Field studies on the Neogene successions in south of izmir reveal that subsequent Neogene continental basins were developed in the region. Initially a vast lake basin was formed during the Early-Middle Miocene period. The lacustrine sediments underwent an approximately NS shortening deformation to the end of Middle Miocene. A small portion of the basin fill was later trapped within the N-S-trending, fault-bounded graben basin, the Cubukludag graben, opened during the Late Miocene. Oblique-slip normal faults with minor sinistral displacement are formed possibly under N-S extensional regime, and controlled the sediment deposition. Following this the region suffered a phase of denudation which produced a regionwide erosional surface suggesting that the extension interrupted to the end of Late Miocene-Early Pliocene period. After this event the E-W-trending major grabens and horsts of western Anatolia began to form. The graben bounding faults cut across the Upper Miocene-Pliocene lacustrine sediments and fragmented the erosional surface. The Cubukludag graben began to work as a cross graben between the E-W grabens, since that period. (C) 2001 Editions scientifiques et medicales Elsevier SAS.