SEDIMENT FAILURES IN THE SHENHU AREA, NORTHERN CONTINENTAL SLOPE OF THE SOUTH CHINA SEA

With the seismic data acquired by the Guangzhou Marine Geological Survey, we studied the types and characteristics of the frequently developed sediments failures in the Shenhu area of the northern South China Sea. The distribution pattern of sediment failures is adopted to reveal the relationship between slope-confined submarine canyons and sediment failures. The sediments failures in the study area can be grouped to two types. The first type, which is mainly located at the ridges in the lower reach of a canyon and hardly affected by seafloor geomorphology, is characterized by multiple continuous wavy reflectors in a pattern of southwards mass movement. The second type is mainly the products of the mass movement from the ridge to the bottom of a canyon, and is obviously affected by the topography of the canyons. At the head of a canyon, sediment failures always occur as slides with continuous reflectors. And in the middle reach there is intensive deformation and dominated by slumps. From the lower reach to the canyon mouth, however sliding/slumping blocks dominate. Since Quaternary, Great amount of sediment charges come from the Pearl River system towards the north. With the help of steep seafloor topography, the activity of sediment failures is accelerated. Sediment re-deformation may widely occur in submarine canyons. In addition, the vertical migration of gas-bearing fluids coming from gas hydrate is also an important factor for sediment instabilities in the study area.