Tracing tsunami impacts in coastal geo- and bio-archives along the west coast of Thailand

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The project aims to identify traces left by tsunami impacts in nearshore geo- and bioarchives of selected coastal areas of western Thailand. The 2004 Indian Ocean Tsunami shall be taken as a prototype since it had a major effect on all coastal ecosystems. In Phase 1 all traces of the 2004 tsunami were studied in nearshore archives on land, in the littoral zone and in the sea (swales, coastal lowlands, lakes, embayments, mangrove swamps, boulder fields, coral reefs). Its fingerprint is being worked out by sedimentological, geochemical and microfaunal analyses. In Phase 2 (this application), traces of former extreme events in the same geo- and bioarchives and in additional ones along the west coast of Thailand shall be examined in detail with respect to their origin (storm or tsunami), intensitv and age (A). In order to reconstruct the tsunami history of the region, the palaeogeographic evolution of the studied sites (B) as well as the sea-level curve for the Middle and Late Holocene (C) has to be reconstructed. Swales of Phra Thong Island, water-filled sinkholes of the tower karst islands in Phang-nga Bay and the coastal plains at Ban Bang Sak and Cape Pakarang turned out to be suitable geo-archives. All of these sites contain multiple event layers with ages of several hundred years up to more than 5.000 years, dated by AMS-14C and OSL. They shall be studied in Phase 2 of the project in detail under the research goals (A), (B) and (C) mentioned above. Living Porites lutea colonies proved to be excellent bio-archives, having stored a continuous record of extreme events of the last 1.000 or so years. Sampling the reefs of Ko Racha Yai, it may be possible to extend this time span up to 2.000 years.