南襄盆地泌阳断陷第三纪湖泊演化探讨
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摘要
采用层序地层学理论与方法 ,综合泌阳断陷湖盆的地质及地震资料 ,以构造不整合面或构造应力转换面作为界面 ,识别并划分构造层序 ,进而探讨泌阳断陷湖盆的成盆机制与成盆史 ;通过泌阳断陷区地震剖面上反射特征的研究及反射界面的识别 ,标定并划分地震层序 ,据此建立断陷湖盆的等时层序地层框架 ,以揭示泌阳断陷湖盆的沉积充填史。在对研究区沉积层序单元逐级划分与剖析的基础上 ,识别出陆相层序的“似凝缩段”,并系统地采集研究区下第三系不同沉积层序“似凝缩段”中的泥质岩石样品 ,经全岩样 X射线荧光光谱分析 ,获取下第三系不同层位水溶性离子浓度在垂向剖面上的分布特征 ,以研究早第三纪泌阳断陷湖盆古湖泊类型演变历程。结果表明 ,泌阳断陷湖盆沉积充填史划分为三个阶段 :初始断陷充填阶段、主断陷充填阶段及坳陷充填阶段 ,并分别对应着三个构造层序。其中第二阶段包括强烈断陷充填、稳定断陷充填及断陷萎缩充填三个亚阶段 ,其沉积速率有由大到小的变化规律。早第三纪泌阳断陷湖盆经历了四个演化历程 :山前洪水洼地→硫酸盐型滨浅湖→正常湖泊→碳酸盐型或硫酸盐型滨浅湖 ;相应地 ,湖盆南部边缘 (陡坡带 )和北部边缘 (缓坡带 )沉积楔状体演变过程分别为 :冲积扇→陡坡型扇三角洲→缓坡型扇三角洲→
Based on theory and method of sequence stratigraphy and synthetically using geological data and seismic profiles of Biyang fault depressed lacustrine basin,tectonic sequences have been identified and classified to probe into basin forming and evolution history of Biyang fault depression by analysis of regional tectonic background and taking structural unconformity or structural stress transformation interface as sequence boundary,and seismic sequences have been demarcated and classified by studying reflection characteristics and recognizing reflection surfaces on seismic profiles of Biyang fault depression.In view of the above,the chorostratigraphic framework model has been established to reveal sediment filling history of Biyang fault depressed lacustrine basin.Based on terrigenous sequence unit classificaton and "Similar Condensed Section" identification in study area,muddy rock samples were systematically collected from "Similar Condensed Section" in different sedimentary sequences of Biyang Palaeogene fault depression.The water soluble ion distribution on Palaeogens sedimentary section was determined by X ray fluorescent spectrum analyses to study palaeo lake type evolution for Biyang Palaeogene fault depressed lacustrine basin.The result shows that sediment filling history of Biyang fault depression can be classified into initial rift,main rift and downwarp filling stages which have in turn formed three tectonic sequences.The second stage includes:intense,stable and dormant rift filling substage which sedimentary rate decreases progressively.Biyang Palaeogene fault depressed lacustrine basin experiences four evolutionary phases:foothill floodng depression→sulfate coastal/shallow lake→normal lake→carbonate or sulfate coastal/shallow lake,in pace with this,the evolutionary process of sedimentary wedge in southern margin which belongs to steep slope zone is alluvial fan→steep slope fan delta→gentle slope fan delta→alluvial fan,and in northern margin which belongs to gentle slope zone is alluvial fan→delta→alluvial fan.In the wake of increasing of sulfate mineral in sediment,Biyang fault depressed lacustrine basin would finally go to death.
Based on theory and method of sequence stratigraphy and synthetically using geological data and seismic profiles of Biyang fault depressed lacustrine basin,tectonic sequences have been identified and classified to probe into basin forming and evolution history of Biyang fault depression by analysis of regional tectonic background and taking structural unconformity or structural stress transformation interface as sequence boundary,and seismic sequences have been demarcated and classified by studying reflection characteristics and recognizing reflection surfaces on seismic profiles of Biyang fault depression.In view of the above,the chorostratigraphic framework model has been established to reveal sediment filling history of Biyang fault depressed lacustrine basin.Based on terrigenous sequence unit classificaton and "Similar Condensed Section" identification in study area,muddy rock samples were systematically collected from "Similar Condensed Section" in different sedimentary sequences of Biyang Palaeogene fault depression.The water soluble ion distribution on Palaeogens sedimentary section was determined by X ray fluorescent spectrum analyses to study palaeo lake type evolution for Biyang Palaeogene fault depressed lacustrine basin.The result shows that sediment filling history of Biyang fault depression can be classified into initial rift,main rift and downwarp filling stages which have in turn formed three tectonic sequences.The second stage includes:intense,stable and dormant rift filling substage which sedimentary rate decreases progressively.Biyang Palaeogene fault depressed lacustrine basin experiences four evolutionary phases:foothill floodng depression→sulfate coastal/shallow lake→normal lake→carbonate or sulfate coastal/shallow lake,in pace with this,the evolutionary process of sedimentary wedge in southern margin which belongs to steep slope zone is alluvial fan→steep slope fan delta→gentle slope fan delta→alluvial fan,and in northern margin which belongs to gentle slope zone is alluvial fan→delta→alluvial fan.In the wake of increasing of sulfate mineral in sediment,Biyang fault depressed lacustrine basin would finally go to death.
引文
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[2] WilsonR C L .Sequence stratigraphy:an introduction[J].Geoscientist,1991,1(1):1～14.
[3] 徐怀大.层序地层学理论用于我国断陷盆地分析中的问题[J].石油与天然气地质,1991,12(1):52～57.
[4] 解习农,李思田.陆相盆地层序地层研究特点[J].地质科技情报,1993,12(1):6～10.
[5] 王东坡,刘立.大陆裂谷盆地层序地层学研究[J].岩相古地理,1994,14(3):1～9.
[6] 顾家裕.陆相盆地层序地层学格架概念及模式[J].石油勘探与开发,1995,22(4):6～10.
[7] 王定一,车自成,张树田,等.南襄盆地构造发育特征及其形成机制[J].石油与天然气地质,1987,8(4):363～372.
[8] 朱水安,徐世荣,朱绍壁,等.河南泌阳凹陷的石油地质特征[J].石油学报,1981,2(2):21～28.
[9] 胡受权.断陷湖盆陆相层序地层学研究[D].成都:成都理工学院,1996.
[10] 孙家振,李兰斌,杨振峰,等.泌阳凹陷的含油气构造特征与演化历史[J].石油学报,1995,16(4):55～61.
[11] MiallA D.Stratigraphic sequences and their chronostratigraphic correlation[J].Journal ofSedimentaryPetrology,1991,61(3):497～505.
[12] ShusterM W.Two- dimensional synthetic seismic and log cross sections from stratigraphic framework models[J].AAPG,1994,78(3):409～431.
[13] VanWagonerJ C.Siliciclastic sequence stratiqraphy in well logs,cores and outcrops:concepts for high- resolutioncorrelation of time and facies[J].AAPG,Methods inExplorationSeries7,1990,74(55):1～240.
[14] 胡受权.古气候变迁对泌阳断陷湖盆陆相层序发育的影响[J].江汉石油学院学报,1998,20(1):1～6
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