Quaternary spatiotemporal evolution and multi-factor driving mechanisms of continental slope canyon–fan systems in Baiyun sag, Pearl River Mouth Basin, South China Sea

Abstract

As potential targets for deep-sea hydrocarbon exploration, continental slope canyon–fan systems preserve records of sea-level fluctuations and paleoclimatic changes. The Quaternary canyon–fan system in the Baiyun sag represents a potential reservoir for sand-rich deposits. However, the mechanism governing its Quaternary spatiotemporal evolution, which is influenced by multiple factors, remains unclear, significantly constraining the prediction accuracy of sand-rich deposits in this area. Based on three-dimensional (3D) seismic, drilling/logging, and paleontological datasets, a Quaternary isochronous stratigraphic framework was established for the northern continental slope of the Baiyun sag. Seismic interpretation techniques were employed to delineate the morphology and architecture of slope canyon group and associated slope fans, which enabled the development of a spatiotemporal evolutionary pattern for canyon–fan systems and the revelation of their multifactorial driving mechanisms. Our study demonstrates that: (1) Within the Quaternary target strata, one second-order (T₀) and five third-order sequence boundaries (SB1–SB5) have been identified, leading to the delineation of five third-order sequence units (Sq1–Sq5) with distinct structural characteristics; (2) Sedimentary geomorphic units such as shelf-margin deltas, submarine gullies, canyons, and slope fans have been recognized, collectively forming a complete deep-water source-to-sink (S2S) system; (3) The evolution of canyon–fan systems commenced during the canyon–fan formation stage (Stage 1) under a transgressive background, progressed through the peak stage of canyon incision and fan progradation (Stages 2–3) under a regressive background, and culminated in the canyon–fan decline stage (Stage 4) under another transgressive background; (4) Macroscopic factors, including tectonic activity and climate–sea level changes, controlled sediment supply and the development of canyon–fan systems, while local factors such as sediment provenance patterns and the distance between canyons and the shelf margin regulated the structural configuration and spatial distribution of these systems. The dominant controlling factors undergo shifts over time. Elucidating the spatiotemporal evolutionary patterns of Quaternary continental slope canyon–fan systems, revealing their multifactorial driving mechanisms, and deepening the understanding of dynamic processes within deep-water S2S systems will provide a theoretical basis for subsequent predictions of sand-rich deposits and offer a practical paradigm for global canyon–fan research.