Insights from geochemistry and diatoms to characterise a tsunami's deposit and maximum inundation limit

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dc.contributor.authorChagué-Goff, Cen_AU
dc.contributor.authorGoff, JRen_AU
dc.contributor.authorWong, HKYen_AU
dc.contributor.authorCisternas, Men_AU
dc.date.accessioned2017-06-30T00:00:02Zen_AU
dc.date.available2017-06-30T00:00:02Zen_AU
dc.date.issued2015-01-01en_AU
dc.date.statistics2017-06-30en_AU
dc.description.abstractGeochemical proxies and diatom assemblages were used in combination with grain size characteristics not only to describe the deposit left behind by the 27 February 2010, Maule tsunami at Las Cañas, Maule Region, Chile, but also to trace the maximum inundation limit of the event. The sandy deposit was laid down between 160 and 260 m inland behind an eroded sand dune and a lagoon but reached only 60% of the total tsunami inundation distance of 380 m, which was marked by organic debris, pumice clasts and wooden logs. It consisted of coarse to medium sand that thinned and fined inland. At the most seaward point, the 22 cm thick deposit exhibited a fining upward unit overlain by a couplet of coarsening–fining upward units, suggesting deposition by at least two waves, while farther inland the fining upward deposit was probably left behind by only one wave. Chemical proxies (Ca/Ti vs Sr/Ba) allow us to distinguish the deposit from the surrounding soil and indicate that it was sourced from the beach and/or dune area, with diatom assemblages confirming the marine origin of the deposit. Saltwater indicators (e.g. Cl, S) provide evidence for the maximum inundation limit beyond the extent of the sandy deposit, despite dilution and dissolution by 500 mm of rainfall in the six months since the tsunami. Marine and marine/brackish diatom assemblages decreased landward but were found up to the inundation limit and immediately beyond, suggesting the effect of diatom-bearing sea spray at the wave front or redistribution of the detrital assemblage associated with tsunami inundation due to wind. While the latter might result in a slight over-estimation of the inundation distance, they can be used in combination with chemical proxies to trace the maximum inundation distance of recent and past tsunamis, thus allowing for a better estimation of the magnitude of past events. Post-depositional processes were found to have affected the thinner sandy deposits (< 5 cm), suggesting that these are unlikely to be preserved in the geological record. This highlights the need to be able to trace the tsunami inundation limit with geochemical and/or diatom proxies without having to rely on sedimentological evidence, as it is now widely recognised that conventional approaches used by tsunami researchers have led to an under-estimation of previous events.© 2014, Elsevier B.V.en_AU
dc.identifier.citationChague-Goff, C., Goff, J., Wong, H. K. Y., & Cisternas, M. (2015). Insights from geochemistry and diatoms to characterise a tsunami's deposit and maximum inundation limit. Marine Geology, 359, 22-34. doi:10.1016/j.margeo.2014.11.009en_AU
dc.identifier.govdoc8361en_AU
dc.identifier.issn0025-3227en_AU
dc.identifier.journaltitleMarine Geologyen_AU
dc.identifier.pagination22-34en_AU
dc.identifier.urihttp://dx.doi.org/10.1016/j.margeo.2014.11.009en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/8817en_AU
dc.identifier.volume359en_AU
dc.language.isoenen_AU
dc.publisherElsevieren_AU
dc.subjectDiatomsen_AU
dc.subjectChileen_AU
dc.subjectTsunamisen_AU
dc.subjectSource termsen_AU
dc.subjectDepositsen_AU
dc.subjectSaltsen_AU
dc.titleInsights from geochemistry and diatoms to characterise a tsunami's deposit and maximum inundation limiten_AU
dc.typeJournal Articleen_AU
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