Local inundation distances and regional tsunami recurrence in the Indian Ocean inferred from luminescence dating of sandy deposits in Thailand

Abstract

<jats:p>&lt;p&gt;&lt;strong&gt;Abstract.&lt;/strong&gt; The Holocene beach-ridge plain of Phra Thong Island (Ko Phra Thong, SW Thailand) provides sedimentary evidence of several palaeotsunamis, in addition to the deposit of the 2004 Indian Ocean tsunami. Due to poor preservation conditions, these palaeoevent layers are restricted to swales. Correlation across beach ridges, which is important e.g. to reconstruct inundation distances, remains a major challenge. A primary tool for establishing a precisely confined correlation of the sand sheets is the use of chronological data. Since the application of radiocarbon dating is limited by the scarcity of appropriate material, this study utilised optically stimulated luminescence (OSL) dating of tsunamigenic quartz grains. Generally, the sediments showed favourable luminescence properties regarding signal intensity, dose recovery and thermal stability. Disturbances of the OSL signal due to partial bleaching were corrected using the minimum age model. At least three palaeoevents – being 490–550, 925–1035 and 1740–2000 yr old – were distinguished by dating the discontinuous sand sheets at four different sites. Besides this chronological framework, the OSL data provide the opportunity to correlate the discontinuous sand sheets between spatially separated sites within the same swale as well as across ridges. This allows for first estimates of inundation distances for the palaeotsunamis documented on Phra Thong Island. Furthermore, the two younger events overlap in age with contemporaneous tsunami and earthquake evidence from other coasts bordering the Indian Ocean.&lt;/p&gt;</jats:p>

Tsunami recurrence in the eastern Alaska-Aleutian arc: A Holocene stratigraphic record from Chirikof Island, Alaska

“…We used single aliquot regeneration protocols (Murray and Wintle, 2003;Wintle and Murray, 2006) to estimate the apparent equivalent dose of the 250-150 μm quartz fractions in many tens of separate aliquots (Table 4; e.g., Wright et al, 2011;Brill et al, 2012;Prendergast et al, 2012). Very fine grains of sand from the upper 2 mm of sampled beds were selected for analysis because the uppermost grains are most likely to have been exposed to light following deposition.…”

Holocene evolution of Phra Thong's beach-ridge plain (Thailand) — Chronology, processes and driving factors

“…1a). Although southwest Thailand is part of the tectonically relatively stable Malay-Thai Peninsula (Tjia, 1996), the seismically active subduction zone of the Sunda Arc is situated directly west of the study area and poses a major source of tsunami-generating earthquakes (Lay et al, 2005) that may trigger waves strong enough to reach the Thai coast (Jankaew et al, 2008;Brill et al, 2011Brill et al, , 2012b. Fig.…”

“…While locally generated wind waves are of minor influence, swell waves with long periods of 10-15 s are clearly dominating (NOAA WAVEWATCH III, 2014). Significantly stronger waves may occur only episodically in the form of tsunamis (2004 Indian Ocean Tsunami and several palaeotsunamis: e.g., Jankaew et al, 2008;Brill et al, 2011Brill et al, , 2012b or during tropical cyclones. Although significant storm inundation is not mentioned in historical accounts (Murty and Flather, 2004) nor archived in the geological record (Phantuwongraj and Choowong, 2012), tropical storms occur in the study area and may be associated with significant coastal erosion and barrier overwash (eyewitness reports of local residents and own observations between 2007 and 2013, Figs.…”

“…The unimodal granulometry consisting of grain-size components C1 or C2 (130-630 μm) in the northern (transect C) and central part (transect E) of the island points to wave swash as the only formation process. Material accreted by the IOT 2004 or the storm in 2007 shows that this sediment (C1 and C2) is mainly derived from offshore (Brill et al, 2012b), whereas the lack of organogenic carbonate (that is still present in modern storm and tsunami washover deposits) can be explained by post-sedimentary leaching in the vadose zone (Brill et al, 2014). On the other hand, the bimodal grain-size composition of ridges in the southern part (transect F) -due to incorporation of moderately rounded, coarse grained quartz of C3 (700-1100 μm) in addition to C1 and C2 -points to a second mode of deposition (Fig.…”

High-frequency Coastal Overwash Deposits from Phra Thong Island, Thailand

“…The four older sand sheets preserved in Swales X and Y show strong sedimentological similarities (sharp erosional contacts, fining upward unimodal coarse sand to coarse silt, containing leaf or bark fragments) to the 2004 IOT deposit, but lack many of the sedimentary structures, microfauna and microflora202130. The palaeo-sand sheets from Swale Y lack preserved diatoms and carbonate microfauna (foraminifera), likely due to temperature-affected dissolution20213032, although it is unclear why the same processes would not have affected the carbonate and unabraided shell material in the intertidal deposits preserved at the base of the swale2132.…”