Stratigraphy of the Neogene Sedimentation and Volcanism in ？ubukluda？ Basin, Western Anatolia

The Lower-Middle Miocene fill of ？ubukluda？ basin, formed as an asimetric depression under the control of strike-slip Tuzla Fault, comprises ？atalca, Bah？ecik, Yenik？y and Tahtal？ formations, all of which are studied under the name ？ubukluda？ group, as well as Cumaovas？ volcanics. Composed of lacustrine and fluvial deposits with coal-bearing marsh interbeds, ？atalca formation has not any observed lower stratigraphic contact. Bah？ecik formation, which overlies the ？atalca formation with an unconformity marked by an abrupt change in the depositional environment, consists of red-claret red conglomerates deposited in a lacustrine fan delta, including freshwater alga-bearing lacustrine limestone interbeds (Sar？mustafa Member). Yenik？y formation overlies the Bah？ecik formation unconformably and contains fan deltaic and lacustrine deposits. The lower part of a fan delta succession, named as Akselvi member, is made from red-claret red fluvial conglomerates with a low-textural maturity. The upper part is a succession that is dominated by fluvial sandstone, pebbly sandstone, conglomerate with interbeds of lacustrine claystone-siltstone. Lacustrine Edil member, overlying Akselvi member with a relationship of lateralvertical transition, contains a laminated-shale dominated succession and bears felsic pyroclastic interbeds, products representing an earlier period for Cumaovas？ volcanism. Became active in late periods of the sedimentation during which Yenik？y formation occurred, Cumaovas？ volcanism has two stages of volcanism marked by calc-alkaline rhyolitic volcanics, showing a lateral interfingering relationship with the deposition of Tahtal？ formation. K-Ar ages ranging from 13,0±0,4 Ma to 13,8 Ma were obtained from rhyolite lavas emplaced on first-stage pyroclastics. The initial stage of phreatomagmatic volcanism originated in the lake where Edil member was deposited. The lake was entirely filled in the main explosion stage marked with pyroclastic flow deposits and rhyolite lavas. With the emplacement of first-stage Cumaovas？ volcanics, the basin in which Yenik？y formation had been deposited was closed and the sub basin was formed in the area where Tahtal？ formation was filled, located in east of the volcanic axis. Composed of mainly braided river deposits, Tahtal？ formation has a lateral interfingering relationship with second-stage Cumaovas？ volcanics. Intermittent lacustrine deposits, described as ？amk？y limestone member, rest on/within Tahtal？ formation initiated with alluvial fan deposits (Sakartepe member) overlying over Bornova Flysch Zone at the southern