Sedimentary environment controls on the accumulation of organic matter in the Upper Ordovician Wufeng–Lower Silurian Longmaxi mudstones in the Southeastern Sichuan Basin of China
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摘要
The Upper Ordovician–Lower Silurian mudstones(including the Wufeng, Guanyinqiao and Longmaxi Formations) in the Sichuan Basin are some of the most important shale gas plays in China. In order to enhance our understanding of the process of formation of organic carbon up to 10%, optical, microscopy and geochemical methods have been used to investigate the petrographic and geochemical characteristics of the formation. Firstly, three mudstone lithofacies were identified based on a wide variety of mudstone laminations. These are:(a) indistinctly laminated mudstone;(b) parallellaminated mudstone; and(c) nonparallel-laminated mudstone. Then, combining with the evidence from depocenter migration, Th/U ratios and total organic carbon, the abundant organo-minerallic fabrics suggest that organic carbon was preferentially deposited and preserved in anoxic, low energy and stagnant water conditions during deposition of the Wufeng and Longmaxi Formations. On the contrary, the Guanyinqiao Formation with poor organic carbon was deposited in oxic and high-energy water conditions.
The Upper Ordovician–Lower Silurian mudstones(including the Wufeng, Guanyinqiao and Longmaxi Formations) in the Sichuan Basin are some of the most important shale gas plays in China. In order to enhance our understanding of the process of formation of organic carbon up to 10%, optical, microscopy and geochemical methods have been used to investigate the petrographic and geochemical characteristics of the formation. Firstly, three mudstone lithofacies were identified based on a wide variety of mudstone laminations. These are:(a) indistinctly laminated mudstone;(b) parallellaminated mudstone; and(c) nonparallel-laminated mudstone. Then, combining with the evidence from depocenter migration, Th/U ratios and total organic carbon, the abundant organo-minerallic fabrics suggest that organic carbon was preferentially deposited and preserved in anoxic, low energy and stagnant water conditions during deposition of the Wufeng and Longmaxi Formations. On the contrary, the Guanyinqiao Formation with poor organic carbon was deposited in oxic and high-energy water conditions.
The Upper Ordovician–Lower Silurian mudstones(including the Wufeng, Guanyinqiao and Longmaxi Formations) in the Sichuan Basin are some of the most important shale gas plays in China. In order to enhance our understanding of the process of formation of organic carbon up to 10%, optical, microscopy and geochemical methods have been used to investigate the petrographic and geochemical characteristics of the formation. Firstly, three mudstone lithofacies were identified based on a wide variety of mudstone laminations. These are:(a) indistinctly laminated mudstone;(b) parallellaminated mudstone; and(c) nonparallel-laminated mudstone. Then, combining with the evidence from depocenter migration, Th/U ratios and total organic carbon, the abundant organo-minerallic fabrics suggest that organic carbon was preferentially deposited and preserved in anoxic, low energy and stagnant water conditions during deposition of the Wufeng and Longmaxi Formations. On the contrary, the Guanyinqiao Formation with poor organic carbon was deposited in oxic and high-energy water conditions.
引文
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Liang DG,Guo TL,Chen JP,et al.Distribution of four suits of regional marine source rocks.Mar Origin Pet Geol.2008;13(2):1-16(in Chinese).
Liang C,Jiang ZX,Cao YC,et al.Deep-water depositional mechanisms and significance for unconventional hydrocarbon exploration:a case study from the lower Silurian Longmaxi shale in the southeastern Sichuan Basin.AAPG Bull.2016;100(5):773-94.https://doi.org/10.1306/02031615002.
Liu W,Xu XS,Feng X,et al.Radiolarian siliceous rocks and palaeoenvironmental reconstruction for the Upper Ordovician Wufeng Formation in the middle-upper Yangtze area.Sediment Geol Tethyan Geol.2010;30(3):65-70(in Chinese).
Liu SG,Deng B,Li ZW,et al.Architecture of basin-mountain systems and their influences on gas distribution:a case study from the Sichuan basin,South China.J Asian Earth Sci.2012;47(1):204-15.https://doi.org/10.1016/j.jseaes.2011.10.012.
Liu SG,Ma WX,Jansa L,et al.Characteristics of the shale gas reservoir rocks in the Lower Silurian Longmaxi Formation,East Sichuan Basin,China.Energy Explor Exploit.2013;31(2):187-219.https://doi.org/10.1260/0144-5987.31.2.187.
