The role of submarine landslides in the initiation and evolution of moat–drift contourite systems

Moat–drift contourite systems, formed by interaction of alongslope bottom currents with bathymetric features, provide critical insights into palaeoceanographic changes. However, the role of submarine landslides in their initiation and evolution remains poorly understood. To investigate these processes, this study utilises multibeam bathymetric and three-dimensional seismic data from the Baiyun Slide, located in the northern South China Sea. The findings reveal a 600-m-wide, 50-m-deep moat incised along the steep escarpment of the Baiyun Slide headwall, flanked by a ~50-m-thick sediment drift. We propose that the landslide-induced escarpment acted as a bathymetric obstacle, locally intensifying bottom-current velocities and promoting flow turbulence and erosion, which facilitated moat formation. In contrast, in areas distant from the escarpment, reduced current velocities allowed for deposition of resuspended sediments, forming the drift deposits that fill the slide scar. While the surrounding slope is dominated by gravity-driven downslope sedimentary processes, the landslide-generated escarpment reconfigured the local depositional system, enabling the formation of a slide-controlled secondary contourite system driven by bottom currents. This system, confined within the negative topography of the slide scar, represents a spatial shift in sedimentation from a regional downslope to a localised alongslope control. As a corollary, we present a conceptual model illustrating how submarine landslides can reshape seafloor morphology to drive bottom current-induced sedimentation in otherwise gravity-dominated deep-marine environments. This study highlights slide-controlled moat–drift contourite systems as significant components of deep-water sedimentary archives, capable of recording dynamic interactions between bottom currents and seafloor topography.