A06_11

Results and findings from an international mortar dating intercomparison MODIS2

Scott M¹,  Lindroos A², Barrett G³, Boudin M⁴, Hajdas I⁵, Olsen J⁶, Maspero F⁷, Marzaioli F⁸, Michaska D⁹, Moreau C¹⁰, Sironic A¹¹, Pawelczyk F¹²

¹University Of Glasgow, Glasgow, United Kingdom, ²Åbo Akademi University, Vaasa, Finland, ³Queens University Belfast, Belfast, United Kingdom, ⁴KIK-Irpa, Brussels, Belgium, ⁵ETH, Zurich, Switzerland, ⁶Aarhus University, Aarhus, Denmark, ⁷Università di Milano Bicocca, Milano, Italy, ⁸Università degli Studi della Campania Luigi Vanvitelli, Caserta, Italy, ⁹Adam Mickieiwcz University, Poznan, Poland, ¹⁰Université Paris-Saclay, Gif sur Yvette, France, ¹¹Rudjer Boškovic Institute, Zagreb, Croatia, ¹²Silesian University of Technology, Gliwice, Poland

Dating of mortars remains an undertaking which a relatively small number of laboratories are engaged in.  At the same there have been developments of different pre-treatment methods, dating of different fractions etc, all of which have the potential to contribute to variability observed in dating results.  It is in this context that a further mortar dating intercomparison has been undertaken.

Three samples from the “International mortar dating” (www.mortardating.com) projects´ sample collection were selected for this inter-comparison study. The consensus was that the samples should represent different chronologies and typologies and come from geographically different regions and have known ages. Because of the large number of laboratories participating in the inter-comparison, the main sample selection criterion turned out to be the size of the samples available. The age of the youngest sample is well known and the age of the two others is known from earlier ¹⁴C dating of mortar, and their context.

Before distribution, the samples were split into pieces and each laboratory received one piece of each sample for characterization of the mortar. The remainder of each sample was crushed further with plastic covered pliers and sieved in a mechanically vibrated sieve series for 15 min whereafter the <150 micrometer (µm) grain-size fraction was collected and homogenized by shaking. Each laboratory received approximately 1000 mg of the fraction in a small glass vial.

The results from the intercomparison and their analysis will be presented, focusing on the variations observed and their potential attribution.