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Identification of Tsunami-induced deposits: the “Tsunamite Problem” - Recent Tsunamis: Historical and archeological record Paleotsunamis: geological record Frequency and occurrence?
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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...
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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
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Depositional setting of tsunami-induced deposits
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Some Geological proxies for tsunami-induced deposits Flat pebble conglomerate Molaar tooth Identifying tsunami deposits using sedimentary features (Pratt, 2002)
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Some Geological proxies for tsunami-induced deposits 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. Identifying tsunami deposits using boulder deposits (Dawson & Stewart, 2007)
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Some Geological proxies for tsunami-induced deposits Identifying tsunami deposits using bivalve shell taphonomy (Donato et al.; 2007)
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A new approach: rock magnetism Magnetic susceptibility, grain-size mean, and radiocarbon chronology along composite perfil of the Lisbon platform. Ages as calendar yr BP; magnetic susceptibility (10 6 SI – blue line) and mean grain-size (μm – black line) Magnetic susceptibility (Abrantes et al., 2007) Spectral analysis?????
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A new approach: rock magnetism Scanning Electron Microscopy (SEM) and Energy Dispersive Spectra (EDS) of Tsunami- induced deposits in spanish coast SEM and EDS analyses
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A new approach: rock magnetism Scanning Electron Microscopy (SEM) and Energy Dispersive Spectra (EDS) of Tsunami- induced deposits in spanish coast SEM and EDS analyses
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A new approach: rock magnetism Scanning Electron Microscopy (SEM) and Energy Dispersive Spectra (EDS) of Tsunami- induced deposits in spanish coast SEM and EDS analyses
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