Sedimentary Signatures of Typhoon: Insight from Core Record in the South China Sea

Sedimentary records of event deposits are crucial for regional natural disaster risk assessments and hazard history reconstructions. This study aims to identify deep-sea typhoon deposits through immediate post-event sampling following super typhoon Haiyan (2013) and typhoon Morakot (2009). After super typhoon Haiyan passed through the South China Sea in 2013, five gravity cores were collected along the typhoon path in the southern South China Sea Basin (>3800 mbsl). The results showed that Super Typhoon Haiyan deposits with clear graded bedding are preserved at the top of all cores. The thickness of the typhoon layers ranges from 20 to 240 cm and is related to changes in typhoon intensity. The lack of river-connected submarine canyon systems limited the transportation of terrestrial sediments from land to sea. Super Typhoon Haiyan-induced large surface waves played an important role in carrying suspended sediment from the Philippines. A distinctive feature is that Mn-rich layers were found at the bottom of the typhoon layers, potentially linked to the soil and rock composition of the Palawan region, which experienced tsunami-like storm surges caused by super typhoon Haiyan. Similar Mn-rich layer characteristics were also observed in the typhoon Morakot (2009) layer in the sediment cores from the lower reach of Gaoping submarine canyon. These Mn-rich layers may serve as a proxy for sediment export from large-scale extreme terrigenous events. This study provides the first sedimentary record of extreme typhoon events in the deep basin of South China Sea, which may shed light on reconstructing regional hazard history.