Post-LGM changes of sedimentary environments and bottom-current activity recorded in shallow-water contourite drifts of the Hupo Basin, East Sea (Sea of Japan)

Shallow-water contourite drifts preserve detailed records of the interplay between waves, currents, and sea-level changes; however, their formative processes remain less constrained than those of deep-water contourites. Here, we examine the post–Last Glacial Maximum (LGM) sedimentary environments and bottom-current activity in the Hupo Basin (HBS), a shelf-perched basin on the eastern Korean margin, where prominent moat–drift systems are present along the western flank of the Hupo Bank (HBK). Bathymetric mapping, sub-bottom CHIRP profiling, and analyses of three piston cores were combined to reconstruct sedimentation since the LGM. The moat–drift morphology reflects the persistent influence of the northward East Korea Warm Current (EKWC), strengthened by Coriolis deflection and controlled by slope gradients and cross-sectional constriction along the HBK. Stratigraphic successions show a shift from sand-rich to mud-rich facies at approximately 8 ka, recording rapid post-LGM sea-level rise and stabilization near present levels, marked by a transgressive surface (TS) and a maximum flooding surface (MFS). Cross-shelf trends reveal a transition from wave-dominated transport in shallower settings to bottom-current control along the HBK, with the moat–drift system forming an unusual onshore-thinning Holocene mud wedge above the MFS. Unlike the fining trend observed commonly toward the thinning end of deep-water contourite drifts, the HBS drift wedge has an overall coarsening trend toward its thinning end because of its unique shallow-water setting adjacent to the wave-dominated shelf. Sortable silt mean size () was evaluated as a proxy for bottom-current strength and found to be broadly reliable since ∼ 6 ka, despite short-lived disturbances caused by storm reworking or periods of weak current activity. Spectral analysis of shows the appearance of centennial-scale cycles after ∼ 2.5 ka, indicating unstable EKWC activity during the late Holocene, consistent with independent sea-surface temperature records. Overall, the HBS provides a well-resolved example of how shallow-water contourites capture the combined effects of sea-level change, waves, and along-shelf currents, offering important insights into Holocene oceanographic and climatic variability.