Geomagnetic paleointensity variations during the last 40 m.y.: Possible relationship between polarity reversal frequency and paleointensity

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A paleomagnetic study was conducted using Eocene to Oligocene sediment cores taken by IODP from the east equatorial Pacific in order to obtain relative paleointensity between 23 and 42 Ma. It was revealed that long-range relative paleointensity records can be contaminated by variations of the relative abundance of biogenic and terrigenous magnetic minerals and sedimentation rates. The positive correlation between polarity reversal frequency and paleointensity that was previously suggested from the data of DSDP Site 522 is not supported. As for short-term variations on the order of 10 kyrs, paleointensity drops were found during stable polarity periods as well as at reversals. This is the same as the characteristics of paleointensity variations known for the last 3 m.y.