【摘要】 万安盆地是其东侧万安走滑断裂发生右旋走滑所派生的扭张应力作用下形成的一个走滑拉张盆地。NE、NEE和SN向的断裂是盆内最主要的断裂,它们在盆内局部形成"三隆四坳"的格局。盆地构造演化经历了基底形成、初始裂谷作用、裂谷发育(第一阶段裂谷作用)、裂谷后早期(第二阶段裂谷作用)、构造反转和裂后期(区域沉降阶段)等几个阶段。根据钻井资料和地震资料中叠加速度建立的时-深关系,在该盆地可划分出4个巨层序界面:MB1,声波基底的顶部(前古近纪);MB2,渐新世顶部(24Ma);MB3,晚中新世(8Ma);MB4,早上新世(4Ma)。每一个巨层序界面(MB)之上都有与之对应的巨层序(MS),从老到新依次为MS1—MS4。盆地晚始新世—渐新世以湖泊-三角洲沉积体系为主;晚中新世时经历了非海相-海陆交互相-陆架沉积体系的过渡;中新世—早上新世为碳酸盐岩-浅海陆架-三角洲沉积体系;早上新世—第四纪为陆架-陆坡-深海沉积体系。更多还原

【Abstract】 The Wan’an Basin is a strike-slip and pull-apart basin formed by the tensile stress derived from the dextral strike-slip movement of the Wan’an fault on its east side.Main faults extend in NE、NEE and SN directions that formed a tectonic pattern of "three swells-four depressions"in the basin.The basin experienced a successive tectonic evolution of basement formation,initial rifting,rifting development(first phase of rifting),early postrifting(second phase of rifting)、tectonic inversion and postrifting(regional subsidence).Based on the relationship of two-way travel time vs.depth between stacking velocities from the seismic data and drilling data from wells,four megasequence boundaries were identified: MB1,the top of the acoustic Pre-Tertiary basement;MB2,the top of the Oligocene(24Ma);MB3,the Late Miocene(8Ma);MB4,the Early Pliocene(4Ma).Above each megasequence boundary(MB),there is a megasequence(MS).They are referred to as MS1 to MS4 from the oldest to youngest,corresponding to a lacustrine-deltaic depositional system of Late Eocene-Oligocene;a transitional system of non-marine-littoral-shelf in Late Miocene;a system of carbonate-shallow water shelf and deltaic system of Miocene-Early Pliocene and a shelf-slope-deep marine system of Early Pliocene-Quaternary,respectively.更多还原