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Source of silica and its implications for organic matter enrichment in the Upper Ordovician-Lower Silurian black shale in western Hubei Province,China:Insights from geochemical and petrological analysis

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Petroleum Science 2022年第1期19卷 74-90页

作者： Quan-Sheng Cai Ming-Yi Hu Bao-Min Zhang Ngong Ngia An Liu Rui-Quan Liao Oumar Kane Hai Li Zhong-Gui Hu Qing-Jie Deng Jun-Jun Shen School of Geosciences Yangtze UniversityWuhanHubei 430100China Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education(China University of Geosciences) WuhanHubei 430074China Wuhan Center of China Geological Survey WuhanHubei 430205China Department of Geology University of BueaP.O.Box 63BueaSouthwestCameroon School of Petroleum Engineering Yangtze UniversityWuhanHubei 430100China

To improve the understanding of the relationship between silica source and organic matter accumulation,the origin of silica and its implications for organic matter enrichment in the Upper OrdovicianLower Silurian(O_(3)w-S_(1)l)black shale in western Hubei Province in the middle Yangtze area,were investigated through geochemical and petrological analyses.The results show that the O_(3)w-S_(1)l black shale is mainly composed of five lithofacies with varying graptolite abundance,total organic carbon(TOC),and silica contents.Biogenic silica and terrigenous siliciclastic input constitute the main silica sources in O_(3)w-S_(1)l black shale and they exhibit an upward inverse variation trend interpreted to be related to sea-level changes.Moreover,with the increase in biogenic silica content or decrease in terrigenous siliciclastic input,TOC values in black shale initially rise and then fall,which is different from originally expected simple linear relationship.We infer that organic matter enrichment and the distribution of silica from different origins are controlled by sea-level changes and variations in terrigenous input in a continental shelf with little hydrothermal influence.An environment with appropriate sea level and terrigenous input should be most favorable for organic matter accumulation,rather than one with excessive high sea level and less terrigenous input.

关键词： Biogenic silica Terrigenous siliciclastic input Organic matter enrichment Black shale Continental shelf sea-level change Wufeng-Longmaxi formations

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Carbon Isotope from Shallow Marine System in North China:Implications for Stratigraphical Correlation and sea-level changes in Cambrian

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Journal of Earth Science 2023年第6期34卷 1777-1792页

作者： Jingxun Zuo Xuejian Zhu Yonglin Chen Wenjian Zhai Henan Institute of Geological Survey Zhengzhou 450001China Nanjing Institute of Geology and Paleontology Chinese Academy of SciencesNanjing 210008China

Cambrian System at the Shatan Section in northern Henan,North China,consists of sedimentary successions of tidal flat and shallow-water carbonate platform facies.Data of carbon isotope(δ^(13)C_(carb))from this section reveals five positive δ^(13)C_(carb)(P_(st-1)-P_(st-5))and five negative δ^(13)C_(carb) excursions(N_(st-1)-N_(st-5)).In the positive excursions,δ^(13)C_(carb) rises to 0.88‰,1.05‰,2.04‰,1.00‰ and 2.97‰,respectively,while in the negative excursions δ^(13)C_(carb) drops to -8.00‰,-3.50‰,-1.00‰,-0.33‰ and around -2.00‰,respectively.On the basis of chronostratigraphy of Cambrian,the most remarkable carbon isotope excursions can be correlated regionally and globally.In addition,one second-order and ten third-order sequences have been recognized at this section.Correlating third-order sequences and chemostratigraphy indicates that carbonates from the basal part of the transgression system tract(TST)and the upper part of the high-water system(LHST)generally have lighter δ^(13)C_(carb) values,whereas massive carbonates with microbialite from the lower part of the high-water system tract(EHST)usually have heavier δ^(13)C_(carb) values.The association of δ^(13)C_(carb) values with sea-level fluctuations suggests that the positive carbon isotope excursions or high δ^(13)C_(carb) values may have been caused by an increase in the marine primary productivity in response to maximum seawater flooding during the transgression.

