The Thrace Neogene Basin situated in northwestern Turkey was initiated by strike-slip faulting that was active from the Early Miocene until the end of the Pliocene. During the Early Miocene, it began to form under the control of the Thrace-Eskisehir Fault Zone, initiated by continental collision in northwestern Anatolia (Late Oligocene-Early Miocene). During the late Early Miocene, the basin was a site of mainly fluviatile and limnic sedimentation to the west and marine sedimentation via the Paratethyan transgression in the north. With the onset of the Middle Miocene, the Thrace Block started to rotate in a counterclockwise sense and escaped westward with respect to the Strandja-Istanbul block owing to rejuvenation of fossil fault systems within it. In this period, warm marine conditions were also established around the Gulf of Saros through a Mediterranean originated transgression. During the Middle-Late Miocene fluviatile and limnic conditions were created over the western Thrace by the westerly propagation of the Thrace-Eskisehir Fault Zone. One of the principal results of the Early-Middle Miocene tectonics is the tilting of the Strandja-Istanbul Block to the south, severing the Tethys and the Paratethys. During the latest Miocene-Early Pliocene period, the Thrace-Eskisehir Fault Zone was deactivated because of the evolution of the North Anatolian Fault Zone to the south. The resurrected Ganos Fault Zone situated on the dissected fossil suture zone in the Sea of Marmara also joined the North Anatolian Fault Zone, uplifting the Gelibolu Peninsula and, thus, severing the connection that existed between the Sea of Marmara and the Paratethys. The Sea of Marmara eventually became an endemic basin by the activity of the North Anatolian Fault Zone. (C) 1999 Elsevier Science B.V. All rights reserved.