Extensional-compressional tectonics associated with the Aegean Arc: comparison with the Andean Cordillera of south Peru - north Bolivia

Abstract

Extensional-compressional tectonics are analysed along the convergent boundaries of the Aegean Arc and of the Andean Cordillera of south Peru and north Bolivia. This paper deals only with deformations of Miocene, Pliocene and Pleistocene ages. The prevailing regime in the Aegean basin is extensional. Yet two compressional tectonic phases of U. Miocene—L. Pliocene and of L. Pleistocene age have been recorded. They are also known in many places all around the Mediterranean. Thus forces that induce compressional tectonics in the Aegean seem to have their origin outside the region. They seem to be linked with changes in the conditions of convergence (change in rate?) between the Arabo-African and Eurasian plates. Beneath the Andean Cordillera of south Peru — north Bolivia, the subduction zone plunges at an angle of 25- 30° as it does under the Aegean Arc. There, as in the Aegean Sea, tectonics are predominantly extensional and several short-lived compressional phases break up this extensional regime. The latter may also be induced by changes of the conditions of convergence, here between the Nazca and South American plates. Beneath central Peru, north of the Nazca Ridge, the subduction zone plunges at a small angle, about 10°. There, neotectonic deformations are different. In the Recent they are essentially compressional or expressed by strike-slip faulting. Geological data from the Aegean and Andes seem to demonstrate that the compressional deformation in the crust above subduction zones is strongly controlled by the stress conditions along convergent boundaries.