Radiocarbon dating of pollen by accelerator mass spectrometry
the average or expected time a given atom will survive before undergoing radioactive decay. The calculations involve several steps and include an intermediate value called the "radiocarbon age", which is the age in "radiocarbon years" of the sample: an age quoted in radiocarbon years means that no calibration curve has been used − the calculations for radiocarbon years assume that the , which for more than a decade after Libby's initial work was thought to be 5,568 years.This was revised in the early 1960s to 5,730 years, which meant that many calculated dates in papers published prior to this were incorrect (the error in the half-life is about 3%).In this study, we demonstrate for the first time the radiocarbon dating of pollen concentrate samples by accelerator mass spectrometry.The dates obtained by this method should provide more reliable radiocarbon chronologies for paleo-environmental studies than have been obtainable by bulk sediment dating.Because the time it takes to convert biological materials to fossil fuels is substantially longer than the time it takes for its in the atmosphere, which attained a maximum in 1963 of almost twice what it had been before the testing began.Measurement of radiocarbon was originally done by beta-counting devices, which counted the amount of beta radiation emitted by decaying atoms in the sample and not just the few that happen to decay during the measurements; it can therefore be used with much smaller samples (as small as individual plant seeds), and gives results much more quickly.
AA(Department of Archaeology Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6), AB(Department of Archaeology Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6), AC(Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6), AD(Department of Archaeology Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6), AE(Department of Archaeology Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6) Radiocarbon dating of bulk sediments has been the standard method for establishing chronologies in the studies of lake sediment cores which have contributed significantly to our knowledge of late Quaternary paleo-environments.In 1939, Martin Kamen and Samuel Ruben of the Radiation Laboratory at Berkeley began experiments to determine if any of the elements common in organic matter had isotopes with half-lives long enough to be of value in biomedical research.They synthesized Libby and several collaborators proceeded to experiment with methane collected from sewage works in Baltimore, and after isotopically enriching their samples they were able to demonstrate that they contained radioactive .The development of radiocarbon dating has had a profound impact on archaeology.In addition to permitting more accurate dating within archaeological sites than previous methods, it allows comparison of dates of events across great distances.
Pollen samples from lake sediments required about 4 h of hand picking, whereas samples from marine sediments required about 8 h labor.