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 event. The physical properties of the composing stratal units compared with the morphological setting of the study area 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 correlating 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.