The role of sediment gravity flows on the morphological development of a large submarine canyon (Taiwan Canyon), north-east South China Sea

High-resolution multibeam bathymetric and multichannel seismic data are used to investigate the morphology of a submarine canyon (Taiwan Canyon), and its surrounding strata, in the north-east South China Sea. This submarine canyon shows two main branches at its head, and changes its orientation from north-west/south-east to east-west due to the effect of a tectonically active seamount. The asymmetry of the submarine canyon's banks in its middle reach is due to the combined action of recurrent slope instability and turbidity currents. In addition, two fields of sediment waves were identified in the study area. Field 1 is located on the south-west levee of the canyon and is fed by turbidity currents from one of its branches, being also associated with marked hydraulic jumps. Field 2 is observed in the southern bank of the lower canyon reach and was formed by the overspill of turbidity currents within the Taiwan Canyon due to the effect of inertial centrifugal forces. Turbidity currents sourced from Dongsha Channel also contributed to forming Field 2. Importantly, trains of plunge pools have been identified along the thalweg of the lower canyon reach, generated by turbidity currents deriving from the submarine canyons in the north of the Taiwan Canyon. These results not only provide a very detailed account of submarine bedforms within and around a large submarine canyon, but also contribute to a better understanding of their origin and development. The high-resolution bathymetric and seismic data in this work reveal how gravity flows can drive erosion and deposition in submarine canyons.

Automated summary

The study utilized high-resolution bathymetric and seismic data to investigate the morphology of a submarine canyon (Taiwan Canyon) in the northeast South China Sea, revealing asymmetrical banks and sediment wave fields. Different sources of turbidity currents entering the canyon led to distinct depositional features, contributing to a better understanding of submarine canyon evolution and formation.