Differential neotectonic rotations in Anatolia and the Tauride Arc: Palaeomagnetic investigation of the Erenlerda? Volcanic Complex and Isparta volcanic district, South-central Turkey

Abstract

In the Anatolian sector of the Alpine-Himalayan collisional belt a palaeotectonic phase of terrane accretion has been succeeded by a neotectonic phase of intracontinental deformation as the Afro-Arabian plate has continued to impinge differentially into the accreted collage. The resulting tectonic escape has, during the last few million years, extruded and rotated blocks in a southwesterly direction. This paper reports a palaeomagnetic investigation of the Erenlerda? Volcanic Complex and Isparta alkaline volcanic district undertaken to extend analysis of crustal rotation into the southwestern part of the Anatolian region, and investigate the interaction with the Isparta angle and the extensional province of western Turkey. The Erenlerda? volcanism comprises three phases of volcanism. The oldest Sille volcanics (11.7-11.4 Ma) yield a mean D=150° I=-52° rotated anticlockwise during early stages of crustal thickening and deformation before a later Miocene episode (c. 10.9-8.9 Ma. D= 183°, I=-47°) and a Mio-Pliocene episode (D=179°, I=-51°). The latter two episodes indicate that no significant rotation has resulted during the neotectonic crustal extrusion in this southwestern sector of Anatolia. Further to the west within the Isparta Angle a 4.7-4.0 Ma alkaline episode yields a mean of D=186°, I=-53° rotated slightly clockwise. The pattern of palaeomagnetic declinations across Anatolia shows rotations that are strongly anticlockwise in the east near the Arabian pincer and diminish towards the west to become zero or slightly clockwise at the western extremity of the collage. The timing of rotation also appears to become younger towards the south. Crustal deformation has therefore been distributed and the net effect of terrane extrusion to the west and south has been to expand the curvature of the Tauride Arc and, by inference, the Cyprian Arc. Where good age control exists in Cappadocia and the Sivas Basin rotations are found to be concentrated within the last few million years and are up to an order higher than rates deduced from global positioning system. The palaeomagnetic data imply that the neotectonic deformation following collision initially produced crustal thickening resulting in uplift of the Anatolian Plateau and was only subsequently accommodated by major differential block rotation during tectonic escape.