Origin and chronology of the Augias deposit in the Ionian Sea (Central Mediterranean Sea), based on new regional sedimentological data

The sedimentological analysis of seven piston cores reveals three sedimentary facies corresponding to the Augias deposit: 1) “homogenite”, 2) “megaturbidite” and 3) “thick sandy turbidite”. These sedimentary facies are distributed within specific morpho-tectonic regions as defined by newly acquired bathymetric data, indicating a strong control by transport and depositional processes. Sixteen radiocarbon dates obtained above and below the Augias deposit indicate a possible time window of about 500 years. This means that we cannot definitively prove a link to the 365 AD Crete earthquake, but we regard it as the most likely trigger. Other depositional models may be plausible, but here we propose a sequence of events as follows: (1) earthquake shock and possible triggering of submarine mass flow in the eastern part of the Ionian Sea (western Hellenic subduction zone); (2) tsunami waves amplified by the confined morphology of the Sicily and Calabria continental shelves inducing an intense re-suspension of fine-grained sediment and massive destabilization at the heads of submarine canyons triggering turbidity currents; (3) gravity driven downslope transport of suspended sediment toward the deep basin and decantation; and (4) a final stage of decantation from seiche waves forming the majority of the homogenite facies in the Ionian Abyssal Plain.