渤海湾盆地中部428构造带近S-N向走滑断裂的形成时期及其在中生代期间的调节转换作用

Formation period of S-N strike-slip fault in the 428 tectonic belt in the central of Bohai Bay Basin and its adjustment and transformation in the Mesozoic

  • 摘要: 渤海湾盆地中部428构造带自印支期以来经历了多期次构造运动叠加改造过程,区域内发育了大量的近S-N向与近E-W向褶皱、断层构造,并控制了潜山的形成。然而目前对428构造带的研究仅局限于探索区域内潜山构造成因及其油气圈闭特性,对区域内的断裂系统,尤其是发育的大量近S-N向断裂的形成时期及其后期演化过程中所起到的调控作用尚不明确。鉴于此,为明确其形成时期、探索其对区域构造格局演化模式所产生的影响,基于前人的研究成果,以石臼坨凸起东侧428构造带为主要研究对象,通过对该区域典型的地震剖面进行精确解析,对其展开了系统性的研究。研究结果表明:① 428构造带与石臼坨凸起东侧连接处存在一条近S-N向走滑断裂;② 该走滑断裂的形成最早可追溯至印支期。根据古生界褶皱和薄底构造的分布特征可知,该走滑断裂最初为近E-W向逆冲推覆断裂的侧向断坡;③ 近S-N向走滑断裂阻挡了燕山期NWW向的逆冲推覆作用,从而控制古生界和中生界大量协调褶皱的发育。而近E-W向断裂表现为压扭性质,控制了中生界雁列式褶皱的形成。基于以上认识,认为该近S-N向走滑断裂在印支-燕山期均起到了重要的调控作用,是一个重要的调节转换带。

     

    Abstract: The 428 tectonic belt in the central Bohai Bay Basin has undergone superposition of multiple tectonic movements since the Indosinian, and thus a great number of near S-N and near E-W folds and faults have developed and controlled the formation of buried hills in the region. Most studies on the 428 tectonic belt focused on exploring the tectonic origin of buried hills and its hydrocarbon trap characteristics, but less research has been conducted on the faults system in the region, especially the formation period of numerous near S-N faults and the regulation role of faults in the later evolutionary process. We conducted a precise analysis of typical seismic profiles in the 428 tectonic belt, and systematically investigated the period of formation of the folds and faults in the region and their influence on the evolutionary pattern of regional tectonics. Results reveal that: (1) A near S-N strike-slip fault exists at the eastern connection between the 428 tectonic belt and the Shijiutuo uplift; (2) a near S-N strike-slip fault was formed during the Indosinian. According to the distribution of the Paleozoic folds and thin-bottom structures, the location of the slip fault should be the lateral fault slope of the near E-W trending reverse thrust fault; (3) the near S-N strike-slip faults in the area obstructed the reversible thrusting in the NWW direction during the Yanshanian, and controlled the formation of a large number of coordinated folds in the Paleozoic and Mesozoic. Moreover, some near E-W faults display a compressional-torsional nature and controlling formation of en echelon folds in the Mesozoic. Therefore, the near S-N strike-slip faults played an important role in tectonic adjustment and transition in this area during the Indosinian-Yanshanian.

     

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