Geomagnetic reversal transitions and d" layer

Abstract

To have found geological sections that record polarity reversals and could be sampled in detail is a great advance in palaeomagnetism (Laj et al., 1991). Reversals over the last 11 Myr (Laj et al., 1988; Valet et al., 1988; Tric et al., 1991a,b) suggest that the core dynamo reverses by the rotation of the dipole through 180°, at least in many cases, rather than, as was thought previously, by the field becoming non-dipolar or by disappearing. The paths of the virtual geomagnetic poles (VGP's) during these transitions seem to fall in two longitude sectors, one through the Americas and the other, 180° away, through Australia and Eastern Asia.