GOLBASI PULL-APART BASIN ON THE EAST ANATOLIAN FAULT ZONE, TURKEY

The East Anatolian Fault Zone (EAFZ) is an active left-lateral strike-slip transform between Arabian and Anatolian plates. Together with North Anatolian Fault Zone it undertakes westward escape of the Anatolian block. So, it has an important role in the recent tectonics of the Eastern Mediterranean region. EAFZ is about 450 km-long in NE-SW trend and extends between Karliova and Kahramanmaras tripple junctions. The fault has a slip rate of 9 mm/year. It consists of five main geometric segments which are connected to each other by restraining and releasing stepovers or bends. In this paper, we present general characteristics of the Golbasi pull-apart basin formed within a releasing stepover geometry between Golbasi-Türkoglu (GTS) and Celikhan-Erkenek (CES) segments of the fault.

There is a 30 km length depression filled with Quaternary sediments along the eastern section of the Golbasi-Turkoglu segment where Golbasi, Azapli and Inekli Lakes are situated. The depression is divided into two sub-basins, connected to each other by a narrow gorge. The eastern basin which is located between CES and GTS named as Golbasi Basin. Around the basin these two segments terminate in K65D and K45D strikes respectively. A serial of normal fault curving towards SE were observed in the northern margin of the basin. Back-tilted surfaces and hanging valleys are the morphological indicators of the normal faulting. The basin floor is 9 km in NE-SW and 2.5 km in NNW-SSE directions. The topography in the northern margin of the basin is higher than in the southern margin. In N-S orientation the basin floor displays an assymetry, dipping towards north. The basin fill is composed of alluvium, alluvial fan and lake sediments. Golbasi Lake, 2.19 km2, is located in the northern part of the basin floor. A piedmont plain was developed along the southern margin of the basin. However, small alluvial fans in the north were formed in front of the normal fault scarps. Our data indicate that the Golbasi basin was formed as a pull-apart basin within a left stepping geometry between CES and GTS where the general trend of the EAFZ changes 15°. The geological data indicate that formation of the Golbasi basin is younger than Pliocene.