Palaeoclimatic analysis of Quaternary terrestrial small mammal assemblages from the Sierra de Atapuerca (Burgos, Spain)

Understanding past climatic changes is one of the central challenges in palaeontological research. The Bioclimatic Model (BM) enables the reconstruction of qualitative and quantitative climatic conditions using the fossil record of rodents and eulipotyphlans. Here, we applied this model to the rich and well-documented fossil record from the localities of the Sierra de Atapuerca karst complex, including six archaeological and palaeontological sites spanning nearly continuously from the Early Pleistocene to the Late Holocene ∼1.2 Ma - 3.1 ka. A typical temperate climate was inferred for most of the sequence, with variations between Mediterranean and temperate climates, and the influence of boreal climates during the Late Pleistocene cold climatic oscillations recorded in El Portalón and El Mirador assemblages. The record from the base of the sequence of Sima del Elefante (TELRU, TE7-TE14) indicates relatively warmer conditions than the current climate, and a trend of thermal increase was observed from the end of Calabrian and Chibanian based on the Gran Dolina levels TD6 and TD8. Additionally, we obtained a thermotype classification reflecting regional-scale climatic changes linked to shifts in altitudinal belts boundaries. This work constitutes the first, diachronic, bioclimatic analysis of the entire biostratigraphic sequence of the Atapuerca site complex, providing an updated synthesis of long-term climatic reconstruction over more than one million years.