Geomagnetic Polarity Reversals in a Late Tertiary Lava Sequence from the Akaroa Volcano, New Zealand

Abstract

Palaeomagnetic measurements and potassium—argon age determinations have been performed on two sequences of lava flows from the Banks Peninsula, New Zealand. Flows from the Stoddart Formation are entirely of reversed polarity and were formed rapidly at 5.85±0.04 My ago. The Akaroa sequence, extruded over a time interval from 9.1 to 8.4 My ago, records seven reversals of the Earth's magnetic field. The geomagnetic polarity time scale constructed from these results agrees well with the time scales postulated from the interpretation of magnetic anomaly patterns over mid-ocean ridges. The age of the polarity reversal terminating the normal period associated with Anomaly 5 is 8.67±0.13 My.