Luminescence Dating of Ditch and Pit Fills from the ACS Ltd. Excavation of Lismullin National Monument, Republic of Ireland

Burbidge, C. and Sanderson, D. (2008) Luminescence Dating of Ditch and Pit Fills from the ACS Ltd. Excavation of Lismullin National Monument, Republic of Ireland. Technical Report. Scottish Universities Environmental Research Centre.

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Abstract

This study supports a new investigation into the construction, occupation and utilisation history of the Lismullin 1 site, containing the Lismullin National Monument, on the route of the M3 Clonee-North of Kells Motorway Scheme, Republic of Ireland (section 2). Optically stimulated luminescence (OSL) profiling and age determinations have been made for five sequences of sediments across the site, including sections through three ditches stratigraphically related to the National Monument, and two sequences through periglacial deposits, colluvium, and pit fills thought to represent the earliest archaeology on the site (section 3). The archaeological significance of the age determinations has been reviewed in the light of the luminescence results and the samples’ depositional contexts, to constrain the deposition/formation dates of the sampled sediments (section 6). A total of 26 field profiling (section 5.1), 13 laboratory profiling (section 5.2), and 9 age (section 5.5) determinations were made. Dose rate determinations were made using thick source beta counting, high-resolution gamma spectrometry, field gamma spectrometry, measured water contents and calculated cosmic dose rates (sections 4.2.1 and 5.3). Equivalent dose determinations were made (sections 4.2.3, 5.4) using the OSL signals from sand sized grains of quartz separated from each sample. Laboratory profiling measurements were made using simplified equivalent dose determination procedures on polymineral coarse and hydrofluoric etched sand-sized mineral grains (section 4.2.2). Luminescence profiling indicated variable levels of residual luminescence signal in these sediments (sections 5.1, 5.2), and variations in luminescence sensitivity that were associated with anthropogenic input to the sediments (section 6.1). Dose rates ranged from 2.0 to 2.7 mGy/a, De values from the dating samples ranged from 5.9 to 154 Gy. Age estimates ranged from 2.6 to 72 ka (section 5.5). Uncertainties on the age estimates were commonly around 3% for the younger samples, but up to 17% for the older samples considered to contain residual OSL signals. Two ditches intersecting the site of the Lismullin National Monument were found to have been cut prior to c. 1500BC and filled through the Mid and Late Bronze Age, until at least 600BC±100 (sections 6.4, 7). These results indicate that both ditches are part of the same system rather than pre- and post- dating the National Monument. Field luminescence profiling of a third ditch indicated that it was much more recent. Sediments in a large pit, sealed by upper fills from which an Early Neolithic potsherd was recovered, yielded an OSL date of 8400BC±800. This placed the construction of the pit within the timeframe for human occupation of Ireland, but relatively poor luminescence behaviour indicated that this was likely to be an age overestimate. Similar sediments beneath the pit yielded much higher age values with greater uncertainties that are considered to result from residual geological OSL signals.

Item Type:Research Reports or Papers (Technical Report)
Status:Published
Glasgow Author(s) Enlighten ID:Sanderson, Professor David and Burbidge, Dr Chris
Authors: Burbidge, C., and Sanderson, D.
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
College of Arts > School of Humanities > Archaeology
Publisher:Scottish Universities Environmental Research Centre

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