High-resolution multibeam bathymetric enables detailed morphological investigation of the area of Manila Trench on the northeastern South China Sea margin, where twenty-three cyclic steps are observed. The identified cyclic steps can be further divided into two groups (Types A and B), namely, thirteen net-erosional and ten net-depositional cyclic steps, based on their sizes and relative locations. Type A cyclic steps occur downstream of the South Taiwan Shoal Canyon and Penghu Canyon, whereas Type B cyclic steps distribute outside the South Taiwan Shoal Canyon levees adjacent to the canyon bend. Principal component analysis (PCA) distinctly identifies the two cyclic step clusters (Types A and B), with cyclic steps length ( L step ) and height ( H step ) are key explanatory variables. The significant differences in flow properties between confined and unconfined turbidity currents crossing cyclic steps are considered to control the formation of Types A and B cyclic steps. Furthermore, net- erosional (Type A) cyclic steps will likely evolve into new submarine canyon-channel systems under continued turbidity currents erosion, altering material transport and deposition patterns to the deep sea in the Manila Trench. Our results improve understanding of the origin and formation of cyclic steps in global submarine canyons.
Yang et al. (Wed,) studied this question.