Passive margin shale sedimentary palaeoenvironment and their controls over organic matter enrichment: a case study of the Lower Silurian Longmaxi Formation in northern Chongqing,Upper Yangtze
CHEN Hao1,2, SHEN Junjun1, TAN Guangchao3, WANG Yuman4, LI Shanshan3, YAN Jiakai3, ZHOU Lin5, LIU Jiyong5
1 Hubei Cooperative Innovation Center of Unconventional Oil and Gas of Yangtze University,Wuhan 430100,China; 2 School of Geosciences,Yangtze University,Wuhan 430100,China; 3 Hydrogeology and Engineering Geology Institute of Hubei Geological Bureau,Hubei Jingzhou 434020,China; 4 Research Institute of Petroleum Exploration and Development,PetroChina, Beijing 100083,China; 5 Exploration and Production Research Institute,Jianghan Oilfield Company,SINOPEC,Wuhan 430070,China
Abstract：At present,there are relatively few studies on sedimentary palaeoenvironment evolution of passive margin. In particular,due to limited understanding of the changing patterns of upwelling current activity,the main controlling factors for organic matter enrichment remain unclear. On these grounds,we investigate passive margin shale sedimentary palaeoenvironments and their controls on organic matter enrichment,based on an integrated core/outcrop,mineral petrology,organic geochemistry and elemental analysis of the Lower Silurian Longmaxi Formation in northern Chongqing. The results show that organic enrichment in the study area is controlled by preservation conditions,terrigenous input and palaeoproductivity,but the main controlling factors vary in different periods. During the Rhuddanian(LM1-LM5 depositional period),the accumulation of organic matter was controlled jointly by preservation conditions,terrigenous input and palaeoproductivity,and the TOC content was the highest. In the early Aeronian(LM6 depositional period),the basin entered the flexural-migration period of enhanced tectonic activity,the barrier in the Yubei area opened,resulting in increased upwelling current activity,and the deteriorated preservation condition was the main cause of the decrease of TOC content. During the mid Aeronian(LM7 sedimentary period),the migration effect was enhanced,with the barrier further opened and the upwelling current reaching an activity peak,and the deteriorated preservation condition and sharply increased palaeoproductivity were the main reasons for little change in TOC content compared to the LM6 deposition period. During the late Aeronian(LM8 depositional period),the barrier opening migrated to the northwest,the TOC content decreased,and the main controlling factors of organic matter enrichment were the same as those of LM1-LM5. During the early Telychian(LM9 deposition period),the sea level dropped to the lowest,the oxygen-rich environment predominated,and the TOC content decreased to the lowest. The preservation conditions were the main factors controlling the enrichment of organic matter. Overall,the changes of controlling factors of organic matter enrichment in different periods in the study area are closely related to the varying sedimentary palaeoenvironments caused by tectonic activities and sea level changes.
CHEN Hao,SHEN Junjun,TAN Guangchao et al. Passive margin shale sedimentary palaeoenvironment and their controls over organic matter enrichment: a case study of the Lower Silurian Longmaxi Formation in northern Chongqing,Upper Yangtze[J]. JOPC, 2024, 26(5): 1072-1089.
