International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

The Savcili Thrust Fault (Kιrsehir, Central Anatolia): a backthrust fault, a suture zone or a secondary fracture in an extensional regime?

Pages: 47 - 56

Authors: M. TEKIN YURUR, YURDAL GENC

Abstract: Large exposures of granitic and metamorphic rocks characterize the geology of Central Anatolia, in Turkey. These basement rocks crop out mainly between the Tuz Gölü and Ecemis fault zones, two major fractures of strike-slip fault character. During the Neogene, detachment faulting along the Tuz Gölü Fault (TGF) zone caused the deposition of several thousand meters of sediments in the large intracontinental Tuz Gölü Basin. In the western parts of Central Anatolia and near Kιrsehir town, another fracture zone runs almost parallel to the SE-trending TGF zone, separated from the TGF by a narrow (~30 km) and rectangular granitic belt. Along this fracture known as the Savcιlι Thrust Fault (STF), metamorphic and plutonic rocks overthrust middle Eocene detrital rocks of the sedimentary cover along a relatively narrow (~100 m) crushing zone. In some previous works, this structure is presented as a backthrust of the Anatolian block, or a suture zone along which two continental Central Anatolian blocks were amalgamated. Recent detailed mineral exploration studies reveal that the area at the north of the STF comprises several low-angle normal faults along the surfaces of which the Eocene and the underlying metamorphic rocks moved southwards until they were juxtaposed to southern granitic rocks along steeply or moderately dipping contacts. The fault surfaces are several km long, slips of a few kilometers are clear and ductile deformation is observed in the Eocene clastic rocks. Immediately to the north of the STF, Eocene rocks are asymmetrically folded with a southern vergence, a displacement sense not compatible with the northerly movement observed at the STF zone and suggesting a causal relationship between thrusting and normal faulting. A possible explanation of this extension may be the southwards tilting of the foreland due to the northwards overthrusting and the following gravitational movements. The folding style in the foreland and the very narrow width of the thrust zone, however, preclude such a crustal loading to induce extension in the foreland. In the Savcιlι area where the thrust fault is observed, we do not see any evidence to account for crustal shortening, as it should be observed in the vicinity of a major compressional structure as previously advanced. How this thrust formed in an extensional regime and how this post-middle Eocene crustal extension is associated with the southern Neogene Tuz Gölü Fault zone remain to be explored.

Keywords: Turkey, Central Anatolia, Kιrsehir metamorphites, Savcili Thrust Fault, Tuz Golu Fault, normal faulting

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