Stable oxygen isotopes of dental biomineral: differentiation at the intra- and inter-tissue level of modern shark teeth

Abstract

In situ oxygen isotopic composition of the sandbar shark (Carcharhinus plumbeus) teeth grown at a constant water temperature and salinity were analysed by high precision and high spatialresolution secondary ion mass spectrometry, targeting dental biomineral within the parallel-bundled enameloid (PBE), the tangle-bundled enameloid (TBE) and the dentine. Measured δ18O values had comparable inter-tissue variability in each tooth analysed. The PBE enameloid had the smallest scatter of oxygen isotope ratios, while the TBE enameloid had slightly higher intra-tissue variation of δ18O, but similar average values. The dentine had largest variability and lower average δ18O. The enameloid of shark teeth is therefore recommended as a target biomineral and a preferential biogeochemical reference for environmental and palaeoenvironmental studies.