Geomagnetic Field Variations in the Past: New Data, Applications and Recent Advances
In the last decades, palaeomagnetic research has provided important information about the past variation of the Earth's magnetic field (EMF) from its origin to the present day. However, questions regarding the origin and evolution of the EMF as well as the frequency and spatial distribution of its variations still remain open to debate. This Special Publication provides new insights into the study of the temporal and spatial evolution of the EMF presenting new data from palaeomagnetic and rock magnetic studies of archaeological materials, sediments and lavas. The papers presented cover a wide range of topics related to archaeology, stratigraphy and climate, including new data from several parts of the world, such as Europe, Africa, Australia, New Zealand, India and the Baltic Sea. This Special Publication aims to present an overview of the most recent secular variation studies and their use to disclose fundamental properties of the EMF evolution.
The first archaeointensity records from New Zealand: evidence for a fifteenth century AD archaeomagnetic ‘spike’ in the SW Pacific Region?
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Published:September 23, 2020
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CiteCitation
Gillian M. Turner, Rimpy Kinger, Bruce McFadgen, Monique Gevers, 2020. "The first archaeointensity records from New Zealand: evidence for a fifteenth century AD archaeomagnetic ‘spike’ in the SW Pacific Region?", Geomagnetic Field Variations in the Past: New Data, Applications and Recent Advances, E. Tema, A. Di Chiara, E. Herrero-Bervera
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Abstract
Hangi 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.
- absolute age
- archaeological sites
- Australasia
- C-14
- carbon
- Cenozoic
- Coromandel Peninsula
- dipole moment
- Holocene
- isotopes
- lacustrine environment
- lake sediments
- magnetic field
- magnetic intensity
- magnetization
- New Zealand
- North Island
- Pacific Ocean
- paleomagnetism
- Quaternary
- radioactive isotopes
- remanent magnetization
- secular variations
- sediments
- South Pacific
- Southwest Pacific
- West Pacific
- Paekakariki New Zealand
- Whitianga New Zealand
- Ohariu Valley
- Great Mercury Island
- Weld Pass