Micromorphological analysis of coastal sediments from Willapa Bay, Washington, USA: A technique for analysing inferred tsunami deposits

Aoibheann A. Kilfeather, Jeffrey J. Blackford, Jaap J M van der Meer

Research output: Contribution to journalArticlepeer-review

Abstract

Tsunami deposits are provisionally distinguished in the field on the basis of anomalous sand horizons, fining-up and fining-landward, coupled with organic-rich, fragmented 'backwash' sediments. In this paper, micromorphological features of a sediment sequence previously interpreted as being of tsunami origin are described. These characteristics are shown to be consistent with the macro-scale features used elsewhere, but show additional details not seen in standard stratigraphies, including possible evidence for individual waves, possibly wave-magnitude progression, organic fragment alignment and intraclast microstructures. Although replication and more complete studies are needed, this analysis confirms the identification of a tsunami in Willapa Bay in ca.1700 AD, while demonstrating a widely applicable technique for confirming or refuting possible tsunami deposits. © Birkhäuser Verlag, Basel, 2007.
Original languageEnglish
Pages (from-to)509-525
Number of pages16
JournalPure and Applied Geophysics
Volume164
Issue number2-3
DOIs
Publication statusPublished - Mar 2007

Keywords

  • Cascadia subduction zone
  • Micromorphology
  • Thin sections
  • Tsunami
  • Washington
  • Willapa Bay

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