ESR dating of quartz from Exile hill, Nevada

Quartz crystals from a geological site dated at 13 Myr contain paramagnetic lattice defects produced by exposure to in situ radiation. Two of these defects, both ESR active, contain information about the age of the mineral. From a γ-ray sensitive ESR signal of unknown identity we infer a lower age bound: T ≥ 7 Myr. The superoxide radical (peroxy) defect, produced naturally by α recoil and reproduced artificially by fast-neutron irradiation, gives a compatible age estimate independent of γ dose: T = 8.7 ± 2.6 Myr. (author)