ESR dating of ancient flints

Natural radioactivity can produce measurable amounts of radiation damage in rocks and glasses, and the gradual accumulation of this damage with time provides a built in ‘clock’ that can be used as a dating tool for geology and archaeology. Although a studied technique for estimating this damage involves measurements of stored thermoluminescent (TL) activity1–4, several authors have reported the direct observation of natural radiation damage by ESR5–7. We describe here ESR measurements on a damage signal which we have found to be present without exception in a wide variety of natural flints. The point defect responsible for the signal is identified and the samples are calibrated with an artificial damage simulation. Preliminary age determinations are presented for several natural flints. Flint artefacts heated in antiquity will have their clock ‘reset’ to zero, and measurements on one sample suggest that the ESR technique may have applications in the study of early cultures.