INTERCOMPARISONS OF RED TL AND ESR SIGNALS FROM HEATED QUARTZ GRAINS

Red thermoluminescence (TL) and electron-spin-resonance (ESR) measurements were made on identically prepared quartz grains, which had been zeroed by a lava flow of the Gravenoire volcano (Clermont-Ferrand, France) during the last glacial period (Wurm glaciation). Samples from two different sites were studied. The additive technique was used in order to evaluate the palaeodoses and the corresponding dose response curves (DRC), approximating saturating exponentials, were fitted on the basis of DRC obtained with laboratory reset samples. Using this technique of regression, results derived from Al and Ti ESR signals and red TL signals converged better than when only the additive DRC were taken into account in a simple exponential fit. Annealing experiments indicated that the traps involved in red TL, Al and Ti ESR centres had different stabilities vs time and temperature; thus the agreement of the palaeodoses derived from the three signals, within error limits, strengthened confidence in the results for each sample. The ages obtained for the two sites agreed with each other, although the palaeodoses and natural radiation dose rates were significantly different: 62.2 +/- 9.0 and 61.3 +/- 9.0 ka.