Anthropogenic pollutants and biomarkers for the identification of 2011 Tohoku-oki tsunami deposits (Japan)

Geochemical approaches in tsunami research: current knowledge and challenges

“…2). Although a thin, fine-grained tsunami deposit can be recognized if it was formed by a recent tsunami, as in the case of the 2011 Tohoku-oki tsunami (Chagué-Goff et al 2012a;Szczuciński et al 2012;Bellanova et al 2020a), in general, it is difficult to determine a tsunami inundation limit from the existence of a visible tsunami deposit in geological layers. Near the inundation limit, tsunami deposits tend to be thin and fine-grained because the weakened tsunami flow cannot transport coarser particles and large amounts of sand; thus, tsunami deposits can be difficult to distinguish from underlying and overlying sediment by visual observation.…”

“…In contrast, geochemical signatures can be detected in both visible and invisible tsunami deposits because the signatures are derived from seawater incursion to identify tsunami deposits. Bellanova et al (2020a) documented biomarkers and anthropogenic markers in tsunami deposits left by the 2011 Tohoku-oki tsunami on the Sendai Plain, Japan, and found that their concentrations differed significantly between pre-and posttsunami deposits. They concluded that anthropogenic markers and biomarkers have the potential to be a valuable proxy for tsunami research due to their high source specificity and relatively good preservation potential.…”

“…These studies indicated the potential of anthropogenic markers and biomarkers for tsunami research, although anthropogenic markers may not be applicable to prehistoric tsunami deposits. Bellanova et al (2020a, b) revived consideration of the preservation potential of biomarkers, as suggested by some previous studies (Alpar et al 2012;Shinozaki et al 2015); in addition, they further explored quantitative assessment of allochthonous biomarkers. Detection of aquatic/marine biomarkers has been attempted (Alpar et al 2012;Shinozaki et al 2015Shinozaki et al , 2016, with varying degrees of success; in some cases, aquatic/marine biomarkers could not be recognized in known tsunami deposits or the underlying layer.…”

“…Detection of aquatic/marine biomarkers has been attempted (Alpar et al 2012;Shinozaki et al 2015Shinozaki et al , 2016, with varying degrees of success; in some cases, aquatic/marine biomarkers could not be recognized in known tsunami deposits or the underlying layer. Another approach has involved comparison of the concentrations of terrigenous and aquatic/marine biomarkers (Bellanova et al 2020a, b). Three ratios, the terrigenous-to-aquatic ratio (TAR), the carbon preference index (CPI), and the odd-to-evenpredominance ratio (OEP), were applied to demonstrate dominance of terrestrial plants or marine organisms, and to ascertain the biogenic or petrogenic origin of n-alkanes in sediments (Bellanova et al 2020a).…”

“…After recent large tsunamis, such as the 2004 Indian Ocean tsunami, the 2009 South Pacific tsunami, the 2010 Maule tsunami, and the 2011 Tohoku-oki tsunami, studies of tsunami deposits dramatically increased and geochemical techniques became more widely applied. Research has been conducted on the geochemical characteristics of tsunami deposits (e.g., Srinivasalu et al 2010;Chagué-Goff et al 2012a, b, 2015Yoshii et al 2013), the temporal variation and preservation potential of tsunami deposits (Szczuciński et al 2007;Chagué-Goff et al 2012b;Shinozaki et al 2016), the presence of geochemical features beyond the distribution limit of sandy tsunami deposits (Goto et al 2011;Chagué-Goff et al 2012a, application of new analytical techniques (Cuven et al 2013;Kuwatani et al 2014), and the use of biomarkers as new geochemical markers (Shinozaki et al 2015;Szczuciński et al 2016;Bellanova et al 2020a, b).…”