Structural evolution of the northern Tuzgölü Basin, Central Anatolia, Turkey

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Located between the Pontide Mountains to the north and the Tauride Mountains to the south, the Tuzgölü (Salt Lake) Basin, Central Anatolia, Turkey, covers about 20,000 km2 area of low topographic relief (Figure 1). The topographic high associated with the Izmir-Ankara suture zone north of the town of Haymana constitutes the basin’s northern boundary; the folded and faulted succession of the Ulukışla Basin to the south is the basin’s southern boundary (Çemen et al., 1999). The basin is bordered by the Tuzgölü fault zone to the east and by the Yeniceoba and Cihanbeyli fault zones to the west. Since the mid-1970s, several geologic studies (e.g., Yüksel, 1970; Arıkan, 1974; Ünalan, 1976; Görür and Derman, 1978; Derman, 1980; Dinçer, 1982; Oktay, 1982; Uygun, 1982) have been conducted in the Tuzgölü Basin and surrounding areas. However, the tectonic setting of the Tuzgölü Basin and its structural evolution remain controversial. Arıkan (1974); Turgut (1978) suggested that the basin was formed as an intracratonic basin during Upper Cenomanian–Oligocene time. However, later studies in the 1980s proposed a forearc basin origin (Şengör and Yılmaz, 1981; Okay, 1982; Görür, 1984; Norman, 1984; Okay, 1987). More recently, Çemen et al. (1999) and Huvaz (2009) suggested that the basin formed as a rift basin in the Late Maastrichtian to Early Paleocene. The main purpose of this study is to investigate the structural evolution of the northern Tuzgölü Basin based on the interpretation of nine available 2D seismic reflection profiles and well logs from three wells drilled in the study area. These data are used to construct structural cross sections based on depth converted seismic lines to determine subsurface structural geometry. The geometry is compared to the Haymana Basin to the north to determine the structural relationship between the Tuzgölü Basin and Haymana Basin. Results of this study indicate that the Tuzgölü Basin experienced extension, which controlled the sedimentation in the basin during Late Cretaceous rifting. Normal faults were formed, which was suggested by conglomerates of the Kartal Formation. During the Eocene, these normal faults were reactivated as strike-slip faults, and these contractional structures are interpreted as resulting from an oblique-slip fault within the study area. This is further evidenced by very thick sedimentary units of Paleocene-Eocene deposits (Karapınar Yaylası Formation seen in wildcat wells. Neotectonic period in the region started in the Early Pliocene when the westward escape of the Anatolian Plate was initiated. A rollover anticline and unconformity between the Paleocene-Eocene Karapinaryaylasi Formation and Mio-Pliocene Koçhisar Formation suggest that the Neotectonic period is dominated by extension, which produced normal faults. This extensional tectonic controlled the sedimentation from Mio-Pliocene to present in the Tuzgölü Basin. In addition, structural evolutionary models for both the Haymana and Tuzgölü Basins suggest that these two basins were formed independently of each other in Late Cretaceous. While the Haymana Basin was developing as a forearc basin, the Tuzgölü Basin was evolved as a rift basin due to Late Cretaceous rifting. These two basins have different structural and sedimentological features until the initiation of Late Miocene to present Neotectonics extension in Anatolia.

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