乌石凹陷古近系层序地层特征及充填演化
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摘要
依据层序地层学、沉积学理论方法,综合地震剖面、钻测井、岩心、古生物、地球化学等资料研究认为;乌石凹陷古近系可识别3种级别不整合面,划分为7个三级地震(测井)层序,是一个进积(加积)—退积—加积序列。构造沉降是控制层序几何形态,充填叠置方式、演化及沉积体系分布的最重要因素:凹陷由多个半地堑在不同层序发育时期以不同方式叠置联结而成;受断层控制,层序外部形态有箱状-楔形、楔形-席状披覆型,边界终止方式有双断终止型、单断终止超覆型;不同构造演化阶段层序内部充填的沉积体系各具特征,初始断陷阶段的SQ1沉积冲积层序,强烈断陷阶段的SQ2—SQ4充填湖相层序,晚期断陷阶段SQ5—SQ7内部充填浅湖和河流三角洲沉积;同沉积断层陡坡带沉降迅速、可容纳空间快速增长,是凹陷的沉积和沉降中心,断陷期主控断裂活动时间和空间的变化导致了凹陷沉积和沉降中心的迁移。
By means of sequence stratigraphy,sedimentology and with comprehensive study of core section,cuttings,well-logging,seismic informations,fossils and geochemistry data the authors recognized three kinds of unconformities and classified the Paleogene into seven seismic sequences of third grade,vertical section of which is transgression,regression and aggradation respectively.Tectonic subsidence play dominant role in their geometric shapes,basin fillings,sequence evolution and sediment distribution in the Wushi Sag.Outline of the sequences are in shape of box-wedge or sheet-wedge and boundaries of sequences are varied from bilateral fault to monoclinal fault overlap,so that the sequences show distinct semigrabens which overlay in different ways.Seven sequences were formed in different stage of tectonic evolution.The sequence of SQ1 formed in initial rift stage and deposited alluvial sequence.Sequences SQ2-SQ4 developed in intense rift stage and sediment lacustrine sequence.Sequences SQ5-SQ7 formed in late period of rift before thermal subsidence and deposit mere and delta sediment.The place adjacent to the synsedimentary fault is the subsidence center and depocenter;meanwhile,controlling fracture migrates in horizontal made subsidence and sedimentary center of the sag changed.
By means of sequence stratigraphy,sedimentology and with comprehensive study of core section,cuttings,well-logging,seismic informations,fossils and geochemistry data the authors recognized three kinds of unconformities and classified the Paleogene into seven seismic sequences of third grade,vertical section of which is transgression,regression and aggradation respectively.Tectonic subsidence play dominant role in their geometric shapes,basin fillings,sequence evolution and sediment distribution in the Wushi Sag.Outline of the sequences are in shape of box-wedge or sheet-wedge and boundaries of sequences are varied from bilateral fault to monoclinal fault overlap,so that the sequences show distinct semigrabens which overlay in different ways.Seven sequences were formed in different stage of tectonic evolution.The sequence of SQ1 formed in initial rift stage and deposited alluvial sequence.Sequences SQ2-SQ4 developed in intense rift stage and sediment lacustrine sequence.Sequences SQ5-SQ7 formed in late period of rift before thermal subsidence and deposit mere and delta sediment.The place adjacent to the synsedimentary fault is the subsidence center and depocenter;meanwhile,controlling fracture migrates in horizontal made subsidence and sedimentary center of the sag changed.
引文
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[12]龚再升,李思田.南海北部大陆边缘盆地分析及油气聚集[M].北京:科学出版社,1997.GONG Zai-sheng,LI Si-tian.Basins analysis and hy-drocarbon accumulation in continental margin of theSouth Sea[M].Beijing:Science Press,1997.
[13]陈发景,汪新文.伸展断陷盆地分析[M].北京:地质出版社,2004.CHEN Fa-jing,WANG Xin-wen.Extension rift ba-sin analysis[M].Beijing:Geological PublishingHouse,2004.
