Palaeoclimatology and provenance of black shales from Wufeng-Longmaxi Formations in southwestern Sichuan Province:From geochemical records of Well Xindi-2
Mou Chuan-Long1,3, Ge Xiang-Ying1,2, Yu Qian1, Men Xin1,3, Liu Wei1, He Jiang-Lin1, Liang Wei1,3
1 Chengdu Institute of Geology and Mineral Resources,Chengdu 610081,China; 2 China University of Geosciences(Beijing),Beijing 100083,China; 3 Shandong University of Science and Technology,Qingdao 266590,China
Abstract：The Late Ordovician-Early Silurian transition was a critical interval in Earth’s history,marked by mass extinction,the Gondwana Glaciation and volcanic events. The end of Ordovician glaciations had a short-lived duration and there is no direct evidence for the glaciation in China. In order to confirm whether the palaeoclimatic changes ever existed during the end of the Ordovician-Early Silurian, we carried out major and trace elemental analyses on the core mudstone samples from the Wufeng-Longmaxi Formations of Well Xindi-2 in southwestern Sichuan Province,and reconstructed palaeoweathering conditions and palaeoclimatology through various chemical weathering indices. The ICVs(index of chemical varition)of all samples are greater than 1,indicating that they are compositionally inmature and first cycle deposits in tectonically active areas. The REE patterns are similar to the granite’s,which are characterized by slight LREE enrichments and accompanied by flat HREE trends with weakly negative Eu anomalies,suggesting that the source rocks are mainly pro-granite and felsic. The A-CN-K triangular diagram,Al2O3/TiO2, Cr/Zr, and Th/Sc ratios indicate that the provenance of the rocks is also primarily felsic. Indicated by the CIA(Chemical Index of Alteration),CIW(Chemical Index of Weathering)and PIA(Plagioclase Index of Alteration),the sediments experienced from moderate to weak then to moderate chemical weathering in the source area,and palaeoclimate shifted from warm to cold and then to warm again during the Late Ordovician-Early Silurian. The low CIA values of the Upper Wufeng Formation(CIAaver=64.14),Guanyinqiao Formation(CIAaver=61.7)and the bottom of Longmaxi Formation(CIAaver=64.61)reflect that there was a short cold climate time in Hirnantian Age,and represent indirect geochemical records in the South China of Gondwana Glaciation.
Mou Chuan-Long,Ge Xiang-Ying,Yu Qian et al. Palaeoclimatology and provenance of black shales from Wufeng-Longmaxi Formations in southwestern Sichuan Province:From geochemical records of Well Xindi-2[J]. JOPC, 2019, 21(5): 835-854.
[1] 陈代钊,汪建国,严德天,韦恒叶,遇昊,王清晨. 2011. 扬子地区古生代主要烃源岩有机质富集的环境动力学机制与差异. 地质科学, 46(1): 5-26. [Chen D Z,Wang J G,Yan D T,Wei H Y,Yu H,Wang Q C.2011. Environmental dynamics of organic accumulationfor the principal Paleozoic source rocks on Yangtze block. Chinese Journal of Geology, 46(1): 5-26] [2] 陈洪德,黄福喜,徐胜林,赵立群,滑心爽. 2009. 中上扬子地区碳酸盐岩储层发育分布规律及主控因素. 矿物岩石, 29(4): 7-15. [Chen H D,Huang F X,Xu S L,Zhao L Q,Hua X S.2009. Distribution rule and main controllong factors of the carbonate rock reservoirs in the Middle and Upper Yangtze Region. Journal of Mineralogy and Petrology, 29(4): 7-15] [3] 陈旭,樊隽轩,王文卉,王红岩,聂海宽,石学文,文治东,陈冬阳,李文杰. 2017. 