关键词： carbon isotope sedimentary rocks sea-level change shallow-water Cambrian System stratigraphy North China

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Petrological and geochemical characteristics of the Ordovician-Silurian black shale in eastern Sichuan and western Hubei,South China:Differential sedimentary responses to tectonism and glaciation

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Journal of Palaeogeography 2023年第1期12卷 129-152页

作者： Quan-Sheng Cai Ming-Yi Hu Oumar Ibrahima Kane Zhi Yang Ya-Ru Wen Qun Luo Ming-Tao Li Zhong-Gui Hu Qing-Jie Deng Cooperative Innovation Center of Unconventional Oil and Gas Yangtze University(Ministry of Education and Hubei Province)Wuhan 430100Hubei ProvinceChina School of Geosciences Yangtze UniversityWuhan 430100Hubei ProvinceChina Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education China University of Geosciences(Wuhan)Wuhan 430074Hubei ProvinceChina Natural Gas Geology Key Laboratory of Sichuan Province Chengdu 610500Sichuan ProvinceChina Research Institute of Petroleum Exploration and Development PetroChinaBeijing 100083China Hubei Geological Survey Wuhan 430034Hubei ProvinceChina Institute of Unconventional Science and Technology China University of Petroleum(Beijing)Beijing 102249China

During the Ordovician-Silurian transition period,the Yangtze area experienced significant environmental changes,which were recorded by the widely distributed black shale of the Upper Ordovician Wufeng and Lower Silurian Longmaxi formations.However,the petrological and geochemical analyses of the Upper Ordovician-Lower Silurian black shale in Well JY1(eastern Sichuan Basin)and Well YY2(western Hubei Province)drill cores show that there are some significant differences with respect to lithology,thickness,and geochemical characteristics despite the long-term similar variation trend in petrology and geochemistry.This may suggest some major environmental changes and their differential influence on black shale deposition in the Yangtze area.Based on the analyses of lithology,total organic carbon(TOC),Mo_(EF),and U_(EF),four long-term sedimentary cycles(one for the Wufeng Formation and three for the Longmaxi Formation)were identified in Well JY1.In Well YY2,only three long-term sedimentary cycles can be recognized(one for the Wufeng Formation and two for the Longmaxi Formation).Different from the gradual increase of the geochemical proxies(such as TOC,MoEF,and NiEF)followed by an abrupt decrease in the Wufeng Formation,these proxies of the Silurian sedimentary cycles in both wells exhibit an abrupt increase at the base followed by a gradual decrease,showing that controlling mechanisms for the Lower Silurian black shale deposition in the study areas were different from those of the Upper Ordovician black shale.However,the black shale of each Silurian cycle in Well JY1 is much thicker than that in Well YY2.Compared with the thick silty mudstone developed in Well JY1 during the Rhuddanian-Aeronian transition,there is a stratigraphic gap in Well YY2 except for a thin calcareous dolostone formed in a strongly restricted environment.These differences indicate that tectonism and glacial eustasy should be the key factors for black shale development,but their influences on the deposition of the Lower Silurian black shale varied

关键词： Ordoviciane-Silurian transition Black shale Sedimentary differences Tectonism Paleoclimate sea-level change Yangtze area

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Controlling Factors on Organic Matter Accumulation of Marine Shale across the Ordovician–Silurian Transition in South China: Constraints from Trace-Element Geochemistry

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Journal of Earth Science 2021年第4期32卷 887-900页

作者： Zhen Qiu Huifei Tao Bin Lu Zhenhong Chen Songtao Wu Hanlin Liu Junli Qiu Research Institute of Petroleum Exploration and Development CNPCBeijing 100083China National Energy Shale Gas Research and Development(Experiment)Center Langfang 065007China Oil and Gas Research Center Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China Key Laboratory of Oil and Gas Reservoirs CNPCBeijing 100083China National Energy Tight Oil and Gas R&D Center Beijing 100083China Institute of Oil and Gas Peking UniversityBeijing 100871China

