Foraminiferal evidence of submarine sediment transport and deposition by backwash during the 2004 Indian Ocean tsunami

Micropaleontological analysis of nearshore to offshore sediments recovered from the southwestern coast of Thailand was performed to clarify the submarine processes of sediment transport and deposition during the 2004 Indian Ocean tsunami. The distribution pattern of benthic foraminifers showed seawa...

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Bibliographic Details
Published in:The island arc 2009-09, Vol.18 (3), p.513-525
Main Authors: Sugawara, Daisuke, Minoura, Koji, Nemoto, Naoki, Tsukawaki, Shinji, Goto, Kazuhisa, Imamura, Fumihiko
Format: Article
Language:English
Subjects:
2004 Indian Ocean tsunami
2004 Sumatra-Andaman earthquake
backwash
foraminifer
Foraminifera
sediment flow
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Summary:Micropaleontological analysis of nearshore to offshore sediments recovered from the southwestern coast of Thailand was performed to clarify the submarine processes of sediment transport and deposition during the 2004 Indian Ocean tsunami. The distribution pattern of benthic foraminifers showed seaward migration after the tsunami event. Agglutinated foraminifers, which are characteristic of an intertidal brackish environment, were identified in the post‐tsunami samples from foreshore to offshore zones. These suggest that sediments originally distributed in foreshore to nearshore zones were transported offshore due to the tsunami backwash. On the other hand, the distribution pattern of planktonic and benthic species living in offshore zones showed slight evidence of landward migration by the tsunami. This suggests that landward redistribution of sediments by the tsunami run‐up did not occur in the offshore seafloor of the study area. Our results and a review of previous studies provide an interpretation of submarine sedimentation by tsunamis. It is possible that tsunami backwashes induce sediment flows that transport a large amount of coastal materials seaward. Thus, traces of paleotsunami backwashes can be identified in offshore sedimentary environments as the accumulation of allochthonous materials. This can be recognized as changes in benthic foraminiferal assemblages.
ISSN:1038-4871
1440-1738
DOI:10.1111/j.1440-1738.2009.00677.x