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Macquaker JHS,Gawthorpe RL.Mudstone lithofacies in the Kimmeridge Clay Formation,Wessex basin:implications for the origin and controls on the distribution of mudstones.J Sediment Petrol.1993;64A(4):927-32.https://doi.org/10.1306/D4267F28-2B26-11D7-8648000102C1865D.
Macquaker JHS,Taylor KG,Gawthorpe RL.High-resolution facies analyses of mudstones:implication for paleoenvironmental and sequence stratigraphic interpretations of offshore ancient muddominated successions.J Sediment Res.2007;77(4):324-39.https://doi.org/10.2110/jsr.2007.029.
Meyer KM,Kump LR.Oceanic euxinia in earth history:causes and consequences.Annu Rev Earth Planet Sci.2008;36(1):251-88.https://doi.org/10.1146/annurev.earth.36.031207.124256.
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Potter PE,Maynard JB,Depetris PJ.Mud and mudstones:introduction and overview,vol.65(24).Berlin:Springer;2005.p.8391-4.
Ran B,Liu SG,Jansa L,et al.Origin of the Upper Ordovician-lower Silurian cherts of the Yangtze block,South China,and their palaeogeographic significance.J Asian Earth Sci.2015;108:1-17.https://doi.org/10.1016/j.jseaes.2015.04.007.
Ran B,Liu SG,Jansa L,et al.Reservoir characteristics and preservation conditions of Longmaxi shale in the Upper Yangtze block,South China.Acta Geologica Sin(Engl Ed).2016;90(6):2182-205.
Rong JY,Chen X,Wang Y,et al.Northward expansion of Central Guizhou Oldland through the Ordovician and Silurian transition:evidence and implications.Sci China(Ser D)Earth Sci.2011;41(10):1407-15.
Sageman BB,Murphy AE,Werne JP,et al.A tale of shales:the relative roles of production,decomposition,and dilution in the accumulation of organic-rich strata,Middle-Upper Devonian,Appalachian basin.Chem Geol.2003;195(1):229-73.https://doi.org/10.1016/S0009-2541(02)00397-2.
Schieber J.Distribution and deposition of mudstone facies in the Upper Devonian Sonyea Group of New York.J Sediment Res.1999;69(4):909-25.https://doi.org/10.1306/D4268AB8-2B26-11D7-8648000102C1865D.
Schulte P,Scheibner C,Speijer RP.Fluvial discharge and sea-level changes controlling black shale deposition during the PaleoceneEocene Thermal Maximum in the Dababiya Quarry section,Egypt.Chem Geol.2011;285(1-4):167-83.https://doi.org/10.1016/j.chemgeo.2011.04.004.
Shanmugam G.Ten turbidite myths.Earth Sci Rev.2002;58(3):313-43.https://doi.org/10.1016/S0012-8252(02)00065-X.
Su WB,He LQ,Wang YB,et al.K-bentonite beds and highresolution integrated stratigraphy of the uppermost Ordovician Wufeng and the lowest Silurian Longmaxi Formations in South China.Sci China.2002;32(3):207-19(in Chinese).
Wang K,Chatterton BDE,Wang Y.An organic carbon isotope record of Late Ordovician to Early Silurian marine sedimentary rocks,Yangtze Sea,South China:implications for CO2changes during the Hirnantian glaciation.Palaeogeogr Palaeoclimatol Palaeoecol.1997;132(1-4):147-58.https://doi.org/10.1016/S0031-0182(97)00046-1.
Werne JP,Sageman BB,Lyons TW,et al.An integrated assessment of a‘‘type euxinic’’deposit:evidence for multiple controls on black shale deposition in the middle Devonian Oatka Creek Formation.Am J Sci.2002;302(2):110-43.https://doi.org/10.2475/ajs.302.2.110.
Wignall PB.Black shales.New York:Oxford University Press;1994.
Wignall PB,Twitchett RJ.Oceanic anoxia and the end Permian mass extinction.Science.1996;272(5265):1155-8.https://doi.org/10.1126/science.272.5265.1155.
Yan DT,Chen DZ,Wang QC,et al.Environment redox changes of the Yangtze Sea during the Ordo-Silurian transition.Acta Geologica Sin(Engl Ed).2008;82(3):679-89.https://doi.org/10.1111/j.1755-6724.2008.tb00619.x.
