Abstract
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Radiocarbon dating of soils and sediments is notoriously problematic for the purposes of dating a specific
event due to their heterogeneous mix of multiple organic fractions, each of which may have a different
radiocarbon age. Numerous studies have failed to agree on which sedimentary fraction or radiocarbon
pre-treatment method, if any, provides the closest agreement between the age of a sedimentary fraction
and that of associated plant macrofossils or charcoal. We tested the stepped-combustion method of
McGeehin et al. (2001), as well as standard radiocarbon humin and humic extraction techniques, using
samples from a chronologically well-constrained perennially-frozen site at Quartz Creek, Yukon Territory,
Canada. The ages in closest agreement with associated radiocarbon-dated plant macrofossils and with
the overlying Dawson tephra were given by the humic and humin fractions, but even these were still
older than the macrofossil ages by up to 4195 260 radiocarbon years. The low temperature (LT) humin
method recommended by McGeehin et al. (2001) yielded ages older than the macrofossils by up to
nearly 4425 240 radiocarbon years. These fractions, while still providing information on the mobility
and potential residence times of carbon in soils and sediments, should not be relied upon to provide
consistently accurate site chronologies.