The Pyeongan Supergroup (upper Paleozoic-Lower Triassic) in the Okcheon Belt, Korea: A review of stratigraphy and detrital zircon provenance, and its implications for the tectonic setting of the eastern Sino-Korean Block

The tectonic setting of the Okcheon Belt in the Korean Peninsula has long been regarded as one of the important topics in discussing East Asian tectonics. The controversial tectonic setting of the Okcheon Belt before the Triassic collision between North and South China limits proper understanding of the late Paleozoic tectonics of East Asia. Focusing on the upper Paleozoic to Lower Triassic Pyeongan Supergroup, coeval sedimentary records in different parts of the Okcheon Belt are reviewed. This study has a clear advantage over previous assessments that build upon comparison between (meta)sedimentary units of unknown age in the region. The Pyeongan Supergroup sediments show high similarity in both stratigraphy and detrital zircon U-Pb ages throughout the Okcheon Belt. They are distinct from their age-equivalents in South China, while sharing characteristics with those in North Korea and North China. Critical criteria include marine influence and enrichment of organic materials at each time period, and relative proportion of Mesoproterozoic-Silurian components in detrital zircon age population. The combined results agree with the view that the entire Okcheon Belt was a single tectonic unit at least by the Late Carboniferous. The results of this study favor the idea of the Sino-Korean Block encompassing the whole Korean Peninsula, and cast doubts on the tectonic models that attribute the southern part of the Korean Peninsula to the South China Block. A retroarc foreland basin setting of the Okcheon Belt with detritus mainly provided from a subduction-related orogen in the continent-sided Japan is inferred from the provenance characteristics of the detrital zircons.