Tropical sand cays as natural paleo-cyclone archives

Sand cays are valuable paleo-archives that can significantly increase our understanding of Holocene tropical cyclone variability. Here we conducted detailed sedimentological and chronological analyses from a 195-cm-depth pit excavated on Guangjin Island (northern South China Sea), a cay influenced by frequent tropical cyclones. Radiometric dating of multiple deposits revealed that foraminifera, soft coral spicules, and gastropod shells yielded variable age distributions, while U/Th ages of pristine Acroporabranches provided a clear record of deposition and cay formation. Based on this robust chronostratigraphy, the proportions of > 2mm grain-size fraction within the deposits corresponded with the frequency of paleo-typhoons recorded by historical records in recent centuries. U/Th ages of Acropora branches from the deposits matched with three known historical typhoon events. Our results highlight the potential of cyclone-deposited sand cays as new archives for recording paleo-cyclones.