Improving archaeomagnetic dating through new data acquisition and method development

Abstract: The Earth’s magnetic field (or geomagnetic field) has been measured for hundreds of years, starting with maritime observations from logbooks for navigation purposes to present day real-time recording by satellites. From these records, the geomagnetic field variation throughout recent time is well-understood. In order to study longer term field variations (on the scale of hundreds to thousands of years), it is necessary to use indirect methods of observation of the geomagnetic field, recovered from lavas and burnt archaeological clays. Reconstructions of the geomagnetic field based on such archaeo-/ palaeomagnetic data can be used both to date certain archaeological and geological materials and to study deep Earth processes where the field is generated. However, the currently available archaeo-/ palaeomagnetic data are not geographically nor chronologically well-distributed. The first aim of this thesis is therefore to provide new archaeomagnetic field determinations from locations that are currently under-represented (either spatially or temporally) in the geomagnetic field records, including southern Africa, New Zealand and the Orkney Isles, UK. New geomagnetic field intensities have been collected from each targeted location and in addition, new geomagnetic field directions from New Zealand have also been produced. Archaeomagnetic dating is challenging in data sparse areas such as these, due to large and often unknown uncertainties of either the data (due to non-ideal formation/ preservation conditions) or the geomagnetic reference curves or both. The second aim of this thesis is to address such problems by introducing alternative methodologies for archaeomagnetic dating, (i) accounting for unknown uncertainties and (ii) using alternative constraints, such as the rate of change of the geomagnetic field to be able to provide chronological information.

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