Anatolia (Türkiye) during the late Eocene and the Eocene–Oligocene Transition: successive warming and cooling, aridification, and implications for the westward dispersal of Asian terrestrial mammals

Abstract

The Eocene–Oligocene Transition (EOT dated at ∼ 34 Ma) represents one of the most significant climatic shifts of the Cenozoic, marking the transition from the last warmhouse state to a coolhouse state. This global cooling had major consequences for terrestrial ecosystems and was synchronous with the dispersal of numerous Asian mammalian clades towards western Europe. However, the terrestrial expression of the EOT exhibits strong regional heterogeneity questioning its role in establishing dispersal corridors associated with floral and faunal turnovers. Here, we describe, date, and document the paleoenvironments of a continental sedimentary section from Balkanatolia, a biogeographic province corresponding to the present-day Balkans (NE Mediterranean region) and Anatolia (Türkiye). This region most likely functioned as a critical stepping stone for the dispersal of Asian mammals toward western Europe. Our sedimentary record represents a fluvio-lacustrine system exposed over a ∼ 200 m section located in Büyükteflek (Çiçekdağı/Kırşehir area, Türkiye), dated by magnetostratigraphy to the Priabonian and the lower Rupelian, including the Oi-1 glaciation (∼ 33.65 Ma). Clumped isotope analyses on pedogenic carbonates across our record show evidence for a Late Eocene Warming starting during the middle Priabonian (ca. 37 Ma), followed by a marked cooling event at the Eocene–Oligocene Glacial Maximum (EOGM). Stable isotopic data and sedimentary facies further indicate that this complete interval is associated with a long-term aridification trend, starting during the Late Eocene warming and culminating at the EOT. Our results provide the first quantitative record of late Eocene warming on land, and our temperature estimates for the earliest Oligocene cooling are consistent with other Eurasian clumped-isotope records. These temperature shifts and associated aridification steps may have acted as contributing drivers of the late Eocene decline of Balkanatolian endemic taxa and likely facilitated the westward expansion of Asia-derived mammals ultimately resulting in the colonization of western Europe.