An oligocene ductile strike-slip shear zone: The Uludag Massif, northwest Turkey - Implications for the westward translation of Anatolia

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Okay A., SATIR M., ZATTIN M., CAVAZZA W., Topuz G.

GEOLOGICAL SOCIETY OF AMERICA BULLETIN, vol.120, pp.893-911, 2008 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 120
  • Publication Date: 2008
  • Doi Number: 10.1130/b26229.1
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.893-911
  • Keywords: ductile shear zone, strike-slip faulting, Rb/Sr ages, apatite fission tracks, amphibolite-facies metamorphism, Turkey, Aegean Sea, METAMORPHIC CORE COMPLEX, GARNET AMPHIBOLITES, TECTONIC EVOLUTION, FAULT ZONE, WESTERN, MIOCENE, GEOCHRONOLOGY, CALIBRATION, EXTENSION, SYSTEM
  • Istanbul Technical University Affiliated: Yes


The Uludag Massif in northwest Turkey represents an exhumed segment of an Oligocene ductile strike-slip shear zone that is over 225 kin long and has similar to 100 km of right-lateral strike-slip displacement. It forms a fault-bounded mountain of amphibolite-facies gneiss and intrusive Oligocene granites. A shear-zone origin for the Uludag Massif is indicated by: (1) its location at the tip of the active Eskisehir oblique-slip fault, (2) pervasive subhorizontal mineral lineation in the gneisses with a right-lateral sense of slip, (3) foliation with a consistent strike, (4) the presence of a subvertical synkinematic intrusion, and (5) the alignment of the Eskisehir fault, synkinematic metagranite, and the strike of the foliation and mineral lineation. The shear zone nucleated in amphibolite-facies gneisses at peak pressure-temperature (P-T) conditions of 7.0 kbar and 670 degrees C, and it preserves Eocene (49 Ma) and Oligocene (36-30 Ma) Rb/Sr muscovite and biotite cooling ages. The shear zone was active during the latest Eocene and Oligocene (38-27 Ma), as shown by the crystallization and cooling ages from synkinematic granite. A 27 Ma postkinematic granite marks the termination of shear-zone activity. The 20-21 Ma apatite fission-track (AFT) ages indicate rapid exhumation during the early Miocene. A 14 Ma AFT age from an Uludag gneiss clast deposited in a neighboring Neogene basin shows that the shear zone was on the surface by the late Miocene. Results of this study indicate that during the Oligocene, crustal-scale right-lateral strike-slip faults were transporting crustal fragments from Anatolia into the north-south-extending Aegean; this implies that the westward translation of Turkey, related to the Hellenic slab suction, started earlier than the Miocene Arabia-Eurasia collision.