Stratigraphic sequences off NE Hainan Island: Controls on sand resource distribution in the South China Sea

Abstract

Sand ridges represent key components of Quaternary transgressive successions. Understanding their sediment routing history is critical for developing predictive models of marine sand resource distribution under rising sea-level scenarios. In the NE Hainan offshore area, while modern sand ridges dominate the seafloor, their sediment provenance and evolutionary trajectory remain poorly constrained, impeding systematic resource exploration. To address this knowledge gap, we integrate high-resolution single-channel seismic profiling with sequence stratigraphic analysis to reconstruct the depositional architecture and sediment routing pathways in this region. Six reflection boundaries and five seismic sequences (SU1-SU5) were distinguished by the abrupt changes in reflection termination patterns, continuity, amplitude variations, and stratal geometry. The stratigraphic record reveals a systematic migration from progradational deltaic facies to transgressive tidal ridges, reflecting a regressive-to-transgressive succession. This evolution is characterized by a complete regressive-transgressive cycle, initiating with forced regression (SU5–SU4) driven by high sediment influx, followed by transgression (SU3–SU1) marked by tidal reworking of antecedent deltaic sands. Such stratigraphic architecture directly controls the distribution of high-quality sandy facies: delta-front sands and tidal-ridge complexes, serving as primary targets for resource exploration. Sequence stratigraphy is shaped by sea-level changes, sediment supply, and hydrodynamics, where SU4 represents the sediment-rich phase while SU2 marks the main sand-ridge construction period. These findings establish a predictive model for marine sand resource exploration by integrating stratigraphic architecture analysis with paleoenvironmental reconstructions to reduce assessment uncertainties.