Chemical and structural changes in Cervus elaphus tooth enamels during fossilization (Lazaret cave): a combined IR and XRD Rietveld analysis

Abstract

Tooth enamel from modern and fossil (Lazaret cave) Cervus elaphus was characterized in order to study the chemical and structural changes during fossilization. Calcium, P, Na, Mg, F, Cl, CO 3, contents were measured by chemical analyses, and infrared (IR) spectroscopy was used to determine H 20, OH −, P0 4 3− and C0 3 2−. Carbonate increases during fossilization and substitutes for PO 4 3− at the B-site and for OH at the A-site. The C0 3 2−-for-PO 4 3− substitution experiences the highest increase. Water and OH contents decrease during fossilization. These chemical changes may be traced by Rietveld structure refinement (XRD). Like human enamel, red deer enamel consists of apatite. A good positive correlation has been found between the a cell parameter and C0 3 2− contents. Refinement of atomic positions and site multiplicity allow us to describe site distortions in P0 4 3− polyhedra and along the 6 3 axis; these distortions are indirect probes of the substituent ions in the apatite structure. At Lazaret cave, the karstic environment is thought to control the chemical and structural changes of the fossil enamels. Fossilization conditions have been favorable for a good conservation of the Cervus elaphus tooth enamels whatever their stratigraphic position and location were. These fossil enamels have experienced only slight structural and chemical changes considering their geological age. This accounts for a rapid burial in continental sediments of Lazaret prehistoric cave. These Lazaret fossil enamels could be considered as stable material which may be used for dating by the ESR and U-Th methods.