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’’ :

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...

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

Depositional setting of tsunami-induced deposits

Depositional setting of tsunami-induced deposits

Depositional setting of tsunami-induced deposits

Some Geological proxies for tsunami-induced deposits

Flat pebble conglomerate

Molaar tooth

Identifying tsunami deposits using

sedimentary features (Pratt, 2002)

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)

Some Geological proxies for tsunami-induced deposits

Identifying tsunami deposits using bivalve shell taphonomy (Donato et al.; 2007)

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?????

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

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

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