**2.3 Tsunami deposit identification**

*Applied Geochemistry with Case Studies on Geological Formations, Exploration Techniques…*

**from shore (m)**

**Elevation above mean sea level (m)**

**Core length (m)**

150 8 1.5 Coastal wetland

40 8 0.7 Coastal wetland

75 3 2.0 Coastal wetland

**Sample environment (m)**

**Site Coordinate location Distance** 

172011.938′ W

171033.585′ W

172004.263′ W

Lano 13037.176′ S;

Ma'asina 13056.607′ S;

Manono-uta 13052.120′ S;

*Core site locations and descriptions used in this study.*

tsunami and 1952 tsunamis originating from the Chile/Peru region, and the 1957 tsunami originating in the Aleutian Islands. However, a distinct calcareous sand unit indicative of the 2009 event was not discernable to the naked eye at the

No discernible calcareous sand deposits were observed in the Manono-uta core, though distinct changes in grain size, organic content (loss on ignition) and indicative pXRF elemental compositions comparable with the characteristics of the 2009 tsunami deposits on eastern Upolu were reported in [19]. At Lano, a distinct calcareous sand deposit was observed at ~1 m depth intercalated between dark

Itrax XRF involves the excitation of a sample by X-rays using either a molybdenum (Mo) or chromium (Cr) anode X-ray tube, causing the sample to fluoresce. That is, the sample emits secondary X-rays that are distinctive of the elements which they were emitted from. The relative intensity of these fluorescent signals provides an indication of the elemental composition of the sample [9, 10]. The Motube is commonly used in most applications and is more appropriate for detecting heavier elements, while the Cr- tube more adequately detects lighter elements. For example, Al and Si. Nevertheless, an X-ray exposure time of approximately 10–20 s on the sample using a Mo- tube and the Itrax Q-spec procedure is adequate for

Itrax elemental data used in this study were initially presented in [19] and were obtained in 2012 using the Itrax core scanner at the Australian Nuclear Science and Technology Organisation (ANSTO). The scanner was fitted with a Mo- tube and a magnetic susceptibility meter, with XRF scans performed on each core at 30 kV and 55 mA using 10 s exposure time and sampled at 500 μm step size. In comparison, Itrax analysis of the Little Pigeon Bay cores were carried out using similar settings at the University of Auckland [8], with a negligible difference of 4 s exposure time

The samples were air dried and the surfaces cleaned to minimize water content and matrix effects in the core prior to analysis. Data quality was ensured through normalization against the Al detected for each core, with profile gaps resolved through interpolation by a moving average curve. This enabled more meaningful trends to be observed in the core sequences. Identified elevated elemental signals relative to adjacent units were compared for consistency with detected changes in unit stratigraphy, grain size, loss on ignition (indicative of organic content if the changes are greater than 5%), and pXRF results for these

**30**

surface of the core.

**Table 1.**

brown soil units.

**2.2 Itrax data and analysis**

between the two datasets [20].

cores, provided in [19].

obtaining acceptable data for these light elements [10].

Normalized data was used to identify distinct elevated elemental signals in the core profiles comparable to benchmark tsunami signatures provided in [8]. Elevated signals at the surfaces of the Ma'asina and Manono cores are particularly screened for benchmark signatures indicative of the 2009 tsunami. Identified elevated elemental units are compared with descriptions of sites, core stratigraphies, and analogue tsunami deposits of the 2009 tsunami in [16, 19], to interpret distinct tsunami episodes in the core profiles.
