Brunhes-Matuyama polarity transition in three deep-sea sediment cores

Abstract

The Brunhes-Matuyama polarity transition was studied in three deep-sea sediment cores obtained from the mid-northern and equatorial Pacific Ocean. Rates of sedimentation vary from 0.7 to 1.1 cm k a ^-1 . The cores were sampled across the transition in 4 mm slices, and each level was further subdivided into three specimens. Inclinations above and below the transition interval are in close agreement with that of an axial dipole field. Estimates of transition duration based on directional change range from 4900 to 8500 years. The transition can be described by a longitudinally confined portion in each of the v.g.p. paths, but is complicated by broad loops in all three records. While fine-scale sampling reveals considerable detail, the notable increase in within-level dispersion observed in the transition and the apparent differences in v.g.p. paths in nearby cores from the same region indicate that factors other than the geomagnetic field may contribute to these transition records.