Plio-Quaternary Sedimentation and Tectonics in the Ionian Area: Clues to the Recent Evolution of the Mediterranean

Abstract

Recent investigations in the eastern and central Ionian Sea provide evidence of fundamental paleogeographic and paleoceanographic changes that have occurred since the Neogene. This evolution supports the model of Messinian shallow-water evaporation within a shallow basin setting. Sedimentary facies indicate a direct relation between Messinian sedimentation and rate of basin subsidence, the latter calculated at about I m/IOOO years. The general pattern of Pliocene sedimentation is the result of relatively slow deposition during continuing subsidence, producing "starved" basin conditions. During Plio-Quaternary time the average rate of subsidence within the basins was about 0.8 m/IOOO years. Raised Quaternary terraces, especially the oldest ones, are too high above present sealevel to have been caused only by eustatic changes. These marine terraces are interpreted as the result of coastal uplift that probably compensated, to some degree, basinal subsidence. The estimated rate of subsidence in marginal areas was about 0.5 mllOOO years. The Messinian "salinity crisis" and the Pliocene morpho-structural "revolution" were likely triggered by tectonics within certain specific areas. The elevated terraces and related subsiding basins, however, are due to a more general and widespread tectonic uplift of regions bordering subsiding basins throughout the Mediterranean area. Most of these marginal regions are situated within the circum-Mediterranean "Alpine" mountain belt. It is concluded that vertical neotectonics has played a primary role in the formation of the Mediterranean Sea during Plio-Quaternary time.