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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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Depositional setting of tsunami-induced deposits
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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 (106 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