Large Vertical Axis Rotations along Neotethyan Sutures in TURKEY

Abstract:

Two Neotethyan Sutures,Izmir-Ankara and Intra-Tauride suture zones meet around Ankara region appx. at right angles.The northerly located Izmir-Ankara Suture zone follows approximately E-W trend and it makes a sharp approximately 90° bend at the east along the western margin of the Çankiri Basin.The Intra-Tauride suture follows approximately the Tuzgölü Fault Zone and trends NW-SE and seems to be overprinted by the structures related to the Izmir-Ankara suture zone. These two sutures meet southeastern corner of the Haymana Basin where the basin makes major eastwards counterclockwise bend.From west to East, the Haymana, Tuzgölü and Çankiri Basins straddle these suture zones and are developed in relation to the subduction and collision processes in the region, making them the perfect sites to unravel deformation history and paleogeography of the Neotethyan suture zones in the region. In order to accomplish this, the tectono-stratigraphic evolution of the basin and its paleogeographical positions, in different time slices, constructed by conducting a very detailed study on the Late Cretaceous to Recent infill of the Haymana, Tuzgölü, and Çankiri Basins. We collected more than 4500 sedimentary paleomagnetic samples for paleomagnetic purposes from 112 different locations within 250 km diameter area.Before the demagnetization process, nearly 3000 core specimens were measured for anisotropy of magnetic susceptibility (AMS) in order to understand deformation amounts and kinematics.The paleomagnetic results show that the region underwent strong clockwise and counterclockwise rotations more than 90° in places, resulting in the present geometry of the suture zones. The central part of the Haymana basin rotated as high as 90° counterclockwise while its northern part together with the southwestern part of the Çankiri basin and northern part of the Tuzgölü basin rotated approximately 30° clockwise contrary to almost all published paleomagnetic data from the region.The restored orientations based on this new paleomagnetic data indicate that Haymana, Tuzgölü Basin and the SW margin of the Çankiri basins were initially oriented N-S prior to Eocene.These results indicate that the most of the paleogeographical maps and evolutionary scenarios and models of the region requires major re-thinking and serious revisions.