The tectonic transition from rifting to strike-slip in the Liaodong Bay Depression, offshore China

Abstract

The Liaodong Bay Depression was shaped by the Bohai Bay rift basin (BBRB) and the Tan-Lu strike-slip fault system (TSFS) in the Cenozoic and has undergone a tectonic transition from rifting to strike-slip. Therefore, it is an ideal region to study the transition from rifting to strike-slip. Based on new 3D serial seismic data interpretation, we investigated the types and formation times of the main faults in the Liaodong Bay Depression and restored them within the palaeogeography of each evolution stage. Our results show that the Liaodong Bay Depression underwent a tectonic transition from rifting to strike-slip: (1) The mantle material upsurge caused by the Izanagi plate trapped in the mantle transition zone led to rifting of the Liaodong Bay Depression from the Palaeocene to the Eocene. (2) In the middle Eocene, the change in the subduction direction of the Pacific plate led to dextral strike-slip movement along the Tan-Lu fault zone. (3) The rifting and strike-slip in the Liaodong Bay depression are related, and the transition from rifting to strike-slip occurred from the middle Eocene to the early Oligocene. The strike-slip faults developed when rifting was weak in the Oligocene. The transition from rifting to strike-slip faulting formed oil-gas accumulation zones along the strike-slip fault zone and thus resulted in the good oil and gas exploration prospects of this area.