Effect of magnetic anisotropy on the experimentally determined palaeointensity of the geomagnetic field
© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences. 2001
Received: 24 April 1999
Accepted: 15 January 2001
Published: 18 June 2014
Rock magnetic properties of the Nile mud are reported. They indicate that the carrier of magnetization in the Nile mudis predominantly magnetite. Fourty air-dried ceramic samples made of Nile mud were manufactured to ceramics by stepwise heating to 700°C at various field intensities between 0.03 mT and 0.09 mT and with various angles θ between the laboratory field (FL) direction and the ceramics. The partial (pTRM) and the total thermoremanent magnetization (TRM) increase linearly as the magnetic field (FL) increases. The rate of increase of the pTRM with both FL and temperature T depends on θ, so that it decreases by 25% as θ increases from 0° to 90°. In extreme cases, the effect of the magnetic anisotropy results in overestimating the determined palaeointensity by 33% and underestimating it by 25% from the correct value. The direction of TRM is the same as that of the ambient magnetic field independent of the anisotropy. Applying the laboratory field in the direction of the stable natural remanent magnetization during a Thellier-type experiment results in accurate determination of the palaeointensity.