【摘要】 四川盆地中部古老的震旦系—寒武系发现了储量过万亿方的特大型油气田,前人研究揭示了乐山—龙女寺持续性古隆起的重要作用,提出德阳—安岳拉张槽(裂陷槽)的存在及其重要的控富生烃凹陷的作用,但其发展和演化以及形成的动力学机制还尚待进一步研究和揭示。在四川盆地大量野外工作及分析的基础上,结合现有钻井和地震等地下资料,以盆地中西部为主要研究区,对晚震旦世—早寒武世该区经历的构造-沉积记录进行了综合分析和探讨。研究揭示了晚震旦世—早寒武世存在3期构造运动,对应桐湾运动的Ⅰ、Ⅱ、Ⅲ幕,分别对应灯影组三段/二段,麦地坪组/灯影组四段以及筇竹寺组/麦地坪组等界面及灯影组三段、麦地坪组和筇竹寺组等层位。桐湾运动Ⅰ幕中发现了典型的重力流滑塌沉积及凝灰岩等火山活动记录,而桐湾运动Ⅱ幕和Ⅲ幕构造界面大部分地区具有叠合特点,形成了区域性的不整合,南部地区可见典型的碎屑流沉积和表生岩溶响应。三幕构造运动总体均表现为先隆起剥蚀再沉降充填的演化过程,隆起剥蚀区和沉降区具有一定的叠合性,并在四川盆地西缘地区形成了近南北向带状展布的灯影组三段和麦地坪组—筇竹寺组两期相对深水陆棚区域(前人称为拉张槽或裂陷槽),而该深水陆棚区也是陡山沱组和灯影组一段和二段的沉积中心区域。认为该相对深水区具有基底的持续继承性,并由灯影组三段至筇竹寺组沉积期具有幕式性活动增强的特点。在此基础上,探讨了该构造活动的动力学成因。更多还原

【Abstract】 A super-giant oil-gas field with geological reserves of more than one trillion cubic meters,located in the middle area of Sichuan Basin,has been found in the Cambrian-Sinian strata.Previous studies revealed the importance of persistent Moxi-Longnüsi paleo-uplift.The existence of Deyang-Anyue intracratonic sag(aulacogen sag)and its important in controlling rich hydrocarbon generation depression was recognized.Nevertheless,the development,evolution and formation of the dynamic mechanism need to be further researched and investigated.Based on a large number of field work and analysis,combined with the existing underground data such as drilling and seismic data,focused on midwest area of Sichuan Basin,the structuresedimentary records during the Late Sinian to the Early Cambrian were analysed and discussed.The correspondingⅠ,Ⅱ,Ⅲepisodes of Tongwan tectonization correspond to the boundary between the Member3 and 2of Dengying Formation,Maidiping Formation and Dengying Formation,Qiongzhusi Formation and Maidiping Formation,and they includ the strara of the Member 3of Dengying Formation,Maidiping Formation and Qiongzhusi Formation.Among those,typical gravity flow slump deposits and volcanic activity records such as tuff were found in the first episode of Tongwan tectonization.Superposed characteristics of structure interface between the second and third episodes of Tongwan tectonization occurred in most areas of Sichuan Basin and formed a regional unconformity.Typical debris flow deposits and supergene karst response can be found in southern region of Sichuan Basin.The evolution process of three episodic tectonization in general has characteristics of uplifting-subsiding,then subsidence filling.The uplift area and subsidnce area have a certain superimposition,and relative deep shelf area(previous intracratonic sag or rift trough)was formed during the sedimentary period of the Member 3of Dengying Formation and the Maidiping Formation in the western margin of Sichuan Basin.It is the central deposition region during the sedimentary period of Doushantuo Formation and the Member 1and 2of Dengying Formation.The study suggested that the relative deep water area was continuingly inherited from the basement,and it has characteristics of episodic activity enhancement during the sedimentary period from the Member 3 of Dengying Formation to Qiongzhusi Formation.Finally,the dynamic genesis was discussed.更多还原