Palaeoenvironmental reconstruction of the late Miocene macroflora of La Bisbal d'Empordà (Catalonia, Spain). Comparison with small mammals

Abstract

The late Miocene flora from La Bisbal d'Empordà (Catalonia, Spain) provides significant data for characterising the coastal vegetation from the north-eastern Iberian Peninsula during a key period in Neogene climatic evolution. To this end, a historical leaf collection from La Bisbal d'Empordà was re-examined, analysed from a palaeoenvironmental viewpoint and compared with data provided by the associated small mammal fauna. This flora dates from 9.6–9.7 Ma in age (early Tortonian) according to small mammal biostratigraphy. The fossil-bearing beds were deposited in the floodplain of a meandering river system. Three palaeoecological assemblages were recognized: 1) Helophytic plant stems related to a wetland community. 2) Torn leaves of Fraxinus sp., Ulmus sp., Zelkova sp., Cedrelospermum sp. Populus balsamoides, Alnus gaudinii, Carpinus sp., Platanus sp., Acer tricuspidatum, Daphnogene sp. and, Laurophyllum sp. which would have belonged to a riparian forest located beyond the wetland community, with Fraxinus being the plant growing in closest proximity; 3) Isolated complete Paliurus seeds, interpreted as mainly wind-transported, which provide evidence of an open and more arid landscape situated distally from the floodplain. The small mammal assemblages associated with this flora are consistent with this palaeoenvironmental interpretation. The paucity of small arboreal mammal taxa and insectivores suggests limited forested vegetation areas, while the more common terrestrial species indicate better developed open landscapes. Our results show a more heterogeneous environment than previously thought and that the riverine processes impinged the flora, somewhat limiting the climatic conclusions that might be derived from leaf physiognomic analyses such as CLAMP.