Characterization of the burning conditions of archaeological pebbles using the thermal sensitization of the 110 °C TL peak of quartz

Abstract

The 110 °C TL glow peak of quartz has been used in dating and retrospective dosimetry due to the pre-dose effect and the sensitivity changes caused by heating. One of the main difficulties related to TL dating is the sureness that the geological signal was completely zeroed by firing. In this study, the sensitivity change of the 110 °C peak and the EPR signal intensity of the E1′ center were combined to account for the burning status of archaeological pebbles. For this, a quartz pebble was sawn into many pieces and each piece was heat-treated at different temperatures from 200 to 800 °C. Powdered aliquots were γ-irradiated and stored into an ice-bath before the TL readout. Peak-maximum temperature, TL intensity and activation energy of the 110 °C peak were determined by glow curve deconvolution methods. The thermal activation characteristic obtained in this study showed a peak maximum at 500 °C and a sensitization ratio higher than 200. The heating temperature also affected the intensity of the E1′ center. The usefulness of the burning pattern was tested by measuring the TL and EPR signals of several archaeological pebbles, initially classified as “burnt”, “unburnt” or “unidentified”, and also from two specimens burnt in a campfire. The main achievement of this study was the possibility to infer the temperature in which a pebble was heated in the past independent of visual signs.