黔渝地区志留系龙马溪组黑色笔石页岩的阶段性渐进展布模式. 中国科学: 地球科学,47(6): 720-732. [Chen X,Fan J X,Wang W H,Wang H Y,Nie H K,Shi X W,Wen Z D,Chen D Y,Li W J.2017. Stage-progressive distribution pattern of the Lungmachi black graptolitic shales from Guizhou to Chongqing,Central China. Science China: Earth Sciences, 60: 1133-1146] [4] 冯连君,储雪蕾,张启锐,张同钢. 2003. 化学蚀变指数(CIA)及其在新元古代碎屑岩中的应用. 地学前缘, 10(4): 539-544. [Feng L J,Chu X L,Zhang Q R,Zhang T G.2003. CIA(Chemical Index of Alteration)and its application in the Neoproterozoic Clastic rocks. Earth Science Frotiers, 10(4): 539-544] [5] 郭旭升,胡东风,文治东,刘若冰. 2014. 四川盆地及周缘下古生界海相页岩气富集高产主控因素: 以焦石坝地区五峰组—龙马溪组为例. 中国地质, 41(3): 893-901. [Guo X S,Hu D F,Wen Z D,Liu R B.2014. Major factors controlling the accumulation and high prouductivity in marine shale gas in the Lower Paleozoic of Sichuan Basin and its periphery: A case study of the Wufeng-Longmaxi Formations of Jiaoshiba area. Geology in China, 41(3): 893-901] [6] 何登发,李德生,张国伟,赵路子,樊春,鲁人齐,文竹. 2011. 四川多旋回叠合盆地的形成与演化. 地质科学, 46(3): 589-606. [He D F,Li D S,Zhang G W,Zhao L Z,Fan C,Lu R Q,Wen Z.2011. Formation and evolution of multi-cycle superposed Sichuan Basin,China. Chinese Journal of Geology, 46(3): 589-606] [7] 黄福喜,陈洪德,侯明才,钟怡江,李洁. 2011. 中上扬子克拉通加里东期(寒武—志留纪)沉积层序充填过程与演化模式. 岩石学报, 27(8): 2299-2317. [Huang F X,Chen H D,Hou M C,Zhong Y J,Li J.2011. Filling process and evolutionary model of sedimentary sequence of Middle-Upper Yangtze craton in Caledonian(Cambrian-Silurian). Acta Petrologica Sinica, 27(8): 2299-2317] [8] 黄云飞,张昌民,朱锐,易雪斐,瞿建华,唐勇. 2017. 准噶尔盆地玛湖凹陷晚二叠世至中三叠世古气候、物源及构造背景. 地球科学, 42(10): 1736-1749. [Huang Y F,Zhang C M,Zhu R,Yi X F,Qu J H,Tang Y.2017. Palaeoclimatology,provenance and tectonic setting during Late Permian to Middle Triassic in Mahu Sag,Junggar Basin,China. Earth Science, 42(10): 1736-1749] [9] 刘树根,马文辛,LUBA Jansa,黄文明,曾祥亮,张长俊. 2011. 四川盆地东部地区下志留统龙马溪组页岩储层特征. 岩石学报, 27(8): 2239-2252. [Liu S G,Ma W X,LUBA J,Huang W M,Zeng X L,Zhang C J.2011. Characteristics of the shale gas reservoir rocks in the Lower Silurian Longmaxi Formation,East Sichuan basin,China. Acta Petrologica Sinica, 27(8): 2239-2252] [10] 刘伟,许效松,冯心涛,孙媛媛. 2010. 中上扬子上奥陶统五峰组含放射虫硅质岩与古环境. 沉积与特提斯地质, 30(3): 65-70. [Liu W,Xu X S,Feng X T,Sun Y Y.2010. Radiolarian silicalites and palaeoenvironmental reconstruction for the Upper Ordovician Wufeng Formation in the Middle-Upper Yangtze area. Sedimentary Geology and Tethyan Geology, 30(3): 65-70] [11] 刘伟,许效松,余谦,闫剑飞,门玉澎,张海全. 2012. 中上扬子晚奥陶世赫南特期岩相古地理. 成都理工大学学报(自然科学版), 39(1): 32-39. [Liu W,Xu X S,Yu Q,Yan J F,Men Y P,Zhang H Q.2012. Lithofacies palaeography of the Late Ordovician Hirnantian in the Middle-Upper Yangtze region of China. Journal of Chengdu University of Technology(Natural Science Edition), 39(1): 32-39] [12] 隆轲,陈洪德,林良彪,徐胜林,程立雪. 2011. 四川盆地白垩纪构造层序、岩相古地理及演化. 地层学杂志, 35(3): 328-336. [Long K,Chen H D,Lin L B,Xu S L,Cheng L X.2011. Cretaceous tectonic sequence and litho-paleogeographic evolution in the Sichuan Basin. Journal of Stratigraphy, 35(3): 328-336] [13] 牟传龙,许效松. 2010. 