Subduction of the ancient and present Pacific plates has contributed to the crustal evolution of the Circum Pacific regions. In particular, the East Asian continental margin is the region where several thousand kilometers-long accretionary complexes were developed due to the northwesternward subduction of the western paleo-Pacific plates, but continental responses to such subduction processes have been poorly understood. We propose here our recent results of sedimentologic, diagenetic and thermochronologic analyses for Jurassic and Cretaceous nonmarine deposits in Korea, and correlate them with the Japanese accretionary events that took place near the Korean Peninsula.
The western paleo-Pacific subduction influenced major tectonism on the East Asian continent from the Jurassic onwards, and oceanic plateaus and marine deposits on the paleo-Pacific plate were accreted to form the Jurassic accretionary complex along the continental margin. In response to such accretion, a large-scale crustal shortening, together with igneous emplacement, had occurred in the Korean Peninsula, resulting in the formation of foreland and piggyback basins. When the subducted oceanic rocks experienced peak metamorphism during the Middle Jurassic to Early Cretaceous, sediment fills in these basins were overthrusted and loaded by the basement rocks, leading to deep burial diagenesis from anchizone to epizone down sequence and ductile deformation in the lowermost strata.
In Early Cretaceous time, a number of extensional basins were developed in the peninsula while some parts of the Jurassic accretionary complex were already exhumed. Diagenetic and thermochronologic analyses of the Lower Cretaceous sediments revealed that the Cretaceous basin-fills were deeply buried and reached the thermal range of the anchizone during early Late Cretaceous, followed by rapid uplift to a shallow level of the apatite partial annealing zone (APAZ) during the latest Cretaceous to Early Paleocene, along with the cooling of Jurassic and Cretaceous granites and uplift of Jurassic basin-fills. The onset of such uplift and the timing of the APAZ were most likely linked to the accretion (Late Cretaceous) and peak metamorphism (latest Cretaceous to earliest Paleocene) of the Cretaceous accretionary complex of Japan, respectively.