NATURAL IRSL INTENSITIES AND APPARENT LUMINESCENCE AGES OF SINGLE FELDSPAR GRAINS EXTRACTED FROM PARTIALLY BLEACHED SEDIMENTS

The single aliquot technique has been applied to single grains of K-feldspar extracted from a well-dated late-glacial marine sediment sample for which standard luminescence dating yielded ages that were in excess of the expected age. Natural infrared-stimulated luminescence (IRSL) intensifies as well as single grain palaeodoses show a wide range of values. Most of the bright grains yield equivalent doses largely in excess of the expected palaeodose, considering the depositional age of the sample. The luminescence emitted by the brightest grains would dominate the signal emitted from aliquots containing many grains. This explains the overestimation of ages obtained using standard luminescence techniques for the sample investigated. Palaeodoses obtained from grains that exhibit low IRSL intensities are close to the expected dose. However, the age derived from these grains is lower than the expected age. Anomalous fading is believed to be the main cause for the age underestimation. This study is the first demonstration of the feasibility of dating a sedimentary event using the luminescence of a single mineral grain.