High-resolution δC intratooth profiles in bovine enamel: Implications for mineralization pattern and isotopic attenuation

We present the first high-resolution carbon isotope and carbonate content profiles generated through the thickness of enamel from a steer fed C₃- then C₄-dominant food. Carbonate contents decrease by ∼2 wt% from the enamel surface to the innermost enamel layer, and each carbon isotope profile shows a mixture of enamel portions mineralized over several months. Downward and outward increasing contribution of C₄ food to the enamel δ¹³C values reveal two components of the mineralization gradient: a vertical component from the tip of the tooth crown to the neck, and a horizontal component from the enamel-dentine junction to the outer enamel. We use our results to infer mineralization parameters for bovines and to calculate expected isotopic attenuations for an array of environmental inputs and microsampling strategies, using the model developed by Passey and Cerling Geochim. Cosmochim. Acta. 66 (2002) 3225-3234]. Although it seems unlikely that any strategy will perfectly isolate discrete time slices, sampling the innermost enamel layer might offer the advantage of significantly reducing the isotope damping that would become independent of the structure of the input signal.