32. geomagnetic intensity and field direction changes associated with the matuyama/brunhes polarity reversal, as recorded in a sediment core from the north pacific1

TLDR: A detailed paleomagnetic record of the Matuyama/Brunhes polarity reversal is recorded in clay sediment samples taken from North Pacific Ocean Drilling Program (ODP) Hole 145-884C.

Abstract: A highly detailed paleomagnetic record of the Matuyama/Brunhes polarity reversal is recorded in clay sediment samples taken from North Pacific Ocean Drilling Program (ODP) Hole 145-884C. In this study, I analyzed 81 1-cm3 samples, taken over -75 cm of core and representing about 16 k.y. of deposition time. Normalized intensity vs. depth plots indicate that at least 7 cycles of substantial intensity fluctuation describe the transition period, with the virtual geomagnetic pole (VGP) moving from high southern to high northern latitudes entirely within the fourth observed cycle. Transitional poles associated with earlier and later intensity lows, as well as the poles that describe the actual VGP reversal path, are distributed in close proximity to the 270° longitudinal meridian. This preference for the longitudinal band, which includes North America, also extends to the higher latitude reversed poles that precede the polarity transition. Because the sampling site is -90° from this preferred longitude, the significance of Hole 884C's VGP confinement remains obscure. However, these results are in general agreement with the high sedimentation rate reversal record obtained earlier from Hole 792A (ODP Leg 126), drilled about 3500 km to the southwest. These conformable directional and intensity results suggest that the field maintained a dipole configuration, perhaps with the addition of a strong secondary equatorial dipole, throughout most of the transition period.