IRSL from fine-grained glacifluvial sediment

Samples of suspended sediment were obtained from the Dora di Ferret, a glacifluvial stream in the Italian Alps, over a period of 24 h. IRSL analysis of the sediment indicates that the residual (I-NAT) signal is almost completely zeroed within 3 km of fluvial transport during daylight hours. In contrast, samples collected at night possess environmental doses (D-E) in excess of 100 Gy, probably the luminescence signal of the parent till from which the fine-grained suspended load has been derived. Quaternary deposits of glacifluvial sediment will contain a mixture of daylight and night transported mineral grains, the resulting complex behaviour accounting for difficulties in luminescence dating such materials. Adaptations of single-aliquot protocols and single-grain protocols appear to offer the best chance of dating glacifluvial deposits accurately. (C) 1999 Elsevier Science Ltd. All rights reserved.