Gd. Acton et al., A TEST OF THE GEOCENTRIC AXIAL DIPOLE HYPOTHESIS FROM AN ANALYSIS OF THE SKEWNESS OF THE CENTRAL MARINE MAGNETIC ANOMALY, Earth and planetary science letters, 144(3-4), 1996, pp. 337-346
A new, global set of palaeomagnetic observations was obtained from ana
lysis of the symmetry of the shape of 203 crossings of the Central mar
ine anomaly, the anomaly observed above seafloor, formed during the Br
unhes normal polarity chron (0-0.78 Ma). The data indicate that the ti
me-averaged field can be described best by a dominant geocentric axial
dipole component, whose position differs insignificantly from the pre
sent spin axis, and by a small geocentric axial quadrupole component (
6.0%(+5.7%)(-6.7%) the size of the dipole component). If we simply ass
ume that the Brunhes palaeomagnetic axis has been aligned with the pre
sent spin axis, the quadrupole component is 6.2% +/- 4.7%, which diffe
rs significantly from a purely dipolar field, and is in good agreement
with estimates from other palaeomagnetic data. Besides expanding the
spatial distribution of palaeomagnetic field observations, an importan
t step in removing biases in prior field estimates caused by poor glob
al coverage, these results illustrate that valuable geomagnetic inform
ation as well as accurate palaeomagnetic poles can be obtained from sk
ewness data.