ABSTRACT
       Ayaş Region lies in Ayaş County, Ankara province and is about 60 km west of Ankara. The area is fairly rugged. Tokludağ and Ayaş Ranges constitute the main elevations. The area is drained by two perennial streams flowing in a westerly direction. The climate is semi-arid.
        The area was mapped in lithostratigraphic units. Karadere Formation, consisting mainly of epimetamorphic schists and phyllites with intercalations of crystalline limestones and quartzites is believed to be of Carboniferous (?) or older age. A plutonic body of granodioritic to quartz dioritic composition, in the size of a small stock, intrudes Karadere Formation, but its age and contact relationship to Çaldağ Formation are unknown. Çaldağ Formation, possibly Permian in age, consists consists of partly crystalline dolomitic limestones unconformably overlying the Karadere Formation. It is unconformahly overlain by the Tokludağ Formation of Upper Jurassic-Neocomian age. Abdüsselam Formation represented by a conglomerate-sandstone sequence of probably Paleocene (?) age rests unconformably on the Tokludağ Formation. The volcanic activity started in Lower Miocene, depositing pyroclastic rocks overlain by flows of andesitic to basaltic composition. Başayaş Formation, consisting of oolitic limestones, mudstones and marls, was deposited in a lagoonal environment during the Middle Miocene. A clayey lignite seam overlies this formation (outside the area) and is believed to be of Upper Miocene age. This is overlain by Karakaya Formation, of late Upper Miocene-early Lower Pliocene age, consisting of andesitic to basaltic lava flows overlain by a thin layer of volcanic glass. Arıklar Formation, represented by conglomerates and sandstones, overlies the Karadere Formation. Recent deposits consist of alluvium and colluvium.