Radiocarbon Dating of Lime Mortar

Autor: Daugbjerg, Thomas Schrøder
Jazyk: angličtina
Rok vydání: 2021
Předmět:
Zdroj: Daugbjerg, T S 2021, Radiocarbon Dating of Lime Mortar . Aarhus Universitet .
Popis: Radiocarbon dating of lime mortar is a chronological method for dating the time of hardening of a mortar sample, or other lime based materials such as lime plaster. Jerash is one of several well-known ancient cities in northern Jordan, and most of its archaeological remains are from the Roman era to the early Islamic period. Mortar dating can contribute with chronologies to the archaeological research in Jerash. However, previous attempts at mortar dating in Jerash met serious challenges. For example a strong contamination of limestone grains in the sand used to produce mortar, which often make results inconclusive. This thesis picks up the methodological challenge of mortar dating in Jerash, and it divides the challenge into the following issues: sampling strategy, characterization, pretreatment, preparation and Jerash chronology.Mortar dating literature has many examples of samples with complications that hinder conclusive results. This thesis reviews environmental processes causing complications, and presents important sampling strategies to avoid them. Characterization methods give information on mortar samples' constituents and possible contaminations. This thesis experiments with different methods of characterization, and finds that characterization can be an effective quality control. Pretreatment methods involve mechanical processes to separate datable material from possible contaminants. This thesis experiments with several pretreatments, and finds that conclusive dating of Jerash samples is not associated with a single pretreatment method or grain size window. Instead, this thesis emphasises characterization as a quality control for iterative pretreatment. Preparation extracts CO2 for radiocarbon dating from pretreated material. This thesis finds that stepwise injection produces significantly more conclusive Jerash mortar dates than the other investigated preparation methods. This thesis' improved methodology produces 18 conclusive dates for Jerash plaster samples. Compared to previous charcoal dating in Jerash, mortar dating has a more secure sample context, and in the produced chronologies there are coinciding plaster dates indicating events with construction or renovation.This project finds several improvements for Jerash mortar dating compared to previous work. Using the sampling strategies, this project finds only 1 complication in 18 Jerash mortar dates. With preparation by stepwise injection, the rate of conclusive to attempted dates is ≈60%. For pretreated powders characterized free of geological carbonates with cathodoluminescence, the rate of conclusive to attempted dates is ≈86%. Coinciding plaster dates in Jerash chronologies represent an improvement toward dating distinct events, compared to extended periods of human activity by charcoal. Furthermore, the proposed methodologies are critically evaluated with known age samples, and for stepwise injection 5 out 5 conclusive dates compare accurately with their expected ages.
Databáze: OpenAIRE
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