Late Neogene and Early Quaternary Paleoenvironmental and Paleoclimatic Conditions in Southwestern Europe: Isotopic Analyses on Mammalian Taxa

Laura Domingo,Paul L Koch,David L Fox,Manuel Hernández Fernández,María Teresa Alberdi,M Soledad Domingo,Richard J Butler

doi:10.1371/journal.pone.0063739

Abstract

Climatic and environmental shifts have had profound impacts on faunal and floral assemblages globally since the end of the Miocene. We explore the regional expression of these fluctuations in southwestern Europe by constructing long-term records (from ∼11.1 to 0.8 Ma, late Miocene–middle Pleistocene) of carbon and oxygen isotope variations in tooth enamel of different large herbivorous mammals from Spain. Isotopic differences among taxa illuminate differences in ecological niches. The δ13C values (relative to VPDB, mean −10.3±1.1‰; range −13.0 to −7.4‰) are consistent with consumption of C3 vegetation; C4 plants did not contribute significantly to the diets of the selected taxa. When averaged by time interval to examine secular trends, δ13C values increase at ∼9.5 Ma (MN9–MN10), probably related to the Middle Vallesian Crisis when there was a replacement of vegetation adapted to more humid conditions by vegetation adapted to drier and more seasonal conditions, and resulting in the disappearance of forested mammalian fauna. The mean δ13C value drops significantly at ∼4.2−3.7 Ma (MN14–MN15) during the Pliocene Warm Period, which brought more humid conditions to Europe, and returns to higher δ13C values from ∼2.6 Ma onwards (MN16), most likely reflecting more arid conditions as a consequence of the onset of the Northern Hemisphere glaciation. The most notable feature in oxygen isotope records (and mean annual temperature reconstructed from these records) is a gradual drop between MN13 and the middle Pleistocene (∼6.3−0.8 Ma) most likely due to cooling associated with Northern Hemisphere glaciation.

Highlights

Profound paleoenvironmental and paleoclimatic events in the late Cenozoic affected life on Earth and gave rise to modern climate regimes and biomes
We used stable isotope analysis of a succession of mammals from 18 localities in Spain ranging in age from 11.1 to 0.8 Ma to reconstruct environmental and climatic changes during the late Neogene and early Quaternary
Tooth enamel d13C values indicate that analyzed taxa may have occupied woodland to mesic C3 grassland and in some cases, open woodland to xeric C3 grassland, with no evidence of significant C4 consumption in any of the genera we studied

Summary

Introduction

Profound paleoenvironmental and paleoclimatic events in the late Cenozoic affected life on Earth and gave rise to modern climate regimes and biomes. Progressive cooling, which began in the middle Miocene (14-13.8 Ma), led to the onset of Northern Hemisphere glaciation ,2.7 Ma [1,2,3]. Reorganized ocean circulation, perhaps associated with initial restriction of circulation between the Pacific and Atlantic, contributed to the Pliocene Warm Period between ,4.7 and 3.1 Ma [4]. Shifts in temperature and ocean circulation were associated with shifts in the global water budget, though impacts varied by region. C4 plants evolved repeatedly from C3 plants, most likely as a response to low atmospheric pCO2, higher temperatures and increasing waterstress [7]

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