Carbon and oxygen stable isotope compositions of late Pleistocene mammal teeth from dolines of Ajoie (Northwestern Switzerland)

Abstract

Fossils of megaherbivores from eight late Pleistocene 14C- and OSL-dated doline infillings of Ajoie (NW Switzerland) were discovered along the Transjurane highway in the Swiss Jura. Carbon and oxygen analyses of enamel were performed on forty-six teeth of large mammals (Equus germanicus, Mammuthus primigenius, Coelodonta antiquitatis, and Bison priscus), coming from one doline in Boncourt (~80ka, marine oxygen isotope stage MIS5a) and seven in Courtedoux (51-27ka, late MIS3), in order to reconstruct the paleoclimatic and paleoenvironmental conditions of the region. Similar enamel δ13C values for both periods, ranging from -14.5 to -9.2‰, indicate that the megaherbivores lived in a C3 plant-dominated environment. Enamel δ18OPO4 values range from 10.9 to 16.3‰ with a mean of 13.5±1.0‰ (n=46). Mean air temperatures (MATs) were inferred using species-specific δ18OPO4-δ18OH2O-calibrations for modern mammals and a present-day precipitation δ18OH2O-MAT relation for Switzerland. Similar average MATs of 6.6±3.6°C for the deposits dated to ~80ka and 6.5±3.3°C for those dated to the interval 51-27ka were estimated. This suggests that these mammals in the Ajoie area lived in mild periods of the late Pleistocene with MATs only about 2.5°C lower than modern-day temperatures.