Evolution of the Miocene sedimentary fill of the Gediz Graben, SW Turkey

The Gediz Graben is a continental extensional basin filled with Miocene to Recent sediments. The evolution of the graben can be expressed in terms of two phases: (i) Miocene half graben phase; and (ii) post-Miocene graben phase. The Miocene half graben phase was governed by the southern margin structure evolution of which significantly controlled the stratigraphic variability in the basin. Alluvial, fluvial and lacustrine systems developed in the graben as a function of distance to the southern margin. Thus, alluvial deposits with coarse-grained facies dominate the southern margin and grade into finer fractions of fluvial and/or lacustrine deposits to the north. This depositional architecture repeated three times during the Miocene and deposited Alaşehir, Çaltılık and Gediz formations. These formations depict distinct thickness and grain size decrease from south to north to emphasize the half-graben configuration for the favour of the southern margin. The post-Miocene graben phase started with the faulting of the northern margin. This resulted in relatively balanced partitioning of the subsidence between the two margins although the preceding asymmetry was inherited by the graben. Sediment influx became bipolar and alluvial fan systems developed along the both margins.