Western Anatolia has been traditionaly accepted as a region extended in N-S direction since the Late Oligocene time. This extension have resulted in approximately E-W trending low- to high-angle normal faults that bounded the graben basins. However, recent studies carried out at the western end of the grabens contradict with the earlier views and suggest the presence of a strike-slip dominated zone of weakness between Izmir and Balikesir. At the east of the zone, a kinematically linked crustal-scale metamorphic core complex, the Menderes Massif, and dissecting approximately E-W and NE-SW basins form the most prominent features of western Anatolia. Detachment fault systems in this province are associated with domal uplift of the Menderes metamorphic core complex of the lower plate and the formation of asymmetric supradetachment basins in the upper-plate. The first phase of extensional collapse in the region is marked by the Lycian orogenic collapse which may have been initiated by the beginning of Oligocene (Rupelian), following the main Menderes metamorphism. Starting in the latest Early Miocene or in the Middle Miocene, the area of the molasse basin was subject to deformation with the Lycian nappes, and to erosion as well. Thus, the molasse basin underwent NW-SE compression while, in the hinterland, the second phase of extensional collapse is marked by the formation of the Miocene detachment-related extensional basins (the Gediz and Büyük Menderes grabens), and granitic intrusions. The presently low-angle normal fault (Gediz Detachment Fault), forming the southern margin of the Gediz graben, along which the metamorphics in the lower plate were progressively deformed and exhumed. The Gediz detachment fault become to desappear across the فzmir-Balkesir Transfer Zone consisting of obliquely oriented strike-slip, normal oblique slip and low angle normal fault. The zone juxtaposes the E-trending Gediz and Küçük Menderes grabens with the NE-trending transtensional supradetachment basin (e.g. Kemalpaa-Torbal Basin). The basin has formed in Miocene time in response to evolution of the low-angle normal fault and strike-slip fault system, which together make up the eastern margin of the basin. As a result, several episodes of extension have been reported within the west Anatolan extensional province. The oldest episode involves normal faults that pre-date Miocene supradetachment basins and attributed these faults to extensional collapse that was partly coeval with the formation of the Oligocene-Lower Miocene piggyback molasse basin in southwest Turkey. The main episode of extension occurred from about 20 to 7 Ma. This episode was characterized by movement on kinematically linked upper crustal detachment faults, high angle normal, oblique and strike-slip faults. The final episode of extension produced predominantly E-W trending rift-mode high angle normal faults and strike-slip faults that have been active since at least 5 Ma.