800 ka of Palaeoenvironmental changes in the Southwestern Mediterranean realm

Abstract

We provided valuable information about the palaeoenvironmental evolution of Southwestern Europe during the last 800 ka through the palynological study of the longest continuous continental Quaternary record in the Iberian Peninsula and in the Southwestern Mediterranean region. The SPD core studied here constituted the longest sequence recovered at the Padul Basin and we improved the chronological precision with respect to previous research. Furthermore, the high sampling resolution provided interesting insights into the main vegetation changes occurred at long-term timescales in the region and allowed correlating these variations with other long continental records of Europe. Dating using palaeomagnetism, amino acid racemisation, U/Th and 14C allowed us to construct a robust Bayesian age-depth function, thereby making it possible to determine the chronological framework for the Padul record. From the palynological content of the samples, which were grouped in 11 clusters, we obtained a large variable number of minor pollen variations totalling 21 palynozones identified along the record. From the statistical analysis of the pollen data, some pollen environmental indexes were defined, allowing the reconstruction of palaeotemperature and palaeohumidity conditions. Five climatic scenarios were established: cold/arid, cold/semi-arid, cold/wet, temperate/wet (Mediterranean-climate), and warm/wet (Mediterranean-climate with higher moisture). Of note, the vegetation in the Padul Basin differed from that of other European basins with long pollen records due to regional characteristics, but main palaeoenvironmental trends were in agreement. Pinus, Steppic, Xerophilous, and Mediterranean taxa in the Padul Basin showed a continuous and dominant presence along the whole record, while only in certain periods did humidity increase, reflected by the expansion of Spores, Deciduous and Mediterranean taxa (especially in Pz 2, 7 and 13), but without any large expansion of deciduous forest. Comparison with other European records revealed the singular bioclimatic position of the Padul Basin in the Southwestern Mediterranean realm, and this part of Iberia can be considered a Quaternary vegetation refuge, mainly for mesophillous taxa and sclerophyllous oak. Although the biomes of the Padul basin and other European basins could not be compared directly, the main palaeoenvironmental trends were coincident (interstadials were marked by warmer periods and greater humidity, whereas stadials were cooler and more arid). These observations suggest that environmental changes in the Padul Basin were in tune with variations in global palaeoclimatic conditions.