The Ionian Abyssal Plain (central Mediterranean Sea): Morphology, subbottom structures and geodynamic history - an inventory

In order to understand the structure and evolution of the Mediterranean Ridge accretionary complex, it is necessary to understand the structure and history of its foreland. The Ionian Abyssal Plain is one of the varying types of foreland. The state of knowledge for that is presented. Its contour and detailed relief are described for the first time. Based on published and hitherto unpublished seismic data, information on the thickness of the Plio-Quaternary and on the Messinian evaporites are presented. Of particular interest are data concerning the pre-Messinian reflectors. They indicate a pattern of tilted blocks and horst-like features created in pre-Messinian time by tensional tectonics. Varying subsidence continued, however, during Messinian time and controlled the thickness of evaporites. At some places (e.g. Victor Hensen Seahill) vertical tectonics seem to be still active. The main tectonic structures of the Ionian Abyssal Plain are not related to the process of the present accretion and subduction at the Africa/Eurasia plate boundary but are pre-existing and should influence the internal structure of the Mediterranean Ridge which is still growing at the expense of the foreland. As a consequence of our structural evidence, we favour the following interpretation: the Ionian Abyssal Plain is not a remainder of the Jurassic Tethyan ocean but originated by extensive attenuation of continental crust.