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


Yurur M. T. , Genc Y.

GEOLOGICA CARPATHICA, cilt.57, ss.47-56, 2006 (SCI İndekslerine Giren Dergi)

  • Cilt numarası: 57 Konu: 1
  • Basım Tarihi: 2006
  • Dergi Adı: GEOLOGICA CARPATHICA
  • Sayfa Sayısı: ss.47-56

Özet

Large exposures of granitic and metamorphic rocks characterize the geology of Central Anatolia, in Turkey. These basement rocks crop out mainly between the Tuz Golu and Ecemis fault zones, two major fractures of strike-slip fault character. During the Neogene, detachment faulting along the Tuz Golu Fault (TGF) zone caused the deposition of several thousand meters of sediments in the large intracontinental Tuz Golu Basin. In the western parts of Central Anatolia and near Kirsehir town, another fracture zone runs almost parallel to the SE-trending TGF zone, separated from the TGF by a narrow (similar to 30 km) and rectangular granitic belt. Along this fracture known as the Savcili Thrust Fault (STF), metamorphic and plutonic rocks overthrust middle Eocene detrital rocks of the sedimentary cover along a relatively narrow (similar to 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 kin long, slips of a few kilometers are clear and ductile deformation is observed in the Eocene elastic 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 Savcili 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 Golu Fault zone remain to be explored.