GEOMORPHOLOGICAL CHARACTERISTICS AND CONTROLLING FACTORS OF THE YITONG CANYON GROUP ON THE NORTHERN SLOPE OF THE SOUTH CHINA SEA

Based on the latest high-resolution multi-beam bathymetric data, as well as the single-channel and multi-channel seismic profiles, this paper analyzed the topographic and depositional features of the group of nine canyons on the northern slope of the South China Sea. The canyon group converges from the continental slope to the deep-sea basin, in "V" shaped cross-sections, with rather symmetrical valley walls and steep slopes. The submarine strata in the study area are disturbed by faults, and developed in a stepped manner. Unstable geological hazards, such as submarine faults, gravity sliding surfaces and small landslides are highly developed, which suggests that the submarine environment of the canyon group is very unstable. Cenozoic tectonic movements, such as the regional subsidence of Xisha Trough, doubtlessly contributed to the formation of the geomorphic pattern of the canyon groups. Agreat amount of sediment debris from the northern shelf was mainly contributed by high-density turbidity currents derived from submarine landslides, collapses and other submarine disasters, which accelerated the further development of the canyon group. Relative sea level changes directly change the sedimentary environment of the study area and provide a more direct channel for the transport of enormous terrigenous clastic materials. This is also one of the important factors that induced the instability of the seabed on the slope and shaped the geomorphological characteristics of the canyon group.