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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS006 Poster presentation 1947
In search of tsunami deposits along the eastern coast of Sicily (Italy)
Dr. Alessandra Smedile
Scienze Geologiche Universit di Catania IASPEI
Maria Serafina Barbano, Paolo Marco De Martini, Daniela Pantosti, Paola Del Carlo,
Flavia Gerardi, Pierpaolo Guarnieri, Claudia Pirrotta, Mario Cosentino
Eastern Sicily has been affected in historical times by large earthquakes followed by devastating
tsunamis, such as the 1169, 1693 and 1908 events.In order to provide a long term assessment for
tsunami recurrence and related hazard, we developed a multi-disciplinary study aimed to recognize and
date historical and paleo-tsunami deposits. We have compiled a georeferenced database storing
information on the effects of known tsunamis (hit localities, inundation areas, run-up heights, etc.). On
the basis of these data coupled with a geomorphological approach (satellite images and aerial
photographs analysis and field surveys), we selected several sites, such as coastal lakes (Ganzirri,
Gornalunga), marshes and lagoons (Fiumefreddo, Priolo and Vendicari oases), potentially suitable for
preserving tsunami deposits. 50 test gouge cores have been dug by hand and engine coring.
Sedimentological and paleontological analyses were carried out in order to reconstruct the
paleonvironment with specific attention to potential paleo-tsunami sandy layers.Magnetic and X-ray
analyses evidenced susceptibility variations and peculiar small-scale sedimentary structures not
detectable trough the standard stratigraphic analysis. Moreover, morphometric and mineralogic analyses
were performed on selected samples through a EDS equipped SEM.Tephra identification and
radiocarbon dating were accomplished to constrain sedimentation rates and to correlate potential paleotsunami
sandy layers with historical earthquakes.Although several of the investigated sites resulted
unfavourable for the preservation of paleo-tsunami deposits, because revealed prevalently fluvial or
marine deposits or highly modified settings, a few sites contain probable paleo-tsunami information.For
example, three sandy/detrital layers, possibly related to paleo-tsunami events, were found at different
depths within a silty-clay to clay prevailing sequence at the Anguillara site (Mascali, north of Catania).
The paleontological analysis pointed out that the two uppermost sandy layers (about at 70 cm and 200
cm) were barren, whereas the assemblage found in the third, deeper sample (at about 350 cm)
consisting of metamorphic rounded clasts, echinoderms fragments, sponges spicules and high
concentration of roots and seeds, was totally different from the rest. The magnetic susceptibility
highlighted lithological differences and few peaks related to volcanic material. The radiocarbon dating,
carried out on a charcoal piece sampled just below the deepest suspicious layer, yielded an age of
1425-1510 AD, suggesting as candidate tsunami responsible for this layer the 1693 earthquake.Also at
the Priolo lagoon, south of the town of Augusta, extensive coring has highlighted a couple of
sandy/detrital layers (at -90 and -160 cm, respectively), showing a distinct micro- and macro-fossil
assemblage. The tsunami-related origin of these layers remains matter of debate and further specific
analyses are in progress to confirm or discard this hypothesis.
Keywords: paleo tsunami, eastern sicily