Sedimentary records of mid-Holocene extreme storm events on the north bank of Hangzhou Bay, East China

Abstract

Reconstructing the long-term history of tropical cyclones is key to understanding their driving mechanisms and to enable better predictions of future extreme storm events. However, the available history of typhoons, based on sedimentary records in the northwest Pacific basin, remains very limited. In this study, we conducted multi-proxy analyses of sedimentary profiles collected from a chenier ridge on the north bank of Hangzhou Bay, East China. We applied evidences from the lithology, grain size, and marine micro-fossils on sediments in these profiles, dated using OSL and AMS 14C, to reveal the mid-Holocene sedimentary environmental evolution and obtain records of extreme storm events. The lithology and foraminiferal assemblages indicate an aggradational succession from intertidal to supratidal flats incorporating two layers of storm deposits preserved in the chenier ridge. The lower layer of storm deposits was formed in the intertidal flats at ca. 6.0 cal. kyr BP, while the upper layer was formed in the supratidal flats at ca. 5.2–4.9 cal. kyr BP. The storm deposits are characterized by coarsened grain size and the prevalence of allochthonous foraminiferal species, including E. advenum, A. annectens, and A. compressiuscula which occur in the inner and middle shelf of East China Sea. The extreme storm events at ca. 6.0 and 5.2–4.9 cal. kyr BP recorded at the chenier ridge have also been described at different sites on the southeast coast of Hangzhou Bay. Together with previously reported storm deposits at ca. 4.5 cal. kyr BP, we suggest that these mid-Holocene extreme typhoon events on the East China coast resulted from global climate changes driven by solar irradiance.