Abstract
At least 14 axial-symmetry ESR lines in Plio-Quaternary enamel fibres were observed by Q-band technique. Some lines follow a 1 T law e.g. the main anisotropic A-line whose g ⊥ = 2.0018 and g ∥ = 1.9977 are close to g eff = 2.0020 and g eff = 1.9975 respectively of the isotropic doublets B- and E-lines. The other lines are blocked below 220K e.g. one isotropic hyperfine ( g = 2.0033, a = 21.6 Gauss) M-septet and one isotropic singlet ( g = 2.0007) D-line. By heating, the M-septet intensity increases up to 250°C and is lost at 280°C; B- and E-lines decrease while a new isotropic ( g = 2.0056) C-line appears. At 300°C, only the two C- and A-lines usually remain and hold up to 400°C. The natural dose rate of fossil enamel is calculated from U-, Th-, K-content and 226 Ra 238 U disequilibrium measured both in enamel and dentine, bones and sediments in contact, by methods of low-background γ-spectrometry, isotopic dilution and fission-tracks mapping. ESR dating of quaternary Proboscidae, Bovidae, Equidae and Cervidae has been attempted by a new comparative method: the A ⊥-line intensity, normalized for the same dose rate and weight, of various fossil dental enamels varies quasi-linearly with the age of the geological sites from which they are issued.
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