Slope instability and submarine-moat initiation: Insights from the northern South China sea margin

Abstract

Submarine landslides that occur on continental margins can reshape the seafloor morphology and form steep slide scarps. Although the emplacement processes of submarine landslides have been well studied, the development of post-slide deposition has long been overlooked. Here, we use high-resolution multibeam bathymetric and three-dimensional seismic data from the northern South China Sea margin to decode how slide scarps affect bottom currents and generate associated bottom current-related features. Distinct features have been identified within the slide scars, such as sediments waves and drifts. In parallel, multiple longitudinal negative topographies are distinguished along the scarps, undercutting into underlying strata with width and depth up to 240 m and 20 m, respectively. These incisional structures are interpreted as moats, formed following the emplacement of landslides, and running along the foot of scarps that parallel to contours. The origin of these moats could thus represent an interaction between slide scars and contourite deposition. We suggested that escarpments act as morphological barriers, regionally affecting the velocity and direction of bottom currents, leading to an intensification of their velocities and their erosive ability. Furthermore, we propose a co-evolution model of submarine landslides and related moats, which elucidates and emphasizes the significance of scarps in moat initiation and evolution. Our results demonstrate that the interaction between escarpments and bottom current flow can lead to topographic remodeling and sedimentary processes on varying continental margins.