Investigation of lime mortars and plasters from archaeological excavations in Hippos (Israel) using Electron Paramagnetic Resonance

Abstract

This study presents the preliminary results of investigation of the lime mortars and plasters from archaeological excavations in Hippos (Israel), using Electron Paramagnetic Resonance (EPR) spectroscopy. The research was conducted in order to characterize the building material and its reaction to ionizing radiation. The ancient settlement Hippos, situated on the east shore of the Sea of Galilee, functioned from the 3 rd cent. BC until it was destroyed by the earthquake in 749 AD. Lime mortars and plasters show carbonate and locally gypsum character of binder and different kind of aggregate. Samples were γ-irradiated and measured using X-band EPR spectrometer. Computer Resolution Enhancement Method was applied to the complex spectra. Some of the γ-induced EPR signals were attributed to CO 2 -and CO 3 3-paramagnetic centres. Exponential growth of the dose response curve above 1 kGy and saturation for doses above 20 kGy was observed. For doses lower than 1 kGy the dose response curve has a linear character. The presence of γ-sensitive carbonate paramagnetic centres could indicate that, after further studies, well-chosen samples of mortars and plasters might be suitable for EPR dating, assuming the centres have been sufficiently bleached during the manufacturing process.

Radiation Defects in Lime Mortars and Plasters Studied by EPR Spectroscopy

“…These centers are detected in an EPR experiment, when the sample is placed in a homogeneous magnetic field and irradiated by a continuous flow of microwaves, which, when resonance condition is fulfilled, entails a transition between two spin states. (Grün 1991;Ikeya 1993Ikeya , 2004 Although the effects of γ radiation on calcium carbonate, especially in the form of calcite, has been investigated very thoroughly (Ikeya 1993(Ikeya , 2004Bahain et al 1994;Callens 1997;Callens et al 1998;Baїetto et al 1999;Polikreti et al 2004;Wencka et al 2005;Kabacińska et al 2017Kabacińska et al , 2019, to our knowledge only our group has analyzed it in lime mortars, first on samples from Sveta Petka church in Budinjak, Croatia (Kabacińska et al 2012), and later from ancient settlement Hippos, Israel (Kabacińska et al 2014b). In these studies, we found several signals generated in lime mortars by γ radiation and examined the dose response curves.…”

“…Full-range EPR spectra (650 mT magnetic field sweep) of investigated samples were previously shown and described in Kabacińska et al (2014b). They are characterized by a presence of common impurities-iron (g-factor values g a = 4.240 and g b = 2.032) (Ikeya 1993;Polikreti et al 2004) and manganese ions (Ikeya 1993;Baїetto et al 1999;Polikreti et al 2004).…”

“…Hip 61 it is a carbonate mortar with a carbonaceous-basaltic aggregate, taken from the northern wall of the facade of the pastophorium, NWC. Few samples (bulk material, grain fraction, suspension) of this mortar were 14 C dated using different pretreatment methods, giving the results: 1080 ± 100 (Gd-18388), 1490 ± 30 (Poz-16078) (Michalska Nawrocka et al 2007;Michalska 2019) Detailed information about the site, the precise location of sample collection points and the applied 14 C dating preparation technique can be found in Nawrocka et al (2005Nawrocka et al ( , 2009; Michalska Nawrocka et al (2007); Kabacińska et al (2014b); Michalska (2019); Michalska and Pawlyta (2019).…”

“…The temperature under the lamp at the sample position did not exceed 65ºC during irradiation. All three samples were γ-irradiated using 60 Co source with doses of 1, 10, 20, 50, 80, and 100 kGy at the Institute of Applied Radiation Chemistry, Technical University of Łódź, and sample 61H additionally with doses of 50, 100, 300, 500, 800, 2210, and 3000 Gy, at the Institute of Molecular Physics, Polish Academy of Sciences in Poznań (see Kabacińska et al 2014b).…”

“…The mortar Hip61 contained different kinds of aggregate, mainly carbonaceous and basaltic ( Figure 1b). Petrography of the samples was previously described in (Michalska Nawrocka et al 2007;Kabacińska et al 2014b; Michalska and Pawlyta 2019). The raw material for their production was the rocks of the Hordos Formation, occurring in the vicinity of Hippos (Michalska and Pawlyta 2019).…”