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Orhan Tatar, Cumhuriyet University (Turkey)
Halil Gursoy, Cumhuriyet University (Turkey)
John D.A. Piper, Liverpool University (United Kingdom)
Ariel Heimann, Geological Survey of Israel (Israel)
B.Levent Mesci, Cumhuriyet University (Turkey)
Fikret Kocbulut, Cumhuriyet University (Turkey)
Orhan Tatar, Cumhuriyet University (Turkey)
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Following collision with Eurasia, the Arabian Shield indenter has continued to deform into the weak Anatolian collisional collage that resulted from subduction of the Neotethyan Ocean. Differential movements have involved rotation and continuing northwards translation and have been accommodated mainly by slip along several major transforms including the northward extension of the Dead Sea Fault Zone (DSFZ) and the East Anatolian Fault Zone (EAFZ). To evaluate post-collisional motions we have investigated the palaeomagnetism of extensive volcanic domains sited at the northern margin of the stable shield in southern Turkey and have aimed to constrain the timing of volcanic activity using K-Ar dating. The age results indicate that volcanic activity occurred mainly during mid-late Miocene times and correlated broadly with the completion of suturing, although volcanic fields in the east of the investigated region are younger and correspond to Neotectonic volcanism in Brunhes and Matuyama chrons. Thermal and alternating field demagnetization of 399 cores from 83 sites in basaltic lavas identify 29 units of normal and 43 of reversed polarity with the remainder having transitional or random directions. Volcanic fields west of the Euphrates (Kilis-Gaziantep region) yielding ages in the range 7.0-20.3 Ma (average 14.9 Ma, SD=4.3Ma) have mean remanence D/I = 352/52° (41 sites, 5.5°) and sites east of the Euphrates line (Urfa region) with ages in the range 10.4-12.1 Ma yield a remanence D/I = 344/48° (20 sites, 7.0°). Anticlockwise rotations with respect to Eurasia are 12.9±4.7° and 20.9±5.8° respectively and contrast with clockwise rotation of 6.3±4.3° in late Matuyama-Brunhes epoch volcanics immediately to the north west of the shield margin where rotational impingement of the shield into blocks within the Karasu Rift at the northern extension of the DSFZ is deforming this zone at the same time as producing left lateral motion at a rate of ∼0.5 cm/year. The data sited on the stable shield are compared with other results from the Arabian Plate to conclude that it has been rotating anticlockwise at an average rate of ∼0.9°/Myr since closure of the Bitlis Suture in mid-Miocene times. In detail this rotation is unlikely to have been precisely uniform because it has been linked to three adjoining interactions namely (i) episodic opening of the Red Sea, (ii) the transition from crustal thickening to tectonic escape in the Anatolian collage and (iii) variable rates of strike slip motion on the DSFZ.
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