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Structural evolution of the Gediz Graben, SW Turkey: temporal and spatial variation of the graben basin

Ciftci, N. B.
Bozkurt, Erdin
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.