In recent years,significant progress in shale gas exploration has been achieved in the Upper Ordovician(Wufeng Formation)–Lower Silurian(Longmaxi Formation)shales in the Upper Yangtze area,South China.Although many studies have been carried out on the Upper Ordovician–Lower Silurian shales,the controlling factors causing organic matter accumulation of these shales remain controversial.This study uses trace-element geochemistry and sedimentological methods to evaluate terrigenous input,redox conditions and primary productivity to explore the mechanisms of organic matter accumulation.The variation of terrigenous fraction elements(Al,Th and Sc)concentrations reflect a mixed influence of sea-level change and weathering.The sea-level of the Upper Yangtze sea went through two cycles of transgression to regression during the Ordovician–Silurian transition.The Linxiang Formation,Kuanyinchiao Bed and the upper part of Longmaxi Formation developed during the periods of regression,whereas the Wufeng Formation and the lower part of the Longmaxi Formation developed during the periods of transgression.The paleo-productivity indexes of TOC content,ratios of Ba/Al and P/Al,and redox conditions proxies of Mo concentration,ratios of U/Th and V/Cr generally display similar variation patterns with respect to the sea-level changes.High TOC contents and Ba/Al and P/Al ratios indicate the paleo-productivity was high on the sea surface,as shown by relatively good positive correlations between Th vs.TOC,and Sc vs.TOC.This indicates that the paleo-productivity was controlled by the nutrients input through weathering.The good positive correlations between redox conditions indexes(U/Th and V/Cr ratios)with TOC content reflects reductive preservation conditions(anoxic to euxinic),thus implying they were an important controlling factor for organic matter accumulation.Nevertheless,redox conditions were closely associated with sea level change and organic matter decomposition.Therefore,the sea-level change and weathering were the primary contro

关键词： productivity redox sea-level change shale gas Sichuan Basin Wufeng-Longmaxi shale

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Roadian-Wordian(Middle Permian)Conodont Biostratigraphy,Sedimentary Facies and Paleotemperature Evolution at the Shuixiakou Section,Xikou Area,Southeastern Qinling Region,China

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Journal of Earth Science 2021年第3期32卷 534-553页

作者： Baojin Wu Hanxiao Li Michael M.Joachimski Paul B.Wignall Haishui Jiang Lina Wang Xianlang Wu Xulong Lai Jiaxin Yan State Key Laboratory of Biogeology and Environmental Geology China University of GeosciencesWuhan 430078China School of Earth Sciences China University of GeosciencesWuhan 430074China GeoZentrum Nordbayern Universitat Erlangen-NürnbergErlangen 91054Germany School of Earth and Environment University of LeedsLeeds LS29JTUK College of Resources Hebei GEO UniversityShijiazhuang 050031China

Focusing on the Shuixiakou Section(Xikou area,Zhen’an County,Shaanxi Province,southeastern Qinling region,China),the Roadian-Wordian conodonts are investigated.More than 2000 conodont elements including 6 genera and 14 species have been obtained.Based on these materials,the Guadalupian Jinogondolella nankingensis and J.aserrata zones have been recognized.The Roadian-Wordian boundary is tentatively defined by the first occurrence of J.aserrata in the lower part of UnitⅢin the Shuixiakou Formation.The sedimentary succession of Xikou area records similar sea-level changes to those observed in Laibin area(South China).The 40 m-thick bioclastic limestone of UnitⅣin this section can be correlated with the reefs of Bed 114 in Laibin area.A temperature drop indicated byδ18Oapatite values suggests this Wordian interval coincides with a period of glaciation and global regression.

关键词： biostratigraphic framework sea-level change paleotemperature Roadian-Wordian boundary Shuixiakou Section

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Paleoecology of Early Ordovician Reefs in the Yichang Area,Hubei:a Correlation of Organic Reefs Between Early Ordovician and Jurassic

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Acta Geologica Sinica(English Edition) 2011年第5期85卷 1003-1015页

作者： Chuantao XIAO Meng LI Wei YANG Mingyi HU Chao LI Key Laboration of Exploration Technologies for Oil and Gas Resources (Yangtze University) Ministry of Education Jingzhou Hubei 434023 China Gas Geology Department of Langfang Branch Research Institute of Petroleum Exploration and Development CNPC Langfang Hebei 065007 China

