U-Pb ages of detrital zircons in lower Palaeozoic quartzites of the Taebaeksan Basin, eastern Sino–Korean Block: sediment provenance response to relative sea-level changes

The Cambrian–Ordovician Taebaeksan Basin overlies the Precambrian basement of the Sino–Korean Block (North China Craton) in the central–eastern Korean peninsula. This corresponds to the occurrence of the global marine transgression over the Great Unconformity in the Cambrian, which is widely recognized. However, the palaeogeography of the Sino–Korean Block during the Early Cambrian–Ordovician remains unclear. This study aimed to identify the provenances and reconstruct the palaeogeography of the eastern Sino–Korean Block. For this purpose, we investigated U-Pb ages of detrital zircons in the lower Cambrian–Ordovician successions using samples collected from the Danyang (i.e. Jangsan), Jeongseon, and Dongjeom areas. Detrital zircons from all samples clearly exhibited predominant clusters of Paleoproterozoic ages (ca. 1875–1861 Ma) and a minor cluster of Neoarchean ages (ca. 2500 Ma). The age spectra from the lower quartzites (Jangsan and Jeongseon formations) are partly distinguished from those in the Taebaeksan Basin, showing bimodal Precambrian peaks, which indicates the preferred drainage system within the Sino–Korean Block. A lack of young detrital zircon ages representing maximum depositional ages in the lower quartzites indicates that there were little igneous activity and little influx of external detritus. The age spectra from the lower quartzites, in contrast, are different from those of the conformably overlying shale (i.e. ~510 Ma Myobong Formation) consisting mainly of Neo–Mesoproterozoic detrital zircons derived from East Gondwana. Paleoproterozoic detrital zircons in the upper quartzite (Dongjeom Formation) were repetitively predominant without Neoproterozoic detrital zircons. The reappearance of predominant Paleoproterozoic zircons is most likely associated with uplifts possibly due to the subduction of the Paleo-Asian Ocean (PAO). We suggest that progressive changes along the eastern margin of the Sino–Korean Block were affected by the regional tectonism, regardless of the global transgression during the Cambrian–earliest Ordovician (ca. 480–500 Ma).