华南地区早古生代沉积演化与油气地质条件. 沉积与特提斯地质, 30(3): 24-29. [Mou C L,Xu X S.2010. Sedimentary evolution and petroleum geology in South China during the Early Palaeozoic. Sedimentary Geoligy and Tethyan Geology, 30(3): 24-29] [14] 牟传龙,周恳恳,梁薇,葛祥英. 2011. 中上扬子地区早古生代烃源岩沉积环境与油气勘探. 地质学报, 85(4): 1-7. [Mou C L,Zhou K K,Liang W,Ge X Y.2011. Early Paleozoic sedimentary environment of hydrocarbon source rocks in the Middle-Upper Yangtze region and petroleum and gas exploration. Acta Geologica Sinica, 85(4): 1-7] [15] 戎嘉余. 1984. 上扬子区晚奥陶世海退的生态地层证据与冰川活动影响. 地层学杂志, 8(1): 19-29. [Rong J Y.1984. Ecostratigraphic evidence of the Upper Ordovician regressive sequences and the effect of glaciation. Journal of Stratigraphy, 8(1): 19-29] [16] 王清晨,严德天,李双建. 2008. 中国南方志留系底部优质烃源岩发育的构造—环境模式. 地质学报, 82(3): 289-297. [Wang Q C,Yan D T,Li S J.2008. Tectonic-environmental model of the Lower Silurian high-quality hydrocarbon source rocks from South China. Acta Geologica Sinica, 82(3): 289-297] [17] 汪泽成,赵文智,彭红雨. 2002. 四川盆地复合含油气系统特征. 石油勘探与开发, 29(2): 26-28. [Wang Z C,Zhao W Z,Peng H Y.2002. Characteristics of multi-source petroleum systems in Sichuan basin. Petroleum Exploration and Development,29(2): 26-28] [18] 许效松,万方,尹福光,陈明. 2001. 奥陶系宝塔组灰岩的环境相、生态相与成岩相. 矿物岩石, 21(3): 64-68. [Xu X S,Wan F,Yin F G,Chen M.2001. Environment facies,ecological facies and diagenetic facies of Baota Formation,of Late Ordovician. Journal of Mineralogy and Petrology, 21(3): 64-68] [19] 徐小涛,邵龙义. 2018. 利用泥质岩化学蚀变指数分析物源区风化程度时的限制因素. 古地理学报, 20(3): 515-522. [Xu X T,Shao L Y.2018. Limiting factors in utilization of chemical index of alteration of mudstones to quantify the degree of weathering in provenance. Journal of Palaeogeography(Chinese Edition), 20(3): 515-522] [20] 严德天,王清晨,陈代钊,汪建国,王卓卓. 2008. 扬子及周缘地区上奥陶统—下志留统烃源岩发育环境及其控制因素. 地质学报, 82(3): 321-327. [Yan D T,Wang Q C,Chen D Z,Wang J G,Wang Z Z.2008. Sedimentary environment and development controls of the hydrocarbon sources beds: The Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation in the Yangtze Area. Acta Geologica Sinica, 82(3): 321-327] [21] 严德天,汪建国,王卓卓. 2009. 扬子地区上奥陶—下志留统生物钡特征及其古生产力意义. 西安石油大学学报: 自然科学版, 24(4): 16-19. [Yan D T,Wang J G,Wang Z Z.2009. Biogenetic barium distribution from the Upper Ordovician to Lower Silurian in the Yangtze area and its significance to paleoproductivity. Journal of Xi’an Shiyou University(Natural Science Edition), 24(4): 16-19] [22] 严德天,王清晨,陈代钊,汪建国,邱振. 2011. 扬子地区晚奥陶世碳酸盐台地淹没事件及其地质意义. 地质科学, 46(1): 42-51. [Yan D T,Wang Q C,Chen D Z,Wang J G,Qiu Z.2011. The Late Ordovician drowning of the Yangtze carbonate platform and its geologic significance. Chinese Journal of Geology, 46(1): 42-51] [23] 闫剑飞,余谦,刘伟,门玉澎. 2010. 中上扬子地区下古生界页岩气资源前景分析. 沉积与特提斯地质, 30(3): 96-103. [Yan J F,Yu Q,Liu W,Men Y P.2010. Perspectives of the Lower Palaeozoic shale gas resources in the middle upper Yangtze area. Sedimentary Geology and Tethyan Geology, 30(3): 96-103] [24] 余谦,牟传龙,张海全,谭钦银,许效松,闫剑飞. 2011. 上扬子北缘震旦纪—早古生代沉积演化与储层分布特征. 