Radiocarbon Dating of St. George’s Rotunda in Nitrianska Blatnica (Slovakia): International Consortium Results

Abstract

An international consortium of radiocarbon (14C) laboratories was established to date the origin of the St. George’s Rotunda in Nitrianska Blatnica (Slovakia), because its age was not well established in previous investigations. Altogether, 20 samples of wood, charcoal, mortar and plaster were analyzed. The 14C results obtained from the different laboratories as well as between the different sample types were in good agreement, resulting in a 14C calibrated age of 783–880 AD (94.2% probability) for the Rotunda. Although the 14C results have very good precision, the specific plateau-shape of the calibration curve in this period caused the wide range of the calibrated age. The probability distribution from OxCal calibration shows, however, that about 86% of the probability distribution lies in the period before 863 AD, implying that the Rotunda could have been constructed before the arrival of Constantine (St. Cyril) and St. Methodius to Great Moravia. The Rotunda thus probably represents the oldest standing purpose-built Christian church in the eastern part of Central Europe.

Radiocarbon Dating of Mortar Charcoals From Medieval Rýzmburk Castle, Northwestern Bohemia

“…However, this interpretation is based only on the radiocarbon dating results relative to the historical estimation. The use of similarly old wood for lime burning has been reported frequently (Povinec et al 2021), and our previously published results for other Czech medieval castles even provided some indication for the use of wood potentially as old as 300-400 years (Pachnerová Brabcová et al 2022).…”

Radiocarbon Dating of St. George’s Rotunda in Nitrianska Blatnica (Slovakia): An Archaeological Comment

“…First of all, my doubts are raised by the fact that the entire analysis in the original paper in question relies on a combined radiocarbon date coming from wood samples (Povinec et al 2021:974), even though the authors had other dates with which to inform their conclusions. Nevertheless, the original paper presents the date 1191 ± 10 BP as a final answer to the question of the rotunda’s chronology.…”

“…As Daugbjerg et al (2022) pointed out results that do not take into account the presence of geological contaminants or secondary carbonates can be accepted without harming the model, provided the sample series passed statistical tests. The methodology for taking mortar samples used during the restoration seems to meet the highest scientific standards (Povinec et al 2021:960–961). Therefore, we can assume that the series of mortar samples (cleaned of charcoal and wood fragments) was obtained and treated with a view to minimise the risk of contamination and bias during establishing the chronology (Daugbjerg et al 2020; Hajdas et al 2020b).…”

“…Its value stems partly from the fact that it is so well preserved. The publication in Radiocarbon (Povinec et al 2021) made the results of radiocarbon dating of samples obtained during the excellent restoration work available to researchers and will facilitate debates surrounding the chronology of the rotunda. Nevertheless, the conclusions drawn in the original paper are puzzling.…”

“…The most problematic aspect of the analysis is the fact that the authors’ reasoning was based on a radiocarbon date (1191 ± 10 BP) obtained by combining the dating of four wood fragments found in the oldest layer of mortar. It is puzzling because the authors obtained 20 radiocarbon dates in total from the site (Povinec et al 2021:Table 1): six from wood samples (W), three from charcoal (C), seven from mortar (M) and four from plaster (P). Five of these dates refer to periods younger than the Early Middle Ages and the time of the rotunda’s construction, but the remaining 15 dates allow performing a more thorough interpretation of the results, e.g.…”