Late Cretaceous and Miocene collisions of the Arabian, Anatolian and Eurasian plates, as shown by widespread ophiolitic exposures along the suture, created favourable geological conditions for the formation of the surface and subsurface structures in the Gaziantep Basin, southeast Turkey. The late Cretaceous (Maastrichtian) emplacement of the Kocali-Karadut ophiolite complex induced subsidence in the northwestern zone of the Kastel Basin during the early Alpine Orogeny and influenced the structural evolution of the foreland area. The Dead Sea Fault, which originated in the Red Sea in Miocene time, propagated towards the northwest in the Suez Gulf and the north-northeast in southeast Turkey, and influenced the structural evolution of the Gaziantep Basin. These two major tectonic events produced many thrusts, thrust-related subsurface and surface anticlines, faults, fractures, flower structures and basaltic flows in the area. Geological and geophysical investigations indicate the existence of two important structural phases. The older structures were formed during the late Cretaceous movements, but they have been reactivated by latest Miocene tectonic activities with appearance of the Strands of the Dead Sea Fault in the sedimentary basin. The geothermal studies show also that, as a result of the Tertiary transgressions and volcanic activity, the northern and southern sectors of the Gaziantep Basin underwent differing subsidence and structural histories.