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. 2024 Aug 28;14(1):19979.
doi: 10.1038/s41598-024-70763-2.

A new multi-analytical procedure for radiocarbon dating of historical mortars

Sara Calandra  1 , Emma Cantisani  2 , Claudia Conti  3 , Barbara Salvadori  2 , Serena Barone  4   5 , Lucia Liccioli  4 , Mariaelena Fedi  4 , Teresa Salvatici  6 , Andrea Arrighetti  7 , Fabio Fratini  2 , Carlo Alberto Garzonio  6
Affiliations

A new multi-analytical procedure for radiocarbon dating of historical mortars

Sara Calandra et al. Sci Rep. .

Abstract

The overarching challenge of this research is setting up a procedure to select the most appropriate fraction from complex, heterogeneous materials such as historic mortars in case of radiocarbon dating. At present, in the international community, there is not a unique and fully accepted way of mortar sample preparation to systematically obtain accurate results. With this contribution, we propose a strategy for selecting suitable mortar samples for radiocarbon dating of anthropogenic calcite in binder or lump. A four-step procedure is proposed: (I) good sampling strategies along with architectural and historical surveys; (II) mineralogical, petrographic, and chemical characterization of mortars to evaluate the feasibility of sample dating; (III) a non-destructive multi-analytical characterization of binder-rich portions to avoid geogenic calcite contamination; (IV) carbonate micro-sample preparation and accelerator mass spectrometer (AMS) measurements. The most innovative feature of the overall procedure relies on the fact that, in case of positive validation in step III, exactly the same material is treated and measured in step IV. The paper aims to apply this procedure to the ancient mortar of the Florentine historical building (Trebbio Castle), selecting micro-samples suitable for dating in natural hydraulic mortars. The discussion of the mortar dating results with the historical-archaeological hypotheses provided significant insights into the construction history of the building.

Keywords: ATR-FTIR; Geogenic and anthropogenic calcites; Historical mortars; Micro-Raman; Microsample preparation; Radiocarbon dating.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Graphical representation of the new multi-analytical procedure for radiocarbon dating of historical mortars.
Fig. 2
Fig. 2
Trebbio Castle: building (a); sampling on the North side, perspective drawing (by Teresa Salvatici and Sara Calandra) (b), and masonry (c).
Fig. 3
Fig. 3
OM (a), OM-CL (b), SEM–EDS (c, d) analyses on lime lump. In (c), BS image of a detail of the lump. In (d), SEM–EDS map layered on the previous area.
Fig. 4
Fig. 4
Results of non-destructive techniques on powders (b-d) and lump selection points (a). Plot of ν2 and ν4 with typical trend lines of geogenic and anthropogenic calcites obtained by ATR-FTIR and TC lump samples (b); OM-CL photomicrographs of lump powders: an anthropogenic sample (TC26L1) and a geogenic sample (TC26L3) (c); comparison among individual Raman spectra of carbonate samples: geogenic calcite (in blue, a reference sample) and anthropogenic calcite of TC samples (1: TC26L1; 2: TC26L2; 3: TC26L4; 4: TC27L1) (d).
Fig. 5
Fig. 5
Calibrated age of the TC samples: TC26L1 + TC26L2 + TC26L4 (a); TC27L1 (b).
See this image and copyright information in PMC

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