Sea level and climatic controls on carbonate turbidite deposition in the middle Eocene Elazığ Basin (eastern Turkey)

The Baskil stratigraphic section of the Neo-Tethyan Elazığ sedimentary basin (eastern Turkey) is a global reference for the Middle Eocene Climatic Optimum (MECO), a transient (∼500 ka) global warming event interrupting a long-term cooling trend. This study integrates new petrographic and paleoecological data on the Baskil section with preexisting high-resolution biostratigraphic, magnetostratigraphic, and geochemical data to provide a comprehensive view of paleoenvironmental changes across the MECO in this area, strategically located along the gateway connecting the Atlantic and Indian oceans. This study aims to interpret shallow water carbonate environments based on the petrographic/paleoecological analysis of calcarenite layers within a turbiditic sequence. The section comprises massive hemipelagic marlstones interbedded with turbidites mainly composed of intrabasinal carbonate grains sourced from carbonate-ramp factories. Bioclastic detrital modes change upsection from predominant orthophragminids derived from middle ramp settings to predominant inner-ramp red algae and encrusting foraminifera. Such variation was triggered by the combination of local factors and global paleoceanographic and climatic changes. The progressive shallowing of the intrabasinal source area is related to a regression which occurred in the Neo-Tethys from ∼41 Ma until the Eocene/Oligocene boundary (∼34 Ma). The permanent decrease in abundance of the orthophragminids parallels the long-term climatic trend towards cooling conditions after the MECO. However, their abrupt reduction, coinciding with increased water column stratification, was also influenced by regional changes in ocean circulation after ∼40 Ma. These changes negatively impacted the specialized orthophragminids thorough increased hydrodynamism in the meso-oligophotic zone, resulting in decreased carbonate production at this depth. The preponderance of encrusting foraminifera coincided with the deterioration of environmental conditions and basin restriction within the Neo-Tethys.