THE DAVUTOGLAN WRENCH FAULT: INTRA-ANATOLIAN PLATE, NEOGENE DEFORMATION, ANKARA PROVINCE, TURKIYE

Approximately 100 km west of Ankara, the northern margin of the Haymana Basin is disrupted by a 12-km wide series of ENE-trending faults, anticlines and monoclines, the largest of which is the topographically expressed, 18-km long Davutoglan wrench fault. These structures deform Miocene fluvial and lacustrine strata north of Cayirhan and the Davutoglan fault crosses beneath Davutoglan village.

Right strike-slip on the several strands of the Davutoglan fault zone is indicated by slickenlines and mesoscopic, fault-surface features, an associated train of right-echelon folds and thrust faults (in a restraining bend), in-line horsts and grabens, and overlapping faults with an associated transfer ramp. Horizontal displacement is less than one kilometer: Vertical offset across the zone is as much as 250 m, down to the north. Offset within the fault zone decreases to the east where deformation continues as an anticline whose axis is of similar trend: To the west the faults merge into a single strand and offset decreases to zero.

Individual faults are well exposed as discreet, polished surfaces in the siliceous limestone and may have a clay-smear character in the mudstone units. These faults acted as fluid conduit, are commonly strongly iron-stained, and locally contain chalcedony veins. The enclosing grey- to green mudstones are bleached to a buff or pale orange-tan color for many meters outward from the fault surfaces.

The Davutoglan fault zone represents deformation within the Anatolian Plate, about 70 km south of the bounding North Anatolian Fault (NAF). The type of deformation, timing, and right-lateral offset suggest an origin under similar regional stresses as those of the NAF. The zone lies along the eastward projection of the Late Cretaceous-Paleocene, northern margin of the Izmir-Ankara suture beneath the Miocene deposits: It may indicate local reactivation of a part of that feature.