Impact of the Middle Eocene Climatic Optimum (MECO) on Foraminiferal and Calcareous Nannofossil Assemblages in the Neo-Tethyan Baskil Section (Eastern Turkey): Paleoenvironmental and Paleoclimatic Reconstructions

The Middle Eocene Climatic Optimum (MECO; ~40 Ma), which interrupted for ~500–600 kyr the long-term cooling trend culminating at Eocene/Oligocene boundary, still requires a comprehensive understanding of biotic resilience. Here we present high-resolution integrated foraminiferal and calcareous nannofossil study across MECO from expanded continuous Tethyan Baskil section (eastern Turkey) that offers complete magneto-biostratigraphic geochemical framework. five phases identified reveal transition oligotrophic (pre-MECO) to eu-mesotrophic conditions, possibly related accelerated hydrological cycle, during initial δ13C negative excursion phases. WARMING PEAK phase, marking highest carbonate dissolution interval, records most striking changes, such as peak in warm eutrophic nannofossils, virtual disappearance planktic large Acarinina Morozovelloides, deep dwellers Subbotina. Benthic foraminifera suggest this phase an improvement quality organic matter seafloor. post-MECO shows only partial recovery pre-event conditions. Large Morozovelloides did not recover their abundance, due cooler conditions phase. Our reconstruction reveals how paleoenvironment marine biota studied Neo-Tethyan setting reacted perturbations.