OPTICAL AND TL DATING ON GLACIOFLUVIAL SEDIMENTS

Three glaciofluvial sediment samples from the Yukki area near Leningrad were studied in order to compare and combine results from optical and thermoluminescence (TL) dating. The formation of the sediments can be related to the end of the last deglaciation of the area and thus the age is around 13 ka. Two of the samples were collected from a kame ridge, where a rapid sedimentation process and consequently poor bleaching of the sediments can be assumed, and one sample was collected from a terrace with slower sedimentation. Poor TL plateaux reflect this situation and TL dating of the samples was not fruitful. The result from optical dating of the kame samples led to ages that were far too high, but for the terrace sample the optical age of 16 ka is quite realistic. It is proposed that when optical dating of rapidly accumulated glaciofluvial sediments is attempted, TL plateau tests should be used to estimate whether the duration of bleaching at deposition had been adequate to achieve a sufficiently low residual signal.