Earth Planets Space, Vol. 64 (No. 10), pp. 875-887, 2012
P. Feldens1, K. Schwarzer1, D. Sakuna1,2, W. Szczuciński3, and P. Sompongchaiyakul4
1Institute of Geosciences, Kiel University,
Otto-Hahn-Platz 1, 24118 Kiel, Germany
2Oceanography and Environment Unit, Phuket Marine Biological Center, P.O. Box 60, Phuket 83000, Thailand
3Institute of Geology, Adam Mickiewicz University, Maków Polnych 16, 61-606 Poznań, Poland
4Department of Marine Science, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
(Received November 22, 2010; Revised August 5, 2011; Accepted September 18, 2011; Online published October 24, 2012)
The coastline of Khao Lak (Thailand) was heavily damaged
by the 2004 Indian Ocean tsunami. Onshore tsunami deposits and
satellite images, which show large amounts of sediment transported
offshore, indicate that the seafloor was impacted by tsunami run-up
and backwash. In this study, high-resolution maps of sediment
distribution patterns and the geological development of the
seafloor are presented. These maps are based on multibeam,
side-scan sonar and seismic profiling surveys offshore Khao Lak.
Paleoreefs, with associated boulder fields and sandy sediment
dominate the inner continental shelf. Patches of fine-grained (silt
to fine sand) sediments exist in water depths of less than 15 m.
The sediment distribution pattern is stable between 2008 and 2010,
apart from small shifts regarding the boundaries of the
fine-grained sediment patches. In one sediment core and several
grab samples an event layer was documented, situated below a cover
of modern sediments which is only a few cm thick. The event-layer
is traced down to 18 m water depth. It consists mostly of sand and
contains compounds of terrigenous origin. It is interpreted as a
2004 Indian Ocean tsunami deposit. However, over large areas of the
study-site, the impact of the tsunami is hardly identifiable by
seafloor morphology or sediment distribution.
Key words: 2004 Indian Ocean tsunami, offshore tsunami deposits, continental shelf, nearshore deposits, Andaman Sea.