A Multidisciplinary Approach and a Double Level of Validation for the Radiocarbon Dating of Mortars
Channel: Recording Archaeology
Date: 10/10/2017

This contribution discusses the importance of a multidisciplinary approach to the application of the radiocarbon dating method to mortar samples, and the need of a double level of validation of the related results for a successful application of the method in archaeological and/or historic research. Application of the radiocarbon dating method to mortar samples was first suggested in the 1960s. Since then, a number of procedures have been developed to successfully apply the method. Unfortunately, despite the simplicity of principles underlying this application, all studies have highlighted drawbacks and limitations, mainly related to the sample contamination from undesirable carbonaceous substances that can alter the results of the dating work. However, recent experiences have demonstrated that it is not just the removal of these contaminants that can guarantee the success of the dating work. Beside this problem, in fact, a number of other factors can affect the usability of the results in archaeological and historic research. These are, for example, the careful evaluation of the stratification in the structure where the samples are taken, the representativeness of the sample in relation to a specific construction phase, and the understanding of the behaviour of the material (i.e. lime) before, during and after its use. To make sure that all factors influencing the successful application of the method are considered, all results should be critically analysed before their use in the archaeological and/or historic research. To be effective, such evaluation should be carried out at two levels: 1) at sample level, in which the quality of the sample is evaluated (e.g. by comparing the results of different CO2 fractions), and (2) at archaeological level in which the representativeness of the sample (even though uncontaminated) should be investigated. The correct application of the laboratory procedures to an uncontaminated sample, in fact, cannot rule out possible errors during the sampling work and, similarly, an AMS results apparently fitting the archaeological record cannot be acquired without an independent evaluation of the quality of the sample. Overall, this means that to successfully apply the radiocarbon dating methods to mortar samples, a multidisciplinary approach should be used. In such approach both, field and laboratory procedures should be carefully planned and carried out, and the results should be critically evaluated at archaeological and laboratory level before their use in historic and archaeological investigations. This contribution aims to highlight details and importance of such approach by presenting a number of cases in which the radiocarbon dating method was applied to mortar samples.

Pesce Giovanni L. Department of Architecture and Built Environment, Faculty of Engineering and Environment, Northumbria University, Newcastle, UK