Chronostratigraphy and petrophysical properties for the middle to late Miocene sediments in the shelf to abyssal plain of the Ulleung Basin, Korea

This study presents the first comprehensive chronostratigraphic framework for the Miocene sediments in the entire Ulleung Basin by integrating zircon U-Pb geochronology, seismic stratigraphy, and petrophysical analyses. The comparison between zircon dating and biostratigraphic constraints enhances the precision of stratigraphic correlations. Total eight maximum depositional ages derived from conventional and sidewall cores from the basin provide refined temporal resolution for key stratigraphic units, enabling a more accurate reconstruction of sedimentary processes and basin evolution during the Miocene. Petrophysical analyses along the synchronous horizons of maximum depositional ages reveal significant variations in shale volume, effective porosity, and Net-to-Gross ratio, reflecting the influence of depositional environments and diagenetic modifications on rock properties. In particular, porosity variations are predominantly influenced by depositional ages and environments as well as burial diagenesis. The results of this study enhance our understanding of the geological history and resource potential in the Ulleung Basin, serving as a foundation for future research on regional stratigraphy, hydrocarbon exploration, and reservoir characterization. Furthermore, this study highlights the importance of integrating high-resolution geochronological methods with petrophysical evaluations to enhance assessments of hydrocarbon resources and CO 2 storage capacity. • Eight maximum depositional ages were identified from core data in the Ulleung Basin. • Six MDAs are traced as chronostratigraphic horizons across shelf, slope, and basin. • Petrophysical properties are analyzed using well log data at the MDA intervals. • Reservoir characteristics are interpreted by depositional environment of each MDA. • Results show reservoir quality is influenced by both depositional age and burial depth.