New findings of Bronze Age homogenites in the Ionian Sea: Geodynamic implications for the Mediterranean

Abstract

Holocene homogenites similar in character and stratigraphic position to those previously recorded in the Ionian Basin, and related to the gigantic tsunami originating from Santorini (Bronze Age eruption) are described from a core transect crossing the deformation front of the Mediterranean Ridge east of Victor Hensen Seahill. Investigations on grain sizes and carbonate content carried out on three cores from three different areas of the Ionian Basin, encompassing the Bronze Age homogenite, revealed important similarities and some differences. The most obvious difference concerns the carbonate content, which is minimum at the base of the unit in a core close to the Messina Abyssal Plain, whereas it is maximum in cores from the Western Mediterranean and Calabrian Ridges, characterized by the typical “cobblestone topography”. A terrigenous versus pelagic nature of the components is documented, and a distal versus local provenance is inferred. Homogenites are critically compared with unifites, a type of re-sediment recently described from the eastern Mediterranean. Comparison includes in particular: (a) source and sediment transport; and (b) triggering mechanism. A substantial difference exists between the sedimentation patterns of the Ionian and Levantine Basins seaward of the Calabrian and Hellenic Arcs in the latest Quaternary, and the difference contains a clear geodynamic message: sedimentation rates increase from the Late Pleistocene to the Holocene in the Ionian Basin, whereas they decrease in the Levantine Basin. The glacio-eustatic signal is well expressed in the Levantine Basin, where the source areas are situated consistently in the south, or on a passive-type, aseismic continental margin (north African margin). In the Ionian Basin on the contrary the glacioeustatic signal is totally obscured by the strong tectonic signal from the active northern continental margin of the Mediterranean.