Further Correlations between the Petrology and Natural Magnetic Polarity of Basalts

A petrological examination has been made of palaeomagnetic basalt samples from Kinghorn, Scotland; Cape Kawajiri, Japan; and Western Iceland. The Kinghorn samples are of Carboniferous age. Previous palaeomagnetic field evidence and magnetic tests had suggested that the Earth's magnetic field had reversed its polarity a few times during the time interval studied. However, there is a distinct petrological difference between specimens of opposite magnetic polarity, which suggests a possible self-reversal mechanism in the basalts. The field evidence and magnetic tests therefore lead to the opposite conclusion to that formed on the basis of petrological observations. The resolution of this dilemma is of considerable importance for the proper interpretation of palaeomagnetic results. Similar petrology-polarity correlations exist in Tertiary basalts from Cape Kawajiri, Japan. The Icelandic basalts show a slight trend towards the same correlation, although the statistics are not significant.