3D Structure of the Mesozoic Tan-Lu FaultZone and Its Impact on Basin Evolution: Insights from the Southern Bohai Bay Basin, NE China

The Cenozoic Tan-Lu Fault Zone, as the largest strike-slip fault system in eastern China, features complex deformation patterns and mechanisms and a tectonic evolution that has been investigated by previous studies.Here, we present high-resolution seismic profiles across the whole southern Bohai Bay basin, where the Tan-Lu Fault Zonetraverses, enabling the identification oftwo types of Mesozoic normal fault systems: an E-W trending fault set, and a NNE trending fault set. Considering the tectonic events that have happened since the Mesozoic and the intersection relationshipbetween the two fault systems, we propose that the E-W trending normalfaults originated fromthe Triassic collision between the South China Block and the North China craton. The NNE trending normalfaults were derived fromstrike-slip faults formed under transpression, due to multiple phases of subduction of the Pacific plate during Jurassic to Late Cretaceous. Both fault systems were subsequently reactivated and transformed into normal faults during the Early Cretaceous rifting, leading to the formation of a cross-graben rift. The widespread Early Cretaceous extension promoted volcanic activity, allowing significant volumes of deep-seated magmatic material to rise along these two sets of faults and to erupt onto the surface. The spatial distribution of the volcanic products was structurally controlled by fault boundaries, leading to the formation of a large-scale, quadrangular Mesozoic volcanic basin.