A detailed record of the lower Jaramillo polarity transition from a southern hemisphere, deep-sea sediment core.

Abstract

The transition itself is recorded across approximatly 70 cm and is represented by >475 specimens from about 160 levels giving intermediate directions. The declinations show little appreciable variation until the inclinations have moved through the near vertical, and then slowly approach values in agreement with a normal polarity field. Assuming a constant sedimentation rate (67m/Ma) through the Jaramillo Subchron, the duration of the transition is estimated to be 11 200-4500 yr (depending on the criteria) for the directional change, whereas the associated intensity variation occurred over 15 000-20 000 yr. This record strongly suggests that the lower Jaramillo transitional field was dominated by different harmonics than the Matuyama/Brunhes transitional field.-from Authors