Core complex development in central Anatolia, Turkey

Abstract

Tectonic models for the central Anatolian segment of the Alpine-Himalayan orogen have not considered this region as part of the Aegean extensional province. We have found evidence, however, for Oligocene-Miocene extension and exhumation of midcrustal rocks in a metamorphic dome (Nigde massif) that is structurally and petrologically similar to Miocene core complexes >500 km to the west. Strong correspondence in the timing and kinematic development of the Menderes (western Turkey) and Nigde core complexes suggests that extensional tectonics and exhumation of mid- to lower-crustal rocks affected much of the eastern Mediterranean region. In the Nigde massif, supracrustal rocks were buried to depths of 16‐20 km at high temperatures (>700 °C) during contraction associated with closure of Neo-Tethyan seaways in late Mesozoic‐early Cenozoic time. Following cooling and decompression to <600 °C and <10 km, metasedimentary rocks underwent a second heating event at low pressures during Miocene magmatism that postdated much of the unroofing of the massif. Development of the Nigde core complex was related to exhumation of thickened and thermally weakened continental crust in the upper plate of a north-dipping subduction zone. The partial subduction of the Tauride carbonate platform in the Eocene resulted in choking of the subduction zone, followed by isostatic rebound and exhumation of the buoyant platform. This in turn caused a rapid emergence of the upper plate, resulting in erosion of upper-crustal rocks and exhumation of midcrustal rocks along the northern edge of the Inner Tauride suture zone. Although northern regions of central Anatolia contain the same protoliths as the Nigde massif and underwent extensive Tertiary magmatism, they did not undergo similar extension, suggesting that core complex development in south-central Turkey was controlled by the location of thickened and thermally weakened crust adjacent to a suture zone.