Thrace Basin basement, comprises interbedded fine to coarse grained clastics from a variety of depositional environments, turbidite, muddy carbonates with local reef developments, river channels and tuffs. More than 400 wells were drilled till 2008; 14 gas and 3 oil fields were discovered and all of them are producing. Main gas productions zones are between Eocene- Oligocene deposits; Hamitabat (turbiditic sandstones), Ceylan (tuffs), Sogucak (reefal limestone), and Osmancik (deltaic sandstone) formations. Shales of Hamitabat and Mezardere formations have good source potentials. Thrace Basin The European side of Turkey is called the Thrace Basin. It is the largest and thickest Cenozoic sedimentary basin
Geography of Turkey of the sizable Greek-speaking community of western Turkey were forced to resettle in Greece, while the majority of the Turkish-speaking residents of Thrace who were not forced out during the Balkan wars were removed to Turkey. The boundary with Bulgaria was confirmed by the Treaty of Lausanne (1923). Since 1991 the more than boundary with the former Soviet Union, which was defined in the 1921 Treaty of Moscow (1921) and Treaty of Kars, has formed Turkey's borders with the independent countries of Armenia, Azerbaijan, and Georgia. The boundary with Iran was confirmed by the Treaty of Kasr-ı Şirin in 1639.