MANTLE DYNAMICS AND CONTINENTAL DEFORMATION RESULTING FROM SLAB TEAR BENEATH THE ISPARTA ANGLE IN SOUTHWESTERN TURKEY

The Isparta Angle (IA) in southwestern Turkey is formed by the intersection of two very different subduction zones: the Hellenic arc to the west and the Cyprian arc to the east. There is substantial evidence that the Hellenic arc is retreating and the Cyprian arc is relatively stationary. Geometry and kinematics implies that there is a tear or gap in the subduction of African oceanic lithosphere beneath the Anatolian plate.

Slab tearing and the subsequent breakoff have been suggested as the cause of isolated intermediate depth seismicity and significant continental deformation found within the Isparta angle and surrounding region. Although the Benioff zones and tomographic images do not yield an unambiguous picture of the subducting slab geometry along the Anatolian African plate boundary, there is strong evidence that there is at least a slab tear across the IA. The intermediate depth seismicity patterns suggest that the Hellenic slab is dipping toward the northwest and the Cyprian slab is dipping toward the northeast. Although global seismic velocity models show very clear evidence of a high velocity slab along much of the Hellenic arc, the subducting slab along the Cyprian arc is much less clear. We would expect to observe relatively hot and thin lithosphere in regions where the tear in the subducting African lithosphere has occurred. Using both tomographic Pn velocity and maps of Sn attenuation, we observe evidence of this type of lithosphere in and around the IA. Slow (~7.6 km/s) and highly attenuating lithosphere exists beneath this portion of the Anatolian plate and geometry of the Benioff zones. Given the relatively poor resolution in the upper mantle for the global models in much of the Eastern Mediterranean, we cannot reliably trace this model to the overlying lithosphere.

The slab tear may be expressed by varied crustal kinematics within the IA. East-West exetnsion is accommodated by normal faults bisecting the IA, whereas, strike-slip and reverse faults bound the edges of the Cyprean and Hellenic arcs. This region offers an excellent natural laboratory to study mantle dynamics and mantle flow around and through a possible tear in the subducting lithosphere using a combination of seismic tomographic methods as well as neotectonics studies to help constrain the deformation in and around the Isparta angle.