Neotectonic evolution of the northwestward arched segment of the Central Anatolian Fault Zone, Central Anatolia, Turkey

Central Anatolia has undergone complex Neotectonic deformation since Late Miocene-Pliocene times. Many faults and intracontinental basins in this legion were either formed, or have been reactivated, during this period. The eastern part of central Anatolia is dominated by a NE-SW-trending, left lateral transcurrent structure named the Central Anatolian fault zone located between Sivas in the northeast and west of Mersin in the southwest. Around the central part, it is characterized by transtensional depressions formed by left stepping and southward bending of the fault zone. Pre-Upper Miocene basement rocks of the region consist of the central Anatolian crystalline complex and a sedimentary cover of Tertiary age. These rock units were strongly deformed by N-S convergence. The entire area emerged to become the site of erosion and formed a vast plateau before the Late Miocene. A NE-SW-trending extensional basin developed on this plateau in Late Miocene-Early Pliocene times. Rock units of this basin are characterized by a thick succession of pyroclastic rocks intercalated with calcalkaline-alkaline volcanics. The volcanic sequence is unconformably overlain by Pliocene lacustrine-fluviatile deposits intercalated with ignimbrites and tuffs. Thick, coarse grained alluvial/ colluvial fan deposits of marginal facies and fine grained clastics and carbonates of central facies display characteristic synsedimentary structures with volcanic intercalations. These are the main lines of evidence for development of a new transtensional Hirka-Kizilirmak basin in Pliocene times. Reactivation of the main segment of the Central Anatolian fault zone has triggered development of depressions around the left stepping and southward bending of the central part of this sinistral fault zone in the ignimbritic plateau during Late Pliocene-Quaternary time. These transtensional basins are named the Tuzla Golu and Sultansazligi pull-apart basins. The Sultansazligi basin has a lazy S to rhomboidal shape and displays characteristic morphologic features including a steep and stepped western margin, large alluvial and colluvial fans, and a huge composite volcano (the Erciyes Dagi).