Evidence of probable paleotsunami deposits on Kho Khao Island, Phang Nga Province, Thailand

Abstract

The 2004 tsunami deposits and probable paleotsunami deposits were studied at the southern Kho Khao Island, on Andaman Sea coast of Thailand. The 2004 tsunami laid down about 8 cm of fining upward medium sand and locally about 40 cm of massive coarse sand with common mud clasts. The sediments were characterized by the presence of marine foraminiferal assemblage; however, already after 5 years many of carbonate foraminiferal tests were partly or completely dissolved. The probable paleotsunami deposits form layer about 1 m thick. It consists of massive very coarse sand with common big shells and mud clasts. Its composition suggests a marine origin and the presence of mud clasts, and similarity to the 2004 tsunami deposits suggests that the layer was left by paleotsunami, which took place probably during the late Holocene, even though two shells within the layer gave 14C ages of 40,000 years or more.