LATE NEOGENE TERRESTRIAL PALEOCLIMATE AND PALEOECOLOGY OF THE IBERIAN PENINSULA: A STABLE ISOTOPIC RECORD FROM MAMMALS

During the late Neogene, terrestrial systems experienced important global transitions, including floral and faunal turnover associated with the expansion of grassland ecosystems and climate change linked to the onset of northern hemisphere glaciation. In the Mediterranean region, these changes were also accompanied by paleogeographic changes associated with the latest Miocene Messinian Salinity Crisis (MSC). We report a record of terrestrial paleoclimate and paleoecology during the Late Miocene, Pliocene, and Pleistocene of Spain based on the stable oxygen isotope composition (δ¹⁸O) of mammal faunas. We use the δ¹⁸O of fossil horse tooth enamel to estimate past mean annual temperature (MAT) since enamel δ¹⁸O from modern horses is a reasonable proxy for the δ¹⁸O of local meteoric water, which is in turn strongly dependent on MAT. We compare our results from Spain with similar data from the Late Miocene of northern Libya to explore regional climate variability during the MSC. We also use δ¹⁸O values within faunas to reconstruct physiological and/or habitat diversity between taxa, and we compare intra-tooth samples of enamel and dentine δ¹⁸O to examine diagenetic alteration.

Our paleotemperature reconstructions indicate MAT for the terminal Miocene of Spain that is approximately 2-3ºC higher than today, with a difference of approximately 6-7ºC between northern and southern Spain. This latitudinal gradient is only 1.5ºC higher than for these same areas today. The difference between modern and Late Miocene MAT is consistent with global cooling during the late Cenozoic. The δ¹⁸O values from Libya are lower than those for southern Spain, suggesting cooler and/or wetter climates in northeastern Africa during the MSC. Intrafaunal δ¹⁸O comparisons are consistent with a semi-aquatic lifestyle for anthracotheres, hippopotamids, and castorids. Comparisons of enamel and dentine δ¹⁸O values suggest slight diagenetic alteration of dentine, but we demonstrate that these δ¹⁸O values can be used to reconstruct reasonable values of diagenetic water δ¹⁸O. Overall, our data do not support large climatic changes in the Iberian Peninsula during the MSC, but are consistent with long-term global cooling and Neogene latitudinal climate gradients in Spain that are slightly sharper than today.