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Sedimentologic Context for Luminescence Dating
 There
are a variety of sediments that have been and can be dated by luminescence.
The selection and sampling of sediment is the first and crucial step in the
luminescence analysis. A luminescence age is a measure of the time since the
last sunlight exposure (or heating) event of the sediment. The reduction in
luminescence, usually by sunlight, must be related to a significant environmental
event (e.g. fault-generated colluvium, dune migration) for a luminescence age
to be meaningful. The luminescence dating of sediment that was exposed to little
or no light during a specific event will yield a spurious age.
 The preferred sediment for OSL dating has had > 1 hr sunlight exposure,
accumulated as relatively homogeneous stratigraphic unit, >30 cm thick and
has not undergone significant water-content variations or diagenetic changes
during burial. Selection of preferred sediment for a stratigraphic setting
often requires a sedimentary facies analysis that considers efficiency of solar
resetting of luminescence and bedding architecture with deposition. In many
sedimentary environments, particularly eolian and littoral, coarse-grained
(100-300 µm) quartz grains is preferred for dating; it is an abundant particle
size that is well solar reset. In other sedimentary settings the fine-grained
(4-11 µm) polymineral or quartz fraction is amenable for dating, particularly
for loess, colluvial, eusturine, and many lacustrine and fluvial environments.
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