Terrace Topography of the Ganquan Plateau in the Xisha Area of the South China Sea

Topography of the Ganquan Plateau in the Xisha area of the South China Sea was studied using multibeam bathymetric data. The top of the Ganquan Plateau was flat with slopes generally less than 1°, but the topography was a three-level terrace tilting toward the southwest with water depth ranging from 550–700 m. At water depth of 600–850 m, submarine terraces commonly developed with up to 5 levels recognized, and the terraces in the west were more developed than those in the east of the Ganquan Plateau. It is preliminarily believed that the top and peripheral terrace topography of the Ganquan Plateau was a result of the combined effects of the global sea level change at the time scale of glacial-interglacial cycle and the crust subsidence of the South China Sea. These two influencing factors might control the development of the other coral reefs in the South China Sea as well. Talus topography developed at the periphery of the Ganquan Plateau at water depth between 850 and 1 300 m, which is speculated to result from deposits of coral fragments transported from the top of reefs. The more developed talus topography in the northwest compared to that in the southeast might be directly related to the southwest tilt of the top of the Ganquan Plateau.