The Ostracoda assemblage of the Eocene-Oligocene transition in northwestern Thrace: Kırklareli–Edirne area (northwestern Turkey)

• Eocene – Oligocene transition are discussed benefiting from ostracods community.
• Eocene-Oligocene transition is discussed at Eastern Thrace for the first time in study.
• Proved that Eocene sea is deeper than Oligocene sea in SE-SW Thrace.
• Paleogene sequence were compared wtih stratigraphical and micropaleontological.
• Especially ostracod faunas were evaluated for the first time in Edirne region.

The aim of the study is to investigate the Eocene–Oligocene transition in detail in northwest Thrace (NW Turkey) with heavy reliance on ostracod fauna. The lithologies formed and the environmental changes during this time period were also studied.The study was carried out in northwest Thrace within the outcropping Koyunbaba, Soğucak, and Ceylan Formations; Mezardere, Osmancık, and Danişmen Formations of the Yenimuhacir Group; and the Taşlısekban and Pınarhisar members of the Danişmen Formation. Rich ostracod fauna indicating an Eocene and Oligocene age and environment are found within these units.The Ostracoda fauna identified were ostracods Triebelina punctata, Bairdia cymbula, Bairdia tenuis, Cyamocytheridea nova, Krithe bartonensis, Krithe angusta, Krithe rutoti, Krithe parvula, Echinocythereis isabenana, Leguminocythereis genappensis, Grinioneis triebeli, Xestoleberis subglobosa and Xestoleberis muelleriana from the Mid-Late Eocene epoch; Cytheromorpha zinndorfi, Hemicyprideis montosa, Neocyprideis williamsoniana, Cladarocythere apostolescui, Hammatocythere hebertiana, Haplocytheridea helvetica, Cytheridea pernota, Callistocythereis vitilis, Cushmanidea cf. scrobiculata, Pterygocythereis fimbriata, Pokornyella limbata, Grinioneis paijenborchiana, Cytheretta tracensis, Macrocypris wrightii and Paracypris bouldnorensis from the Late Eocene-Early Oligocene epoch; and Novocypris eocenana, Novocypris striata, Moenocypris forbesi, Candona (Pseudocandona) fertilis, Candona (Lineocypris) sp. and Cypridopsis soyeri from the Early-Late Oligocene epoch.The study was also correlated to previous research conducted on Eocene–Oligocene age ostracods around the area, in northwestern Europe, and in the Paris–Akiten Basin, in view of similar age-environment relationships determined by said studies.On the basis of evidence from the lithologic content of the beds and the micropaleontological investigation, the fossil community identified in this study indicates that the sea reached deeper levels in the Eocene epoch than during the Oligocene epoch.