抄録
The red-TL emission from quartz grains was developed for thermoluminescence dating of strata related to fossil bones of Elephas Naumanni on the basis of following reasons ; (1) long-life of the corresponding trapped electrons, (2) the linear TL-response over widely absorbed doses compared with those of blue-TL, and (3) invariable appearance of red colour on TL colour photo-graphs from naturally exposed quartz grains. The quartz fractions were purified by means of water-washing separation, sieving treatment, magnetic separator, and chemical etching treatment with HF-solution, from original soil samples. For the evaluation of paleodose using an additive dose method, some portions of quartz grains were subjected to artificial irradiation with known doses from 60Co source and the induced TL-intensities were measured with a TL-measuring apparatus installed with a red-filter. The paleodose obtained was corrected for fading effects with the sunlight prior to sedimentation. In the estimation of annual dose, a gamma-ray spectrometry was applied to each soil sample to know naturally occurring radioactive quantities including 238U, 232Th, and 40K and respective water content were also considered. The finally evaluated ages (45〜123ka BP) of seven strata were found to be satisfactorily acceptable from other geological informations. The strata related directly to the fossil bones of Elephas Naumani in Kashiwazaki City was dated to be around 100- 120 ka BP.
