Abstract: Deposits ranging from Upper Cretaceous (Maestrichtian) to Lower Tertiary in age crop out in Haymana - Polatlı region. At the base of these deposits there are Temirözü, Mollaresul, Dereköy Formations which are outof scope of present study. The formations, starting from Maestrichtian are as follows: Haymana Formation (Maestrichtian) is in flysch faeies, and 1850 m thick. Maestrichtian aged Beyobasi Formation is represented by coral sandstonesand conglomerates and 125 m thick. Çaldağ Formation (Montian) which is represented by algal limestones and 1187 mthick, crops out near Haymana. In the North, West and South of the region, this unit shows interfingering with redcolored Kartal Formation, and in the Southeast of the region wedges out to Yeşilyurt Formation which contains limestone .blocks. Thanetian aged Kirkkavak Formation is represented by algal limestone and black marls and 640 m thick.Ilgmlikdere Formation (Ilerdian) is in flysch facies and. 350 m thick. Eskipolatli Formation (lower parts Herdian, upperparts Cuisian) consists of marls with sandstone and limestone and limestone bands. Cuisian - Lutetian aged ÇayrazFormation consists of sandy limestones with abundan NummuUtes. This unit is equivalent to Beldede Formation (conglomerates, marls, limestones) in the North and West, and to Yamak Formation, which is in flysch facies, in the Southeast of the region. Neogene overlies all these formations unconformably. The thickness of the Upper Cretaceous -Lower Tertiary deposits is 5800 m in the region. Deposition was continious with the exception of the local unconformitybetween Çayraz and Eskipolatli Formations in the North of Haymana. Lateral and vertical facies changes are abundant. Interpretation of the facies studies shows that there existed a semicircle-shaped shelf near Haymana; Çaldağ andÇayraz Formations are deposited on this shelf. Behind the shelf partly continental units, Kartal, and Beldede, and infront of the shelf flysch units, Haymana, Yeşilyurt, and Yamak were deposited. Throughout Late Cretaceous - EarlyTertiary times, Haymana - Polatlı basin is believed to be joined with the Salt _ Lake basin toward the Southeast, andflysch deposits are accumulated in this part of the region. This shows that the North and West parts of the regionwere filled with sediments and were uplifted afterwards.