Animal, Vegetable or Mineral? Characterising shell-lime, maerl-lime and limestone-lime mortar evidence from the Late Norse and Medieval site of Tuquoy, Orkney

Author(s): Mark Thacker, John Hughes, Nic Odling3
Paper category: Proceedings
Book title: Proceedings of the 5th Historic Mortars Conference
Editor(s): José Ignacio Álvarez, José María Fernández, Íńigo Navarro, Adrián Durán, Rafael Sirera
ISBN: 978-2-35158-221-3
e-ISBN: 978-2-35158-222-0
Publisher: RILEM Publications SARL
Publication year: 2019
Pages: 758-777
Total Pages: 20
Language : English

Abstract: Recent examination of an extensive curated assemblage of mortar samples, recovered from
the Late Norse and Medieval site of Tuquoy (Orkney) during excavation in the 1980s,
suggested the collection was associated with distinct groups of compositionally contrasting
materials related to discrete constructional events. Subsequent petrographic analysis
supported this early interpretation and presented evidence for a remarkable series of phase-
specific mortars, bound with a range of different biogenic and geogenic lime source
materials - including marine shell, coralline algae (maerl) and limestone. Wider landscape
survey highlighted the broad range of exposed calcareous materials in the coastal and
sedimentary environments dominating the Northern Isles of Scotland today, and that many
of these different potential lime sources were exploited by craftspeople at different times in
the Medieval and later period is now clear.
Given the high significance of the Tuquoy mortar study for our understanding of the
development of this culturally important site, and as a prelude to more general publication
of the wider archaeological project, a further investigation of selected samples from the
mortar assemblage is now being undertaken through a range of geoscientific techniques.
This paper presents emerging evidence from a comparative petrographic, SEM-EDS and XRD
study designed to further characterise these various mortar materials, and challenge those
previous interpretations of contrasting building lime sources. Like most environmental
archaeological investigations, this study is essentially concerned with interpreting the
depositional histories of surviving materials, but with a particular focus on establishing the
distinction between (anthropogenic) kiln relict and (natural) added temper mixtures when
both contain biogenic and geogenic clasts.

Online publication : 2019
Publication type : full_text
Public price (Euros) : 0.00

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