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Abstract:
In order to test the accuracy of quartz optically stimulated
luminescence (OSL) dating for young dune sediments (<100 a), a series of
aerial images of a migrating sand dune is used to cross validate OSL
ages. The investigated dune is situated on the northern part of the
island of Sylt (southern North Sea). Based on aerial images and a map
from 1925 to 2009 and the internal architecture of the dune obtained by
ground-penetrating radar (GPR), an independent age model has been
developed to attribute sedimentary-architectural elements of the dune to
time. The annual rate of dune migration is calculated to be around 4.1
m/a. Along a 245 m transect oriented parallel to the direction of dune
movement, 13 samples for OSL dating were collected at equidistant
locations. Sand-sized quartz (150-250 mu m) was used for determining the
equivalent dose (D-e) applying a single-aliquot regenerative-dose (SAR)
protocol. Results show that the oldest OSL age from the investigated
recent dune appeared to be 110 +/- 10 a, whereas the modern analogue was
dated to 34 +/- 3 a. In comparison with the aerial images, the OSL ages
show a systematic overestimation of 10-40 a for six out of seven younger
samples, which are expected to be younger than similar to 60 a. This
offset is negligible for older samples, but a substantial error in these
younger ages. The overestimation is originated from a combination of
small thermal transfer of 4 -12 mGy during preheat and incomplete
bleaching in medium OSL component causing a residual dose of about 15
mGy. The contribution of the incompletely bleached medium component
cannot be removed totally by an early background subtraction approach.
Despite the observed offset for youngest samples, this study
corroborates the suitability of the OSL technique to date young dune
sediments (<100 a). (c) 2012 Elsevier B.V. All rights reserved.
