Effect of geochemical alteration of depositional environment on combined ESR-U series dating of herbivore teeth

In archaeological dating, the geochemical alteration of depositional environments may affect the measurement of external dose rate, which will cause the inaccuracy of dating result of methods basing on the principle of radiation exposure, such as thermoluminescence (TL) and electron spin resonance (ESR) dating. In this study, tooth fossils from three different depositional environments in Arago cave, south of France, were analyzed by combined ESR-U series method and the potential effects of geochemical alteration and inhomogenous of depositional environment on the dating results were revealed. The study shows that the age of samples from non-altered quartz mineral environment was dated about 330 ka, while the teeth from the other two environments (carbonated and phosphate areas) were dated around 480 ka, the former is about 150 ka younger than the latter. This phenomenon is probably caused by the overestimation of external dose rate in quartz mineral area. The study suggests that the dating researchers should pay much attention to geochemical alteration of depositional environment of samples. (authors)