Analytical Methods:Isotopes
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Contents |
[edit] Stable Isotope Analysis
| Scale | Requires specialist equipment and specialist knowledge for interpretation |
| Questions | Identify and trace soil inputs, study of soil management and cultivation practices, palaeoenvironmental study |
| Samples and storage | |
| Time and cost | |
| General comments | Isotopes of C, N, O, H and Pb have all been used in geoarchaeology |
[edit] Questions
Stable isotopes are non-radioactive, i.e. they do not decay over time. Many chemical elements have more than one isotope, including H, O, C, N, Sr and Pb. As the isotopes have slightly differing weights the relative frequency of the different isotopes can be affected by a range of geological, environmental and biological processes (kinetic fractionation). These differences have been exploited as a means of tracing soil inputs (Wilson et al., 2006), studying past land management practices (Fernandez et al., 2005; Simpson et al., 1999), and providing palaeoclimatic information.
Case studies where stable isotope analysis has been used in archaeology include:
[edit] Samples
[edit] Analysis
For isotope analysis careful sample preparation is required to isolate and concentrate the elements of interest. Sample preparation will usually be carried out by the laboratory responsible for analysis.
Mass spectrometers are used in isotopic analysis, in particular Isotope Ratio Mass Spectrometers are used (IRMS), but also Thermal Ionisation Mass Spectrometers (TIMS). Mass spectrometers use magnetic fields to separate ions according to their mass and electrical charge; this enables the identification of isotopes of elements which have the same charge but different mass.
[edit] Data and interpretation
[edit] References
- Fernandez, F.G., Johnson, K.D., Terry, R.E., Nelson, S., and Webster, D. (2005) Soil resources of the ancient maya at Piedras Negras, Guatemala. Soil Science Society of America Journal, 69, 2020-2032.
- Simpson, I.A., Boll, R., Bull, I.D., Evershed, R.P., Petzke, K.-J. and Dockrill, s. (1999) Interpreting early land management through compound specific stable isotope analyses of archaeological soils. Rapid Communications in Mass Spectrometry, 13, 1315-1319.
- Wilson, C.A., Bacon, J.R., Cresser, M.S., and Davidson, D.A. (2006) Lead isotope ratios as a means of sourcing anthropogenic lead in archaeological soils: a pilot study of an abandoned Shetland croft. Archaeometry, 48, 501-509.
[edit] Related techniques
- Element concentration analysis
- Multi-element concentration analysis
- Radiogenic isotope analysis
- Biomolecules
