A03_P05

OSL mortar dating inter-comparison study. The second round of MODIS, MOrtar Dating Inter-comparison Study

Panzeri L¹, Martini M¹, Maspero F¹, Galli A¹, Urbanova P², Guibert P², Sanjurjo Sánchez J³

¹Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca and CUDAM, Milano, Italy, ²(2) Archéosciences-Bordeaux UMR 6034, CNRS-Université Bordeaux Montaigne, Bordeaux, France, ³(3)          Instituto Universitario de Geología, Universidade da Coruña, A Coruña, Spain

Two physical dating methods currently enable us to date binders: radiocarbon (¹⁴C) dating and optically stimulated luminescence (OSL). During the first MODIS (MOrtar Dating Inter-comparison Study), which was initiated by specialists in ¹⁴C dating in 2014, two laboratories with expertise in luminescence dating joined the group. They attempted to apply the OSL dating to mortar samples selected for the MODIS study.

Due to the lack of a detectable signal when using “the single grain” procedure on these samples, both OSL laboratories based the dating process on the analyses of coarse quartz fractions measured by the multigrain technique. The results obtained showed general agreement both between OSL laboratories and with ¹⁴C dating results. Following this first step, a new inter-comparison experiment was set up in 2018 during the Mortar Dating International Meeting (Bordeaux, FR).

When applying the OSL method, it is necessary to evaluate environmental dose rate received by each sample. The context in situ from which mortar samples are extracted thus needs to be known when OSL dating is used, contrary to the ¹⁴C method.

As the needs for the selection of samples convenient for an inter-comparison are not the same between ¹⁴C and OSL, it has been decided to choose two different sample sets, one to share between the radiocarbon labs and one for the OSL dating. As for the OSL samples the Bordeaux group proposed three samples that were available in a sufficient quantity to be divided between participants. The data obtained within this inter-comparison will be discussed.