Single aliquot regenerative dose method for ESR dating using X-ray irradiation and preheat

Abstract

Equivalent dose (De) estimations in electron spin resonance (ESR) dating have mostly been done by the multiple aliquot additive dose (MAAD) method despite disadvantages. In this study, we used X-ray irradiations and applied the single aliquot regenerative dose (SAR) technique to ESR De measurements of a volcanic quartz with independent age control. As the SAR protocol involves multiple steps of irradiations and readouts during a short period of time using a single aliquot, the thermal stabilities of the Al and Ti centres from natural and X-ray irradiated aliquots were compared by a pulse annealing test. The thermal stability of natural and regenerated ESR signals is significantly different for both Al and Ti centres and preheats are therefore considered necessary after artificial irradiations. The X-ray dose rate for quartz was calibrated using the same sample which was heated and irradiated with a known gamma dose. The SAR De values using the natural sample were obtained by means of a preheat plateau test. To check and correct for possible sensitivity change induced by the annealing used to reset the natural ESR signals, the single aliquot regeneration and added dose (SARA) method was applied. The SARA De values for the Al and Ti centres were in agreement, however, this De value overestimated the expected De from the independent age control, possibly because our sample was too old for the SARA method.