VARIATION OF U-MICRODISTRIBUTION IN FOSSIL HIPPARION TEETH AS A COMPLICATING FACTOR IN DATING STUDIES

Five Upper Miocene fossil Hipparion molars were studied for U-distribution by Fission Track. U-uptake has reached the whole mass of the teeth and no saturation fronts seem to occur in the interior layers. Mean U-concentration in dentine, cement and enamel was 157, 139 and 78 ppm, respectively. U(enamel)/U(dentine) almost-equal-to 0.5 is considerably higher than 0.1 reported in the past for Upper-Quaternary mammoth teeth. These features are disadvantageous for ESR-dating in Hipparion enamel, although a long-lived signal (g = 2.0018) is apparent. Leaching phenomena occur in the outer regions of these teeth. Inner enamel folding seems to have hindered a more uniform U- distribution in the teeth.