The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

Chaoshan Plain in the coastal northern South China Sea is one of the most densely populated areas in China and is the birthplace of Teochew culture. Understanding its past landscape evolution and paleo-environmental change requires valid chronological studies. Previous studies mainly focused on the onshore boreholes, but high-resolution chronostratigraphic data of its offshore boreholes is still limited which hinders a detailed interpretation of the depositional processes in the neritic Chaoshan Plain. In this study, quartz Optically Stimulated Luminescence (OSL) dating was applied to provide high-resolusion chronology on two offshore cores, RPHYZK01 and RPHYZK02, near Nan'ao Island, Shantou. The obtained ages ranged from >57 ka (minimum age) to 1.6 ka. A hiatus between ~35–16 ka was identified in both cores, with brownish-yellow clayey silts (~35 ka) below and grayish black clayey silts (~16 ka) above, reflecting strong erosion likely linked to sea level lowstands during the last glacial maximum (LGM). The post-LGM deposition could be divided into two stages, including (i) slow deposition between 16 ka and 2 ka with a depositional rate averaged to ~0.29 m/ka, likely with an unrecognized hiatus during ~16–9 ka, and (ii) rapid deposition after 2 ka with a depositional rate averaged to ~3.3 m/ka. The relatively slow deposition and possible hiatus in stage (i) likely reflects limited terrestrial sediment input or strong wave erosion within ~16–2 ka. The following post-2 ka sharp rise in the sedimentation rate may have been driven by intensified agricultural practices and land use that increased soil erosion on Nan'ao Island, which served as a key hub of the Maritime Silk Road that started at ~202 BC.