Turkish Journal of Earth Sciences

Northern Margin of the Gediz Graben: Age and evolution, west Turkey




In Karataş area, four different Plio-Quaternary lithostratigraphic units, up to 226 m total thickness, are exposed. They include,in ascending stratigraphical order, the Lower Pliocene Balçiklidere, Middle-Upper Pliocene Ulubey and Lower-Middle Pleistocene Asartepe formations and (?) Upper Pleistocene- Holocene Kula Volcanics. The Balçıklıdere Formation, which nonconformably overlies the Basement rocks, is made up of stacked fining-upward sequences of conglomerate, sandstone and siltstone,mudstone with calische bands and thought to be deposited on a southerly flowing braid plain. The lacustrinal carbonates of the Ulubey Formation are overlying conformably the braid plain deposits and unconformably the Basement rocks. The Asartepe Formation unconformably overlies the older units and is composed of stacked coarsening and fining-upward sequences of grain/matrix-supported conglomerates, pebbly sandstones and siltstone-mudstones with rare caliche bands which are probably deposited in the proximal to mid-fan and partly distal areas of southwestwards propagating alluvial fan system. The youngest unit is the alkali basaltic lava flows of Kula Volcanics which outpoured, flowed and filled depressions above all older units. Structural elements of the Karataş segment of the Gediz Graben are high-angle extensional faults, namely the Kırdamları fault, Filiztepe fault segments, Karataş fault and Gediz River fault in NW-SE, WNW-ESE, NW-SE and NE-SW directions, respectively. They have controlled the fluvio-lacustrinel depositional settings throughout the tectonostratigraphic evolution of the Karataş segment. Kırdamlari fault, which is the northernmost boundary fault of the Gediz Graben, marks the initiation of subsidence at the northern margin of the Gediz Graben. It is evidenced by the deposition of Balçıklıdere Formation during Early Pliocene. Intracontinental crustal extension in the study area and its neighborhoods is thought to have formed in the Neotectonical evolutionary framework of West Turkey. It might have been caused by both the WSW escapement of the Anatolian Block and northern subduction of the African Plate beneath the West Anatolia to Aegean Sea.

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