In this paper we examine the magnetic polarity for Pacific Basin seamounts exclusive of the Hawaiian Ridge. On Pacific crust older than 65 Ma, seamounts of normal polarity predominate. On crust younger than 65 Ma, seamounts exhibit normal and reversed polarity as well as mixed polarity. We show that viscous components do not dominate seamount magnetization, and we suggest that a large number of normal seamounts were formed during a major magmatic event postulated for the period 110–70 Ma. This period overlaps with the long Cretaceous normal period (118–84 Ma) and corresponds to 85% normal polarity for Earth's magnetic field. The correspondence of a period of high magmatic activity with a long period of normal polarity supports the possible correlation between those processes responsible for magma production and for magnetic field generation.

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