ISOTOPIC AND ELEMENTAL PROFILES IN MODERN MAMMAL TEETH AND WHAT WE CAN LEARN FROM THEIR PALEO-COUNTERPARTS

Bioapatites from teeth and other skeletal hardparts record information about environmental conditions under which the material is deposited. Much like in carbonates, chemical analysis of fossil bioapatite can therefore be used as a means to reconstruct climate and paleoenvironment. Mammal teeth grow sequentially, meaning that large, slow-growing teeth have the advantage of recording sub-annual scale environmental variations in a highly diagenesis-resistant bioapatite record. Extraction of seasonally resolved (paleo)environmental records from tooth enamel requires measurements on a very high spatial resolution. In this study, high-resolution micro-X-Ray Fluorescence line scans are implemented to obtain elemental abundance records at 25 µm resolution along the growth axis of teeth of modern cattle (Bos taurus) and horse (Equus ferus caballus). We also analyzed oxygen (carbonate and phosphate) and carbon stable isotopes of the enamel from the same teeth, and compared the results of stable isotopes and elemental abundance to document changes in the chemical composition of the teeth along the growth axis. Applying both methods on modern teeth of known origin, the relationship between elemental ratios, stable isotopes and known environmental parameters is investigated. Results from different tooth positions within the mammal jaw are also studied and compared. Stable isotope results from teeth in eruption sequence are used to show overlapping records seasonal cyclicity. Differences in results from phosphate-stable oxygen isotopes and carbonate stable oxygen isotopes as well as elemental records are used to test the reliability and reproducibility of different sampling and pretreatment techniques.