The Early Ordovician System is composed mainly of a series of carbonate platform deposits interbedded with shale and is especially characterized by a large number of organic reefs or buildups that occur widely in the research area.The reefs have different thicknesses ranging from 0.5 m to 11.5 m and lengths varying from 1 m to 130 m.The reef-building organisms include Archaeoscyphia, Recepthaculitids,Batostoma,Cyanobacteria and Pulchrilamina.Through the research of characteristics of the reef-bearing strata of the Early Ordovician in the Yichang area,four sorts of biofacies are recognized,which are(1) shelly biofacies:containing Tritoechia-Pelmatozans community and Tritoechia-Pomatotrema community;(2) reef biofacies:including the Batostoma,Calathium-Archaeoscyphia, Pelmatozoa-Batostoma,Archeoscyphia and Calathium-Cyanobacteria communities; (3) standing-water biofacies:including the Acanthograptus-Dendrogptus and Yichangopora communities;and(4) allochthonous biofacies:containing Nanorthis-Psilocephlina taphocoense community.The analysis of sea-level changes indicates that there are four cycles of sea-level changes during the period when reef-bearing strata were formed in this area,and the development of reefs is obviously controlled by the velocity of sea-level changes and the growth of accommodation space.The authors hold that reefs were mostly formed in the high sea level periods.Because of the development of several subordinate cycles during the sea-level rising,the reefs are characterized by great quantity, wide distribution,thin thickness and small scale,which are similar to that of Juassic reefs in northern Tibet.The research on the evolution of communities shows that succession and replacement are the main forms.The former is favorable to the development of reefs and the latter indicates the disappearance of reefs.

关键词： organic reef paleoecology sea-level change Early Ordovician Yichang area

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Quaternary Neotectonic Configuration of the Southwestern Peloponnese, Greece, Based on Luminescence Ages of Marine Terraces

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Journal of Earth Science 2013年第3期24卷 410-427页

作者： Constantin Athanassas Ioannis Fountoulis Laboratory of Archaeometry Institute of Materials Science N.C.S.R.'Demokritos' Department of Dynamic Tectonic and Applied Geology Faculty of Geology and Geoenvironment National and Kapodistrian University of Athens

This project studies marine terraces in western Messenia, southwestern Peloponnese, Greece, to propose a model of neotectonic configuration and paleogeographic evolution of western Messenia during the Quaternary. GIS analysis of topographic data and geological mapping revealed flanks of raised terraces created on Quaternary marine deposits. Luminescence ages of sediments from the three westernmost marine terraces tend to be consistent OIS-5, OIS-7 and OIS-9, respectively, thus agreeing with the three latest warm stages of the Pleistocene. Moreover, the type and the extent of deformation of the dated marine terraces allowed us to reflect on the neotectonic configuration of western Messenia as well as to conclude that progressive differential uplift over the last 300 ka has induced a dome-like structure to the upper crust of western Messenia.

关键词： Quaternary Southwest Greece neotectonics sea-level change marine terrace lumines- cence dating tectonic uplift.

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Carbon-Isotope Excursions Recorded in the Cambrian System,South China:Implications for Mass Extinctions and sea-level Fluctuations

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Journal of Earth Science 2018年第3期29卷 479-491页

作者： Jingxun Zuo Shanchi Peng Yuping Qi Xuejian Zhu Gabriella Bagnoli Huaibin Fang Henan Institute of Geological Survey Zhengzhou 450001China State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and PaleontologyChinese Academy of SciencesNanjing 210008China Department of Earth Sciences University of PisaVia S.Maria53Pisa 56126Italy

Cambrian carbonates with abundant fossils of agnostoid trilobites deposited on the southern slope （Jiangnan slope belt） of the Yangtze Platform and in the Jiangnan deepwater basin are well exposed in the Wangeun Section of western Hunan, South China, and in the Duibian A Section of western Zhejiang, southeastern China, respectively. To better understand the response of carbonisotope excursions to depositional environment changes, mass extinctions and eustatic events, we collected 530 carbonate samples in fresh roadcut exposures of the two measured sections for analysis of carbon and oxygen isotopic compositions. Data of δ^13C from the Wangcun Section, western Hunan, South China, demonstrate that the Cambrian carbon-isotope profile includes three remarkable positive excursions CPEwc-1, 2, 3 in the Upper Series 2, in the Lower and in the Middle Furongian Series. Three distinctive negative excursions CNEwc,-1, 2, 3 were separately tested in the Lower Terreneuvian Series, Lower Series 3 and in the Upper Furongian Series. Similarly, in the corresponding horizons in the Duibian A Section, Zhejiang Province, southeastern China, three positive excursions CPEdb-1, 2, 3 and three negative excursions CNEdb-1, 2, 3 also have been discovered. We interpret these significant carbon-isotope excursions as being associated with enhanced biogenic prodnctivity, mass extinctions and eustatic events.

