The first archaeointensity records from New Zealand: evidence for a fifteenth century AD archaeomagnetic ‘spike’ in the SW Pacific Region?

Abstract

AbstractHangi stones, used to retain heat in traditional Maori earth ovens (hangi), may carry records of Earth's magnetic field when they were last used. Sixteen archaeological features, including 12 hangi, from eight sites were sampled and their palaeomagnetic data used to construct the first archaeointensity record for New Zealand, covering the past 700 years. A combination of radiocarbon dating of associated charcoal and archaeomagnetic dating of palaeomagnetic directions was used to obtain a ‘preferred’ date of each palaeointensity. A plot of virtual axial dipole moment (VADM) for the SW Pacific region outlines steady VADM values of about 8 × 1022 A m2 from 1000 to 1300 AD and 9.5 × 1022 A m2 from 1500 AD to the present, with a sharp peak in the early fifteenth century when the VADM reached about 13 × 1022 A m2. This peak bears many similarities to archaeomagnetic ‘jerks’ and ‘spikes’ in Northern Hemisphere records from the first millennia BC and AD. However, it is the first such feature to be found in the Southern Hemisphere at this date, suggesting, in accordance with recent modelling, that it may be a feature of the non-dipole field, associated with rapid growth and decay of an intense flux patch on the core–mantle boundary.