Stratigraphic and paleoenvironmental interpretation of the larger benthic foraminifera assemblages and stable isotope analysis from the middle Eocene of Cappadocia, Turkey

摘要

This study investigates the changes in paleoenvironmental conditions in the northern branches of the Neo-Tcthys by employing geochemical proxies and shell data of larger benthic foraminifera (LBF) located in central Cappadocia. Three measured stratigraphic sections are studied from the Altipinar Formation (Boztepe Member), which is dated as middle Eocene. Three genera and five species were recorded as a result of the palcontological analyses, namely, Alveolina sp., Assilina exponens, Nummulites aturicus, Nummulites maximus and Nummulites perforatus. Composed of clayey sandy limestones, the Boztepe Member is represented by SBZ (Shallow Benthic Zones) 16-17 (late Lutetian/early Bartonian). In the Cappadocia region, a warming event was characterized by a temperature increase of 3°C to 4.5°C, and the warming started after 41.0 Ma (younger than the Lutetian /Bartonian boundary). The peak warming occurred around 40.0 Ma (early Bartonian). This period corresponds to the Middle Eocene Climatic Optimum (MECO). which was a significant global warming event. The findings of this study are confirmed by numerous studies that the global warming event occurred in the middle Eocene (between 41.8 and 39.7 Ma.). Additionally, while paleoenvironmental changes had no effect on the shell shape of Assilina exponens, they had a significant effect on the shell shape of Nummulites perforatus. The diameter/thickness ratio of benthic foraminifera tends to be smaller in shallow conditions than in deep conditions. This was observed as their shell shapes became more spherical.