Luminescence Dating in Fluvial Settings: Overcoming the Challenge of Partial Bleaching

Optically stimulated luminescence (OSL) dating is a versatile technique that utilises the two most ubiquitous minerals on Earth (quartz or K-feldspar) for constraining the timing of sediment deposition. It has provided accurate ages in agreement with independent age control in many fluvial settings, but is often characterised by partial bleaching of individual grains. Partial bleaching can occur where sunlight exposure is limited and so only a portion of the grains in the sample was exposed to sunlight prior to burial, especially in sediment-laden, turbulent or deep water columns. OSL analysis on multiple grains can provide accurate ages for partially bleached sediments where the OSL signal intensity is dominated by a single brighter grain, but will overestimate the age where the OSL signal intensity is equally as bright (often typical of K-feldspar) or as dim (sometimes typical of quartz). In such settings, it is important to identify partial bleaching and the minimum dose population, preferably by analysing single grains, and applying the appropriate statistical age model to the dose population obtained for each sample. To determine accurate OSL ages using these age models, it is important to quantify the amount of scatter (or overdispersion) in the well-bleached part of the partially bleached dose distribution, which can vary between sediment samples depending upon the bedrock sources and transport histories of grains. Here, we discuss how the effects of partial bleaching can be easily identified and overcome to determine accurate ages. This discussion will therefore focus entirely on the burial dose determination for OSL dating, rather than the dose-rate, as only the burial doses are impacted by the effects of partial bleaching

Provenance of archaeological limestone with EPR spectroscopy: The case of the Cypriote-type statuettes

The present work demonstrates the potential of EPR spectroscopy as a useful technique in provenance investigation of archaeological finds of limestone. The case of the small, Cypriote-type limestone statuettes found in most major Archaic sanctuaries of the Eastern Mediterranean is used as an illustrative application. Ancient and modern limestone quarries of Cyprus, Samos, Rhodes and Egypt were sampled in order to form a reference data bank for the likely places of origin. Samples were also taken from statuettes exhibited in the archaeological museums of Nicosia (2 samples), Samos (14 samples) and Copenhagen (National Archaeological Museum, 19 samples). All quarry and archaeological samples were analysed with EPR spectroscopy. The quarry samples from Rhodes were easily distinguished from the other quarry samples and were not treated further because they produce material of low quality and compactness. A detailed study of the EPR spectroscopy results leads to the determination of a number of parameters, which separate the reference group of Samos from those of Cyprus and Egypt. The structure of the EPR spectra in the region around g=2.0000 is characteristic for these different quarrying areas. Diagrams where each quarry area is represented by a field were drawn and the archaeological samples were plotted on them. All the analysed statuettes (except for one, which is most probably of Samian limestone) appear to be carved in Cypriote limestone. Consequently, the results of this research offer a decisive argument in favour of the Cypriote origin for statuettes of this type found in the Aegean. © 2004 Elsevier Ltd. All rights reserved