[2]邓宏文,王洪亮,李熙喆.层序地层基准面的识别、对比技术及应用[J].石油与天然气地质,1996,17(3):177-183.DENG Hong-wen,WANG Hong-liang,LI Xi-zhe.I-dentification and correlation techniques of sequencestratigraphic base-levels and their application[J].Oiland Gas Geology,1996,17(3):177-183.
[3]薛良清.层序地层分析在裂谷盆地油气勘探中的应用[J].石油学报,2000,21(5):7-11.XUE Liang-qing.Application of sequence stratig-raphyic analysis to hydrocarbon exploration of rift ba-sin[J].Acta Petrolei Sinica,2000,21(5):7-11.
[4]樊太亮,朱玲.吉尔嘎朗图凹陷沉积层序几何构型[J].石油与天然气地质,1998,19(2):99-105.FAN Tai-liang,ZHU Ling.Geometric architecture ofsedimentary sequence in Jirgalangtu Sag[J].Oil andGas Geology,1998,19(2):99-105.
[5]康西栋,赵文翠,潘治贵.北部湾盆地层序地层格架及其内部构成[J].地球科学———中国地质大学学报,1994,19(4):493-502.KANG Xi-dong,ZHAO Wen-cui,PAN Zhi-gui.Studyon architecture of sequence stratigraphic framework ofBeibuwan Basin[J].Earth Science—Journal of ChinaUniversity of Geosciences,1994,19(4):493-502.
[6]刘海龄,杨恬,朱淑芬,等.南海西北部新生代沉积基底构造演化[J].海洋学报,2004,26(3):54-67.LIU Hai-ling,YANG Tian,ZHU Shu-fen,et al.Tectonic evolution of Cenozoic sedimentary basementsin the northwestern South China Sea[J].Acta Oceano-logica Sinica,2004,26(3):54-67.
[7]邓宏文,王洪亮,翟爱军,等.中国陆源碎屑盆地层序地层与储层展布[J].石油与天然气地质,1999,20(2):108-114.DENG Hong-wen,WANG Hong-liang,ZHAI Ai-jun,et al.Sequence stratigraphy and reservoir distributionin China’s terrigenous clastic basin[J].Oil and GasGeology,1999,20(2):108-114.
[8]顾家裕,郭彬程,张兴阳.中国陆相盆地层序地层格架及模式[J].石油勘探与开发,2005,32(5):11-15.GU Jia-yu,GUO Bin-cheng,ZHANG Xing-yang.Se-quence stratigraphic framework and model of the conti-nental basins in China[J].Petroleum Exploration andDevelopment,2005,32(5):11-15.
[9]林畅松,刘景彦,张英志,等.构造活动盆地的层序地层与构造地层分析[J].地学前缘,2005,12(4):365-374.LIN Chang-song,LIU Jing-yan,ZHANG Ying-zhi,etal.Sequence stratigraphy and tectono-stratigraphic a-nalysis of tectonically active basins[J].Earth ScienceFrontiers,2005,12(4):365-374.
[10]李斌,孟自芳,李相博,等.泌阳凹陷下第三系构造特征和沉积体系[J].吉林大学学报(地球科学版),2005,35(3):332-339.LI Bin,MENG Zi-fang,LI Xiang-bo,et al.Thestructural features and depositional systems of theEarly Tertiary in Biyang sag[J].Journal of Jilin Uni-versity(Earth Science Edition),2005,35(3):332-339.
[11]朱伟林,江文荣.北部湾盆地涠西南凹陷断裂与油气藏[J].石油学报,1998,19(3):6-10.ZHU Wei-lin,JIANG Wen-rong.Relations betweenfractures and hydrocarbon reservoirs in Weixinan sag[J].Acta Petrolei Sinica,1998,19(3):6-10.
[12]龚再升,李思田.南海北部大陆边缘盆地分析及油气聚集[M].北京:科学出版社,1997.GONG Zai-sheng,LI Si-tian.Basins analysis and hy-drocarbon accumulation in continental margin of theSouth Sea[M].Beijing:Science Press,1997.
[13]陈发景,汪新文.伸展断陷盆地分析[M].北京:地质出版社,2004.CHEN Fa-jing,WANG Xin-wen.Extension rift ba-sin analysis[M].Beijing:Geological PublishingHouse,2004.
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