干旱区生态环境知识资源中心

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 similar to 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 delta C-13 values (relative to VPDB, mean -10.3 +/- 1.1 parts per thousand; range -13.0 to -7.4 parts per thousand) are consistent with consumption of C-3 vegetation; C-4 plants did not contribute significantly to the diets of the selected taxa. When averaged by time interval to examine secular trends, delta C-13 values increase at similar to 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 delta C-13 value drops significantly at similar to 4.2-3.7 Ma (MN14-MN15) during the Pliocene Warm Period, which brought more humid conditions to Europe, and returns to higher delta C-13 values from similar to 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 (similar to 6.3-0.8 Ma) most likely due to cooling associated with Northern Hemisphere glaciation.