FEATURES OF CANYON MORPHOLOGY AND THEIR ORIGIN IN THE SHENHU AREA,NORTHERN SLOPE OF THE SOUTH CHINA SEA

Detailed interpretation of morphology and shallow stratigraphic structure were carried out base on high-resolution multi-beam water depth data and single-channel seismic profiles. Three canyons and four channels were recognized in the study area. The bird view of the shape and length of the canyons or channels vary greatly in a range of 8~25km long, 1.5~4 km wide, with a maximum incised depth up to 175 m. The shallow strata of the study area can be divided to two parts from bottom to top:namely U1 and U2 respectively. The seismic reflection in general is characterized by a high frequency, strong amplitude, medium-high continuation, and parallel to sub-parallel pattern. However, the reflection in the canyon is chaotic with low continuation or even discontinued. The research result indicates that slumping was well developed in the sequence U2 in the canyons area, which has close relationship with the occurrence of gas hydrate. The canyons or channels were initially formed by the decomposition of gas hydrate and further developed under the control of NW trend faults and the erosion of bottom current. The canyons and channels were formed in Quaternary according to its shape and stratigraphic position. The results may contribute to the study of oceanic morphology and the exploration of gas hydrate in the region.