Measurements on 8 intrusive igneous bodies belonging to the central intrusive complex of Mull show that the earlier parts of the complex are reversely magnetized, whereas the later parts are normally magnetized.

Interpretation of these results and of published polarities of other parts of the Tertiary igneous succession is ambiguous because of the possibility of overprinting due to the heat of the central complex. Model 1 assumes that all polarities are primary and requires a polarity sequence R-N-R-N-R; Model 2, which assumes overprinting, requires only R-N-R.

A combination of radiometric dating and reference to the polarity time-scale limits the duration of activity to c. 3.5 Ma, at about 58 Ma.

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