Structural Evolution of the Tuzgölü Basin in Central Anatolia, Turkey

Abstract

The Central Anatolian segment of the Alpine-Himalayan orogen contains "interior" basins, the largest of which is the Tuzgölü (Salt Lake) basin (>20,000 km2). It is bounded on the east by the Tuzgölü (Salt Lake) fault zone and on the west by the Yeniceoba and Cihanbeyli fault zones. Structural, stratigraphic, and sedimentologic evidence suggests that the Tuzgölü basin started as a fault-controlled basin during late Maastrichtian tectonism when the present-day northwest-trending faults that bound the basin were initiated. These faults may have been formed as normal faults suggesting extension or strike-slip faults with a normal component of movement indicating a large transtension at the time of their initiation. The late Maastrichtian faults were reactivated as strike-slip faults in response to late Eocene compression in the region that produced the Central Anatolian thrust belt to the north and the late Eocene south-dipping thrust faults of the Ulukisla basin to the south. This reactivation is suggested by structurally repeated and missing Paleocene-Eocene deposits in some of the basin's wildcat wells. The late Eocene regression in the Tuzgölü basin was caused by the combined effects of Eocene shortening and a large environmental change. Late Eocene evaporites suggest that the basin was dry before the start of the Neotectonic period, while during the Neotectonic itself the Tuzgölü fault zone was reactivated again, predominantly as a normal fault with a right-lateral strike-slip component. This is evidenced by (1) a major unconformity between the post-Eocene Koçhisar Formation of the Tuzgölü basin and the underlying Eocene rock units; (2) a well-developed rollover anticline observed on seismic reflection profiles; and (3) a right-step along the Tuzgölü fault zone seen in the field.