[1] 何庆,高键,董田,何生,翟刚毅,邹高峰. 2021. 鄂西地区下寒武统牛蹄塘组页岩元素地球化学特征及沉积古环恢复. 沉积学报, 39(3): 686-703. [He Q,Gao J,Dong T,He S,Zhai G Y,Zou G F.2021. Elemental geochemistry and paleo-environmental conditions of the Lower Cambrian Niutitang Shale in western Hubei Province. Acta Sedimentologica Sinica, 39(3): 686-703] [2] 吕炳全,王红罡,胡望水,沈伟锋,张玉兰. 2004. 扬子地块东南古生代上升流沉积相及其与烃源岩的关系. 海洋地质与第四纪地质, 24(4): 29-35. [Lü B Q,Wang H G,Hu W S,Shen W F,Zhang Y L.2004. Relationship between Paleozoic upwelling facies and hydrocarbon in southeastern marginal Yangtze Block. Marinegeology & Quaternary Geology, 24(4): 29-35] [3] 陆扬博. 2020. 上扬子五峰组和龙马溪组富有机质页岩岩相定量表征及沉积过程恢复. 中国地质大学博士学位论文: 133-135. [Lu Y B.2020. Quantitative characterization of lithofacies andreconstruction of the sedimentary process for Upper Yangtze Wufeng and Longmaxi organic-rich shales. Doctoral dissertation of China University of Geosciences: 133-135] [4] 李艳芳. 2017. 上扬子地区晚奥陶世—早志留世页岩地球化学特征、有机质富集及古环境意义. 兰州大学博士学位论文: 33-34. [Li Y F.2017. Geochemical characteristics and organic matter accumulation of Late Ordovician-Early Silurian Shale in the Upper Yangtze Platform,and implications for paleoenvironment. Doctoral dissertation of Lanzhou University: 33-34] [5] 李艳芳,吕海刚,张瑜,张小龙,邵德勇,闫建萍,张同伟. 2015. 四川盆地五峰组—龙马溪组页岩U-Mo协变模式与古海盆水体滞留程度的判识. 地球化学, 44(2): 109-116. [Li Y F,Lü H G,Zhang Y,Zhang X L,Shao D Y,Yan J P,Zhang T W.2015. U-Mo covariation in marine shales of Wufeng-Longmaxi Formations in Sichuan Basin,China and its implication for identification of watermass restriction. Geochimica, 44(2): 109-116] [6] 卢贤志,沈俊,郭伟,冯庆来. 2021. 中上扬子地区奥陶纪—志留纪之交火山作用对有机质富集的影响. 地球科学, 46(7): 2329-2340. [Lu Z X,Shen J,Guo W,Feng Q L.2021. lInfluence of mercury geochemistry and volcanism on the enrichment of organic matter near the Ordovician Silurian Transition in the Middle and Upper Yangtze. Earth Science, 46(7): 2329-2340] [7] 邱振,江增光,董大忠,施振生,卢斌,谈昕,周杰,雷丹凤,梁萍萍,韦恒叶. 2017. 巫溪地区五峰组: 龙马溪组页岩有机质沉积模式. 中国矿业大学学报, 46(5): 1134-1143. [Qiu Z,Jiang Z G,Dong D Z,Shi Z S,Lu B,Tan X,Zhou J,Lei D S,Liang P P,Wei H Y.2017. Organic matter enrichment model of the shale in Wufeng-Longmachi formation of Wuxi area. Journal of China University of Mining and Technology, 46(5): 1134-1143] [8] 邱振,邹才能,王红岩,董大忠,卢斌,陈振宏,刘德勋,李贵中,刘翰林,何江林,魏琳. 2020. 中国南方五峰组—龙马溪组页岩气差异富集特征与控制因素. 天然气地球科学, 31(2): 163-175. [Qiu Z,Zou C N,Wang H Y,Dong D Z,Lu B,Chen Z H,Liu D X,Li G Z,Liu H L,He J L,Wei L.2020. Discussion on characteristics and controlling factors of differential enrichment of Wufeng-Longmaxi shale gas in South China. Natural Gas Geoscience, 31(2): 163-175] [9] 戎嘉余,黄冰. 2014. 生物大灭绝研究三十年. 中国科学: 地球科学, 44(3): 377-404. [Rong J Y,Huang B.2014. Study of mass extinction over the past thirty years: a synopsis(in Chinese). Science China: Earth Sciences, 44(3): 377-404] [10] 沈俊,施张燕,冯庆来. 2011. 古海洋生产力地球化学指标的研究. 地质科技情报, 30(2): 69-77. [Shen J,Shi Z Y,Feng Q L.2011. A study of geochemical indicators of paleomarine productivity. Geological Science and Technology Information, 30(2): 69-77] [11] 孙珍,刘思青,庞雄,姜建群,毛爽. 2016. 被动大陆边缘伸展—破裂过程研究进展. 热带海洋学报, 35(1): 1-16. [Sun Z,Liu S Q,Pang X,Jiang J Q,Mao S.2016. Recent research progress on the rifting-breakup process in passive continental margins. Journal of Tropical Ocean, 35(1): 1-16] [12] 王玉满,王淑芳,董大忠,李新景,黄金亮,张晨晨,管全中. 2016. 川南下志留统龙马溪组页岩岩相表征. 地学前缘, 23(1): 119-133. [Wang Y M,Wang,S F,Dong D Z,Li X.J,Huang J L,Zhang C C,Guan Q Z.2016. Lithofacies characterization of Longmaxi Formation of the Lower Silurian,southern Sichuan. Earth Science Frontiers, 23(1): 119-133] [13] 王玉满,李新景,董大忠,张晨晨,王淑芳. 2017. 上扬子地区五峰组—龙马溪组优质页岩沉积主控因素. 天然气工业, 37(4): 9-20. [Wang Y M,Li X J,Dong D Z,Zhang,C C,Wang S F.2017. Main factors controlling the sedimentation of high-quality shale in Wufeng-Longmaxi Fm,Upper Yangtze region. Natural Gas Industry, 37(4): 9-20] [14] 王玉满,陈波,李新景,王皓,常立诚,蒋珊. 2018. 