岩石学报, 27(3): 672-680. [Yu Q,Mou C L,Zhang H Q,Tan Q Y,Xu X S,Yan J F.2011. Sedimentary evolution and reservoir distribution of northern Upper Yangtze plate in Sinian-Early Paleozoic. Acta Petrologica Sinica, 27(3): 672-680] [25] 张春明,张维生,郭英海. 2012. 川东南—黔北地区龙马溪组沉积环境及对烃源岩的影响. 地学前缘, 19(1): 136-145. [Zhang C M,Zhang W S,Guo Y H.2012. Sedimentary environment and its effect on hydrocarbon source rocks of Longmaxi Formation in Southeast Sichuan and Northern Guizhou. Earth Science Frontiers, 19(1): 136-145] [26] 张金川,聂海宽,徐波,姜生玲,张培先. 2008. 四川盆地页岩气成藏地质条件. 天然气工业, 28(2): 151-156. [Zhang J C,Nie H K,Xu B,Jiang S L,Zhang P X.2008. Geological condition of Shale gas accumulation in Sichuan Basin. Natural Gas Industry, 28(2): 151-156] [27] Armstrong-Altrin J S.2015. Evaluation of two multidimensional discrimination diagrams from beach and deep-sea sediments from the Gulfof Mexico and their application to Precambrian clastic sedimentaryrocks. International Geology Review, 57(11-12): 1444-1459. [28] Armstrong-Altrin J S,Lee Y I,Verma S P,Ramasamy S.2004. Geochemistry ofsandstonesfromthe Upper Miocene Kudankulam Formation,southern India: Implicationsfor provenance,weathering,and tectonic setting. Journal of Sedimentary Research, 74(2): 285-297. [29] Armstrong-Altrin J S,Lee Y I,Kasper-Zubillaga J J,Carranza-Edwards A,Garcia D,Eby G N,Balaram V,Cruz-Ortiz N L.2012. Geochemistry of beach sands along the westernGulf of Mexico,Mexico: Implication for provenance. Chemie der Erde-Geochemistry-Interdisciplinary Journal for Chemical Problems of the Geosciences and Geoecology, 72: 345-362. [30] Bhatia M R.1983. Plate tectonics and geochemical composition of sandstones. The Journal of Geology, 91(6): 611-627. [31] Bhatia M R.1985. Composition and classification of Paleozoic flysch mudrocks ofeastern Australia: Implications in provenance and tectonic setting interpretation.Sedimentary Geology, 41(2-4): 249-268. [32] Bhatia M R,Crook K A W.1986. Trace element characteristics of graywackesand tectonic setting discrimination of sedimentary basins.Contributions to Mineralogy and Petrology, 92(2): 181-193. [33] Brenchley P J,Marshall J D,Harper D A T,Buttler C J,Underwood C J.2006. A late Ordovician(Hirnantian)karstic surface in a submarine channel,recording glacioeustatic sea-level changes: Meifod,central Wales. Geological Journal, 41: 1-22. [34] Chen C,Mu C L,Zhou K K,Liang W,Ge X Y,Wang X P,Wang Q Y,Zheng B S.2016. The geochemical characteristics and factors controlling the organicmatter accumulation of the Late Ordovician-Early Silurian black shalein the Upper Yangtze Basin,South China. Marine and Petroleum Geology, 76: 159-175. [35] Chen X,Rong J Y,Fan J X,Zhan R B,Mitchell C E,Harper D A T,Melchin M J,Peng P A,Finney S C,Wang X F.2006. The Global Boundary Stratotype Section and Point(GSSP)for the base of the Hirnantian Stage(the uppermost of the Ordovician System). Episodes, 29: 183-196. [36] Cox R,Lowe D R,Cullers R L.1995. The influence of sediment recycling and basement composition on evolution of mudrock chemistry in the southwestern United States.Geochimica Et Cosmochimica Acta, 59: 2919-2940. [37] Cullers R L.1995. The controls on