ASSESSING THE ACCURACY OF THERMOLUMINESCENCE FOR DATING BAKED SEDIMENTS BENEATH LATE QUATERNARY LAVA FLOWS, SNAKE RIVER PLAIN, IDAHO

Baked sediments beneath lava flows on the Snake River Plain, Idaho, wi th independent age control by either C-14 or K/Ar dating were analyzed to evaluate the accuracy of the thermoluminescence (TL) technique. Th e age of flows ranges from approximately 2 to 100 ka and multiple TL a nalyses by the total bleach method yielded ages that overlap at one si gma with independent chronologic control. The TL signal of one sample of baked sediment beneath a lava flow with an inferred age of at least 641 +/- 54 ka was near saturation, perhaps reflecting a relatively hi gh environmental dose rate, and is not datable by TL. This study under scores several major limitations of luminescence geochronology, the na tural spatial and temporal variability in environmental radioactivity and the susceptibility of silicate minerals to the growth and retentio n of a luminescence signal. Despite these limitations, the results dem onstrate the utility of luminescence geochronology to date volcanic er uptive events during the Quaternary.