Abstract
Abstract. We have investigated the benthic foraminiferal fauna from sediment event layers associated with the 2004 Indian Ocean tsunami and former storms that have been retrieved in short sediment cores from offshore environments of the Andaman Sea, off Khao Lak, western Thailand. Species composition and test preservation of the benthic foraminiferal faunas exhibit pronounced changes across the studied sections and provide information on the depositional history of the tsunami layer, particularly on the source water depth of the displaced foraminiferal tests. In order to obtain accurate bathymetric information on sediment provenance, we have mapped the distribution of modern faunas in non-tsunamigenic surface sediments and created a calibration data set for the development of a transfer function. Our quantitative reconstructions revealed that the resuspension of sediment particles by the tsunami wave was restricted to a maximum water depth of approximately 20 m. Similar values were obtained for former storm events, thus impeding an easy distinction of different high-energy events.
Highlights
The devastating tsunami of 26 December 2004 that originated from a 9.3 magnitude submarine earthquake off the northwest coast of the Indonesian island Sumatra (Stein and Okal, 2005) (Fig. 1) had severe impacts on the coastlines of southeastern Asia (Bell et al, 2005; Tsuji et al, 2006)
The surface sediments are composed of a mixture of siliciclastic and carbonate particles of varying proportions and grain sizes
Differences are characterized by the sand content (> 63 μm) ranging from approximately 6 and to almost 100 % (Table S1)
Summary
The devastating tsunami of 26 December 2004 that originated from a 9.3 magnitude submarine earthquake off the northwest coast of the Indonesian island Sumatra (Stein and Okal, 2005) (Fig. 1) had severe impacts on the coastlines of southeastern Asia (Bell et al, 2005; Tsuji et al, 2006). Little is known on the exact provenance and transport dynamics of sediment particles in tsunamigenic offshore deposits Specific sedimentological characteristics such as thickness of the high-energy layer, its grain size distribution and sorting have been studied by several authors in order to distinguish between storm and tsunami events (e.g., Morton et al, 2007; Kortegaas and Dawson, 2007; Dahanayake and Kulasena, 2008). These studies revealed that it is often difficult to separate a storm layer from a tsunami layer from the sedimentological record alone
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