The late Early Pleistocene flora of Oriolo, Faenza (Italy): assembly of the modern forest biome

Abstract

The late Early Pleistocene was the last time of equable climate in northern Central Italy, reflected in its large mammal fauna and numerous palynological records. Reliably dated leaf fossils from this time are rare, but provide crucial information on local and regional vegetation, biogeographic relationships, and species turnover coinciding with the assembly of modern forest biomes. Here we investigated a rich assemblage of leaf and fruit impressions (63 fossil-taxa) from the Oriolo quarry, Faenza (Ravenna), dated to the latest Calabrian, preserved in transgressive coastal deposits. The fossil assemblage represents riparian vegetation and xeric alluvial habitats in the lowlands and forest vegetation above the alluvial plain. Forest-building trees were deciduous, but comprised several taxa characteristic of open scrubland or forest edges. The composition of the flora reflects a dynamic process of assembling modern forest biomes in western Eurasia. While most taxa correspond to modern submediterranean and temperate woody species, some others represent late occurrences of taxa today confined to refugia outside Italy (Parrotia, Gleditsia, Pterocarya), and a few are Miocene/Pliocene relics indicating final floristic links with East Asia (Japan) and/or North America (Tsuga cf. chiarugii, Carya cf. minor) and Pleistocene endemism in Italy (Berberis auriolensis, Acer aemilianum).