BACKGROUNDIn recent years, a series of important progressions has been made in the study of single-grain technology in optical stimulated luminescence (OSL) dating, which greatly improves the accuracy of dating and provides more space for geological and archaeological dating. A detailed single-grain dating has been carried out in globally important archaeological sites and many new archaeological discoveries have been made. The single-grain OSL technology is developed on the basis of photoluminescence monolithic technology. The single quartz or feldspar grains of the sample are independently tested, and the precise age of the sample is obtained based on the measurement results of a large number of grains, combined with error theory, statistical analysis and geological sedimentation characteristics.

OBJECTIVESTo understand the development process, experimental process and research difficulties of single-grain OSL technology.

METHODSEquivalent dose (D_e) data were obtained by single-grain OSL dating protocol. Error theory and statistical principle were used for D_e value analyzing.

RESULTSSingle-grain OSL dating gets each grain's signal for a sample to determine the D_e value for a sample, rather than the more conventional single-aliquot approach, which each aliquot consists of several 10-1000s of grains. This method was especially beneficial in archaeological contexts where:(1)An individual grain was the smallest fundamental unit for optical dating, providing detailed information on each grain for sample of interest. (2)Individual grains may respond differently even using the same machine under the same measurement conditions, while multi-grain aliquot cannot distinguish the grains suited to SAR procedure and the grains not, resulting that aliquots can be compromised by these ill-suited grains especially when they dominate the OSL signal. (3)Concerning about post-depositional disturbances, beta microdosimetry, possibility of roof spall contamination and non-homogeneous bleaching, these contaminant grains can be recognized by the distribution pattern of single-grain D_e values and be removed prior to age calculation. In order to get the exact D_e, there were 5 rejection and acceptation criteria and 4 age models. Some geological and archaeological samples had over dispersion value (OD) up to 20% or even more than 50% for dark samples. It is important to choose the right rejection and acceptation criteria and age model. This technology can provide new method and necessary support.

CONCLUSIONSSingle-grain OSL technology provided the possibility of precise geological archaeology, especially for samples with D_e dispersion due to insufficient bleaching. By carrying out single-grain OSL dating, choosing the right rejection and acceptation criteria and selecting different age models, a more reliable age can be obtained, avoiding wrong D_e. This method is suitable to establish a chronological framework for many geological and archaeological sites.