Sedimentological record of tsunamis on shallow-shelf areas: The case of the 1969 AD and 1755 AD tsunamis on the Portuguese Shelf off Lisbon

Sedimentary deposits left by the 2004 Indian Ocean tsunami on the inner continental shelf offshore of Khao Lak, Andaman Sea (Thailand)

“…Table 2 summarises major features of tsunami deposits on the inner shelf or within 15 km of land that were generated by the eruption of Santorini in ca. 1630-1550BC (Goodman-Tchernov et al, 2009, the eruption of Krakatau in 1883 (van den Bergh et al, 2003), earthquakes on the Portuguese margin in 1755 and 1969 (Abrantes et al, 2008), several tsunamis in the Mediterranean (Smedile et al, 2011) and the 2004 Indian Ocean tsunami (Paris et al, 2010 and present study). Several sedimentological studies (e.g., Massari and D'Alessandro, 2000;Takashimizu and Masuda, 2000;Fujiwara and Kamataki, 2007) on potential shallow marine tsunami deposits from the geological past are not included in the discussion because they are not related to a specific tsunami event but are interpreted as being tsunami-generated based on sedimentological properties.…”

“…Sugawara et al (2009) reported nearshore impacts of the 2004 tsunami in the Andaman Sea in water depths of 6 to 30 m based on the distribution of foraminifera in surface sediments. In several other studies (e.g., Abrantes et al, 2008;Goodman-Tchernov et al, 2009;Smedile et al, 2011), offshore tsunami deposits were interpreted from event layers composed of sediments that were coarser than the ambient marine sediments, contained indicators of a terrigenous provenance and specific microfossil assemblages. However, there have been no unique criteria for identifying offshore tsunami deposits.…”

The first geological record of a palaeotsunami on the southern coast of the Baltic Sea, Poland

“…In addi tion, a tsu nami does not ex plain the gen e sis of the hemi spheri cal hol lows at Rowy by it self. Around the world, tsu nami events along flat coastal low lands have been re corded as thin lay ers of sand up to 0.5 m thick that ex tended be tween several hun dred metres and sev eral kilo metres in land (Hindson et al, 1996;Benson et al, 1997;Clague et al, 2000;Dawson and Shi, 2000;Goff et al, 2000Goff et al, , 2010Smoot et al, 2000;Bryant and Nott, 2001;Scheffers and Kelletat, 2003;Jaffe and Gelfenbaum, 2007;Mor ton et al, 2007;Abrantes et al, 2008;Choowong et al, 2008;Pe ter son et al, 2008;Fujino et al, 2008;Peter son and Cruikshank, 2011;Pe ter son et al, 2013). The sand came from the ero sion of a rel a tively nar row near shore and beach zone (Dawson, 1994;Jaffe and Gelfenbaum, 2007;Morton et al, 2007) and cov ered the man tle re lief, which showed no signs of ero sional un con formity at its base (Dominey-Howes et al, 2006;Dominey-Howes, 2007;Choowong et al, 2008;Szczuciński, 2008;Piotrowski et al, 2013).…”

“…The thick ness of the TD var ies from 0.23 m to 3.05 m and av er ages 1.09 m, which is sig nif i cantly greater than the thick nesses of tsu nami lay ers re ported from along low-en ergy coasts around the world. Data from such coasts show that tsu nami lay ers are usu ally 1-50 cm thick and are of ten <5 cm thick (Hindson et al, 1996;Benson et al, 1997;Clague et al, 2000;Dawson and Shi, 2000;Goff et al, 2000;Smoot et al, 2000;Bryant and Nott, 2001;Scheffers and Kelletat, 2003;Jaffe and Gelfenbaum, 2007;Mor ton et al, 2007;Abrantes et al, 2008;Choowong et al, 2008;Pe ter son et al, 2008;Fujino et al, 2008;Goff et al, 2010;Pe terson and Cruikshank, 2011;Pe ter son et al, 2013). The rel a tively large thick ness of the TD at Rowy is prob a bly caused by the subsurface palaeorelief.…”

Internal structure of event layers preserved on the Andaman Sea continental shelf, Thailand: tsunami vs. storm and flash-flood deposits

“…However, while the tsunami's impact increases with decreasing water depth towards the coastline, only very few offshore tsunami deposits have been reported until now. Therefore, it is not surprising that the described offshore deposits of historical tsunami -not considering inferred tsunami paleorecords on geological timescales (Le Roux and Vargas, 2005;Fujiwara and Kamataki, 2007;Spiske et al, 2014) -are highly variable in thickness, texture and structure (e.g., van den Bergh et al, 2003;Abrantes et al, 2008;Goodman-Tchernov et al, 2009;Paris et al, 2010;Smedile et al, 2011;Sakuna et al, 2012;Milker et al, 2013). Reported offshore tsunami deposits range from centimeters to 1 m in thickness while spanning grain sizes from mud to boulders, including terrigenous and marine sediments over one or several layers.…”