RECORDS OF GEOMAGNETIC REVERSALS FROM VOLCANIC ISLANDS OF FRENCH-POLYNESIA .1. PALEOMAGNETIC STUDY OF A POLARITY TRANSITION IN A LAVA SEQUENCE FROM THE ISLAND OF HUAHINE

We report the behavior of the earth's magnetic field for a transition recorded in lavas at the volcanic island of Huahine in French Polynesia, south-central Pacific Ocean. Detailed intermediate fields are observed that record an apparent N-N excursion. The available K-Ar ages indicate that most volcanic rocks of the southern part of Huahine erupted at a time close to the Kaena subchron. Gaps in the paleomagnetic sampling or a hiatus in the volcanic activity during the Kaena event may have led to the partial record of a complete polarity transition, missing the fully reversed state. Nevertheless, numerous flows have recorded intermediate fields that somewhat constrain reversal models. The beginning of the transition shows inclination steepening, consistent with a zonal model of geomagnetic field reversal based on an axial quadrupole. -from Authors