Characteristic Mollusc, Larger Foraminifera Findings and Environmental Interpretations of the Middle Eocene Kocaçay Formation Deposits Around Ayvalıca (Bayat, Çorum)

Abstract

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.

Keywords

• çankırı-çorum basin
• middle eocene
• kocaçay formation
• ostrea
• velates
• nummulites