Geoscience Reference
In-Depth Information
Table 17.6
Causes and consequences of luminescence dating challenges.
Potential
difficulty
Physical explanation
Environmental context
Consequence
Possible solution
Signal
saturation
Geologically stable
electron traps fill up
Sample is buried for a
very long period of
timeorthedoserateis
particularly high
Possible to obtain a
minimum age
Application of new
techniques such as
isothermal TL may
extend the datable
burial age limit of
some sediments
Incomplete
bleaching
Some electrons remain
trappedevenaftera
bleaching event
Sediment is
insufficiently exposed
to light during
transport
Residual dose remains
and
D
e
is
overestimated.
Differential exposure
of grains results in a
wide distribution of
D
e
values
Signal distribution
analysis allows
identification of the
problem. In most
cases single grain
dating and the use of
age models enables
the correct burial age
to be determined
Post-
depositional
mixing
Biotic activity within the
sediment mixes grains
from chronologically
distinct depositional
events
Wide (and often skewed)
D
e
distributions
The use of single grain
dating, mixture
modelling and
Bayesian statistics
may enable the
identification of
depositional events,
even when mixed
Signal
instability
Electrons 'leak' from
traps. Some traps
(responsible for a part
of the luminescence
signal) are more prone
to this happening than
others
Dependent on specific
properties of the
quartz or feldspar
grains
Incorrect age
A stable part of the
signal can be isolated
and measured using a
number of techniques
Dose rate
change over
time
The level of ionising
radiation is not
constant over time
Disequilibrium may
occur between the
parent and daughter
isotopes where one or
the other is removed
from the system.
Ingrowth of duricrete
material during burial
will also change the
dose rate
Incorrect age
Disequilibrium can be
measured and
corrected for in young
sediments. In older
sediments,
equilibrium may have
been reestablished
and past
disequilibrium will
remain undetected
Beta
heterogeneity
The level of ionising
radiation is not
spatially constant
within the sample
Hot spots and buffer
zones may occur
within the sediment
matrix, causing some
grains to receive
disproportionately
more radiative dose
during the burial
history than others
Wide (and often skewed)
D
e
distributions.
Difficult to
differentiate from
bioturbation
Using particular age
models, a good
estimate of burial age
can be obtained.
Errors will be larger
