3D-architecture and Neogene evolution of the Malatya Basin: Inferences for the kinematics of the Malatya and Ovacik fault zones

Abstract

The 3D-architecture of the Malatya Basin was studied using remote sensing, seismic interpretation, and palaeostress analysis in the context of the Malatya-Ovacik fault zone. The results indicate that the Ovacik and Malatya fault zones are not different segments of a single 'so called' Malatya-Ovacik fault zone; rather, they are two different fault zones that have operated independently. In addition, the Ovacik fault zone is delimited in the west by the Malatya fault zone, which extends farther north from the point of supposed junction. Maximum individual deflection of streams along the Ovacik fault zone is about 9.3 km, and summation of all stream deflections along different segments of the Ovacik fault zone indicates that sinistral displacement of the Ovacik fault zone has been not more than 20 km following development of the drainage system in the region. Evidence for three different deformation phases were recognized in the Malatya Basin. Deformation phase 1 was characterized by NW - SE-directed extension and operated in the Early to Middle Miocene interval. Deformation phase 2 was characterized by WNW-ESE-directed compression and a vertical sigma(2) which indicates transcurrent tectonics. It operated in the Late Miocene to Middle Pliocene. Deformation phase 3 was characterized by NNE-SSW-directed compression, and vertical stress is interchanged with sigma(2) and sigma(3); this is interpreted as due to near equal magnitudes of these stresses, resulting in stress permutation and interchange of intermediate and minor stress. Deformation phase 3 commenced in the Late Pliocene and has been active since then. The infill of the Malatya Basin has wedge-like geometry in E - W and N - S directions and the basin fed detritus mainly from its eastern margin. During field studies in the basin, a number of inverted normal faults were encountered; these apparently developed as growth faults in the Early to Middle Miocene time interval and then were reactivated or inverted during post-Middle Miocene compressional phases.