Submarine Small-Scale Features of Cyclic Steps in the Penghu Canyon: Implications for the Migration of Canyon

Abstract

The submarine canyons are an important clue to study the evolution process of seafloor geomorphology and they generally indicate the significant linear grooves on the seafloor related to seafloor geodynamic erosion during the evolution of geomorphology. The submarine canyons or canyon groups are not only the channels for the sediment transport from shallow sediments with land-based sources to the deep sea in the sediment source-sink system, but also a key temporary sediment deposition area to study sediment transport patterns and the evolution of submarine geomorphology. In this paper, we processed and analyzed the multibeam bathymetry data acquired in the South China Sea continental margin by the research vessel “Dongfanghong 3” in 2020. Based on fine submarine geomorphological features identified from multibeam bathymetry data, we construct the formation pattern of the cyclic steps. The six cyclic steps (wavelengths of 1–6 km and wave heights of 19–81 m) are found in the lower section of the Penghu canyon and they appeared at the conjunction part of the Penghu and the Taiwan canyon. Based on location and the wavelength variations of the cyclic steps, we propose that the cyclic steps are formed by turbidity current flow along the Penghu and the Taiwan canyons. The axis of the cyclic step CS4–CS6 is shifted westward by about 5° compared to the axis of the cyclic step CS1–CS3. The inconsistency in the axis direction of the cyclic steps CS1–CS3 and CS4–CS6 suggests that is where the migration of the Penghu canyon occurred.