysian oldland through the Ordovician-Silurian transition:Emerging evidence and possible dynamics.SCIENCE CHINAEarth Sciences,2010,53(1):1-17.
[8]SU Wenbo,LI Zhiming,ETTENSOHN F R,et al.Distribution of black shale in the Wufeng-Longmaxi Formations(Ordovician-Silurian),South China:Major controlling factors and implications.Journal of Earth Science,2007,32(6):819-827.
[9]SU Wenbo,LI Zhiming,SHI Xiaoying,et al.K-bentonites and black shales from the Wufeng-Longmaxi Formations(Early Paleozoic,South China)and Xiamaling Formation(Early Neoproterozoic,North China):Implications for tectonic processes during two important transitions.Earth Science Frontiers,2006,13(6):82-95.
[10]SU Wenbo,HE Longqing,WANG Yongbiao,et al.K-bentonite beds and high-resolution integrated stratigraphy of the uppermost Ordovician Wufeng and the lowest Silurian Longmaxi Formations in South China.SCIENCE CHINAEarth Sciences,2003,46(11):1121-1133.
[11]XIE Shangke,WANG Zhengjiang,WANG Jian,et al.LA-ICP-MS zircon U-Pb dating of the bentonites from the uppermost part of the Ordovician Wufeng Formation in the Haoping section Taoyuan,Hunan.Sedimentary Geology and Tethyan Geology,2012,32(4):65-69.
[12]HU Yanhua,ZHOU Jibin,SONG Biao,et al.SHRIMP zircon U-Pb dating of the bentonites from the uppermost part of the Ordovician in the Wangjiawan section Yichang,Hubei,China.SCIENCE CHINA Earth Sciences,2008,51(4):493-498.
[13]WU Lanyu,LU Yongchao,JIANG Shu,et al.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,2018,45(5):806-816.
[14]SHU Yi,LU Yongchao,Ll U Zhanhong,et al.Development characteristics of bentonite in marine shale and its effect on shale reservoir quality:A case study of Wufeng Formation to Member 1 of Longmaxi Formation,Fuling area.Acta Petrolei Sinica,2017,38(12):1371-1381.
[15]LI Denghua,LI Jianzhong,HUANG Jinliang,et al.An important role of volcanic ash in the formation of shale plays and its inspiration.Natural Gas Industry,2014,34(5):56-65.
[16]QIU Zhen,JIANG Zengguang,DONG Dazhong,et al.Organic matter enrichment model of the shale in WufengLongmachi Formation of Wuxi area.Journal of China University of Mining&Technology,2017,46(5):1134-1142.
[17]MA Yongsheng,CAI Xunyu,ZHAO Peirong.China’s shale gas exploration and development:Understanding and practice.Petroleum Exploration and Development,2018,45(4):561-574.
[18]CHEN Xu,RONG Jiayu,ZHOU Zhiyi,et a1.Middle Guizhou uplift and Yichang uplift through the Ordovician and Silurian transition.Chinese Science Bulletin,2001,46(12):1052-1056.
[19]WANG Yi,FAN Junxuan,ZHANG Yuandong,et al.On the Ordovician-Silurian Depositional Hiatus at Taiyanghe,Enshi,Hubei Province.Journal of Stratigraphy,2011,35(4):361-367.
[20]WANG Yuman,CHEN Bo,LI Xinjing,et al.Sedimentary characteristics of the upwelling facies shale in Longmaxi Formation of the Lower Silurian,northeast Sichuan.Acta Petrolei Sinica,2018,39(10):1092-1102.
[21]JOMES B,MANNING D A.Comparison of geochemical indices used for the interpretation of palaeoredox conditions in ancient mudstones.Chemical Geology,1994,111(1):111-129.