Drumclay

: a tree-ring dated narrative for an Irish crannog

Abstract

Tree-ring chronologies provide unparalleled resolution for archaeological sites. Dendrochronology can give an exact calendrical date, and in Britain and Ireland this is largely confined to oaks and pines. Other species such as black alder (Alnus glutinosa (L.) Gaertn.) are often preserved in waterlogged conditions, but are less commonly used to construct chronologies. Alder is a short-lived species with a growth pattern that is highly susceptible to local environmental factors. For this reason it is not suitable for traditional dendrochronology. Tree-ring analysis of alder assemblages can, however, produce valuable relative chronologies that can be anchored to a timeline using 14C dating and wiggle-match age-modelling. This project aims to establish if tree-ring analysis of alder samples from an early medieval crannog (Drumclay, Co. Fermanagh) could be used to develop an annually resolved narrative of site construction, occupation and abandonment, and to shed light on early medieval settlement in Ireland more generally. Visual and statistical cross-correlation of multiple radii from 834 samples was undertaken to construct tree-ring sequences from individual trees, contexts and features, culminating in a master alder chronology spanning 116 years. The results demonstrate that a robust annual chronology can be created from alder samples providing that a large assemblage exists that can withstand the rejection of spurious ring patterns arising from sample-specific issues. Identification of the AD 774/775 14C anomaly within the sequence has anchored the relative chronology to a yearly calendrical timeline. The chronology reveals that the site was first constructed in AD 811 and allows the subsequent expansion and development of the site to be tracked on a year-by-year basis over a 30-year period. Significantly, the precision of the alder chronology has enabled a comparison of the narrative of this site with both historical and environmental records at an annual resolution. The alder chronology highlights the rapid replacement of dwellings at 1-10 year intervals at Drumclay, which has implications for estimates of structure and site longevity at other early medieval sites in Ireland. The chronology also enables validation and refinement of previously proposed chronologies for a range of artefact typologies. An oak chronology for the upper levels of the site reveals that the transition from round to rectangular houses at Drumclay occurred in the later 10th century. The study demonstrates the feasibility of constructing a refined chronology for wetland sites using short-lived trees, and shows how tree-ring analysis can provide more comprehensive insights into early medieval settlement.

Thesis is embargoed until 31 July 2027.

Date of Award	Jul 2024
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Northern Ireland Department for the Economy
Supervisor	Gill Plunkett (Supervisor), Colm Donnelly (Supervisor) & David Brown (Supervisor)