Seismic stratigraphy and development of a modern isolated carbonate platform (Xuande Atoll) in the South China Sea

Xuande Atoll is an isolated carbonate platform that has developed since the early Miocene. This study conducted high-resolution seismic surveys and shallow drilling to understand its internal structure and development. Five seismic sequences were observed (from bottom to top): SQ1 (early Miocene), SQ2 (middle Miocene), SQ3 (late Miocene), SQ4 (Pliocene), and SQ5 (Quaternary). The seismic data indicated that the platform formation started in the early Miocene and flourished during the early and middle Miocene. The platform shrank before the isolated platform formed in the middle Miocene. The final shrinking stage occurred in the southern and western parts of the platform at the end of the Miocene, which may reflect rapid tectonic subsidence and increased terrigenous sediment inputs owing to the formation of the semi-marginal sea. The peri-platform contains a falling sea-level sequence that was dominated by mass wasting deposits.

Automated summary

This study used high-resolution seismic surveys and shallow drilling to investigate the internal structure and development of Xuande Atoll, an isolated carbonate platform formed since the early Miocene. Five seismic sequences were identified, indicating the platform formation and expansion during the early and middle Miocene, followed by a shrinking stage before the formation of the isolated platform in the middle Miocene. The final shrinking stage in the late Miocene may be attributed to rapid tectonic subsidence and increased terrigenous sediment inputs due to the formation of the semi-marginal sea. The peri-platform area showed a falling sea-level sequence predominantly characterized by mass wasting deposits.