THERMOLUMINESCENCE IN SUSPENDED SEDIMENT OF GLACIER MELTWATER STREAMS

To determine the factors controlling natural levels of thermoluminescence (NTL) of fluvioglacially transported suspended sediment, samples were taken at hourly intervals from a meltwater stream emanating from Solheimajokull in southern Iceland. The NTL of the samples were measured and compared with fluctuations in suspended-sediment load and in flow depth of the stream. It was found that the ratio of the 325-degrees-C and the 375-degrees-C regions of the NTL spectrum was more closely related to sediment load and flow depth than were the individual regions themselves. Analysis of the patterns suggests that NTL fluctuations are related to changes over time in the sources of sediment entrained by the stream. It is inferred that these changes relate to diurnal temperature cycles plus precipitation events. Such fluctuations raise doubts as to the validity of bulk sampling procedures in TL dating of Quaternary fluvioglacial sediments.