Post-Rift Faulting Migration, Transition and Dynamics in Zhu Ⅰ Depression, Pearl River Mouth Basin

Ye Qing; Shi Hesheng; Mei Lianfu; Shu Yu; Liu Hailun; Tian Wei; Yan Hao

doi:10.3799/dqkx.2017.008

Abstract：Post-rift fault plays an important role in hydrocarbon accumulation of the Neogene in Pearl River Mouth basin,but understanding of the features and dynamics evolution is to be enhanced in this paper,post-rift fault system in Zhu Ⅰ depression is studied by geometric and kinematic analysis methods using high quality 3D seismic reflection data.The analysis reveals two episodes of faulting in the post-rift stage,namely,Nanhai-phase faulting and Dongsha-phase faulting.Transition of fault geometry and kinematics from Nanhai-phase to Dongsha-phase indicates a change of dynamics.Both Nanhakphase faulting and Dongsha-phase faulting have migration.The former migrates from south to north,and the latter migrates from east to west.The two periods of faulting are both extensional faults,with a slight component of shear in Dongsha-phase.Regional extensional direction transforms from NNE10°-15° in Nanhai-phase faulting to NNE20°-25° in Dongsha-phase faulting,with 5°-10° clockwise rotation.The Nanhai-phase faulting is related to the remaining extension in the northern margin of SCS.The Dongsha-phase faults formed after the cease of the sea-floor spreading of SCS.Coincidently,direction of the regional intermediate principal strain (σ2) during the Dongsha-phase faulting is consistent with the collision direction between the Luzon arc and the Eurasian plate.This feature of the Dongsha-phase faulting in Zhu Ⅰ depression confirms the conclusion that Dongsha movement is the result of the collision between the Luzon arc and the Eurasian plate since Middle Miocene.This study is significant for better understanding of Nanhai movement and Dongsha movement.