• Direct Bone Dating in a Small CO2 Counter

      Berger, Rainer (American Journal of Science, 1983-01-01)
      A small 200ml capacity CO2 proportional counting system has been developed which uses only 100mg of carbon for complete filling. Thus, with respect to the small quantities needed, it compares favorably to dedicated accelerators at significantly lower cost. The performance of this equipment is demonstrated using a variety of samples including some human bone fragments from La Jolla which had been estimated to be 28,000 years old by aspartic acid racemization analysis.
    • Non-Concordance of Radiocarbon and Amino Acid Racemization: Deduced Age Estimates on Human Bone: Implications for the Dating of the Earliest Homo Sapiens in the New World

      Taylor, R. E. (American Journal of Science, 1983-01-01)
      Radiocarbon determinations, employing both decay and direct counting, were obtained on various organic fractions of four human skeletal samples previously assigned ages ranging from 28,000 to 70,000 years on the basis of their D/L aspartic acid racemization values. In all four cases, the 14C values require an order of magnitude reduction in age.
    • Radiocarbon Dating of Fossil Eggshell

      Long, Austin; Hendershott, Richard; Martin, P. S. (American Journal of Science, 1983-01-01)
      Controlled feeding experiments demonstrate that the 14C content of the carbonate fraction of fossil avian eggshell should reliably reflect the 14C activity of feed and contemporary atmospheric CO2 regardless of amounts of 14C depleted scratch injested. Consideration of biochemical pathways and exchange rates across lung membranes leads to the possibility that the carbonate fraction may, in some instances, be slightly 14C depleted. 14C dates on eggshell carbonate should require little or no correction. As with marine shell carbonate, normal soil-forming processes may alter the surficial carbon isotopes in eggshell carbonate. 14C dates on the protein fraction should be even more reliable than those on the carbonate fraction, but only if special precautions or separation techniques exclude non-indigenous carbon from the sample. Original protein contents are likely to be too low for conventional 14C dating techniques.