Archaeomagnetic dating sites
Once a stable magnetic direction has been obtained, this is dated by comparing it with the secular variation curve showing changes in the Earth’s field over time (Clark 2007).
The secular variation curve is compiled from direct measurements of the field which extend back to AD1576 in Britain, and, prior to that, from archaeomagnetic measurements from features dated by other methods.
The strengths of archaeomagnetic dating are that it dates fired clay and stone, for example hearths, kilns, ovens and furnaces, which occur frequently on archaeological sites; it dates the last use of features, providing a clear link to human activity; it is cost effective and is potentially most precise in periods where other dating methods, e.g. Archaeomagnetic dating is based on a comparison of the ancient geomagnetic field, as recorded by archaeological materials, with a dated record of changes in the Earth’s field over time in a particular geographical area, referred to as a secular variation curve.
Magnetometers used are sufficiently sensitive for only small samples (c.
The vast majority of UK studies are dating by direction, as intensity dating is not commercially viable at present For archaeological material to be suitable for dating using magnetic direction it must contain sufficient magnetised particles, and an event must have caused these particles to record the Earth’s magnetic field. soils, sediments, clays, contain sufficient magnetic minerals.
There are primarily two types of archaeological events which may result in the Earth’s magnetic at a particular moment being recorded by archaeological material: heating and deposition in air or water.
The method has been shown to provide valuable archaeological information and supplement the suite of chronological tools available.
In addition, the development of archaeomagnetic dating as a method, and the wider understanding of the Earth’s magnetic field, is hindered by the lack of data from Scotland.