Material
Representative material
The matter how material represents
a particular event determines how it can contribute to an investigation. Any doubt about this point
from the beginning reduces the usefulness of the final analysis result.
However, if no other material is available, even material with some doubt
can be used to set some limits.
Suitable material
Whether the sample material is suited for reconstruction of a time event
(in case of a dating analysis) or a local pattern (in case of a tracer
study) depends also on the knowledge about the uptake and the fixation
of radionuclide in a specific chemical fraction in the sample material. It
will be described for the different sorts of materials analyzed.
Samples for
14C analysis
Sizes of carbon containing materials used for analysis.
The listed sample sizes correspond to an amount of 1 mg carbon after
preparation.
|
Sort of material |
Size [mg] |
Remark |
|
Wood, charcoal |
2 - 5 |
growth interval |
|
Plants, seeds |
2 - 5 |
one year event |
|
Peat |
5 - 10 |
contamination by roots (too young) or reservoir age (too old) |
|
Bone |
30 - 100 |
complicated by retention period (growth) and dietary effects (through marine food) |
|
Shells, foraminiphera |
30 |
possible reservoir age |
|
Pottery - food remains |
2 - 5 |
well-suited |
|
Pottery - matrix |
1000 |
only suited for carbon fractions larger than a few percent |
|
Mortar - charcoal pieces |
2 - 5 |
mortar can be dated with pieces of charcoal (recognized as such) |
Samples for
10Be analysis
Materials used for analysis are sediments, bedrock and meteorites. In
sediments 10Be is assumed to be attached to the outer side of the
grains. In the preparation process this fraction is separated in a leaching
procedure. Sample sizes needed vary from 0.1 gram (deep-sea sediment)
to 1 gram of sediment. In bedrock and meteorites the 10Be is in
the matrix, and requires total dissolution. The sample size needed is about
0.1 g for meteorites and about 10 g for bedrock.
Samples for
26Al,
36Cl analysis
Materials used for analysis are bedrock and meteorites. In bedrock and
meteorites 10Be is in the matrix, and requires total dissolution.
The sample size needed is about 0.1 g for meteorites and about 10 g
for bedrock.