The study was carried out within the Horasan Formation around Köprüköy located east of Erzurum. This formation outcrops in the region of Erzurum-Pasinler-Horasan forming the northernmost outcrop of neo-tectonic sediments in Eastern Anatolia. The unit is composed of pebble stones, clays and marl iterations. Ostracod, gastropod and pelecypod species are observed in the levels of clay stone with soft clasts and marl in the area. Generally, ostracod species which are unique to the Ponto-Caspian basin were described in these units within the scope of the study. These are ostracod species such as Amnicythere idonea Mandelstam, Markova, Rozyeva and Stepanajtys, Candona (Caspiocypris) erzurumensis Freels, Candona (Caspiocypris) araxica Freels, Candona (Caspiocypris) aff. alta (Zalanyi), Candona (Lineocypris) aff. granulosa Zalanyi, Bakunella cf. dorsoarcuata (Zalanyi), Bakunella cf. subtriangularis (Sveyer), Candona (Candona) lycica Freels, Candona (Candona) armenia Freels, Candona (Candona) aff. elongata (Svejer), and Fossilyocypris sarızensis (Şafak, Nazik and Şenol). There are also micro mollusk species such as Gyraulus inornatus and Dreissena polymorpha present in the sequence. Among these genera; Candona (Candona) is found in fresh water; Candona (Caspiocypris), Candona (Lineocypris), and Fossilyocypris indicate fresh - brackish water (oligohaline), Bakunella rarely characterizes fresh water but mostly brackish water, Amnicythere characterizes brackish water, and Gyraulus, Dreissena characterizes fresh water conditions. The ostracod fauna determined in this study indicates an age interval of Late Miocene-Pliocene for the formation and clearly supports previous studies in terms of age and environmental correlations.