Patch reefs as sources of long and continuous skeletal records of horizontal reef expansion in Dongsha Atoll, South China Sea

Atolls are annular midocean reefs with various topographical features. The reef rim of an atoll encloses a central lagoon and lagoonal patch therein. Two hypotheses explaining the origins in lagoons have been developed: karst hypothesis growth hypothesis, which emphasize role uneven erosion timing accretion (especially horizontal expansion), respectively, formation reefs. In this study, we investigated trends locations, depths, ages, sizes, other features flat-top pinnacle-top Dongsha Atoll South China Sea by analyzing bathymetric LiDAR images performing U-Th dating on samples collected from atoll. Three our main findings were consistent hypothesis: (1) differences ages centers different reflected times at each reached surface started to expand horizontally; (2) top surfaces individual had old young peripheries, reflecting growth; (3) all examined more live corals their tips than surrounding bases. We observed no positive correlation between diameters reefs; that is, larger did not necessarily older centers, indicating complex factors affect expansion age patterns Overall, study provide support for use as sources easily accessible long-term coral skeletal records. They may therefore serve reference future studies asymmetric relevant topics.