南海西部陆坡平顶海山和海丘地形特征

西太平洋发育有大量的平顶海山，但在南海目前尚未见到关于平顶海山的详细报道。基于多波束测深数据，在南海西部陆坡识别出13个平顶海山和1个平顶海丘。平顶海山和海丘主要分布于西沙群岛和中沙群岛附近海底，以及海隆和海岭上。其中2个平顶海山为链状海山，位于中沙北海隆。南海西部陆坡的平顶海山和海丘山顶平台面积均超过3 km2，山顶水深范围184~631 m，位于陆坡中部的平顶海山和海丘山顶水深较小，而位于陆坡边缘的平顶海山山顶水深较大。通过对比西太平洋平顶海山，初步探讨了南海西部陆坡平顶海山和海丘地形特征指示的地质意义。

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.