Sequence stratigraphy in the Middle Ordovician carbonate successions (Yeongheung Formation), mid-east Korea: Paleogeographic implications for a land-detached ramp-type platform

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This study reveals the origin of the stratigraphic discrepancy between the Yeongweol and Taebaek groups and reconstructs paleogeographic model for the Taebaeksan Basin on the Sino-Korean Craton (SKC). The global sea-level fall in the earliest Middle Ordovician would have subaerially extensively exposed the Lower Ordovician peritidal successions, forming the solution-collapsed breccia zones on the Sauk-Tippecanoe bounding surface. The successive rise in sea level generated the fine-grained siliciclastic successions in the Taebaek Group during early transgression since the carbonate production of the group was hampered by the strong input of siliciclastic sediments from terrestrial sources. However, such successions are absent in the Yeongweol Group because the Yeongweol platform was distant from the siliciclastic sources and sustained carbonate production due to isolation from terrestrial influences. The Yeongweol Group is interpreted as a “land-detached (isolated) ramp-type platform” as it responded to sea-level fluctuations with restricted terrestrial influence, whereas the Taebaek Group can be described as a “land-attached ramp-type platform” affected by a large input of siliciclastic sediments during lowstand and early transgression. Based on the comparison of stratigraphic patterns and configurations of land-attached and -detached ramp-type successions, this study concludes that the Yeongweol sequence would have been formed on a land-detached (isolated) carbonate ramp-type platform located at the SKC along the northeastern Gondwana margin.