Non-axisymmetric behaviour of Olduvai and Jaramillo polarity transitions recorded in north-central Pacific deep-sea sediments

Abstract

The causes of the reversals of the Earth's magnetic field can be investigated by studying the palaeomagnetic record preserved in rocks. A proper documentation of reversal phenomena should yield valuable information about the generation of the field. Deep-sea sediments provide a globally and temporally distributed set of polarity transition records. Our studies^2–4 of the Olduvai (1.88–1.72 Myr)¹ and Jaramillo (0.94–0.88 Myr)¹ subchrons using deep-sea sediments showed that the time-averaged behaviour of the geomagnetic field during these reversals proved to be reliably recorded, independent of the latitude and longitude of the sample site. Here we test some phenomenological transition models and present directional data, virtual geomagnetic poles (VGPs) and related directions in rotated declination, inclination (D′, I′) space⁵, using two records of the Olduvai reverse–normal–reverse (R–N–R) and two records of the Jaramillo R–N–R polarity transitions. These data are better explained by the flooding rather than the standing field model, but they also indicate a degree of asymmetry of the transitional field.