Radiocarbon Dating of Charcoals From Historical Mortars From Týřov and Pyšolec Castles

Abstract

Organic inclusions in lime binders provide useful samples for radiocarbon dating of historical objects. Two Czech castles Týřov and Pyšolec from Late Middle Ages were explored, and tens of charcoals were found in their walls. The radiocarbon content of the charcoals was measured with accelerator mass spectrometry. The dating results showed that none of the charcoals were younger than the known historical ages (Týřov: 1260 - 1270, Pyšolec: 1300 - 1340), but some were considerably older. Two charcoals from Pyšolec castle dated to Palaeolithic, likely originating from fluvial sediments added as an aggregate to the mortar. When excluding these two charcoals, the others indicated most likely dates being 50–100 y older than the building dates of the castles. This systemic effect corresponds to the age of wood used for lime burning and shall be accounted for when dating mortars using charcoals.

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).…”

“…Inevitably, this may include very old organic materials, e.g., from fluvial sediments or from using older fuel sources, such as peat (Tubbs and Kinder 1990). Recently, we have reported the inclusion of several palaeolithic charcoals in mortar of Pyšolec, a medieval Czech castle, independently dated to 1300–1340 AD (Pachnerová Brabcová et al 2022). Even if the charcoals originate from wood used in lime burning, the so-called “old wood problem” can occur (Schiffer 1986; Michalska Nawrocka et al 2007).…”

“…Even if the charcoals originate from wood used in lime burning, the so-called “old wood problem” can occur (Schiffer 1986; Michalska Nawrocka et al 2007). Although it seems unlikely to some investigators (Rutgers et al 2002), in addition to young wood such as branches or small trees, a considerably older wood from large trunks might have been used as a fuel, with ages potentially exceeding 100 years (Pachnerová Brabcová et al 2022). On the other hand, charcoals may be younger than the building itself if sampled from sites that underwent later repairs or reconstructions or may appear younger if they were contaminated by mould or lichen (Van Strydonck et al 1992; Mathews 2001).…”

Extensive Survey on Radiocarbon Dating of Organic Inclusions in Medieval Mortars in the Czech Republic

“…In the bergfried of Rýzmburk, 13 charcoals were found, and they all survived the pretreatment and were dated. At Týřov, three additional, wood samples were collected and dated, complementing samples presented previously (Pachnerová Brabcová et al 2022b). The original sample weights and ABA yields are listed in Table 1, together with the samples' conventional 14 C ages as well as calendar date intervals.…”

“…The third site is the northern tower of Rýzmburk castle (Pachnerová Brabcová et al 2022a), previously dated to the early phase of Rýzmburk development, 1260-1278 or pre-1300 (Lehký 2012; Razím 2019). Fourth, inclusions were analyzed from the bergfried of Týřov castle (Pachnerová Brabcová et al 2022b); the previous results were extended by three wood samples. Týřov (49.9735N, 13.7903E) was founded by Wenceslas I, Bohemian king in 1230-1253, who in 1249 imprisoned there his rebellious son, future king Ottokar II of Bohemia.…”