Reconstructing flow patterns from tsunami deposits with no visible sedimentary structure

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dc.contributor.authorKain, CLen_AU
dc.contributor.authorChagué-Goff, Cen_AU
dc.contributor.authorGoff, JRen_AU
dc.contributor.authorWassmer, Pen_AU
dc.contributor.authorGomez, CAen_AU
dc.contributor.authorHart, DEen_AU
dc.date.accessioned2017-02-20T03:54:05Zen_AU
dc.date.available2017-02-20T03:54:05Zen_AU
dc.date.issued2014-01-01en_AU
dc.date.statistics2017-02-20en_AU
dc.description.abstractHigh energy coastal events, such as tsunamis, commonly leave sediment deposits in the landscape that may be preserved in the geological record. A set of anomalous sand and silt layers intercalated between soil units was identified alongside an estuary in Okains Bay, Banks Peninsula, New Zealand. Okains Bay, comprised of a coastal plain of Holocene progradational dune ridges, was flooded by tsunamis in 1868 and 1960. Previous research has assessed the relationship between tsunami flow patterns and sediment deposits for recent events, and we aim to extend this application to older deposits where flow patterns were not recorded and sedimentary structures are not visually apparent. A multi-proxy approach was used to investigate the sediment deposits at twelve sites along a 2 km length of the estuary margin and map inundation patterns. Measurements of Magnetic Fabric (MF: Anisotropy of Magnetic Susceptibility) were used to determine the flow direction during deposition, alongside stratigraphy and particle size analyses to assess wave energy. Flow direction results were overlaid on a digital elevation model of the study site to interpret flow patterns. Deposits became thinner and particle size decreased with distance from the coast, indicating waning flow energy with distance inland. MF results indicate that inundation occurred via the estuary channel, with primary flow directions oriented perpendicular or sub-perpendicular to the channel at each site. On a smaller scale, results showed evidence of current reversal at some sites, with flow directed alternately away from and towards the estuary channel. This is consistent with uprush and backwash patterns observed in tsunami wave sequences. Topographic control of flow patterns is also evident from the data. This research demonstrates a method for investigating older, structurally-degraded deposits and has implications for the reconstruction of paleotsunami inundation from their sedimentary deposits. © AGUen_AU
dc.identifier.citationKain, C., Goff, J. R., Chagué-Goff, C., Wassmer, P., Gomez, C., & Hart, D. E. (2014). Reconstructing flow patterns from tsunami deposits with no visible sedimentary structure. Paper presented at the AGU Fall meeting, San Fransisco, 15-19 December 2014.en_AU
dc.identifier.conferenceenddate19 December 2014en_AU
dc.identifier.conferencenameAGU Fall meetingen_AU
dc.identifier.conferenceplaceSan Francisco, Californiaen_AU
dc.identifier.conferencestartdate15 December 2014en_AU
dc.identifier.govdoc7906en_AU
dc.identifier.otherNH21A-3822en_AU
dc.identifier.urihttps://agu.confex.com/agu/fm14/meetingapp.cgi/Paper/4322en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/8320en_AU
dc.language.isoenen_AU
dc.publisherAmerican Geophysical Unionen_AU
dc.subjectShoresen_AU
dc.subjectTsunamisen_AU
dc.subjectSedimentsen_AU
dc.subjectGeologyen_AU
dc.subjectNew Zealanden_AU
dc.subjectDataen_AU
dc.titleReconstructing flow patterns from tsunami deposits with no visible sedimentary structureen_AU
dc.typeConference Abstracten_AU
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