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

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.