Internal deformation of continental blocks within converging plates: insights from the Ovacık Fault (Anatolia, Türkiye)

Abstract

: The active tectonics of Anatolia is mostly characterized by its westward motion with respect to Eurasia between the Hellenic subduction in the west and Arabia-Eurasia continental collision in the east. Although most of the deformation is suggested to be confined along Anatolia’s boundary elements, viz. the North and East Anatolian shear zones, recent studies indicate a higher magnitude of internal strain accumulation, especially along the parallel/subparallel strike-slip faults of its central province. We present the first morphochronology-based slip rate estimate for one of these strike-slip structures, the Ovacık Fault, by using cosmogenic 36 Cl dating of offset fluvial deposits. At the Köseler Site (39.3643°N, 39.1688°E), two faulted risers, bounding the alluvial fan with its subplanar surface (NF1/NF1’) and the inset terrace tread (NF1/T2), are offset 19–24 and 15–22 m, respectively. The scattered surface ages and variability of 36 Cl concentrations in depth profiles suggest strong evidence for inheritance in alluvial fan and terrace deposits; thus, we used modelled depth-profile ages for both surfaces. The modelled ages 8–10 ka for NF1 and 6–8 ka for T2 yield slip-rate estimates 2.4 +0.5/–0.4 mm/a and 2.8 +0.7/–0.7 mm/a, respectively, for the upper-tread reconstruction of the NF1/NF1’and the lower-tread reconstruction of the NF1/T2. Our results together with previous slip-rate estimates for other structures show a significant internal deformation for Anatolia, especially along its subparallel strike-slip faults. These secondary faults slice Anatolia into several pieces giving rise to the formation of the Malatya-Erzincan, Cappadocian, and Central Anatolian slices, where the geometry is strongly controlled by the distribution of the Tethyan accretionary complexes.