Back to basics: Qualitative spectral analysis as an investigatory tool, using calcite as a case study

The Interlab Comparison Project reported at the last meeting of this symposium illustrated a major difficulty in using ESR for dating in archaeology and geology. Different laboratories obtained varying (in some cases widely varying) accumulated environmental doses (De) for the same material. Given the range of factors which may affect De, a simple quick means of identifying crucial factors affecting De is essential in order to target research effectively. Qualitative visual analysis of the ESR spectrum provides such a tool. The complex ESR spectrum is considered in the first instance as the superposition of a number of independent peaks. The changing shape of the spectrum under different conditions can be described in terms of varying contributions of the contributing peaks. This paper outlines the necessary concepts and presents a straightforward procedure by which constituent peaks and their relevant properties may be identified with minimal effort. This enables appropriate methods to be selected which will enhance the dating peak relative to other interfering peaks, reducing systematic bias in the estimate of De. Speleothem calcite is used as a case study to demonstrate the effectiveness of this pragmatic approach. The concepts and procedures should be equally valuable when examining the ESR dating potential of other materials.