Paleosecular variation during sequential geomagnetic reversals from Hawaii

摘要

Paleomagnetic directions measured from 175 flows in four volcanic sequences on the island of O'ahu (Hawaii) cover about 0.3 m.y. of geomagnetic field changes and include detailed records of the successive Gilbert-Gauss (3.57 Ma) and Lower Mammoth reversals (3.33 Ma). The dominant pattern of the directional changes is the presence of large inclination variations with increasing amplitude and steep values during the transitional periods. The morphology of these recurring features during different transitions is reminiscent of the characteristics of the non-dipole field inferred from studies of paleosecular variation in the Pacific. These observations are consistent with transitional mechanisms yielding the emergence of non-dipole components with characteristics similar to those during periods of stable polarity. The three different records of the lower Mammoth reversal show that clusters of transitional pole positions are not reproducible between parallel sections and are thus linked to local eruptions and not to long-lived states of the transitional field.