U-Pb Age Dating and Geochemistry of Soft-Sediment Deformation Structure-Bearing Late Cretaceous Volcano-Sedimentary Basins in the SW Korean Peninsula and Their Tectonic Implications

Cretaceous volcano-sedimentary basins and successions in the Korean Peninsula are located along NE-SW- NNE-SSW-trending sinistral strike–slip fault systems. Soft-sediment deformation structures (SSDS) of lacustrine sedimentary strata occur Wido, Buan, Haenam areas southwestern Peninsula. In this study, systematic geological, geochronological, geochemical investigations volcanic-sedimentary were conducted to constrain origin timing SSDS-bearing strata. The is conformably underlain overlain by volcanic rocks, it contains much volcaniclastic sediment interbedded with tuffs. studied SSDSs interpreted have formed ground shaking during syndepositional earthquakes. U-Pb zircon ages rocks within ca. 87–84 Ma, indicating that active volcanism was concurrent sedimentation. Geochemical characteristics indicate these mostly rhyolitic similar subduction-related calc-alkaline from an continental margin. This suggests study area earthquakes related proximal activity due oblique subduction Paleo-Pacific Plate Late Cretaceous.