the major-and trace-element evolutionof shales,siltstones and sandstones of Ordovician to Tertiary age in theWet Mountains region,Colorado,U.S.A. Chemical Geology, 123(1): 107-131. [38] Cullers R L,Podkovyrov V N.2000. Geochemistry of the Mesoproterozoic Lakhanda shales in southeastern Yakutia,Russia: Implications for mineralogical and provenance control,and recycling. Precambrian Research, 104(1): 77-93. [39] Cullers R L,Podkovyrov V N.2002. The source and origin of terrigenous sedimentary rocks in the Mesoproterozoic Ui group,southeastern Russia. Precambrian Research, 117(3): 157-183. [40] Dickinson W R,Suczek C A.1979. Plate tectonics and sandstone compositions. AAPG Bulletin, 63: 2164-2182. [41] Fedo C M,Nesbitt H W,Young G M.1995. Unraveling the effects of Kmetasomatism in sedimentary rocks and paleosols with implicationsfor palaeoweathering conditions and provenance. Geology, 23: 921-924. [42] Fedo C M,Young G M,Nesbitt H W.1997. Paleoclimatic control on thecomposition of the Paleoproterozoic Serpent Formation,HuronianSupergroup,Canada: A greenhouse to icehouse transition. PrecambrianResearch, 86: 210-223. [43] Harnois L.1988. The CIW index: A new chemical index of weathering. Sedimentary Geology, 55: 319-322. [44] Hayashi K I,Fujisawa H,Holland H D,Ohomoto H.1997. Geochemistry of 1.9 Ga sedimentary rocks from northern Labrador,Canada.Geochimica Et Cosmochimica Acta, 61: 4115-4137. [45] Harper D A T,Hammarlund E U,Rasmussen C M Ø.2014. End Ordovician extinctions: A coincidence of causes. Gondwana Research, 25: 1294-1307. [46] Hofmann A.2005. The geochemistry of sedimentary rocks from the Fig Tree Group,Barberton greenstone belt: Implications for tectonic hydrothermal and surface processes during mid-Archaean times. Precambrian Research, 143: 23-49. [47] Huang H Y,He D F,Li Y Q,Li J,Zhang L.2018. Silurian tectonic-sedimentary setting and basin evolution in the Sichuanarea,southwest China: Implications for palaeogeographic reconstructions. Marine and Petroleum Geology, 92: 403-423. [48] Liu Z H,Algeo T J,Guo X S,Fan J X,Du X B,Lu Y C.2017. Paleo-environmental cyclicity in the Early Silurian Yangtze Sea(SouthChina): Tectonic or glacio-eustatic control?Palaeogeography Palaeoclimatology Palaeoecology, 466: 59-76. [49] Luo Q Y,Zhong N N,Dai N,Zhang W.2016. Graptolite-derived organic matter in the Wufeng-Longmaxi Formations(Upper Ordovician-Lower Silurian)of southeastern Chongqing,China: Implications for gas shale evaluation. International Journal of Coal Geology, 153: 87-98. [50] McLennan S M.1989. Rare Earth Elements in sedimentary rocks: Influence of provenance and sedimentary processes. Review in Mineralogy, 21(1): 169-200. [51] McLennan S M,Taylor S R.1991. Sedimentary rocks and crustal evolution: Tectonic setting and secular trends. The Journal of Geology, 99(1): 1-21. [52] McLennan S M,Hemming S R,McDaniel D K,Hanson,G N.1993. Geochemical approaches to sedimentation,provenance and tectonics. Special Paper of the Geological Society of America,284: 21-40. [53] Nesbitt H W,Young G M.1982. Early Proterozoic climates