¹⁴C Mortar Dating: The Case of the Medieval Shayzar Citadel, Syria

Abstract

This paper reports the results from applying the Cryo2SoniC (Cryobreaking, Sonication, Centrifugation) protocol to some lime mortars sampled from the citadel of Shayzar (Syria). The overall aims of this project are 1) to use the properties offered by high-precision accelerator mass spectrometry (AMS) radiocarbon dating for the evaluation of absolute chronology with its typical robust time constraints (i.e. 25 14C yr), and 2) to apply the dating directly to the citadel structures in order to prevent possible biasing effects potentially affecting indirect 14C dating on organic materials found at the study site. The analyses presented in this paper have been mainly performed as a preliminary check of the Cryo2SoniC methodology in order to assess its applicability to this study site by comparing observed mortar results with archaeological expectations about the citadel development phasing and charcoals found encased in mortars. Petrographic and mineralogical thin-section analyses by optical microscopy (TSOM), X-ray powder diffraction (XRD), and scanning electron microscopy plus energy dispersive spectroscopy (SEM/EDS) investigations were carried out for characterization of the mortar samples to verify the occurrence of some features, related to their production technology, which may introduce dating offsets. The resulting 14C calibrated ages were in agreement with the archaeological expectations based on type and stratigraphic site reconstructions, in situ inscriptions, and written sources. Such results showed also a general (with 1 exception) statistical agreement among the charcoals and the analyzed mortars simultaneously, confirming the archaeological expectations for the Shayzar citadel. Results presented in this paper indicate good accuracy for the applied procedure for chronology reconstruction and highlight the capability of Cryo2SoniC to further characterize the Shayzar site.

The Cannero Castle (Italy): Development of Radiocarbon Dating Methodologies in the Framework of the Layered Double Hydroxide Mortars

“…30 g of manually disaggregated material for each sample were subjected to the separation protocol in order to extract the SGs from the other mortar components based on their grain sizes. The procedure consists in a sonication and wet gravimetric sedimentation in ultrapure decarbonated water for 24 hr, centrifugation and filtration of the fine fraction (Nonni et al 2017;Addis et al 2019). The obtained SGs were analyzed by XRPD in order to evaluate the presence of contaminants for the radiocarbon dating.…”

Preparation and Dating of Mortar Samples—Mortar Dating Inter-Comparison Study (MODIS)

“…Collected CO 2 is graphitized and measured by the AMS CIRCE System . The 14 C ages for both SAND and SUSP fractions are analyzed with the SUSP fraction considered most suitable Nonni et al 2013). …”

“…The preparation protocol of mortar at Poznań laboratory described in Michalska et al (2017 this volume;Nawrocka-Michalska et al 2007) has been developed based on experience of different scientific groups (Folk and Valastro 1979;Van Strydonck et al 1986;Heinemeier et al 1997;Lindroos et al 2007;Goslar et al 2009;Nawrocka et al 2009;Marzaioli et al 2013;Nonni et al 2013;Ringbom et al 2014;Hayen et al 2016). …”

Hydrotalcite and Hydrocalumite in Mortar Binders from the Medieval Castle of Portilla (Álava, North Spain): Accurate Mineralogical Control to Achieve More Reliable Chronological Ages

“…The first procedures to date the binder consisted of the hydrolysis of lime binder particles of different grain size fractions by using diluted hydrochloric acid (HCl) or 85% ortophosphoric acid (H 3 PO 4 ) [12,13,16,17,[19][20][21][32][33][34][35]. When carbonate aggregates appear, mechanical/physical methods of binder extraction are an alternative to chemical methods to avoid contamination by carbonate aggregates in the fraction used for hydrolysis [29,30,36]. The use of lime lumps in mortar for radiocarbon dating has been reported by Van Strydonck et al [16] and Lindroos et al [17] since these lumps represent a pure binder when the lime is scarcely mixed with the aggregates [37,38].…”