Coeval extension and compression in Late Mesozoic–Recent thin-skinned extensional tectonics in central Anatolia, Turkey

The central Anatolian crust is composed of high-grade metamorphic rocks covered by Tertiary shallow marine to continental sedimentary rocks, with a Middle Miocene-Recent volcanic activity in Cappadocia. After the Late Cretaceous closure of the Tethyan Ocean and following plate collision, core complexes formed in Niğde and Kırşehir regions of central Anatolia. Recent geophysical studies indicate the presence of low seismic velocity zones beneath central Anatolia, interpreted as regionally thinned and/or hot mantle lithosphere, or asthenospheric upwelling. We present new structural data covering a ∼300 km WSW–NNE trending transect between Konya and Yozgat cities to suggest that central Anatolian Cenozoic tectonic regime is extensional and the narrow fold/thrust zones once taken as evidence of crustal convergence resulted from gravitational movements. Curie point depths map of central Anatolia shows a large-scale (diameter >140 km) upwarping (c. 15 km) of the regional crust we interpret as due to asthenospheric upwelling. These considerations suggest that (1) the central Anatolian crust deforms by extension. Transcurrent faults like the Central Anatolian Fault Zone accommodate the crustal stretching by transfer faulting; (2) post-Late Cretaceous crustal extension favored the placement of hot and low density asthenospheric material in Cappadocia by processes that may be explained by Rayleigh–Taylor instability phenomenon; (3) In central Anatolia, large post-Eocene horizontal crustal displacements (we estimate a minimum of 50 km) are not achieved by crustal contraction as previously proposed but thin-skin extensional tectonics and (4) Tethyan suture lines need to be reviewed since their traces may be modified by later extensional displacements.