Post-late cretaceous rotational evolution of neotethyan sutures around Ankara region

Thesis Type: Doctorate

Institution Of The Thesis: Middle East Technical University, Faculty of Engineering, Department of Geological Engineering, Turkey

Approval Date: 2016

Thesis Language: English


Principal Supervisor (For Co-Supervisor Theses): Nuretdin Kaymakcı

Co-Supervisor: Atilla Arda Özacar


The central Anatolia comprises various continental fragments belonging to Laurasia at the north and Gondwana at the south. These amalgamated continental fragments (micro continents) delineated by ophiolitic remnants of Tethyan oceanic lithosphere which were consumed due to ~N to S convergence. Around Haymana Basin the closure of the Neotethys Oceans lead to amalgamation of the Pontides (Laurasian affinity) in the north, Tauride and Kırşehir blocks (Gondwana affinity) in the south. The main purpose of this study is to unravel vertical axis rotations in around Haymana Basin using paleomagnetic tools and its deformation history and kinematics using Anisotropy of Magnetic Susceptibility vectors. In this respect, late Cretaceous to Pliocene infill of the Haymana and adjacent basins namely, Alcı-Orhaniye, Tuz Gölü and Kırıkkale-Bala basins in the central Anatolia are systematically sampled and around ~5000 sedimentary paleomagnetic samples for paleomagnetic purposes from 119 different locations within a 250 km diameter area were collected. Before the demagnetization process, nearly 3000 core specimens were measured for anisotropy of magnetic susceptibility (AMS) to reveal their magnetofabric characteristics. The paleomagnetic results show, that the region underwent strong clockwise and counterclockwise rotations -even more than 90° in places- resulting the present geometry of the suture zones. Overall Haymana Basin has rotated more than 90° counterclockwise while its northern and south parts and northern part of the Tuz Gölü Basin rotated approximately 30° clockwise senses, which disagrees with almost all the published paleomagnetic data from the region. The restored orientations, based on the new data indicate that Haymana, Tuz Gölü Basin and the Kırıkkle-Bala Basin which constitutes the SW continuation of the Çankırı Basin were initially oriented in N-S direction prior to Eocene. These results are greatly differing from previously published results from the region which assumes that the İzmir-Ankara-Erzincan Suture Zone was oriented E-W. These imply that almost all of the paleogeographical maps and evolutionary scenarios and models of the region requires major re-thinking and serious revisions.