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winds. Seven samples were collected from exposed paleosols and one sample was collected
from the base of the dune. Quartz within the 100-200 μm size fraction was dated using the
single aliquot regenerative (SAR) method. The resulting dates cover a period ranging from a few
hundred years to 7,000 years.
Luminescence dating has several advantages over other dating methods. Luminescence
techniques can provide ages for deposits not datable by other geochronometric methods, such as
C-14, since it can be applied directly to sand grains (Berger, 1988). Additionally, the age range
for OSL is approximately 50-800,000 years B.P. (Berger, 1995). For some samples, both quartz
and feldspar have sufficient sensitivity to produce ages as young as one year, but currently there
are no reliable techniques for doing this (Huntley and Lian, 1999).
OSL versus Radiocarbon Dating
Carbon-14 dating is geochronometric technique that is commonly used in coastal
geology. It is based on the beta decay of 14 C atoms produced in the upper atmosphere (Bard,
1998). This method has numerous disadvantages. It is not possible to measure the ratio between
the parent isotope, 14 C and the daughter product, 14 N (Bard, 1998). To be able to calculate a true
calendar age, the initial 14 C/ 12 C ratio of each sample must be known. A calibration is therefore
needed, because the C-14 concentration in the atmosphere has fluctuated over time in response to
variations in cosmic ray intensity, changes in climate, atomic bomb testing and the burning of
fossil fuels (Bard et al., 1990; Stuiver et al., 1991; Bard, 1997). Calibration involves evaluating
past variations of atmospheric 14 C/ 12 C. For the Holocene period (the past 10,000 years) it is
possible to find both living and fossil pines and oaks and compare 14 C levels to tree ring counts
(Bard, 1998). Beyond the Holocene, calibration becomes difficult because there are few living
or fossil trees of that age. Extending the calibration curve beyond 10,000 years can be done by
the high precision U-Th dating of corals (Bard et al., 1990; Bard et al., 1998). Using Carbon-14
dating, it is possible to obtain maximum ages of 45,000 years B.P. However, OSL dating has a
wider range and does not require extensive calibration. An additional advantage of OSL over
radiocarbon is that it can be used in areas where quartz is more abundant than organic or shell
material. This makes it an ideal method for dating deposits in coastal depositional environments.
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