Volcaniclastic tide-modulated tempestite in a coastal tuff ring, Jeju Island, Korea.

The need for more accurate and extensive records of storm activity is increasing because of growing population and infrastructure in coastal areas. Records of past storm activity have consequently been sought from diverse sedimentary proxies in marginal marine environments, as well as historical documents. In this paper, we introduce a unique record of a 3.7 ka BP storm event preserved in a coastal tuff ring on Jeju Island, Korea. The tuff ring formed mostly above high tide level by primary volcanic processes, but contains three interbeds of horizontally laminated to hummocky/swaly cross-stratified deposits with intervening mud drapes up to an altitude of ~4.6 m above high tide level. These interbeds were formed by wave activity in a swash to surf zone when the sea level rose several meters above normal high-tide level during a storm event, and the triple intercalation of the wave-worked deposits reflects three tidal cycles during a storm event that lasted 1.5 day. Jeju Island contains the most complete record of an ancient storm event ever reported in the tuff ring, and highlights the significance of coastal volcanoes in the study of extreme depositional events in coastal areas, such as storms and tsunamis.