Fault-block rotations at the edge of a zone of continental extension; southwest Turkey

Abstract

The NE-SW-trending Burdur, Acigöl and Baklan basins of southwest Turkey are bounded by normal faults, which became active in Quaternary times. Prior to this a more widely spaced system of Pliocene basins had existed. Each of the Quaternary basins has a half-graben geometry with a major NW-dipping fault on its southeast side. Previous studies of the 1971 Burdur earthquake, caused by movement on the fault bounding the Burdur Basin, have shown this fault to flatten slightly at depth. Deformation in the hangingwall of the fault controlling the Pliocene basin in the Burdur region suggests a planar fault geometry. It is suggested that the Pliocene fault rotated to its present shallow orientation, then became inactive and acted as a detachment, at depth, for the more recent Quaternary fault. Quaternary faults bounding the Burdur, Acigöl and Baklan basins have a sinistral strike-slip component, with slip vectors indicating extension in an NW-SE direction. This is at variance with regional N-S extension in western Turkey. A solution for this contrast is found by invoking block rotations about vertical axes in a deforming zone between the rapidly extending Aegean region to the west and the stable unstretched Anatolian Plateau to the east.