Open Access

K-Ar ages of the Auckland geomagnetic excursions

Earth, Planets and Space201456:BF03353410

https://doi.org/10.1186/BF03353410

Received: 15 January 2004

Accepted: 20 February 2004

Published: 29 June 2014

Abstract

K-Ar age determinations were made on two monogenetic volcanoes in the Auckland volcanic field, New Zealand, which have recorded the Auckland geomagnetic excursions. For the Wiri volcano with the north-down intermediate paleomagnetic direction, five samples gave a weighted mean age of 27 ± 5 (1σ) ka. For the Hampton Park volcano with the west-up intermediate direction, three samples gave a weighted mean of 55 ± 5 (1σ) ka. Since these two K-Ar ages are distinguished at 2σ level, it is inferred that at least two geomagnetic excursions can be recognized in Auckland. The age of the Hampton Park is barely distinguished from the established age range of the Laschamp excursion (39–45 ka) at 2σ level. The age of the Wiri coincides with the age of c. 30 ka in which excursions have been found from sedimentary and volcanic records. The reported excursions from volcanic rocks show a VGP cluster in the central to northern Pacific region which is distinct from the VGP paths or clusters during polarity reversals.

Key words

K-Ar age Auckland geomagnetic excursion Auckland volcanic field