A PALEOMAGNETIC SECULAR VARIATION RECORD FOR NEW-ZEALAND DURING THE PAST 2500 YEARS

A record of the secular variation of the geomagnetic field over New Ze aland for the past 2500 years has been compiled by measuring and avera ging logs of the primary magnetization of five cores of lacustrine sed iment from Lake Pounui. A time-scale is provided by four radiocarbon a ge determinations. The record is constrained by historical observation s for the last 350 years and is in good agreement with instantaneous p alaeomagnetic directions from lava flows. This is the first continuous record of secular variation from New Zealand and one of only a few fr om the southern hemisphere. Together with existing Australian records, the results show significant evidence of westward drift of the geomag netic field over the past 2500 years. It contains new information for modelling the geomagnetic secular variation in the southern hemisphere and will also be valuable for dating applications within New Zealand.