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An Oligocene ductile strike-slip shear zone; the Uludag Massif, northwest Turkey; implications for the westward translation of Anatolia

A. I. Okay, M. Satir, M. Zattin, W. Cavazza and G. Topuz
An Oligocene ductile strike-slip shear zone; the Uludag Massif, northwest Turkey; implications for the westward translation of Anatolia
Geological Society of America Bulletin (August 2008) 120 (7-8): 893-911

Abstract

The Uludag Massif in northwest Turkey represents an exhumed segment of an Oligocene ductile strike-slip shear zone that is over 225 km long and has approximately 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.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 120
Serial Issue: 7-8
Title: An Oligocene ductile strike-slip shear zone; the Uludag Massif, northwest Turkey; implications for the westward translation of Anatolia
Affiliation: Istanbul Teknik Universitesi, Avrasya Yerbilimleri Enstitusu ve Jeoloji Muhendisligi Bolumu, Istanbul, Turkey
Pages: 893-911
Published: 200808
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 87
Accession Number: 2008-104168
Categories: Structural geologyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., 5 tables, geol. sketch map
N40°00'00" - N40°00'00", E29°00'00" - E29°30'00"
Secondary Affiliation: Universitaet Tuebingen, DEU, Federal Republic of GermanyUniversita di Bologna, ITA, Italy
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200836
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