Yan DT,Chen DZ,Wang QC,et al.Geochemical changes across the Ordovician-Silurian transition on the Yangtze Platform,South China.Sci China Earth Sci.2009;52(1):38-54.https://doi.org/10.1007/s11430-008-0143-z.
Yang R,He S,Wang X,et al.Paleo-ocean redox environments of the Upper Ordovician Wufeng and the first member in lower Silurian Longmaxi Formations in the Jiaoshiba area,Sichuan Basin.Can J Earth Sci.2016;53:426-40.https://doi.org/10.1139/cjes-2015-0210.
Zhai GM.Petroleum geology of China.Beijing:Petroleum Industry Press;1989.p.96-109(in Chinese).
Zhao JH,Jin ZJ,Jin ZK,et al.Applying sedimentary geochemical proxies for paleoenvironment interpretation of organic-rich shale deposition in the Sichuan Basin,China.Int J Coal Geol.2016;163:52-71.https://doi.org/10.1016/j.coal.2016.06.015.
Aplin AC,Macquaker JHS.Mudstone diversity:Origin and implications for source,seal,and reservoir properties in petroleum systems.AAPG Bull.2011;95(12):2031-59.https://doi.org/10.1306/03281110162.
Arthur MA,Sageman BB.Marine black shales:depositional mechanisms and environments of ancient deposits.Annu Rev Earth Planet Sci.1994;22(1):499-551.https://doi.org/10.1146/annurev.ea.22.050194.002435.
Arthur MA,Sageman BB.Sea-level control on source-rock development:perspectives from the Holocene Black Sea,the midCretaceous Western Interior Basin,and the late Devonian Appalachian basin.Spec Publ.2005;82:35-59.https://doi.org/10.2110/pec.05.82.0035.
Bureau of Geology and Mineral Resources of Guizhou Province(BGMRGP).Regional geology of Guizhou province.Beijing:Geological Publishing House;1987(in Chinese).
Bureau of Geology and Mineral Resources of Sichuan Province(BGMRSP).Regional geology of Sichuan province.Beijing:Geological Publishing House;1991(in Chinese).
Chen X,Rong JY,Fan J,et al.A global correlation of biozones across the Ordovician-Silurian boundary.Acta Palaeontogica Sin.2000;39(1):100-14(in Chinese).
Chen X,Rong JY,Li Y,et al.Facies patterns and geography of the Yangtze region,South China,through the Ordovician and Silurian transition.Palaeogeogr Palaeoclimatol Palaeoecol.2004;204(2-4):353-72.https://doi.org/10.1016/S0031-0182(03)00736-3.
Chen X,Melchin MJ,Sheets HD.Patterns and processes of latest Ordovician graptolite extinction and recovery based on data from south China.J Paleontol.2005;79(5):842-61.https://doi.org/10.1666/0022-3360(2005)079%5b0842:PAPOLO%5d2.0.CO;2.
Chen SB,Zhu YM,Wang HY,et al.Shale gas reservoir characterisation:a typical case in the southern Sichuan Basin of China.Energy.2011;36(11):6609-16.https://doi.org/10.1016/j.energy.2011.09.001.
Chen X,Fan JX,Chen Q,et al.Toward a stepwise Kwangsian orogeny.Sci China(Ser D)Earth Sci.2014;57(3):379-87.
Feng HZ,Erdtmann BD,Early Wang HF.Paleozoic whole-rock Ce anomalies and secular eustatic changes in the Upper Yangtze region.Sci China(Ser D)Earth Sci.2000;43(3):328-36.https://doi.org/10.1007/BF02906829.
Ghadeer SG,Macquaker JHS.The role of event beds in the preservation of organic carbon in fine-grained sediments:analyses of the sedimentological processes operating during deposition of the Whitby Mudstone Formation(Toarcian,Lower Jurassic)preserved in northeast England.Mar Pet Geol.2012;35(1):309-20.https://doi.org/10.1016/j.marpetgeo.2012.01.001.
Guo TL,Zhang HR.Formation and enrichment mode of Jiaoshiba shale gas field,Sichuan Basin.Pet Explor Dev.2014;41(1):31-40.https://doi.org/10.1016/S1876-3804(14)60003-3.
Guo QJ,Shields GA,Liu CQ,et al.Trace element chemostratigraphy of two Ediacaran-Cambrian successions in South China:implications for organosedimentary metal enrichment and silicification in the early Cambrian.Palaeogeogr Palaeoclimatol Palaeoecol.2007;254(1-2):194-216.https://doi.org/10.1016/j.palaeo.2007.03.016.
