Mediterranean extension and the Africa-Eurasia collision

A number of tectonic events occurred contemporaneously in the Mediterranean region and the Middle East 30-25 Myr ago. These events are contemporaneous to or immediately followed a strong reduction of the northward absolute mo tion of Africa. Geological observations in the Neogene extensional basins o f the Mediterranean region reveal that extension started synchronously from west to east 30-25 Myr ago. In the western Mediterranean it started in the Gulf of Lion, Valencia trough, and Alboran Sea as well as between the Maur es massif and Corsica between 33 and 27 Ma ago. It then propagated eastward and southward to form to Liguro-Provencal basin and the Tyrrhenian Sea. In the eastern Mediterranean, extension started in the Aegean Sea before the deposition of marine sediments onto the collapsed Hellenides in the Aquitan ian and before the cooling of high-temperature metamorphic core complexes b etween 20 and 25 Ma. Foundering of the inner zones of the Carpathians and e xtension in the Panonnian basin also started in the late Oligocene-early Mi ocene. The body of the Afro-Arabian plate first collided with Eurasia in th e eastern Miditerranean region progressively from the Eocene to the Oligoce ne. Extensional tectonics was first recorded in the Gulf of Aden, Afar trip le junction, and Red Sea region also in the Oligocene. A general magmatic s urge occurred above all African hot spots, especially the Afar one. We expl ore the possibility that these drastic changes in the stress regime of the Mediterranean region and Middle East and the contemporaneous volcanic event were triggerred by the Africa/Arabia-Eurasia collision, which slowed down the motion of Africa. The present-day Mediterranean Sea was then locked bet ween two collision zones, and the velocity of retreat of the African slab i ncreased and became larger than the velocity of convergence leading to back arc extension. East of the Caucasus and northern Zagros collision zone the Afro-Arabian plate was still pulled by the slab pull force in the Zagros su bduction zone, which created extensional stresses in the northeast comet of the Afro-Arabian plate. The Arabian plate was formed by propagation of a c rack from the Carlsberg ridge westward toward the weak part of the African lithosphere above the Afar plume.