The Matuyama-Brunhes geomagnetic reversal from two deep-sea cores of the Eastern Equatorial Atlantic

International audienceMatuyama-Brunhes geomagnetic polarity transitions recorded in Holes 659C and 664D, cored with the hydraulic piston corer during Ocean Drilling Program Leg 108, were selected for detailed study. The sections containing the reversals, as identified by shipboard results, were sampled using "U" channels. Few intermediate polarity directions were obtained from Hole 659C; consequently, no interpretation of this record in terms of transitional field behavior was attempted. However, the record from Hole 664D, located at the equator, is characterized by a gradual easterly progression of the declination from reverse to normal polarity and no deviation of the inclination from a mean value of 0°. The field intensity was reduced to about 20% of its pretransitional value. The absence of inclination changes combined with easterly declinations constrains the Virtual Geomagnetic Pole path to lie along the meridian 90° to the east. Such behavior does not resemble transitional field models, which neglect nonzonal terms. A comparison of this record with other reliable records shows that the behavior of the geomagnetic field during this reversal cannot be explained by a model involving a simple field geometry