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OSL Dating of Earthen Mortars from a Medieval Building in Northwestern Spain: Crypt of Basílica da AscensiÓn (Allariz, Ourense)

Published online by Cambridge University Press:  04 August 2020

Jorge Sanjurjo-Sánchez*
Affiliation:
University Institute of Geology, University of A Coruña, ESCI, Campus de Elviña, 15071A Coruña, Spain
Rebeca Blanco-Rotea
Affiliation:
Santiago de Compostela University, Facultade de Xeografía e Historia, 15782Santiago de Compostela, Spain
Marco V García-Quintela
Affiliation:
Santiago de Compostela University, Facultade de Xeografía e Historia, 15782Santiago de Compostela, Spain
Christopher Ian Burbidge
Affiliation:
Environmental Protection Agency of Ireland, Dublin, Ireland
*
*Corresponding author. Email: jorge.sanjurjo.sanchez@udc.es.

Abstract

There are few papers that focus on optically stimulated luminescence (OSL) dating of earthen mortars. These mortars are abundant in historical buildings in northwestern Spain. The Basílica da AscensiónyForno da Santa building is an unfinished church built on a previous structure that was transformed into a crypt (Allariz, Ourense, NW Spain). Previous archaeological studies established a sequence of phases of construction, the first dating back to the Iron Age, with significant changes occurring in the Early and Late Medieval ages. The only datable material in the crypt is earthen mortar. Thus, eight mortar samples (seven joint mortars and one wall infill) were taken, seven of them dated by OSL. The dose rate was assessed, and the expected equivalent doses estimated based on the established archaeological age. Several grain sizes (from fine to coarse) were used in small multigrain aliquots to assess the equivalent doses and ages. No evidence of partial bleaching was observed in most samples and grain sizes. The resulting ages are younger than expected for most samples. This is explained by the fact that joints were repaired with new mortar from the 16th century onwards.

Type
Research Article
Copyright
© 2020 by the Arizona Board of Regents on behalf of the University of Arizona

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Footnotes

Selected Papers from the Mortar Dating International Meeting, Pessac, France, 25–27 Oct. 2018

References

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