Characteristic mollusc, larger foraminifera findings and environmental interpretations of
the Middle Eocene Kocaçay formation deposits around Ayvalıca (Bayat, Çorum)
Although the Çankırı-Çorum Basin was studied for various purposes such as geological,
stratigraphical, tectonic, coal and oil exploration, studies on fossils are limited. Especially there
have not been detailed studies on molluscs and larger foraminifera. The research area is located at
the vicinity of Ayvalıca (north of Çankırı-Çorum basin). The Middle Eocene Kocaçay formation,
which outcrops in the Çankırı-Çorum Basin, is widespread around Bayat Çorum in the north of the
basin, Sulakyurt Kırıkkale in the west, Çiçekdağı Kırşehir in the south and Sungurlu Çorum in the
middle of the basin. The formation is composed of conglomerate, carbonated sandstone, limestone
and sandy marls and also includes rich larger foraminifera and molluscs. This study mainly focuses
on taxonomy and environmental interpretations of Ostrea roncaensis (Partsch in coll. Bayan, 1870)
de Gregorio, 1884, Velates perversus (Gmelin, 1791) species from Mollusca and Nummulites
beaumonti d’Archiac and Haime, 1853, N. aturicus Joly and Leymerie,1848, N. perforatus (de
Montfort, 1808) and Assilina exponens (Sowerby, 1840) species from larger Foraminifera. In
addition, considering faunal features from bottom to top Ostrea roncaensis, Velates perversus,
Nummulites aturicus and Assilina exponens Abundance Biozones were identified. The age range
of the Kocaçay Formation is determined as Lutetian-Bartonian. Lithological and faunal contents
indicate that sediments of the Kocaçay formation were deposited within lagoon to nummulitic sets
in a shallow marine environment
