Uranium series disequilibrium detection and annual dose determination: A case study on Magdalenian ferruginous heated sandstones (La Honteyre,France)

Disequilibria in uranium series and their consequences on the annual dose determination in luminescence dating studies are now well-known, but only a few studies refer to the systematic research of this kind of phenomenon, and eventually to how the problem has been misguided. The present work aims at considering a new case study: anciently heated ferruginous sandstones from a Magdalenian archaeological site have been dated by thermoluminescence. In this work, uranium series disequilibrium has been detected both in samples and surrounding sediments, using high resolution low background gamma spectrometry measurements. Further investigations, in particular with alpha-spectrometry measurements and geochemical considerations, helped us to understand when and how the disequilibrium began, and it led us to propose a specific simple model, based on a continuous and regular enrichment in uranium, for the evaluation of the mean annual dose absorbed by the samples to be dated. This work deals with the results of gamma and alpha-spectrometry as well as the dose variation model proposed and the dating results obtained, in terms of annual dose determination and in terms of age obtained.