Characteristic of the Bodong segment of the Tanlu Fault Zone, Bohai sea area, eastern China: Implications for hydrocarbon exploration and regional tectonic evolution

Abstract In the Bodong segment of the Tanlu Fault Zone (TLFZ), the largest strike-slip fault zone in Eastern China, there are three sags with varying degrees of modification by strike-slip faults. These sags provide an opportunity to examine TLFZ-controlled factors on basin development. The North Bodong sag (NBDS) which was not transformed by TLFZ, entered a rifting stage and post-rifting stage, while the Middle Bodong (MBDS) and South Bodong sags (SBDS) influenced by the TLFZ underwent more complex evolution, including i) a rifting stage, ii) a strike-slipping stage, iii) a structurally quiescent stage and iv) a reactivation stage. There exist two structural changes at about 30.3 Ma and 5.3 Ma, marking the migration of the depocenter and a high activity rate of the TLFZ-related faults. The structural transformation makes hydrocarbon vertically migrate difficult along faults in sag zones, making the slope and the rise zones the main areas for hydrocarbon accumulation due to lateral migration along the unconformity. The differences between the time of the initial rifting of the basin and the strike-slip motion of the TLFZ provides direct evidence for the idea that the Bohai Bay Basin is a rift basin strongly reworked by strike-slip movement. The change from rifting to strike-slip at 30.3 Ma is mainly the result of the combined action of the Indian-Asian collision and the subduction of the Pacific Plate, and the reactivation of the TLFZ at 5.3 Ma is a response to the accelerating subduction of the Pacific Plate.