关键词： carbon-isotope excursion mass extinction sea-level change Cambrian South China.

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Transgressions and the sea-level changes of the western Taiwan Strait since the Late Pleistocene

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Acta Oceanologica Sinica 1993年第4期12卷 617-627页

作者： Lan Dongzhao, Zhang Weilin, Chen Chenghui, Xie Zaituan, Yu Yongfen and Cai Feng Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, China Third Inst. of Oceanography State Ocenic Administration Xiamen 361005 China China

The sedimentary sequences since the Late Pleistocene can be divided into Layers E, D, C, B, A from old to young according to systematic analysis of grain-size, pollen and spore, diatom, foraminifera, radiocarbon dating and paleogeomagnetism of 16 sedimentary cores from the sea area of the western Taiwan Strait. The results proved the existences of the Langqi transgression (upper section of Layer D) formed in middle and late stages of early Wurm glacial period, Fuzhou transgression (Layer C) formed in Wurm sub-interglacial period and Changle transgression (Layer A) formed in postglacial period. It was also the first time to discover the Jinmen transgression (Layer E) formed in Riss -Wurm interglacial period. In this paper it is proposed that most part of the Taiwan Strait emerged as land in the early stage of early Wurm glacial period, and was still under sublittoral environment in late Wurm glacial period, as well as the existence of Dongshan Continental Bridge was in 8×103 a BP.

关键词： Taiwan Strait sedimentary sequence transgression sea-level change

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Devonian Frasnian-Famennian Transitional Milankovitch Cycles and High-Resolution Stratigraphic Correlation

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Acta Geologica Sinica(English Edition) 2001年第4期75卷 354-363页

作者： GONG Yiming Faculty of Earth Science, China University of Geosciences, Wuhan, 430074LI Baohua Laboratory of Marine Geology, Tongji University, Shanghai 200092and WU Yi Guangxi Institute of Geology, Nanning 530023 China Univ Geosci Fac Earth Sci Wuhan 430074 Peoples R China Tongji Univ Lab Marine Geol Shanghai 200092 Peoples R China Guangxi Inst Geol Nanning 530023 Peoples R China

Four hierarchical cyclothems, superbundlesets, bundlesets, bundles and laminae, have been identified from the Devonian Frasnian-Famennian carbonate strata in Guangxi, South China. Their hierarchical structures, ratio relationships and sequence in conodont zones are continuous and stable and can be traced across different facies zones and sedimentary basins. Our data show that hierarchically organized superbundlesets, bundlesets, bundles and laminae correspond to the long eccentricity, eccentricity, obliquity or precession and sub-Milankovitch cycles respectively. Their periods were 400,000, 100,000, 33,333, 16,667 and 8,000–17,000 a, respectively. The ratios of long eccentricity to eccentricity, eccentricity to obliquity, and eccentricity to precession in the Devonian are 1:4, 1:3 and 1:6 respectively. Using these hierarchical Milankovitch cyclothems, chronostratigraphical division and correlation can be realized at a resolution of 100 ka or 10 ka at the Frasnian-Famennian transition. The time intervals of the Upper rhenana Zone, linguiformis Zone, and the Lower, Middle and Upper triangularis Zone are 0.6, 0.8, 0.3, 0.3 and 0.3 Ma, respectively. sea-level changes of the Frasnian-Famennian transition were not coherent and synchronous at the resolution of 100 ka or 10 ka in the basin-slope carbonate sequences of Guangxi, South China.

关键词： Milankovitch cycle high-resolution stratigraphic correlation sea-level change numerical dating Devonian Guangxi South China

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