南海西沙海域甘泉海台的阶梯状地形

通过多波束水深资料，研究了南海西沙海域甘泉海台地形特征。甘泉海台顶面平坦，坡度通常＜1°，但存在3级阶梯状地形，水深范围介于550~700 m，这3级阶梯状地形总体向南西倾斜。在600~850 m水深范围内，甘泉海台普遍发育水下阶地，识别出的水下阶地多达5级，其中西侧阶地发育程度优于东侧。初步认为：甘泉海台顶部和周缘阶梯状地形是冰期―间冰期旋回尺度上全球海平面变化和南海地壳沉降共同作用的结果，这２个因素可能也控制着南海其他珊瑚礁的发育演化。在850~1 300 m水深范围内，甘泉海台周缘存在倒石堆状地形，推测主要是珊瑚礁碎屑从礁顶搬运沉积的产物，甘泉海台西北侧比东南侧倒石堆地形更加发育的现象估计与甘泉海台顶面向南西倾斜直接相关。

Terrace Topographyof 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.