Balikkaya formation consists of olistostromal units with a burgundy coloured mudstone, siltstone and pelagic limestone matrix containing various sizes of UpperJurassic-Lower Cretaceous limestone (Bilecik Limestone) blocks and Triassic Karakaya Complex blocks, which crop out in the west, south and southwest of Biga Town in Biga Peninsula (NW Anatolia). The matrix of Balikkaya formation, of which age and sedimentary environment are controversial, contains Late Cretaceous (Maastrichtian) Abathomphalus mayaroensis (Bolli), Abathomphalus sp., Rosita fornicata (Plummer), Globotruncanidae, early Paleocene (Danian) Morozovella pseudobulloides (Plummer), late Paleocene (Thanetian) Morozovella velascoensis (Bolli), early Eocene Acarinina pentacamarata (Subbotina), middle Eocene Turborotalia frontosa (Subbotina), Turborotalia cerroazulensis (Cole), Orbulinoides beckmanni (Saito), Hantkenina sp. pelagic foraminifera and Radiolariafossils representing the deep marine environment. These paleontological, lithological and sedimentological data obtained from Balikkaya formation show that Balikkaya formation developed in a deep marine environment under tectonic control starting from Late Cretaceous and ending in early-middle Eocene. This pelagic unit indicates the presence of a extensional tectonic regime on the Biga Peninsula and the fault activity along the southeastern edge of the Thrace Basin in the Late Cretaceous-Middle Eocene time interval.