Some Current Problems on the Tectonic Evolution of the Mediterranean During the Cainozoic

Abstract

The Cainozoic history of the Mediterranean and its mountainous frame may be conveniently divided into two stages, not everywhere synchronous. The earlier stage was a continuation of the late Mesozoic Alpide convergence, dominated by subduction tectonics and that culminated in the continental collisions from the Betic and the Rif cordilleras and the Pyrenees via the Provence chains and the Tellian Atlas, Sicily, and the Apennine/Corsican collisional system, the Alps, Carpathians, Dinarides, Hellenides, the Balkan ranges and the Anatolian mountain ranges to the Caucasus and the Zagros. During this episode, subduction led to back-arc basin generation in the western Mediterranean, and the resulting tectonics is little different from the southeast Asian and western Pacific systems, despite the commonly and unjustifiably overemphasized differences. Both compressional arcs and collisions led to widespread fore- and hinterland deformation creating complex germanotype orogens such as the Iberian and the Catalan chains, and the High and Saharan Atlas. The second stage corresponds in the western Mediterranean with the continued rapid expansion of back-arc basins accompanied by trenchward jumping of extensional loci creating remnant arcs such as the Corso-Sardinian block, collisions of migratory arcs with continental margins and eventual dimunition of orogenic deformation, except where the subduction of the Eastern Mediterranean interfered as in offshore Calabria. In the Eastern Mediterranean, this stage led to the collisional assembly of a tectonic collage in Anatolia and eventually to the collision of Arabia with Eurasia, to the opening of the Aegean Sea, and to the concurrent expulsion of Anatolia westwards from the collision front of the Arabian promontory with Eurasia along the Bitlis suture in southeastern Turkey. Tectonic escape has played a very major role in the Cainozoic tectonics of the Mediterranean and shares the responsibility, together with extensional arcs, for the extremely contorted plan view of the Mediterranean Alpides. Wherever “extensional orogenic collapse” has occurred in the Mediterraenan Alpides (Betic/Rif/Alboran Sea system, the Tyrrhenian Sea, the Pannonian Basin, and the Aegean Sea), it invariably has been caused or at least triggered by either extensional arcs (no collapsing orogen extended over a flat subduction zone in the Mediterranean) or by escape (if not part of an extensional arc, orogenic collapse invariably has occurred in the Mediterranean at the leading part of an escaping fragment: e.g., the Alboran Sea, the Pannonian Basin, the Aegean Sea). I conclude that there is no “special” Mediterraean tectonics, as there are no “Mediterranean type” orogens, for there seems to be no aspect of the tectonic evolution of the Mediterranean that cannot be directly compared with some presently active orogenic belt and/or basin complex elsewehere in the world. The overall kinematic (but not temporal!) evolution of the Mediterranean, except in the Eastern Mediterranean, seems to be much as Argand portrayed it nearly seventy years ago. I think that this shows the power of the regional geological methods, now much amplified, but not replaced, by geophysical measurements.