Guo L,Jiang ZX,Zhang JC,Li YX.Paleoenvironment of Lower Silurian black shale and its significance to the potential of shale gas,southeast of Chongqing,China.Energy Explor Exploit.2011;29(5):597-616.https://doi.org/10.1260/0144-5987.29.5.597.
Haq BU,Schutter SR.A chronology of Paleozoic sea-level changes.Science.2008;322(5898):64-8.https://doi.org/10.1126/science.1161648.
Huang ZC,Huang ZJ,Cheng ZN.Volcanic rock and radiolarian silicilith of Wufeng Formation in Lower Yangtze region.Acta Sedimentol Sin.1991;9(2):1-14(in Chinese).
Kimura H,Watanabe Y.Ocean anoxia at the Precambrian-Cambrian boundary.Geology.2001;29(11):995-8.https://doi.org/10.1130/0091-7613(2001)029%3c0995:OAATPC%3e2.0.CO;2.
Li Y,Matsrumoto R,Kershaw S.Sedimentary and biotic evidence of a warm-water enclave in the cooler oceans of the latest Ordovician glacial phase,Yangtze Platform,South China block.Isl Arc.2005;14(4):623-35.https://doi.org/10.1111/j.1440-1738.2005.00472.x.
Li YF,Fan TL,Zhang JC,et al.Impact of paleoenvironment,organic paleoproductivity,and clastic dilution on the formation of organic-rich shales:a case study about the Ordovician-Silurian black shales,southeastern Chongqing,South China.Arab JGeosci.2015;8(12):10225-39.https://doi.org/10.1007/s12517-015-1944-y.
Liang DG,Guo TL,Chen JP,et al.Distribution of four suits of regional marine source rocks.Mar Origin Pet Geol.2008;13(2):1-16(in Chinese).
Liang C,Jiang ZX,Cao YC,et al.Deep-water depositional mechanisms and significance for unconventional hydrocarbon exploration:a case study from the lower Silurian Longmaxi shale in the southeastern Sichuan Basin.AAPG Bull.2016;100(5):773-94.https://doi.org/10.1306/02031615002.
Liu W,Xu XS,Feng X,et al.Radiolarian siliceous rocks and palaeoenvironmental reconstruction for the Upper Ordovician Wufeng Formation in the middle-upper Yangtze area.Sediment Geol Tethyan Geol.2010;30(3):65-70(in Chinese).
Liu SG,Deng B,Li ZW,et al.Architecture of basin-mountain systems and their influences on gas distribution:a case study from the Sichuan basin,South China.J Asian Earth Sci.2012;47(1):204-15.https://doi.org/10.1016/j.jseaes.2011.10.012.
Liu SG,Ma WX,Jansa L,et al.Characteristics of the shale gas reservoir rocks in the Lower Silurian Longmaxi Formation,East Sichuan Basin,China.Energy Explor Exploit.2013;31(2):187-219.https://doi.org/10.1260/0144-5987.31.2.187.
Macquaker JHS,Bohacs KM.On the accumulation of mud.Science.2007;318(5857):1734-5.https://doi.org/10.1126/science.1151980.
Macquaker JHS,Gawthorpe RL.Mudstone lithofacies in the Kimmeridge Clay Formation,Wessex basin:implications for the origin and controls on the distribution of mudstones.J Sediment Petrol.1993;64A(4):927-32.https://doi.org/10.1306/D4267F28-2B26-11D7-8648000102C1865D.
Macquaker JHS,Taylor KG,Gawthorpe RL.High-resolution facies analyses of mudstones:implication for paleoenvironmental and sequence stratigraphic interpretations of offshore ancient muddominated successions.J Sediment Res.2007;77(4):324-39.https://doi.org/10.2110/jsr.2007.029.
Meyer KM,Kump LR.Oceanic euxinia in earth history:causes and consequences.Annu Rev Earth Planet Sci.2008;36(1):251-88.https://doi.org/10.1146/annurev.earth.36.031207.124256.
O’Brien NR.Significance of lamination in Toarcian(Lower Jurassic)shales from Yorkshire,Great Britain.Sediment Geol.1990;67(1-2):25-34.https://doi.org/10.1016/0037-0738(90)90025-O.
