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Identification of Tsunami-induced deposits: the “Tsunamite Problem”

Identification of Tsunami-induced deposits: the “Tsunamite Problem”. Recent Tsunamis: Historical and archeological record Paleotsunamis: geological record  Frequency and occurrence?. Geological record of paleotsunamis. “Tsunamite’’ :

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Identification of Tsunami-induced deposits: the “Tsunamite Problem”

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  1. Identification of Tsunami-induced deposits: the “Tsunamite Problem” • Recent Tsunamis: Historical and archeological record Paleotsunamis: geological record  Frequency and occurrence?

  2. Geological record of paleotsunamis “Tsunamite’’ :  tractive-current-reworked conglomerates (Yamazaki et al.,1989)  sediments transported by the tsunami wave itself and tsunami-induced current deposits (Shiki and Yamazaki, 1996) • = Tempestites (storm-induced sediments) • The term tsunamite is not a self-defining expression of a single depositional process and refers to an amalgamation of issues at several levels (Shanmugan, 2006): • Turbidites, debris flows, seismites, etc...

  3. Geological record of paleotsunamis  What are the geological proxies for tsunami-induced deposits??? As a extraordinary event, a tsunami can trigger a variety of processes including turbidity currents and debris flows. Pure Sedimentology  Multidisciplinary approach : - Sedimentology – Petrology – Paleontology - Perspectives: Rock Magnetism – Geochemistry  Function of the paleoenvironment: - Peculiar zones such as estuary and lagoon - Seismites in deeper water

  4. Depositional setting of tsunami-induced deposits

  5. Depositional setting of tsunami-induced deposits

  6. Depositional setting of tsunami-induced deposits

  7. Some Geological proxies for tsunami-induced deposits Flat pebble conglomerate Molaar tooth Identifying tsunami deposits using sedimentary features (Pratt, 2002)

  8. Some Geological proxies for tsunami-induced deposits Identifying tsunami deposits using boulder deposits (Dawson & Stewart, 2007) Large coral-reef fragments deposited on Pakarang Beach, near Khao Lak, Thailand, by the 26 December 2004 tsunami. The high energies needed to remove these boulders may ensure they have a higher preservation potential than other tsunami-related onshore sediments.

  9. Some Geological proxies for tsunami-induced deposits Identifying tsunami deposits using bivalve shell taphonomy (Donato et al.; 2007)

  10. A new approach: rock magnetism Magnetic susceptibility (Abrantes et al., 2007) Magnetic susceptibility, grain-size mean, and radiocarbon chronology along composite perfil of the Lisbon platform. Ages as calendar yr BP; magnetic susceptibility (106 SI – blue line) and mean grain-size (μm – black line)  Spectral analysis?????

  11. A new approach: rock magnetism SEM and EDS analyses Scanning Electron Microscopy (SEM) and Energy Dispersive Spectra (EDS) of Tsunami-induced deposits in spanish coast

  12. A new approach: rock magnetism SEM and EDS analyses Scanning Electron Microscopy (SEM) and Energy Dispersive Spectra (EDS) of Tsunami-induced deposits in spanish coast

  13. A new approach: rock magnetism SEM and EDS analyses Scanning Electron Microscopy (SEM) and Energy Dispersive Spectra (EDS) of Tsunami-induced deposits in spanish coast

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