The fit of the land-derived polarity timescale,from paleomagnetic and K/Ar studies of exposedbasalts, with the polarity record emerging from marine magnetic anomalies (MMAs) (Vine andMatthews, 1963; Vine, 1966; Pitman and Heirtzler,1966; Heirtzler et al., 1968) resulted in a convincingargument for synchronous global geomagnetic polarity reversals, thereby attributing them to the mainaxial dipole. The results relegated self-reversal,detected in the 1950s in the Haruna dacite from theKwa district of Japan (Nagata, 1952; Nagata et al.,1957; Uyeda, 1958), to a rock-magnetic curiosityrather than to a process generally applicable tovolcanic rocks.