Problems Encountered in the U-Th Dating of Fossil Red Deer Jaws (Bone, Dentine, Enamel) from Lazaret Cave: a Comparative Study with Early Chronological Data

Abstract

Previous chronological data such as biochronological data, U-series and electron spin resonance (ESR) data on stalagmitic flowstone E and samples from the sea deposit B are discussed. Most of these early studies show a deposition of the archaeological levels C during the oxygen isotopic stage 6. For testing the U-Th dating, the method was applied for the first time to the three tissues (bone, dentine and enamel) from fossil Cervus elaphus jaws in order to date directly the archaeological levels of Lazaret Cave. Twenty-seven bones, 21 dentine and 17 enamel samples from 30 jaws and two tibias have been analysed by alpha spectrometry. The results show a large range of apparent dates with an open system behaviour. For the majority of samples the ages range between 50 and 200ka. The main set of data shows that the ages increase upward in the stratigraphic sequence, with low values near the base of the sequence. The U-Th apparent ages of dentine are in better agreement with the ages of their respective enamels than with bones. The older the U-Th ages of the bones the larger the uranium content difference between the bone and dentine samples from the same mandible is observed. For some samples from all levels of the continental fill, a sequence of episodes of uranium isotope leaching and accumulation has resulted in increased uranium isotope ratios and modified uranium content yielding anomalous ages. At Lazaret Cave, U-Th dating on bone and dentine was not successful, but data will be used for ESR dating.