Early to mid-Holocene rapid sea-level rise and coastal response on the southern Yangtze delta plain, China

We used accelerator mass spectrometry (AMS) ¹⁴C-dated sediments of the Holocene basal supratidal flat to upper tidal flat facies in 11 cores on the southern Yangtze delta plain to reconstruct relative sea levels of 8.5-8.0 cal ka BP. Three cores were further AMS ¹⁴C dated and used to examine the evolution of sedimentary geomorphological environments in response to the rapid sea-level rise during the early to mid-Holocene. Results demonstrate relative sea-level rise of around 30mm a^-1 from 8.5 to 8.3 cal ka BP and around 10mm a^-1 from 8.3 to 8.0 cal ka BP. Retrogradation from supratidal to lower tidal flat environments occurred in response to the rapid sea-level rise at 8.5-8.3 cal ka BP, and aggradation from middle to upper tidal flat occurred at 8.3-7.9 cal ka BP. Further retreat of the tidal flat at 7.9-7.2 cal ka BP implies a mean sea-level rise rate exceeding 5mm a^-1 at this time. We suggest that the rapid relative sea-level rise during 8.3-8.5 cal ka BP and subsequent slower rise caused drastic changes in the coastal zone and that these changes are key phenomena for understanding the coastal response to future sea-level rise.