Tsunami and storm deposits preserved within a ria-type rocky coastal setting (Siracusa, SE Sicily)

Sedimentological and palaeoecological observations, accompanied by archaeological determinations and absolute dating, have been carried out on a recent beach-barrier system succession located 20 km south of Siracusa, south-eastern Ionian coast of Sicily (Italy). These deposits fill the back edge of a ria incised within Miocene limestones and are composed of three main stratal units characterized by distinct sedimentological features. The two lower units, formed by cross-bedded sands and laminated clays, recorded the development of a small confined beach-barrier depositional system, influenced by frequent high-energy events. The upper unit, represented by chaotic coarser sediments, can be attributed to a destructive marine high-energy event. The physical properties of the composing stratal units and the morphological setting of the study area have allowed us to reconstruct a suite of storm- and tsunami-related marine depositional processes that might have occurred in recent times along this area of elevated seismicity. In particular, absolute dating and archaeological determinations allow to correlate the upper unit to a tsunami wave triggered by the 1693 A.D. catastrophic earthquake. The same depositional mechanism can also account for some of the coarse levels occurring into the underlying stratal units.