Fossil mega- and micro-flora from Bernasso (Early Pleistocene, southern France): A multimethod comparative approach for paleoclimatic reconstruction

Abstract

Bernasso is an Early Pleistocene locality that has a well-dated floral fossil content including both pollen grains and megaremains. Pollen record shows vegetation changes corresponding to two glacial and one interglacial periods. The megafloral fossil assemblage was interpreted as an association of present-day Mediterranean and Caucasian taxa that developed during a late interglacial stage of the beginning of the Pleistocene. In the present study, climatic reconstruction using the Climate Leaf Analysis Multivariate Program (CLAMP) and the Leaf Margin Analysis (LMA) methods based on the megaflora on one hand and using the Climatic Amplitude Method (CAM) based on the pollen flora on the other hand have been used to check the qualitative climatic estimates based on the comparison between paleovegetation data and similar modern ecosystems. CLAMP and LMA analyses show that the Bernasso climate was colder than the present-day climate of Southern France and of the Hyrcanian and Euxinian regions. On contrary, CAM shows mean annual temperatures higher than the modern Bernasso temperature and equivalent to the temperature of the Hyrcanian and Euxinian regions. Mean annual precipitation and relative humidity reconstructed by CLAMP and CAM are in agreement and indicate that the climate was wetter than today at Bernasso. The differences between the three methods highlight important methodological biases that could be solved by including additional calibration sites in Europe and in the Mediterranean region.