DISTRIBUTION OF GUYOTS ON THE NORTHWESTERN SLOPE OF SOUTH CHINA SEA AND THEIR TOPOGRAPHIC FEATURES

The Ocean Drilling Program has made clear the internal structure of guyots in the west Pacific. However, little literatures are available in the region of the South China Sea concerning guyots or flat-top seamounts. Recently, on the northwestern slope of the South China Sea we have found nine flat-top seamounts and knolls exceeding 3 km² in area based on multi-beam bathymetric data. In this paper, the topographic features of these guyotsare analyzed. It is found that they are mainly distributed on some topographic rises near submarine platforms submerged undera water depth of 184-631m. The most obvious one is the Pingnan Seamount to the north of the Zhongsha Islands. It consists of several small flat-top seamounts in a northwest line, rather similar tothe Megallan Seamounts in the West Pacific. According to the evolutionary model of theguyots in the west Pacific, the flat-top topographic featuresstarted from volcanic islands. They were erodedwhen they were close to the sea level, and coral reefs would develop to compensate the subsidence and made the top flat. Certainly the identification of flat-top seamounts and knolls in the South China Sea will help future geological and geophysical surveys in the region though the evolutionary details are not clear at present.