Tectono-stratigraphic and thermal evolution of the Haymana Basin, Central Anatolia, Turkey


Thesis Type: Doctorate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Geological Engineering, Turkey

Approval Date: 2015

Student: ERHAN GÜLYÜZ

Supervisor: NURETDİN KAYMAKCI

Abstract:

The Haymana Basin is located on the southernmost tip of the Central Pontides and straddles between the İzmir-Ankara-Erzincan Suture Zone at the north and Intra-Tauride Suture Zone at the south. These suture zones designate the former positions of various branches of the Neotethys Ocean in Turkey, the basins evolved within these zones record the progressive closure of the Neotethys and the collision between Taurides, Kırşehir Block and Pontides during late Cretaceous to Eocene time interval. The Haymana Basin is one of the best area because of its crucial position and continuous Late Cretaceous to Middle Eocene marine deposits to unravel the evolution of the Neotethys. In addition to Neogene cover units, four upper Cretaceous to Paleogene key sequences are defined based on depositional environments. These sequences grade laterally and vertically into each other and are continuous from the Late Cretaceous to Eocene whereas local progressive syn-sedimentary unconformities and frequent depocenter migrations are common. Additionally, post–middle Paleocene to middle Eocene sequences coarse upwards. These characteristics possibly reflect a response to local uplift and subsidence in front of south-verging thrust faults in a tectonic setting of transition from fore-arc to collisional settings, subsequent to the terminal subduction of the Neotethys at the end of early Paleocene. vi The Haymana Basin is represented by two structural segments based on the trends of E–W and WNW–ESE directed structures at the south-eastern and north-western segments, respectively. The balanced cross-sections indicate ~4% and ~25 shortening at the north-western and south-eastern segments, respectively. The differences in amount of shortenings might be result of reduce in the effectiveness zone of Dereköy basin bounding thrust fault towards west and large vertical block rotations controlled by a strike-slip fault which might be the westward extension of Hirfanlar-Hacıbektaş fault zone into the Haymana basin that dissects the Kırşehir Block into two sectors. Fault kinematic analysis, based on 623 fault-slip data from 73 stations, indicates that the basin was subjected to initially N–S extension and then a N–S directed compression and coeval E–W extension during late Cretaceous–early Miocene time interval. Thermo-chronometric samples collected from the basinfill were analyzed in order to unravel the thermal and exhumation history of the basin by using Apatite-Helium (AHe) dating and fission track length measurement techniques. AHe dating results indicate that the south-eastern segment of the basin started to uplift at least before 35.29 ± 3.5 Ma whereas north-western segment, 21.83 ± 2.2 Ma. Thermal models also show ~14 Ma differences in initiation of uplift in these two structural segments. They also indicate gradual subsidence until late Eocene (9.2m/kyr) and following rapid uplift (14.1m/kyr) until early Miocene for the south-eastern segment. It is proposed that the Haymana Basin was a fore-arc basin developed at the southern margin of the Pontides along the northward subducted Neotethys Ocean, then after Paleocene, the basin evolved into foreland settings in front of a south-vergent fold and thrust belt developed during continental collision. Additionally the north-westward movement of Kırşehir Block caused the basin to rotate along vertical axes and promoted its exhumation.