Volcanic facies analysis of the Quaternary Hantangang Basalt, Korea: implications for lava flow field architecture and emplacement history

Abstract Basaltic lava flows are a common component of the stratigraphic fill in volcanically rich basins. However, unlike their sedimentary counterparts, detailed facies analysis and their incorporation into stratigraphic fill are still in their infancy. This study applies a modified volcanic facies analysis to the Quaternary Hantangang Basalt in the central Korean Peninsula. The Hantangang Basalt consists of four volcanic facies small lobe, pillow lava, lobate flow, and sheet flow, each representing individual flow units. These facies are grouped into five facies associations that reflect depositional or emplacement settings: FA1 (Unconfined flow field), FA2 (Confined valley-fill flow field), FA3 (Fluvial-influenced flow field), FA4 (Upslope marginal flow field), and FA5 (Lava delta). Understanding these facies and their associations enables reconstruction of the flow field-scale architecture and emplacement history of the Hantangang Basalt. Spatially, the proximal Area 1 (Cheorwon) is characterized by FA1, with ponded, compound-braided architectures; the medial Area 2 (Pocheon) by FA2, exhibiting tabular, ribbon-like flows; and the distal Area 3 (Yeoncheon) by a heterogeneous combination of FA1, FA3, FA4, and FA5, reflecting the influence of lava–fluvial interactions and lava-induced damming on the fluvial plain. Stratigraphic units across these areas are correlated based on the facies characteristics, stratigraphic position, and inferred emplacement relationships. The proposed facies framework emphasizes flow-unit scale classification and hierarchical organization, allowing integration with conventional sedimentary facies models. This approach enhances interpretations of volcanic architecture, emplacement dynamics, and stratigraphic relationships in basaltic lava flow-dominated basins and provides a template for analyzing similar volcanic fields worldwide.