Ostracoda Assemblages And Palaeoenvironmental Characteristics Of The Soma Formation (Late Miocene-Pliocene), Ivrindi - Nw Balikesir, Turkey

In the present study, a non-marine ostracods assemblage was defined from the Upper Miocene-Pliocene Soma Formation cropping out Ivrindi (NW Balikesir). The Soma Formation composed mainly of clayey limestone, marl, tuffite, sandstone and conglomerate in the study area. Fourteen of 22 samples collected from the measured section have ostracod fossils and six species belonging to five genera have been identified in the area. These ostracod species are Cyprideis torosa, Cyprideis pannonica, Heterocypris salina, Heterocypris sp, Ilyocypris sp and Limnocythere sp. In general, species richness, diversity and preservation of the ostracod assemblages were poor throughout the section. The brackish water species Cyprideis were dominantly found at the lower level of the section, while Ilyocypris species, which generally survive in river mouths and can also live in oligohaline environments as well as slightly brackish water, was detected at the middle and upper levels of the section. These fossil assemblages suggest that in the study area, the bottom sequences of the Soma Formation were deposited under brackish water environment and changed to limnic condition at the upper levels during late Miocene-Pliocene.