CLAMP-based palaeoclimatic analysis of the late Miocene (Tortonian) flora from La Cerdanya Basin of Catalonia, Spain, and an estimation of the palaeoaltitude of the eastern Pyrenees

Abstract

We analyse the late Miocene (early Tortonian) climate of the La Cerdanya Basin (Catalonia, Spain) using the Climate Leaf Analysis Multivariate Program (CLAMP) based on an assemblage comprising twenty-nine dicot leaf taxa. Results show a mean annual temperature of 11.4 ± 2.1 ◦C. The coldest mean monthly temperature was 1.8 ± 3.4 ◦C while the warmest was 21.6 ± 2.5 ◦C. Growing season was 6.8 ± 1.1 months in duration. Precipitation during this period was 1082 ± 317 mm, reaching 661 ± 38 mm in the three wettest consecutive months, while in the three driest months it was 194 ± 229 mm. These results indicate a permanently humid temperate climate, with warm and wet summers. Compared with published palaeoclimatic results obtained using the Coexistence Approach method, our CLAMP analysis indicates lower temperatures and higher rainfall during the driest month. The climatic parameters are consistent with the occurrence of a temperate mixed evergreen and broadleaf deciduous fossil assemblage in the late Miocene of the La Cerdanya Basin. The assemblage contains more taxa in common with coeval localities from northern and central Europe than with Mediterranean sites; its closest modern analogue is with the montane flora from Honshu Island (Japan). Palaeoaltitudinal estimation using the terrestrial lapse rate method suggests that the La Cerdanya Basin was positioned at 1100-1550 m during early Tortonian times. These results challenge previous palynological and isotopic studies that inferred a palaeoaltitude of c. 600 m in early Tortonian-Messinian times.