AMS radiocarbon ages of mammal fossils from lake Nojiriko, Nagano Pref. and environmental changes during the last glacial age

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  • ナウマンゾウ,オオツノシカのAMS<14>^C年代と<13>^C/<12>^C比による最終氷期の気候変動

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Abstract

Giant mammals such as Elephas naumanni and Elephas primigenius inhabited the Japan Island during the last glacial period and it might mean that there was 'LAND BRIDGE' between the Japan Island and continent at the time. So, to clarify the ^<14>C age when they were living in the Japan Island, ^<14>C-dating of the mammals has been done by Accelerator Mass Spectrometry of collagens extracted from the molar tooth and tusk. A extraction method of collagen from 1 to 5g of the molar and tusk samples was examined to obtaine accurate ages for 20 to 50 thausand years old fossils. Both of HCl-soluble collagen and HCL-insoluble gelatin collagen were prepared from each of a single sample by 1.2N HCI demineralization. The HCI-soluble and HCI-insoluble gelatin collagen from the same sample coincide well for respective values of C/N ratio, δ^<13>C and radiocarbon age. The radiocarbon age of well-preserved molar and tusk containing gelatin collagen more than 1% closely coincides with that of wood samples from the same horizon. For the poorly preserved samples containing less than 1% of gelatin collagen, the ^<14>C dating indicates the age youger in several thousands years than the wood samples. The AMS radiocarbon daing has been performed mainly for fossil elephant (Elephas naumanni) excavated from the Upper Pleistocene Nojiri-ko formation, Ngano Prefecture. The ^<14>C ages obtained from the well-preserved samples range from 35,000 to 50,000 years BP. Horn samples of giantic deers containing collagens more than 1% also show the same ^<14>C-ages at those of the fossil elephant from the same horizon.

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