UNDERWATER BLEACHING OF SIGNALS FROM SEDIMENT GRAINS - NEW EXPERIMENTAL-DATA

The results of an underwater bleaching experiment are reported. The pu rpose of the experiment was to evaluate the degree to which thermolumi nescence (TL) and optically stimulated luminescence (OSL) signals are reduced by a three hour exposure to light at different water depths. S amples of quartz and feldspar separates were annealed in the laborator y and then given fixed doses of laboratory beta radiation before expos ure. The results indicate that a three hour light exposure is sufficie nt to zero the optical signals down to water depths of 10 m for feldsp ar infra-red stimulated luminescence and 12-14 m for quartz OSL. The T L results for the same quartz and feldspar samples exhibit some bleach ing effects, with TL signals at 14 m water depth being reduced to 50-6 5% of the initial value. Scatter of the TL results limits their interp retation.