A New Approach to Archaeological Dating Using Geomagnetic Field Modelling

Details of the geomagnetic field are recorded in fired archaeological material such as kilns, hearths, pottery, bricks and tiles. As the geomagnetic field varies over time this information can be experimentally recovered and used as a dating tool. Currently in the UK only in situ material can be dated this way as only the directional variations of the magnetic field are known (unlike in many other countries where the full vector is known). Current practise is to use a reference curve constructed from data reduced to a reference location, and to reduce the magnetic data in the same way before comparing with the curve. This is because the geomagnetic field varies spatially as well as temporally. Whilst this works, the change in position introduces errors. We propose to take a different approach to archaeomagnetic dating by producing a geomagnetic field model specifically for the UK. This will mean that directional and intensity information for ANY UK location can be generated and used to date material. The data to be included in the model will come from already existing databases, literature and most importantly new experimental determinations from well dated archaeological material. At present there is minimal intensity data so this will be the focus of experimental work. The microwave method will be used to determine the intensity of the field from dated UK samples supplied by agreed collaborators. The final output will be a dating tool for the UK that will be applicable for all burnt archaeological material. Once established in the UK this type of modelling can then be applied globally.