Tectonic evolution of the Gediz Graben: field evidence for an episodic, two-stage extension in western Turkey


Bozkurt E. , Sozbilir H.

GEOLOGICAL MAGAZINE, cilt.141, ss.63-79, 2004 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 141 Konu: 1
  • Basım Tarihi: 2004
  • Doi Numarası: 10.1017/s0016756803008379
  • Dergi Adı: GEOLOGICAL MAGAZINE
  • Sayfa Sayıları: ss.63-79

Özet

Western Turkey is one of the most spectacular regions of widespread active continental extension in the world. The most prominent structures of this region are E-W-trending grabens (e.g. Gediz and Buyuk Menderes grabens) and intervening horsts, exposing the Menderes Massif. This paper documents the result of a recent field campaign (field geological mapping and structural analysis) along the southern margin of the modern Gediz Graben of Pliocene (similar to 5 Ma) age. This work provides field evidence that the presently low-angle ductile-brittle detachment fault is cut and displaced by the high-angle graben-bounding normal faults with total displacement exceeding 2.0 km. The evolution of the N-S extension along the Gediz Graben occurred during two episodes, each characterized by a distinct structural styles: (1) rapid exhumation of Menderes Massif in the footwall of low-angle normal fault (core-complex mode) during the Miocene; (2) late stretching of crust producing E-W grabens along high-angle normal faults (rift mode) during Pliocene-Quaternary times, separated by a short-time gap. The later phase is characterized by the deposition of now nearly horizontal sediments of Pliocene age in the hanging walls of the high-angle normal faults and present-day graben floor sediments. The evolution of extension is at variance with orogenic collapse and/or back-arc extension followed by the combined effect of tectonic escape and subduction rollback processes along the Aegean-Cyprean subduction zone. Consequently, it is misleading to describe the Miocene sediments exhumed on shoulders of the Gediz Graben as simple graben fill.