Ramped pyrolysis radiocarbon dating of lime lumps

Establishing the earliest mortar-based construction phase of Turku cathedral, Finland

Bibliographic Data

ID4719105
AuthorsGerard T Barrett (0000-0002-3424-5263, Queen's University Belfast, corresponding author), Kerry Allen (0000-0002-7661-2340), Kerry R Allen (0000-0003-4071-5695, Queen's University Belfast), Paula J Reimer (0000-0001-9238-2146, Queen's University Belfast), Åsa Ringbom (0000-0002-7774-496X, Åbo Akademi University), Jesper Olsen (0000-0002-4445-5520, Aarhus University), A Lindroos (0000-0003-3157-9396, Åbo Akademi University)
Year2023
Volume61
Pages201-210
Publication date2023-05-01
Peer ReviewedYes
Open AccessYes
TypeARTICLE
VenueJournal of Cultural Heritage (JOURNAL)
Journal identifiersISSN: 1296-2074 • E-ISSN: 1778-3674
PublisherElsevier BV (PUBLISHER)
DOI10.1016/j.culher.2023.04.004
OpenAlexW4367856898
LanguageEN
Citations received4
References cited35

Ramped pyrolysis radiocarbon dating was carried out on lime lumps from what was believed to be the oldest remains of Turku Cathedral, Finland, the first sacristy. Lumps extracted from bulk mortar from five sampling locations were analysed. For each sample, 5–6 fractions of CO2 from different temperature fractions were radiocarbon dated. One of the five samples exhibited significant contamination for its lowest temperature fractions. For the remaining samples, the age-temperature profiles were well-behaved, exhibiting a plateau of dates that were in statistical agreement and indicative of samples where only a single carbonate source (lime binder from the construction phase) is contributing to the radiocarbon dates. For each of the five samples, the combined radiocarbon age resulted in a calibrated age with a large probability distribution mode (typically > 85% probability) in the late 13th century AD. Combining the radiocarbon dates from all five samples (21 fractions in statistical agreement, χ2-test: df = 20, T = 7.1, 5% = 31.4) provided an age of 709 ± 11 yr BP and a calibrated age of 1276–1296 cal. AD (95.4%). This result finds excellent agreement with historical sources, previous mortar dating work, and a single radiocarbon date on organic material also embedded in some of the bulk mortar. The results demonstrate that ramped pyrolysis, applied to well-selected lime lumps, is (A) a useful diagnostic tool for establishing how reliable a sample is and (B) an accurate, precise, and repeatable technique for radiocarbon dating mortar. The results further confirm that Turku Cathedral's first sacristy was constructed from stone and mortar in the late 13th century AD. Additionally, using Turku Cathedral sacristy as a case study, two Bayesian models were presented to illustrate how, in general, mortar dating and Bayesian statistics might, in future, be applied to examine building construction dynamics for the case of (chronologically) ordered or unordered mortar derived radiocarbon dates

Archaeology · Carbonate · Geography · Lime · Lime mortar · Metallurgy · Mineralogy · Mortar · Radiocarbon dating · Archaeology and ancient environmental studies · Building materials and conservation · Cultural Heritage Materials Analysis · Materials Science · Geology · Paleontology

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