Sequence Stratigraphic Evolution of Late Miocene–Early Pliocene in the Central Song Hong Basin, Vietnam: Controls on Sediment Routing and Reservoir Predictability

Abstract

The Cenozoic Song Hong Basin (SHB), in the northwestern East Vietnam Sea (South China Sea), underwent major stratigraphic and depositional changes during the Late Miocene–Early Pliocene, a critical interval shaped by relative sea‐level fluctuations, tectonics, and intensified monsoonal sediment supply. These factors reconfigured sediment dispersal and paleotopography, controlling the distribution of reservoir and seal architectures. Understanding these controls is essential for reconstructing depositional histories and assessing hydrocarbon potential. This study provides the first high‐resolution characterization of the Late Miocene–Early Pliocene succession in the western sector of the central SHB by integrating seismic interpretation, biostratigraphy, gamma‐ray log analysis, and forward stratigraphic modeling. Three third‐order sequences, constrained by biostratigraphy (SU1: 6.8–5.3 Ma, falling‐stage systems tract [FSST]; SU2: 5.3–3.8 Ma, LST; and SU3: 3.8–2.3 Ma, TST), record the evolution from falling‐stage shelf‐margin delta deposition to lowstand basin‐floor sedimentation and subsequent transgressive marine flooding, reflecting changes in accommodation, sediment supply, and climatic conditions from the humid Late Miocene to the cooler, drier Early Pliocene. Sand‐rich shelf‐margin deltas and basin‐floor turbidite fans developed during SU1 and SU2, sourced mainly from the Vietnamese hinterland, constitute the principal reservoir targets, whereas the mud‐rich transgressive deposits of SU3 provide an effective regional seal. Sensitivity analyses using forward stratigraphic modeling indicate that sediment discharge, sand–mud ratio, and paleotopography exert first‐order controls on turbidite fan geometry, sand dispersal, and reservoir connectivity. Comparison between the modeled depositional trends and 3D s eismic root mean square (RMS) amplitude anomalies demonstrates the complementary value of integrating process‐based forward modeling with seismic interpretation for predicting sand‐prone depositional systems. These results provide new insights into the controls on Late Miocene–Early Pliocene basin evolution and establish a predictive framework for reservoir distribution in monsoon‐influenced continental margin basins.