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In 2003, I wrote a short article about luminescence dating - also called optical dating - for the newsletter of
The Geochemical Society. I used it a basis for this page.
Luminescence dating is an
often used technique in archeology, but is still pretty new in earth science.
Luminescence dating
The Netherlands Centre for Luminescence dating (NCL)
was established on January 1, 2003
and the symposium in celebration of that event took place on March 20, 2003. It included the signing of the
collaboration agreement by representatives of University of Groningen, the Netherlands Institute of Applied
Geoscience TNO - National Geological Survey (TNO-NITG), TU Delft, Utrecht University, the Universiteit van
Amsterdam and the Vrije Universiteit.
In the earth sciences, luminescence dating was still a fairly new technique then (but not in archeology).
It allows geologists to determine when a mineral in sediments was last exposed to light or heat.
There are two varieties: optically stimulated luminescence dating and thermoluminescence dating.
Luminescence dating works for time scales of decades up to a few hundred thousand years.
That makes
it the only technique that can span an entire glacial cycle (i.e., about 100,000 years) and therefore
enables earth scientists to unravel, for instance, the development of glaciation. For comparison:
the limit of 14C dating is about 40,000 years.
Another example of an application of luminescence dating is the reconstruction of coastal evolution
(think of migrating dunes, for example). Finding out how such a landscape developed in the past can help predict how it may
develop in the future. That connects the technique with societal concerns, which helps to get it supported financially.
The method was initially developed in the 1960s for dating pottery. It is based on the facts that 1)
quartz and other minerals such as zircon (pictured as a pebble from Kenya above, next to a quartz crystal from Spain)
in sediments absorb the ionizing radiation that is produced by U, Th and K,
which are also present in those sediments and 2) that this clock is reset by light or heat.
(The radiation frees electrons that are then trapped at lattice defects and light or heat releases them again.)
Illuminating or heating samples elicits luminescence and the amount of produced luminescence is
proportional to the accumulated radiation dose. It's basically also how a dosimeter works.
The web site of English Heritage has extensive information on luminescence dating and other short-term dating techniques:
If you are interested in English heritage, you may want to take a look at a page about
Fort Cumberland in Hampshire.
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