Exploratory Single Grain OSL Analysis of Sediments from Capu di Locu, Corsica

Single grain optically stimulated luminescence (OSL) measurements have been conducted on retained material from sediment samples collected during excavations of Neolithic monuments at Capu di Locu, Belvédère, SW Corsica. One sample was taken from a presumed burial chamber at Tola and two from the lower fill of the construction pit of a menhir at Stantare. Analysis was conducted on 150-250 µm quartz grains previously separated for single aliquot regeneration (SAR) measurements, and on 250-500 µm grains prepared for this analysis. Single grain measurements, including analysis of blank discs prior to dispensing mineral grains, were conducting on a Risø DA-20 automatic reader, with 800-1000 grains measured for each of two samples, and approximately 350 grains for the third sample. These exploratory measurements have demonstrated that a relatively large proportion (>20%) of mineral grains produce significant OSL counts for both the natural stored dose and following a 25 Gy artificial dose. Previous analysis of these samples using multi-grain aliquots measured using a single aliquot regeneration (SAR) protocol had shown broad dose distributions, with mixtures of aliquots of different ages. The single grain measurements have confirmed that these are mixed age deposits. Two samples show stored dose distributions around mean values which correspond to archaeological ages, for the third the stored dose distribution is significantly broader with no apparent archaeological age component. Further statistical analysis of these data would be required to attempt to resolve archaeological age material, that could potentially be used to further constrain construction dates for these monuments. It is expected that similar luminescence properties would be exhibited by mineral grains from other samples collected during the excavations of these sites, and it is possible that further single grain OSL analysis of other parts of the site may produce dose distributions with less mixing and more readily resolved components with archaeological ages. Meanwhile SG apparent ages were obtained from the Tola sample which are consistent with previous estimates, and two new estimates have been achieved from the Stantare site which indicate potential for recovering archaeological ages in the 3rd to 4th millennium BC from the Menhir site

Luminescence dating of wind-blown sands from the Broo Peninsula, Shetland

This report provides a temporal framework to support University of Stirling geo-archaeological investigations near Huesbreck, Broo Pennisula (Shetland), examining how the early modern population there, adapted to harsh climate conditions in the 18-19th centuries, when enhanced aeolian activity led to an influx of sand to the area, leading to adaption’s in farming practices, and abandonment of several sites. Five sediment samples were submitted to the luminescence laboratories at SUERC for dating. All samples were subjected to laboratory preparation of sand-sized quartz, and purity checked using scanning electron microscopy. Dose rates for the bulk sediment were evaluated using analyses of the uranium, thorium and potassium concentrations obtained by high resolution gamma spectrometry coupled with beta dose rate measurement using thick source beta counting, and in situ field gamma spectroscopy. Equivalent doses were determined by OSL from 32 aliquots of quartz per sample using the quartz single-aliquot-regenerative (SAR) procedure. The material exhibited good OSL sensitivity and produced acceptable SAR internal quality control performance. Radial plotting methods revealed good internal homogeneity in the dose distributions obtained for each sample. The chronology established for the sampled sands on the site spans from the mid 16th century (AD 1540 ± 40; SUTL2441) through to the early 19th century (AD 1810 ± 25), with the dates falling within three clusters - the waning stages of the Little Ice Age, the mid 18th century (AD 1730 ± 25 to 1760 ± 25) and the early 19th century (AD 1810 ± 25). In the wider region, periods of sand movement and deposition in the mid 18th century, and early to late 18th century, are documented in sediment statigraphies sectioned at the Old Scatness Broch, Scatness