Abstract: The Eşendere Group, identified in the Mordoğan sub-basin on the western edge of the Foça Depression, consists of the alluvial Saip, palustrine Boyabağ and lacustrine Çukurcak limestone formations. The Eşendere Group unconformably overlies the lacustrine deposits of the middle Miocene Hisarcık Formation. The Saip Formation consisting of alluvial fan deposits, reflects the beginning of late Miocene sedimentation. The Boyabağ Formation, which was described in this study for the first time, represents a palustrine mud flat succession and is located between the Saip Formation and the lacustrine Çukurcak Limestone. The Çukurcak Limestone is the last unit in the Eşendere Group. Hipparion aff. giganteum and Hippopotamodon major, that were found in the mudstone dominant succession of the Boyabağ Formation, are the first records from the MN10 biozone in the Western Aegean region. Based on these large mammal records, we assume that late Miocene sedimentation in the Foça Depression began ~10 million years ago.