Stratigraphic architecture and marine preservation in rift basins: a coupled model of tectonics, eustasy, and sediment networks

Sequence stratigraphy is a vital tool for interpreting stratal records and paleoenvironmental changes; however, its application to rift basins is often oversimplified using passive-margin models that neglect the complex interplay between eustasy and tectonic controls. In rift basins, the dynamic coupling of axial and transverse sediment systems forms a complex routing network that profoundly influences basin architecture and facies distribution. We present a coupled numerical model that integrates multi-directional sediment sources with tectonic subsidence and eustatic sea-level cycles. By systematically investigating the ratios between the basin-equilibrium timescale (Teq), the tectonic timescale (Tt), and the sea-level-forcing duration (Tz), we evaluate stratigraphic responses across varying forcing scenarios. Our results reveal that key horizons, such as sequence boundaries and maximum flooding surfaces, are inherently fragmented and diachronous, particularly toward the hanging-wall margin where accommodation is rapidly exhausted. Notably, “up-strike” segments (e.g., the Jeju Basin) can maintain a significant marine fraction (approximately 25–30% in our model), even in regions traditionally perceived as terrestrially dominated. This preservation is facilitated by localized depocenters and transgressive bays formed through the interaction of multi-sourced sediment supply and tectonic subsidence. This study provides a rigorous quantitative framework and a stratigraphic model for re-evaluating the depositional history and hydrocarbon potential of underexplored segments in tectonically active extensional basins.