Luminescence Dating of Sediments from Droughduil Mound, Dunragit

This report presents details of the application of Optically Stimulated Luminescence (OSL) dating sediments from Droughduil mound, Dunragit. OSL dating operates by measuring the intensity of luminescence signals which are induced by long term exposure of minerals such as quartz to ionising radiation in the environment. OSL signals are bleached by exposure to daylight, and build up while the sample is enclosed in the archaeological monument. Providing the sample has been reset at time of deposition, the combination of OSL measurements of the radiation dose received and assessment of the environmental radioactivity of the sample and its context can be used to date depositional events. A series of samples were collected from Droughduil mound during a site visit on 29th August 2002. A total of eleven dating samples were collected from exposured sections using plastic tubing, and accompanied by in-situ measurements of the local gamma radiation fields of the site were used for dating measurements. Bulk samples were also collected for the purpose of laboratory gamma spectrometry . The quartz single-aliquot regenerative OSL dating procedure was applied successfully to all eleven samples. Radiation dosimetry combined field gamma spectrometry, thick source beta counting and high resolution gamma spectrometry. In all cases it was possible to use the OSL data to determine equivalent doses for the samples. A stratified sequence of dates were obtained from the base of the mound, indicating past land use stretching back to the mid 3rd millenium BC. Material collected from contexts thought to predate the cairn construction on the site, and others thought to post-date the cairn collapse, suggest construction and use of the cairn in the mid-late 2nd millenium BC