Sedimentary Processes and Source-to-Sink System of the Zhuhai Formation in the Southern Steep Slope Zone of the Zhu III Depression Offshore SE China

The Pearl River Mouth Basin is a significant hydrocarbon basin in the northern part of the South China Sea, where deep hydrocarbon exploration has become increasingly important research in recent years. However, the current understanding of the source-to-sink and depositional systems of the Paleogene Zhuhai Formation is still limited, which restricts the exploration and discovery of large-scale sand bodies. Based on core observation, heavy mineral analysis, and well-seismic integrated analysis, this paper clarifies the development of a fan delta-tidal flat depositional and the source-to-sink systems of the Zhuhai Formation. The bedrock in the source region primarily consists of granite, Mesozoic sandstone, and tuff. The source region is divided into five parts (A1–A5), with seven main valleys (V1–V7) developed, supplying sediments to five depositional areas (S1–S5). Additionally, a fault-slope type coupled valley–fan depositional model is established for the study area, revealing the spatiotemporal distribution and main controlling factors of the fan delta system in a steeply dipping boundary fault environment. Catchment area, valley length, and cross-sectional area show a strong positive correlation with sedimentary system scale. Increased elevation difference enhances sediment transport potential energy, while reduced width-to-depth ratio strengthens hydrodynamic forces, promoting sedimentary sand body development and sedimentary system expansion.