The distribution and characteristics of very large subaqueous sand dunes in the Dongsha region of the northern South China Sea

Analysis of multi-beam bathymetric and high-resolution multi-channel seismic data acquired by the Guangzhou Marine Geological Survey reveals the presence of deep-water very large subaqueous sand dunes in the Dongsha region of the northern South China Sea. These subaqueous sand dunes are distributed as patches on the upper continental slope at depths of 230-830 m below water. It is suggested that their formations and migrations are influenced by a NW SE toward near-seabed flow for supplying sediments and energies to maintain sand dunes. The flow scours the seafloor, generating three erosion strips which are separated by subaqueous, sand dune zones. A highly correlated exponential relationship is defined by sand dunes geometric parameters in the Dongsha region, with a trough-to-trough wavelength range of 55 similar to 510 m and wave heights of 1.5 similar to 20 m. Sand dune wavelengths increase with growing seawater depth, but the larger wave heights are found at water depths of 500 similar to 700 m. It is the current hydrodynamic conditions that bring up both geometric parameters relationships and sand dunes' NE-SW trending ridges.