Evidence for shifting environmental conditions in Southwestern France from 33 000 to 15 000 years ago derived from carbon-13 and nitrogen-15 natural abundances in collagen of large herbivores

A paleoenvironmental reconstruction of terrestrial environments in Southwestern France between 33 and 15 cal kyr BP is provided using δ13C and δ15N variations in collagen of three herbivorous mammals. Altogether 161 analyses have been carried out on collagen extracted from skeletal fragments of reindeer, horse and Bos/Bison from four successive chronological phases covering the end of MOIS 3 and MOIS 2. The δ13C values of ungulate collagen are clearly separated between the studied species. They are interpreted as reflecting a stable dietary adaptation in a changing environment. The variations of δ15N values of ungulate collagen are significant, especially between specimens from MOIS 3 and specimens from MOIS 2, with a minimum during the Last Glacial Maximum. This phenomenon seems to reflect changes in the activity of nitrogen cycling processes associated with permafrost development. Carbon and nitrogen isotopic composition of fossil herbivore collagen are worth investigating as paleoecological and paleoenvironmental tracers in Upper Pleistocene periglacial continental contexts.