Lutetian swamp-freshwater palynoflora from Bultu-Zile (central Anatolia, Türkiye): Implications for Eocene ecosystems of Balkanatolia

Abstract

Balkanatolia is a south-eastern European biogeographic province that, during the Early and Middle Eocene, comprised low topography islands sustaining endemic mammalian fauna. The environmental and climatic context of the duration and, then, the end of this faunal endemism is still debated. Therefore, palynology could help us to characterize these environments and climates. Most Lutetian palynofloras from this region deposited in terminal fluvial settings (e.g. mangrove, deltaic, or shallow marine environments). Here, we present the first description of the palynoflora from Bultu-Zile, a Lutetian embrithopod-bearing locality in the Pontides (Türkiye). Unlike other Balkanatolian sites, the Bultu-Zile assemblage accumulated in a calm swamp-freshwater environment, preserving a distinctive pollen and spore record dominated by swamp and freshwater indicators such as Polypodiaceae, Lygodiaceae, Osmundaceae, Cupressaceae, and Ludwigia (Onagraceae). This depositional context also documents the earliest occurrences of Azolla (Salviniaceae) and Corsinipollenites oculusnoctis (Ludwigia, Onagraceae) in Türkiye. Lowland-riparian and montane indicators are also present in the assemblage (e.g. Fagaceae, Myricaceae, Cyrillaceae/Clethraceae, Juglandaceae, Mastixiaceae, Lythraceae, Sapotaceae, Ilex, Armeria, Icacinaceae, and Vitaceae). Quantitative climatic reconstructions using both the Coexistence Approach and CREST suggest a wet temperate climate with hot and wet summers. The Bultu-Zile palynoflora aligns with the broader Lutetian environmental and climatic framework of Balkanatolia and supports a scenario of climatic and vegetational continuity from Western Europe to Central Asia, with evergreen Fagaceae-Juglandaceae forests and mangroves along the shorelines. These findings imply that Balkanatolian faunal endemism persisted primarily due to insular isolation rather than climatic or environmental barriers.