The tsunami induced by the collapse of the Santorini caldera, during the Minoan (Bronze-age) eruption, originated gigantic turbidites deposited in the abyssal plains of the Ionian Sea as well as on the floor of small ponded basins of the Mediterranean and Calabrian ridges characterized by the so-called "Cobblestone topography". The present paper reviews previous findings of this unusual sediment type and provides additional information concerning discoveries made during a recent oceanographic cruise (September, 1984) on the Sirte abyssal plain and Katia basin. Deep-sea cores which contain the Minoan "homogenite" described after its first identification in 1981 are 30 till now. Three discrete types may be distinguished, each of them related to a peculiar physiographic setting. (a) "Closed Cobblestone": several meters thick pelagic turbidites of local provenance, limited to the floor of small-sized ponded basins within the Mediterranean and Calabrian ridges. (b) "Abyssal Plain": more than 10 m thick turbidites recorded in the Messina and Sirte abyssal plains. Their source area is very large and the composition includes terrigenous sand. (c) "Open Cobblestone": this type is exclusive of the outer slopes of the Mediterranean ridge facing the Sirte A.P. Unlike in types (a) and (b), the base of Minoan homogenites is erosional instead of depositional. Occurrence of this unusual sediment type is not limited to the depressions but extends to positive physiographic features, as a result of up-hill migration of turbidites originated by the tsunami waves on the African margin, after crossing the narrow Sirte abyssal plain.
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Con il contributo del Ministero per i Beni e le Attività Culturali