川东北地区下志留统龙马溪组上升洋流相页岩沉积特征. 石油学报, 39(10): 1092-1102. [Wang Y M,Chen B,Li X J,Wang H,Chang L C,Jiang S.2018. Sedimentary characteritc of welling facies shale in Lower Silurian Longmaxi Formation,northeast Sichuan area. Acta Petrolei Sinica, 39(10): 1092-1102] [15] 王玉满,李新景,王皓,蒋珊,陈波,马杰,代兵. 2019. 四川盆地东部上奥陶统五峰组—下志留统龙马溪组斑脱岩发育特征及地质意义. 石油勘探与开发, 46(4): 653-665. [Wang Y M,Li X J,Wang H,Jiang S,Chen B,Ma J,Dai B.2019. Developmental characteristics and geological significance of the bentonite in the Upper Ordovician Wufeng-Lower Silurian Longmaxi Formation in eastern Sichuan Basin,SW China. Petroleum Exploration and Development, 46(4): 653-665] [16] 王玉满,王红岩,沈均均,拜文华,董大忠,邱振,李新景,王灿辉. 2020. 川北—鄂西地区下志留统龙马溪组上段厚层斑脱岩的新发现及地质意义. 石油学报, 41(11): 1309-1323. [Wang Y M,Wang H Y,Shen J J,Bai W H,Dong D Z,Qiu Z,Li X J,Wang C H.2020. A new discovery and geological significance of thick-layered bentonites in the Upper Member of Lower Silurian Longmaxi Formatio in the Northern Sichuan-Western Hubei area. Acta Petrolei Sinica, 41(11): 1309-1323] [17] 肖斌. 2019. 四川盆地北缘五峰组—龙马溪组黑色页岩有机质富集主控因素研究. 成都理工大学博士学位论文: 126-133. [Xiao B.2019. Study on the main controlling factors of organic matter accumulation in the black shale of Wufeng-Lonmaxi Formations in the northern margin of Sichuan Basin,China. Doctoral dissertation of Chengdu University of Technology: 126-133] [18] 肖斌,刘树根,冉波,杨迪,韩雨樾. 2019. 基于元素Mn、Co、Cd、Mo的海相沉积岩有机质富集因素判别指标在四川盆地北缘的应用. 地质论评, 65(6): 1316-1330. [Xiao B,Liu S G,Ran B,Yang D,Han Y Y.2019. Identification of organic matter enrichment factors in marine sedimentary rocks based on elements Mn,Co,Cd and Mo: application in the northern margin of Sichuan Basin,South China. Geological Review, 65(6): 1316-1330] [19] 昝博文,刘树根,冉波,叶豪,杨迪,黄瑞,夏国栋,焦堃. 2017. 扬子板块北缘下志留统龙马溪组重晶石结核特征及其成因机制分析. 岩石矿物学杂志, 36(2): 213-226. [Zan B W,Liu S G,Ran B,Ye H,Yang D,Huang R,Xia G D,Jiao K.2017. An analysis of barite concretions from lower Silurian Longmaxi Formation on the northern margin of the Yangtze block and their genetic mechanism. Acta Petrologica et Mineralogica, 36(2): 213-226] [20] 张聪,黄虎,侯明才. 2017. 地球化学方法在硅质岩成因与构造背景研究中的进展及问题. 成都理工大学学报(自然科学版), 44(3): 293-304. [Zhang C,Huang H,Hou M C.2017. Progress and problems in the geochemical study on chert genesis for interpretation of tectonic background. Journal of Chengdu University of Technology(Science and Technology Edition), 44(3): 293-304] [21] 张明亮,郭伟,沈俊,刘凯,周炼,冯庆来,雷勇. 2017. 古海洋氧化还原地球化学指标研究新进展. 地质科技情报, 36(4): 95-106. [Zhang M L,Guo W,Shen J,Liu K,Zhou L,Feng Q L,Lei Y.2017. New progress on geochemical indicators of ancient oceanic redox condition. Geological Science and Technology Information, 36(4): 95-106] [22] 张水昌,张宝民,边立曾,金之钧,王大锐,张兴阳,高志勇,陈践发. 2005. 中国海相烃源岩发育控制因素. 地学前缘, 12(3): 39-48. [Zhang S C,Zhang B M,Bian L Z,Jin Z J,Wang D Y,Zhang X Y,Gao Z Y,Chen J F.2005. Development constraints of marine source rocks in China. Earth Science Frontiers, 12(3): 39-48] [23] 赵淑娟. 2012. 南海北部陆缘东沙运动的构造特征及其对被动大陆边缘构造演化的启示. 