Single grains dating of volcanic quartz from pyroclastic flows using Red TL

The potential benefit of red thermoluminescence (RTL) dating of quartz is related to the signal's stability over time scales of 100 ka to 1 Ma. RTL dating has been tested on volcanic quartz grains in a late Pleistocene pyroclastic flow which erupted from the Toya caldera in Hokkaido, Japan. New TL equipment installed with a small X-ray irradiator facilitated using the regenerative dose method for single grain (or aliquot) for RTL dating. A suitable combination of filters and photomultiplier gave effective RTL readouts while eliminating the black body emission of the heating device. Preliminary examination of the output showed that the new equipment provided RTL signals even from single quartz grains. The RTL signal did not show any sensitivity changes after 10 cycles of reproducibility, making it suitable for a construction of a regenerative dose curve for each grain and aliquot, with no correction for sensitivity changes. The ages resulting from the regenerative dose method are in good agreement with that of a multiple aliquot slide method and approximately concordant with ages estimates based on previous geological evidence.