Potter PE,Maynard JB,Depetris PJ.Mud and mudstones:introduction and overview,vol.65(24).Berlin:Springer;2005.p.8391-4.
Ran B,Liu SG,Jansa L,et al.Origin of the Upper Ordovician-lower Silurian cherts of the Yangtze block,South China,and their palaeogeographic significance.J Asian Earth Sci.2015;108:1-17.https://doi.org/10.1016/j.jseaes.2015.04.007.
Ran B,Liu SG,Jansa L,et al.Reservoir characteristics and preservation conditions of Longmaxi shale in the Upper Yangtze block,South China.Acta Geologica Sin(Engl Ed).2016;90(6):2182-205.
Rong JY,Chen X,Wang Y,et al.Northward expansion of Central Guizhou Oldland through the Ordovician and Silurian transition:evidence and implications.Sci China(Ser D)Earth Sci.2011;41(10):1407-15.
Sageman BB,Murphy AE,Werne JP,et al.A tale of shales:the relative roles of production,decomposition,and dilution in the accumulation of organic-rich strata,Middle-Upper Devonian,Appalachian basin.Chem Geol.2003;195(1):229-73.https://doi.org/10.1016/S0009-2541(02)00397-2.
Schieber J.Distribution and deposition of mudstone facies in the Upper Devonian Sonyea Group of New York.J Sediment Res.1999;69(4):909-25.https://doi.org/10.1306/D4268AB8-2B26-11D7-8648000102C1865D.
Schulte P,Scheibner C,Speijer RP.Fluvial discharge and sea-level changes controlling black shale deposition during the PaleoceneEocene Thermal Maximum in the Dababiya Quarry section,Egypt.Chem Geol.2011;285(1-4):167-83.https://doi.org/10.1016/j.chemgeo.2011.04.004.
Shanmugam G.Ten turbidite myths.Earth Sci Rev.2002;58(3):313-43.https://doi.org/10.1016/S0012-8252(02)00065-X.
Su WB,He LQ,Wang YB,et al.K-bentonite beds and highresolution integrated stratigraphy of the uppermost Ordovician Wufeng and the lowest Silurian Longmaxi Formations in South China.Sci China.2002;32(3):207-19(in Chinese).
Wang K,Chatterton BDE,Wang Y.An organic carbon isotope record of Late Ordovician to Early Silurian marine sedimentary rocks,Yangtze Sea,South China:implications for CO2changes during the Hirnantian glaciation.Palaeogeogr Palaeoclimatol Palaeoecol.1997;132(1-4):147-58.https://doi.org/10.1016/S0031-0182(97)00046-1.
Werne JP,Sageman BB,Lyons TW,et al.An integrated assessment of a‘‘type euxinic’’deposit:evidence for multiple controls on black shale deposition in the middle Devonian Oatka Creek Formation.Am J Sci.2002;302(2):110-43.https://doi.org/10.2475/ajs.302.2.110.
Wignall PB.Black shales.New York:Oxford University Press;1994.
Wignall PB,Twitchett RJ.Oceanic anoxia and the end Permian mass extinction.Science.1996;272(5265):1155-8.https://doi.org/10.1126/science.272.5265.1155.
Yan DT,Chen DZ,Wang QC,et al.Environment redox changes of the Yangtze Sea during the Ordo-Silurian transition.Acta Geologica Sin(Engl Ed).2008;82(3):679-89.https://doi.org/10.1111/j.1755-6724.2008.tb00619.x.
Yan DT,Chen DZ,Wang QC,et al.Geochemical changes across the Ordovician-Silurian transition on the Yangtze Platform,South China.Sci China Earth Sci.2009;52(1):38-54.https://doi.org/10.1007/s11430-008-0143-z.
Yang R,He S,Wang X,et al.Paleo-ocean redox environments of the Upper Ordovician Wufeng and the first member in lower Silurian Longmaxi Formations in the Jiaoshiba area,Sichuan Basin.Can J Earth Sci.2016;53:426-40.https://doi.org/10.1139/cjes-2015-0210.
Zhai GM.Petroleum geology of China.Beijing:Petroleum Industry Press;1989.p.96-109(in Chinese).
Zhao JH,Jin ZJ,Jin ZK,et al.Applying sedimentary geochemical proxies for paleoenvironment interpretation of organic-rich shale deposition in the Sichuan Basin,China.Int J Coal Geol.2016;163:52-71.https://doi.org/10.1016/j.coal.2016.06.015.