中国科学院(海洋研究所)硕士学位论文: 4-10. [Zhao S J.2012. Structures of the Dongsha Movement at the northern margin of the south China Sea: implications for the evoution of the passive continental margins. Masteral dissertation of Chinese Academy of Sciences(Institute of Oceanology): 4-10] [24] Adachi M,Yamamoto K,Sugisaki R.1986. Hydrothermal chert and associated siliceous rocks from the Northern Pacific: their geological significance as indication of ocean ridge activity. Sedimentary Geology, 47: 125-148. [25] Algeo T J,Liu J S.2020. A re-assessment of elemental proxies for paleoredox analysis. Chemical Geology, 540: 119549. [26] Jones B,Manning D A C.1994. Comparison of geochemical indices used for the interpretation of palaeoredox conditionsin ancient mudstone. Chemical Geology, 111: 111-129. [27] Ma Y Q,Fan M J,Lu Y C,Guo X S,Hu H Y,Chen L,Wang C,Liu X C.2016. Geochemistry and sedimentology of the Lower Silurian Longmaxi mudstone in southwestern China: implications for depositional controls on organic matter accumulation. Marine and Petroleum Geology, 75: 291-309. [28] Ma Y Q,Lu Y C,Liu X F,Zhai G Y,Wang Y F,Zhang C.2019. Depositional environment and organic matter enrichment of the lower Cambrian Niutitang shale in western Hubei Province,South China. Marine and Petroleum Geology, 109: 381-393. [29] Murray R W,Leinen M.1996. Scavenged excess aluminum and its relationship to bulk titanium in biogenic sediment from the central equatorial Pacific Ocean. Geochimica Et Cosmochimica Acta, 60: 3869-3878. [30] Pedersen T F,Calvert S E.1990. Anoxia vs productivity: what controls the formation of organic-carbon-rich sediments and sedimentary rocks? AAPG Bulletin, 74(4): 454-466. [31] Qiu Z,Zou C N,Benjamin J W M,Xiong Y J,Tao H F,Lu B,Liu H L,Xiao W J,Simon W P.2022. A nutrient control on expanded anoxia and global cooling during the Late Ordovician mass extinction. Communications Earth & Environment, 3(1): 82. [32] Sweere T,Boorn S V D,Dickson A J,Reichart G J.2016. Definition of new tracemetal proxies for the controls on organic matter enrichment in marine sediments based on Mn,Co,Mo and Cd concentrations. Chemical. Geology, 441: 235-245. [33] Taylor S R,McLennan S M.1985. The lcontinental crust: its composi-tion and evolution. Oxford: Blackwell Scientific Publications. [34] Tribovillard N,Algeo T J,Lyons T,Riboulleau A.2006. Trace metals as paleoredox and paleoproductivity proxies: an update. Chemical Geology,232(1/2): 12-32. [35] Ulrike H,Oliver E,Karin Z.2007. Distribution of organic-walled dinoflagellate cysts in shelf surface sediments of the Benguela upwelling system in relationship to environmental conditions. Marine Micropaleontology, 64: 91-119. [36] Wang S F,Zou C N,Dong D Z,Wang Y M,Li X J,Huang J L,Guan Q Z.2015. Multiple controls on the paleoenvironment of the Early Cambrian marine black shales in the Sichuan Basin,SW China: geochemical and organic carbon isotopic evidence. Marine and Petroleum Geology, 66: 660-672. [37] Wang Y M,Li X J,Dong D Z,Zhang C C,Wang S F.2017. Major controlling factors for the high-quality shale of Wufeng-Longmaxi Formation,Sichuan Basin. Energy Exploration and Exploitation, 35: 444-462. [38] Yan D T,Chen D Z,Wang Q C,Wang J G.2009. Geochemical changes across the Ordovician-Silurian transition on the Yangtze Platform,South China. Science in China Series D: Earth Sciences, 52: 38-54. [39] Yang S C,Hu W X,Wang X L.2021. Mechanism and implications of upwelling from the Late Ordovician to early Silurian in the Yangtze region,South China. Chemical Geology, 565: 120074. [40] Young G M,Nesbitt H W.1998. Processes controlling the distribution of Ti and Al in weathering profiles,siliciclastic sediments and sedimentary rocks. Journal of Sedimentary Research, 68(3): 448-455. [41] Zhao S Z,Li Y,Min H J,Wang T,Nie Z,Zhao Z Z,Qi J Z,Wang J C,Wu J P.2019. Development of upwelling during the sedimentary period of the organic-rich shales in the Wufeng and Longmaxi Formations of the Upper Yangtze Region and its impact on organic matter enrichment. Journal of Marine Science and Engineering, 7(4): 99.
