The Haymana Basin is located in the south of the Izmir-Ankara suture zone in Central Anatolia, Turkey. Convergence and collision of the Eurasia and Godwana continents during the late Cretaceous to the late Eocene caused the formation of the Haymana Basin and the Izmir-Ankara suture zone (Sengor and Yilmaz, 1981; Gorur et al., 1984, 1998; Kocyigit et al., 1988; Kocyigit, 1991, Huseynov, 2007). Although detailed stratigraphic and sedimentologic studies of different rock units in the Haymana Basin have been carried out (Unalan et al., 1976, Ciner et al., 1995, Ciner et al., 1996, Derman, 2007), the tectonic origin and fault mechanisms in the basin remain controversial. Some researchers proposed that the Haymana Basin formed as a forearc basin and cited the existence of calc-alkaline Galatean volcanics and ophiolitic basement as evidence for its forearc basin origin (e.g., Sengor and Yilmaz 1981; Gorur et al., 1984; Esmeray, 2008). Recently, it has been proposed that the Haymana Basin is a foreland basin developed on the footwall block of the leading edge thrust of the Izmir-Ankara suture zone (Gulyuz et. al., 2014). In this study, four seismic reflection profiles and well log data were used to investigate structural evolution of the Haymana Basin along with five geologic cross sections based on geologic mapping and field study during the summer of 2015. Interpretation of the depth converted seismic profiles and cross sections constructed during this study suggest that a detached thrust fault system brings the Cretaceous Derekoy ophiolites to the surface. The pillow basalt and deep marine sedimentary rocks were observed and mapped at the surface during the field study. This section constitutes the base of the Haymana basin sedimentary succession. This study suggests that the Haymana Basin initiated as a forearc basin in late Cretaceous and continued to receive sediments in the forearc setting until the middle Eocene.