Catastrophic events such as tsunamis or typhoons leave unique signatures in the geologic and geomorphic record. The sedimentary analysis of these events presents an opportunity to better understand the sedimentary and hydrodynamic processes. Characterizing the sediment provenance may contribute to understand the sedimentary fingerprint of catastrophic coastal events.
In this study, X-Ray Diffraction (XRD) and X-Ray Fluorescence (XRF) techniques were applied in an attempt to determine sediment provenance of tsunami deposits based on mineralogy and sediment composition at Phra Thong Island, Thailand. Here, the 2004 Indian Ocean Tsunami wave height was over 19m. The preliminary results from selected thirty samples by using XRD indicated that quartz dominates all sediment mixtures with more than 90 – 95 weight% on average and could not be used to discriminate tsunami deposits. XRF, however, provided additional information on trace element composition. Since XRF analyses were not greatly affected by quartz saturation, cluster and discriminant function analyses were employed in order to investigate the statistical differences between the sample groups. The XRF results indicated that the onshore group is easily distinguished from the offshore and trench groups; whereas the offshore and trench group were statistically similar. This implies that the main source of non-quartz material in the tsunami deposit comes from offshore marine sediments.
Next steps, we would re-run XRD analysis for finer fraction and then analyze all samples in both XRD and XRF in order to get more detailed results.