The origin of Neogene tectonic rotations in the Galatean volcanic massif, central Anatolia

Abstract

A paleomagnetic study was carried out on Neogene volcanic rocks at 30 sites within the Galatean massif (40.4A degrees N, 31.5A degrees E) to determine possible block rotations due to stress variations. Two phases of rotation could be characterized as the result of Neogene volcanic activity. We suggest that the first stage of rotation was isolated in Early Middle Miocene calc-alkali rocks, with a relative counterclockwise rotation of R +/- A Delta R = -20.2 +/- A 9.3A degrees with respect to Eurasia. This accommodates the south-westward rotational collapse of the Western Anatolia peninsula across a pole on the Bitlis suture. In the neotectonic period, on other hand, a relative clockwise rotation of R +/- A Delta R = 27.3 +/- A 6.4A degrees with respect to Eurasia is predicted. In contrast to the uniform clockwise rotations, extremely large clockwise rotations up to 264A degrees are restricted in a narrow zone between two dextral faults. We believe that the second stage rotations support the idea of individual microblock rotations due to deformation along the North Anatolian Fault zone.