The limestones of Upper Eocene Soucak Formation are up to 100 m thick in the North of Thrace basin. The Upper Eocene Soucak Formation consists mainly of shallow water carbonates, and four principal depositional microfacies have been identified: (1) benthic foraminiferal wackestone-packestone, (2) algal-benthic foraminiferal wackestone-packestone, (3) coralgal boundstone, (4) planktonic foraminiferal wackestone-mudstone. A depositional model has been proposed based on the fossil and lithofacies assemblages, which suggests that the inter-reef supplies Miliolidaes and that the core reef supplies algae, corals to the fore-reef and deep sea environment.