Sequence Stratigraphy Characteristics and Main Controlling Factors of the Tectonic Active Basin:As an example from Permian of the Kebai Area in the northwestern Junggar Basin
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摘要: 准噶尔盆地西北缘克—百断裂带是二叠系发育起来的大型叠瓦冲断系统,构造活动对盆地沉积充填过程具有重要的控制作用。二叠系为火山岩和碎屑岩混积地层,分析表明二叠系为层状地层,存在由相对湖平面变化形成的、可作为层序界面的不整合面。根据不整合面和岩层层面对含火山岩系地层进行层序地层的划分和对比,将二叠系划分为5个二级层序,12个三级层序。下二叠统(PSQ1—PSQ7)以火山岩相和沉积岩相共存为特征;中上二叠统(PSQ8—PSQ9)沉积相类型主要包括冲积扇、扇三角洲和湖相。构造活动对层序的控制作用主要表现为构造沉降、火山活动、古地貌特征。构造沉降实质上是逆冲造山导致的挠曲沉降,反映了前陆逆冲作用与盆地挠曲沉降的盆山耦合过程,挠曲沉降是层序形成的内因和主要控制因素;火山作用形成的快速堆积的火山岩体,对含火山岩系地层层序的形成和演化有重要影响;受构造活动影响形成的坡折带控制了层序地层样式和沉积物充填。Abstract: The Kebai fault zone in the northwestern Junggar Basin is a largescale imbricate thrust system which originated in Permian. The tectonic activity played an important role in controlling the sedimentary process. Permian is a mixing accumulated formation which contains volcanics and clastic rocks. Through the analysis, it has been pointed that Permian is a laminar formation and has unconformities that are formed by the relative lake level change and can be regarded as the sequence boundary. Permian is divided into 5 secondorder sequences and 12 thirdorder sequences according the unconformities and the stratal surfaces. Lower Permian (PSQ1PSQ7) is characteristic as volcanic facies and sedimentary facies coexisting; the main sedimentary facies of MiddleUpper Permian are fluvial fan, fan delta and lacustrine facies. The main control actions of the tectonic activity to the sequence are tectonic subsidence, volcanic activity and features of palaeogeomorphic. The essence of the tectonic subsidence is flexural subsidence leaded by the thrusting orogenesis, which reflects the basinmountain coupling process between foreland thrusting action and the flexural subsidence. Flexural subsidence is the internal and dominating factor; the volcanic rock mass which is formed by the volcanic action and deposited fast had important impact on the formation and evolution of the sequence; the slope breaks that are formed by tectonic activity controlled sequence architecture and the sedimentary filling.
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Key words:
- Junggar Basin
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