A 4400-Year-Old Extreme Paleo-Storm Surge Recorded in the Dongzhai Port Chenier, Hainan Island, China

Identifying paleo-storm surge deposits and extreme storm surge events holds significant scientific and practical importance for understanding the recurrence patterns of super typhoon-induced surges and predicting future storm hazards. Current research predominantly focuses on historical and modern storm surges, with less attention given to prehistoric extreme surges. This study investigates a 3.2-m-thick chenier at Wushu Village, Dongzhai Port, Hainan Island. Analyses of sedimentary structures, shell provenance, accelerator mass spectrometry (AMS)¹⁴C dating, and estimates of overtopping deposit elevation demonstrate that this chenier records an extreme storm surge event approximately 4400 years ago. The chenier's overtopping deposits accumulated on a Late Pleistocene alluvial plain landward of the Holocene highstand paleo-shoreline. Nine AMS ¹⁴C dates on shells range from 4402 to 6647 cal yr BP, exhibiting age reversals and co-occurrence of younger and older shells. The deposit is well-sorted and displays sedimentary structures diagnostic of high-energy deposition, including hummocky cross-stratification, current cross-stratification, and erosional scours. Comparative analysis of shell assemblages and ages between the chenier and underlying paleo-lagoon deposits within Dongzhai Port indicates that the chenier shells were reworked from these older lagoon sediments. The reconstructed paleo-elevation of the overtopping deposits indicates a storm surge height of 5.5 m above modern sea level. This exceeds the 4.58 m surge documented during the 2014 Super Typhoon Rammasun along the Dongzhai coast. Considering the potential influence of astronomical tides on total water levels, we infer that the extreme storm surge height 4400 years ago was likely superimposed on a contemporaneous high astronomical tide.