## 4 Results and Discussion
### Mortar Radiocarbon Dating  
Once the binder fraction was purified through thermal heating and reduced to graphite (C), the samples underwent measurement of the \({}^{14}\)C isotopic ratio using Accelerator Mass Spectrometry (AMS). The radiocarbon dates obtained from the mortar and plaster samples, as well as from the charcoal sample (MV_SS_01_C) collected within mortar MV_SS_01, are reported in Table 4 and Figure 6.  
Samples MV_SS_01, MV_SS_01_C, and MV_SS_02 were taken from the chapel of San Quirico and originate, respectively, from the mortar, a fragment of charcoal within the mortar (01), and the white finishing layer. The calibrated ages place the samples between the late 12 th and 13 th centuries and are reliable and in agreement with each other.  
The sample taken at the entrance of the chapel of Santa Margherita (MV_SS_07) yields a calendar age between 1300 and 1400. The observed age aligns with archaeological hypotheses placing the construction of the celebratory apse at Santa Margherita within the 13 th or 14 th century, and thus later than the oldest part of the church, which is dedicated to [PERSON], as well as the portion dedicated to [PERSON] (11 th-12 th centuries). Within the same chapel, sample MV_SS_10 was taken from the white finishing layer adjacent to the inscription \"1541\", indicating that the plaster should precede this date. The radiocarbon results place the sample between 1440 and 1511 (83%) and 1591-1620 (12%) (Figure S11), calendar AD age range (2\(\sigma\)), so, given the inscription, we can assume that the finishing layer  
\begin{table}
\begin{tabular}{l l l l l l l} \hline \hline
**Lab Code** & **Sample Code** & **Fraction** & **\({}^{14}\)C Age** & \
\begin{tabular}{l} **Cal AD Age** \\ **Range (2\(\sigma\))** \\ \end{tabular} &
\begin{tabular}{l} **Cal AD Age** \\ **Range (1\(\sigma\))** \\ \end{tabular} & **Reliable Age?** \\ \hline DSH10245\_SG & MV\_SS\_01 & SG\_01 & 749 \(\pm\) 50 & AD 1179–1387 & AD 1227–1289 & Yes \\ \hline DSH10222\_CH & MV\_SS\_01\_C & charcoal & 867 \(\pm\) 19 & AD 1159–1223 & AD 1175–1216 & Yes \\ \hline DSH10213\_SG & MV\_SS\_02 & SG\_01 & 768 \(\pm\) 21 & AD 1225–1280 & AD 1232–1278 & Yes \\ \hline DSH10214\_SG & MV\_SS\_07 & SG\_01 & 635 \(\pm\) 37 & AD 1287–1398 & AD 1298–1393 & Yes \\ \hline DSH10215\_SG & MV\_SS\_08 & SG\_01 & 246 \(\pm\) 25 & AD 1526–1800 & AD 1641–1795 & No \\ \hline DSH10216\_SG & MV\_SS\_10 & SG\_01 & 403 \(\pm\) 23 & AD 1440–1620 & AD 1447–1487 & Yes \\ \hline \hline \end{tabular}
\end{table}
Table 4: Radiocarbon dating results of the mortar samples (SGs) and the charcoal fragments found in the mortar sample, reporting calibrated calendar ages in the ranges of 1\(\sigma\) and 2\(\sigma\).  
Figure 6: Calibrated dates of the \({}^{14}\)C measurements of mortar samples and charcoal (in red) by means of OxCal 4.4 [45] and the IntCal 20 calibration curve [31].  
was executed between 1440 and 1511. Therefore, the result is consistent with the data. The only date that appears unreliable is related to the sample taken from the margin of a fresco inside the chapel of Santa Margherita (sample MV_SS_08). According to historical sources, the fresco could be attributed to the same painter who created the fresco cycle inside the church of San Salvatore and the chapel of the Crucifixion, during the period when the care of the complex was entrusted to the Augustinians (around the mid-1400s). The mortar sample was taken at the edge of the fresco itself, without involving the painted layer, out of respect for the artwork. Therefore, the analysis for the date obtained (calibrated age, 1526-1800 AD 2\(\sigma\)) might have been contaminated by subsequent restoration interventions performed during the 20 th century.