and platemotions inferred from major element chemistry of lutites. Nature, 299: 715-717. [54] Nesbitt H W,Young G M.1984. Prediction of some weathering trends of plutonic and volcanic rocksbased on thermodynamic and kinetic considerations.Geochimica et Cosmochimica Acta, 48(7): 1523-1534. [55] Nesbitt H W,Young G M.1989. Formation and diagenesis of weathering profiles. Journal of Geology, 97: 129-147. [56] Nesbitt H W,Young G M.1996. Petrogenesis of sediments in the absence of chemical weathering: Effects of abrasion and sorting on bulkcomposition and mineralogy. Sedimentology, 43(2): 341-358. [57] Purevjav N,Roser B P.2012. Geochemistry of Devonian-Carboniferous clastic Sediments of the Tsetserleg terrane,Hangay Basin,central Mongolia: Provenance,source weathering,and tectonic setting. Island Arc, 21(4): 270-287. [58] Ran B,Liu S G,Jansa L B,Sun W,Yang D,Ye Y H,Wang S Y,Luo C,Zhang X,Zhang C J.2015. Origin of the upper Ordovician-lower Silurian cherts of the Yangtze block,South China,and their palaeogeographic significance. Journal of Asian Earth Sciences, 108: 1-17. [59] Roser B P,Korsch R J.1988. Provenance signatures of sandstone-mudstone suites determined using discriminant function analysis of major-element data. Chemical Geology, 67(1): 119-139. [60] Sugitani K,Yanmashita F,Nagaoka T,Yamamotod K,Minamie M,Mimurad K,Suzuki K.2006. Geochemistry and sedimentary petrology of Archean clastic sedimentary rocks at Mt. Goldsworthy,Pilbara Craton,Western Australia: Evidence for the early evolution of contimental crust and hydrothermal alteration. Precambrian Research, 147: 124-147. [61] Taylor S R,McLennan S M.1985. The Continental Crust: Its Compositionand Evolution. Oxford: Blackwell Scientific Publications,1-312. [62] Wang J P,Deng X J,Wang G,Li Y.2012. Types and biotic successions of Ordovician reefs in China.Chinese Science Bulletin, 57(10): 1160-1168. [63] Wang S F,Dong D Z,Wang Y M,Li X J,Huang J L,Guan Q Z.2016a. Sedimentary geochemical proxies for paleoenvironmentinterpretation of organic-rich shale: A case study of the Lower Silurian Longmaxi Formation,Southern Sichuan Basin,China. Journal of Natural Gas Science and Engineering, 28: 691-699. [64] Wang X Q,Zhu Y M,Lash G G,Wang Y.2019. Multi-proxy analysis of organic matter accumulation in the UpperOrdovician-Lower Silurian black shale on the Upper Yangtze Platform,south China. Marine and Petroleum Geology, 103: 473-484. [65] Wang Y M,Dong D Z,Huang J L,Li X J,Wang S F.2016b. 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, 43(1): 45-53. [66] 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 theWufengeLongmaxi Fm,Upper Yangtze region.Natural Gas Industry, 4: 327-339. [67] Wronkiewicz DJ,Condie KC.1987. Geochemistry of Archean shales from the Witwatersrand Supergroup,South Africa: Source area weathering and provenance. Geochimica Et Cosmochimica Acta, 51(9): 2401-2416. [68] Wronkiewicz D J,Condie K C.1989. Geochemistry and provenance ofsediments from the Pongola Supergroup,South Africa: Evidence for a 3.0-Ga-old continental craton. Geochimica Et Cosmochimica