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_Journal of Structural Geology 32 (2010) 623e640_ _Contents lists available at ScienceDirect_ _Journal of Structural Geology_ _journal homepage: www.elsevier.com locate jsg_ _Coeval extension and compression in Late Mesozoic–Recent thin-skinned extensional tectonics in central Anatolia, Turkey_ _Yurdal Genç*, Mehmet Tekin Yürür_ _University of Hacettepe, Department of Geological Engineering, Beytepe campus, 06800, Ankara, Turkey_ _article info_ _Article history: Received 30 March 2009 Received in revised form 19 March 2010 Accepted 29 March 2010 Available online 2 April 2010_ _Keywords: Basin and range tectonics Crustal stretching Post-collisional collapse Cappadocia Central Anatolia Turkey_ _abstract_ _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 Nigde and Kars 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–ENE 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;_ _(4) Tethyan suture lines need to be reviewed since their traces may be modified by later extensional displacements._ _© 2010 Elsevier Ltd. All rights reserved._ _1. Introduction_ _Geodynamic studies (e.g., McKenzie, 1972) of the eastern Mediterranean have defined a plate configuration where three large continental plates, Africa, Arabia and Eurasia meet at the eastern Mediterranean (Fig. 1). The convergence and collision between the Arabian and Eurasian plates caused the lateral extrusion of a continental block, the Anatolian microplate that moves westerly relative to Eurasia to escape this plate convergence zone. This motion is accommodated along two major strike-slip fault zones, the North and East Anatolian fault zones. High-relief topographic zones are associated with these fault zones while the internal part of the Anatolian microplate, central Anatolia, displays a morphologically relatively flat region, with the exception of two large stratovolcanoes, Erciyes and Hasandag._ _Central Anatolia is marked by large depressions like the Tuzgolu and Konya basins, some of them bounded by long fault zones such as the Tuzgolu and Central Anatolian fault zones. While the Anatolian microplate boundary and the western Anatolian region (the Aegean zone) are associated with a pronounced seismic activity, the weak seismicity of central Anatolia is interpreted as due to the relatively more rigid behavior of the internal parts of the Anatolian microplate (e.g., Jackson and McKenzie, 1988)._ _The geology of central Anatolia was investigated by several workers in the past decades (Ketin, 1955; Erguvanli, 1961; Seymen, 1981, 1984, 2000; Erkan and Ataman, 1981; Goncuoglu, 1977). Most of the recent works deal with:_ _(1) The geochemistry of the upper Miocene–Recent volcanic rocks of the Cappadocian Volcanic Province (Fig. 1), of calc-alkaline character for the earlier episodes followed later by those of alkaline character, interpreted as the beginning of crustal extension in Late Miocene (e.g., Innocenti et al., 1975; Deniel et al., 1998; Kurtoglu et al., 2001; Sen et al., 2004);_ _(2) The metamorphic rocks of the Nigde Massif (Fig. 1), a metamorphic core complex formed in the Late Cretaceous (e.g., Whitney and Dilek, 1997). Umhoefer et al. (2007) attribute the alternating exhumation and subsidence periods of the Nigde Massif to kinematic changes of a large transcurrent fault zone, the Central Anatolian Fault Zone (Fig. 1)._ _Structural studies in the region encompass the ductile deformational characteristics of the crystalline rocks (for Kars: Seymen, 1981, 1984, 2000; for Nigde: Gautier et al., 2008), the Tuzgolu Fault Zone (Dirik and Goncuoglu, 1996; Cemen et al., 1999; Ozsayin and Dirik, 2007), the Central Anatolian Fault Zone (Yetis, 1978; Kocyigit and Beyhan, 1998) and fault kinematics of central Anatolia (Dhont et al., 1998). Dhont et al. (1998) proposed that the central Anatolian crust experienced extension in Neogene–Quaternary times, in contradiction with most of the previous studies (e.g., Sengor et al., 1985) and some recent works (e.g., Umhoefer et al., 2007) for who the regional crust deforms by strike-slip faulting. Recently, Yurur and Genç (2006) studied the western part of one of the important faults of the region, the Savcilar Thrust Fault, and concluded that the convergence the fault accommodates results from gravitational movements, in disagreement with previous work that attributed more important tectonic roles to this structure (backthrust of the Anatolian compressional deformations, Sengor and Yilmaz, 1981; a central Anatolian suture zone, Gorur et al., 1984)._ _Recent seismological studies suggest the presence of low velocity zones beneath central Anatolia, interpreted as evidence for a hot and/or thinned mantle lithosphere, or for the upwelling of asthenospheric material (Al-Lazki et al., 2003; Gok et al., 2003; Meier et al., 2004; Toksuz et al., 2008; Gans et al., 2009). Curie point depth maps of Turkey (Aydin et al., 2005) or of central Anatolia (Ates et al., 2005) show that the 580°C isotherm, a temperature considered to cause changes in rock magnetization, rises up to 8 km beneath central Anatolia. Ates et al. (2005) associate this with the Cappadocian magmatic activity._ _Following the seismological findings, the eastern Anatolian crust is proposed to be supported by asthenosphere (Sengor et al., 2003). On a larger scale, GPS-based studies led McClusky and Reilinger (2004) to propose that the Anatolian microplate motion is driven by gravitational forces._ _All these studies advocate that gravitational forces drive the Anatolian microplate and some relatively shallow and hot material zones exist beneath the Anatolian crust, including central Anatolia. In spite of all these data of mostly geophysical origin and even though there is some structural data from the metamorphic massifs (e.g., Seymen, 1981; Whitney and Dilek, 1997) or the Neogene–Quaternary rocks (Dhont et al., 1998), we do not still have a good knowledge of how the central Anatolian crustal deformational characteristics are consistent with these models. To fill this gap, we have studied the brittle deformational characteristics of the Cenozoic rocks in central Anatolia over a 300 km WSW–ENE trending transect between Konya and Yozgat cities. We present several new geological cross-sections from zones of major deformation combined with kinematic data we have collected to better constrain the geometric characteristics of the regional deformation. In the light of this new field data, we discuss some hypotheses advanced for central Anatolia and propose a new geodynamic model for this region._ _1.1. Methodology and material_ _In addition to available regional topographic and geological maps, we used topographic maps obtained by Shuttle Radar Topography Mission (SRTM) and released by NASA (2007) at 90 m resolution. We find these digital documents particularly useful in flat areas where metric-sized topographic anomalies, like small volcanic cones or recent faults vertically offsetting the landscape for a few meters, are easily determined. We used, in places, ASTER satellite images of 30 m spatial resolution viewed in stereoscopy. Analyses of these documents are controlled by field observations we undertook in several stations where we used kinematic analysis on faulted surfaces to detail some lithological contacts or deformational characteristics of outcrops._ _2. Regional morphology_ _In central Anatolia, the Tuzgolu fault is the most pronounced morphologic feature. The fault separates a topographically more elevated northeastern sector, with marked NW-trending crestal lines of the ranges separated by small basins, from a southwestern sector with smaller relief and the large Tuzgolu and Konya basins (Figs. 2 and 3). The longest stream of the country, the Kizilirmak River, crosses the northeastern sector in a large curve. Two large subactive stratovolcanoes, the Erciyes and Hasandag structures, culminate at 3917 m and 3268 m._ Ключевые слова: e, r, o