Characteristics of Rocky Basin Structure of Yongshu Reef in the Southern South China Sea

摘要

Based on detailed drilling and surveying data, the rock structure of a small atoll in Yongshu Reef which stands over 2000 m above the sea-floor in the southern South China Sea was studied. The data revealed that the body of Yongshu Reef can be roughly identified as two layers: the un-cemented loose sediment layer (biological sediments) and the cemented solid rock layer (limestone). The maximum thickness of the loose sediment layer is in the lagoon center, approximately 20 m and its minimum thickness is the outside solid rock layer on the top of reef, forming a basin-like structure, termed as the "rocky basin structure." This structure together with the tower-shaped reef body makes it very stable for engineering construction.