Acta, 53: 1537-1549. [69] Wu J,Liang C,Hu Z Q,Yang R C,Xie J,Wang R Y.2019. Sedimentation mechanisms and enrichment of organic matter in the Ordovician Wufeng Formation-Silurian Longmaxi Formation in the Sichuan Basin.Marine and Petroleum Geology, 101: 556-565. [70] YanD T,ChenD Z,Wang Q C,Wang J G.2009a. Geochemical changes across the Ordovician-Silurian transition on the Yangtze Platform,South China. Science ChinaEarth Science, 52: 38-54. [71] Yan D T,Chen D Z,Wang Q C,Wang J G,Wang Z Z.2009b. Carbon and sulphur isotopic anomalies across the Ordovician-Silurian boundary on the Yangtze Platform,South China.Palaeogeography Palaeoclimatology Palaeoecology, 274: 32-39. [72] Yan D T,Chen D Z,Wang Q C,Wang J G.2010. Large-scale climatic fluctuations in the latest Ordovician on the Yangtze block,South China. Geology, 38: 599-602. [73] Yan D T,Wang H,Fu Q L,Chen Z H,He J,Gao Z.2015. Geochemical characteristics in the Longmaxi Formation(Early Silurian)of south China: Implications for organic matter accumulation. Marine and Petroleum Geology, 65: 290-301. [74] Yang R,He S,Hu Q H,Hu D F,Yi J Z.2017. Geochemical characteristics and origin of natural gas from Wufeng-Longmaxi shales of the Fuling gas field,Sichuan Basin(China). International Journal of Coal Geology, 171: 1-11. [75] Young G M,Nesbitt H W.1999. Paleoclimatology and provenance of the Glaciogenic Gowganda Formation(Paleoproterozoic),Ontario,Canada: A chemostratigraphic approach. Geological Society of America Bulletin, 111(2): 264-274. [76] Zaid S M.2012. Provenance,diagenesis,tectonic setting and geochemistry of Rudiessandstone(Lower Miocene),Warda field,Gulf of Suez,Egypt. Journal of African Earth Sciences, 66-67: 56-71. [77] Zaid S M.2015. Geochemistry of sandstones from the Pliocene GabirFormation,north Marsa Alam,Red Sea,Egypt: Implication for provenance,weathering and tectonic setting. Journal of African Earth Sciences, 102: 1-17. [78] Zhao J H,Jin Z K,Jin Z J,Wen X,Geng Y K.2017. Origin of authigenic quartz in organic-rich shales of the Wufeng andLongmaxi Formations in the Sichuan Basin,South China: Implicationsfor pore evolution. Journal of Natural Gas Science and Engineering, 38: 21-38. [79] Zhao S Z,Li Y,Min H J,Yu Q,Wang Z J,Deng T,Liu H,Chen J.2019. Mechanisms controlling organic matter enrichment in the LowerSilurian Longmaxi Formation black shale unit,southwestern marginof the Yangtze Platform,China. Arabian Journal of Geosciences, 12: 252-267. [80] Zhou L,Algeo T J,Shen J,Hu Z F,Gong H,Xie S,Huang J H,Gao S.2015. Changes in marine productivity and redox conditions during the late Ordovician Hirnantian glaciation. Palaeogeography Palaeoclimatology Palaeoecology, 420: 223-234. [81] Zhu Y Q,Wang X Z,Feng M Y,Pu K,Cai J C.2018. Palaeo-redox environment analysis of Longmaxi Formation shale in southern Sichuan basin by XRF and ICP-MS. Science Asia, 44: 109-117. [82] Zou C N,Qiu C,Poulton S W,Dong D Z,Wang H Y,Chen D Z,Lu B,Shi Z S,Tao H F.2018. Ocean euxinia and climate change “double whammy” drove the Late Ordovician mass extinction. Geology, 46: 535-538.
