Quantitative and qualitative characteristics of foraminiferal species within the inferred paleotsunami deposits of southwestern Andaman Island were examined using sediment samples from six geoslice sections up to a depth of ~2.5m. In this study, it is considered that the foraminiferal assemblages of the 2004 tsunami deposit (Unit b) as a modern analogue to trace similar events in the geological past. Paleontological and quantitative data analysis suggests 2 biofacies in the stratigraphy. Biofacies I is indicative of a subtidal sediment provenance and its mixing with intertidal sediments due to the tsunami, whereas, Biofacies II is an intertidal/marshy sediment provenance/environment. Foraminiferal tests >180µm in dimension in the tsunami facies (Biofacies I) show abrasion marks, which otherwise show high preservation potential than the pre-tsunami (Biofacies II) that indicates high dissolution activity and low preservation potential. Based on these inferences, 4 tsunami zones, 4 marsh zones, and 1 basin filling zone was elucidated in the stratigraphical column. In order to refine the chronostratigraphy of this area, the contemporaneous foraminifera recovered from a 15cm thick paleotsunami deposit (Unit g) were dated using 14C accelerator mass spectrometry (AMS). The AMS age suggests that AD 1005-1190 was the predecessor of 2004 Sumatra-Andaman earthquake (Mw 9.3) and associated Indian Ocean tsunami.

You do not have access to this content, please speak to your institutional administrator if you feel you should have access.