The Great Unconformity in the eastern Sino-Korean Block: A synthesis of Taebaek Group stratigraphy, fault controls, and global correlations

초록

The Great Unconformity is a complex, globally significant boundary whose local expression is shaped by the interplay between eustasy and tectonics. The Taebaek Group in eastern Korea provides a key window to this process. Our comprehensive analysis of stratigraphy, lithology, paleontology, and detrital zircon geochronology confirms a major unconformity separating the Precambrian Jangsan Formation from the Cambrian Myeonsan-Myobong sequence. Key evidence includes distinct lithological differences across a well-defined erosional surface, reworked Jangsan clasts within the basal conglomerate of the Myeonsan Formation, different fossil assemblages, contrasting zircon age populations, diagenetic patterns, and stratigraphic thickness variations potentially controlled by syndepositional fault activity. We use these findings to develop a new tectono-sedimentary model where the proto-Dongjeom Fault controlled both accommodation space and depositional patterns. This model demonstrates that while eustatic sea-level rise drove the Cambrian transgression, local fault activity governed the development of the unconformity surface and the architecture of the overlying facies. These findings refine regional correlations and underscore how tectonic inheritance can create unique local signatures within globally recognized stratigraphic sequences, with direct implications for the concentration of associated paleoplacer mineral deposits. Overall, this study advances our understanding of how tectonic inheritance and eustatic forcing together shaped one of Earth's most significant stratigraphic boundaries.

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