The structural evolution of the Miocene to Recent Gediz Graben is intimately related to the evolution of its southern margin. This margin is shaped by a time-transgressive, composite structure that possesses flat-ramp geometry with three separate dip domains: a low-angle shallow segment; a steeper middle segment; and a low-angle deeper segment. This geometry was probably produced by one of two mechanisms, which operated perpendicular to the general trend of the graben, resulting in gradual back-rotation followed by abandonment of the shallow segment as it was dissected by the high-angle normal fault(s). The geometry of the southern margin structure is not simple along-strike. It includes broad undulations and discrete fault segments, developed by large-scale fault growth processes through segment linkage. The along-strike growth of the southern margin-bounding structure is responsible for the composite character of the Gediz Graben and controls the observed stratigraphic variability. Two sub-basins aligned with the major segments of the southern graben margin structure have been investigated. The Salihli and Alasehir sub-basins comprising 3000 m sedimentary thickness are separated by an intervening basement high, that is covered by a thin veneer of post-Miocene sediments. The two sub-basins, which evolved as isolated basins during most of the graben history, amalgamated during post-Miocene time to form the composite configuration of the graben. There is a general east to west trend of growth for the Gediz Graben.