Architectures of the turbidite channel in the head area of a slope-parallel directional submarine turbidite channel system: A case study of the Central Canyon Area, Qiongdongnan Basin, South China Sea

Abstract

Significant volumes of sediment are deposited in deep-sea regions via turbidite channel systems, which function as critical conduits for the transport of sediment from shelf environments to the abyssal plain; concurrently, complex sedimentary processes—such as erosion, incision, and sedimentation—play an integral role in the development of diverse architectural features. In particular, the head area of slope-parallel submarine turbidite channel systems is marked by significant sediment transport, yet the rapidly changing topography has limited our understanding of their architectural stacking patterns. In this study, we selected the head area of the Central Canyon Area (CCA) in the Qiongdongnan Basin (QDNB) as a case study and constructed various patterns of turbidite channel system architecture along the turbidity flow direction. Based on >200 m of core samples, we identified nine lithofacies and determined the transition patterns of turbidite flows from coarse-grained equilibrium flow, fine-grained equilibrium flow, depositional flow, and erosion flow. Furthermore, utilizing high-resolution 3D seismic data, we measured the geomorphological parameters of the channel systems, including the static aspect ratio, cross-sectional asymmetry, angles of channel-complex growth trajectories, and stratigraphic mobility numbers. By applying an empirical formula that correlates turbidite channel system morphology with layer-averaged flow velocity, we calculated the corresponding Froude numbers. Finally, we reconstructed the evolution of the turbidite channel system architecture in different hierarchies.① In the initial depositional stage, coarse-grained and fine-grained equilibrium flows developed. The turbidite channel system complex presented high aspect ratios and asymmetry values in upstream depocentre areas, transitioning to lower aspect ratios in midstream regions while maintaining high asymmetry. This architecture is characterized by steady vertical accretion types, with the predominant filling types being layer-filled, cut-stack, and interbedded mass transport deposits (MTDs). ② During the rapid accumulation stage, a shift to lower aspect ratios and asymmetry values occurs, revealing diverse turbidite channel systems, primarily lateral accretion types with layered filling, lateral products, and cut-stack patterns dominating the channel stacks. ③ In the reworking MTD stage, a sharp change in the aspect ratio signals a dominance of lateral accretion-type channel systems interbedded with MTDs.

Furthermore, we identify key factors influencing the architecture of turbidite channel system stack patterns across different stages and speculate on deposition patterns in slope-parallel submarine channel heads. Statistical analysis of the morphological parameters revealed that during the initial deposition and rapid accumulation stages, the topographic slope angle and turbidity currents were the primary influences on channel accumulation. In contrast, during the reworking MTD stage, turbidity currents and sediment deposition rates appear to be key factors affecting channel architecture. This comprehensive evaluation advances our understanding of turbidite channel system evolution and its architectural responses to dynamic sedimentary processes.