Equivalent thermal history (HE)(HE) of ferruginous sandstones based on the thermal activation characteristics of quartz

The thermal history of four quartz-rich ochre samples from an Upper Palaeolithic site was studied. This work is based on the changes in thermal activation characteristics (TAC) of the 110∘C TL peak of the quartz inclusions. An isothermal study of a previously unheated sample has highlighted the importance of the duration of annealing on the sensitization of quartz. In fact, the sensitivity change as a function of the duration of annealing is not monotonic. For that reason it seems necessary to consider the “equivalent thermal history” HEHE rather than an “equivalent temperature”. Isochronal annealing experiments demonstrate that the initial rise of sensitization overestimates the true HEHE by about 100∘C. Using a geological sample we have thus developed an empirical approach which allows the true HEHE of artifacts to be determined. Reheating of ochre originally heated in antiquity results in desensitization of the TAC.