Magnetic moments in the past: Developing archaeomagnetic dating for application in UK archaeology

The applicants have recently collaborated on, and published, research which establishes a methodology for using measurements of the past magnetic field of the Earth for dating archaeological materials in the last 4000 years in the UK. The primary aim of this project is to realise the potential of this research by developing its practical application in UK archaeology.

Building a chronology is the single most important step in the study of the human past and scientific dating is now fundamental to archaeological investigations. Archaeomagnetic dating has great potential: 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, such as radiocarbon dating, are problematic. There is increasing interest in using archaeomagnetic dating as part of the suite of chronological tools available to archaeologists. This is demonstrated by the explicit requirement to consider its use in recent best practice guidance produced for the development-led archaeology sector and by its increasing use in excavations conducted by the commercial archaeological sector (it is estimated that 50-100 archaeomagnetic dates per year are currently commissioned).

However, whilst academic research establishes the scientific basis for the use of the method, it has yet to be adopted routinely. This is partly due to a lack of accessible information allowing evaluation of its suitability in specific archaeological circumstances and partly because there is no coordinated, centralised record of existing archaeomagnetic measurements. This project will address these deficiencies by developing a web-based resource and database which will collate all existing UK archaeomagnetic data and allow the user to address specific questions, such as the expected errors in a particular period, the suitability of specific types of features and the existence of previous studies in the same region or on the same type of feature. Archaeomagnetic dates are produced by comparing measurements of magnetic direction obtained from archaeological materials with a record of geomagnetic field variations built up from archaeomagnetic studies of archaeological features dated by other methods. The proposed project will not only allow users to calibrate magnetic measurements to obtain dates, but it will also allow new data to be incorporated in the geomagnetic field model, thus improving the technique for future use. The latter aspect is particularly important as the technique improves as more data is collected for the calibration record.

The project combines academic research at the University of Bradford with the expertise of English Heritage in developing best practice within the English archaeological sector. The project outcomes will primarily be useful to archaeologists working in both commercial and research settings and to those advising and budgeting for archaeological investigations.