The influence of oceanographic processes on contourite features: A multidisciplinary study of the northern South China Sea

Abstract

This study examines how multiscale oceanographic processes interact with the seafloor to influence the development of contourite features in northern part of the South China Sea. The multidisciplinary approach used in this study combines physical oceanographic monitoring, numerical simulation, multibeam echosounding, seismic reflection profiling, and sediment core interpretation. The contourites detected and interpreted herein include depositional (drifts and sediment waves), erosional (channels, moats and furrows), and mixed erosional and depositional features (terraces and irregular depressions). This study finds that climatic variation influences the intensity of quasi-steady, along-slope regional water circulation which in turn influences the long-term development of primary (10–100 km) contourite depositional systems. Energetic but intermittent oceanographic processes (such as eddies and internal waves) generate smaller secondary features within the contourite depositional systems resulting in a complex, local seafloor morphology. Westward to south-westward migrating mesoscale eddies locally enhance regional water mass circulation and trigger sub-mesoscale flows which can generate (1–10 km) irregular depressions along their paths. Westward-propagating internal solitary waves form sedimentary waves. With the aid of numerical modelling results, a sedimentary model is proposed to explain how oceanographic processes influence sedimentary processes and determine a hierarchy of associated feature formation. This model can help advance understanding of how bottom currents influence sedimentary processes along continental margins and abyssal plains.