NZPSV1k and NZPSV10k: New Palaeosecular Variation Master Records for New Zealand – Applications for Dating and Field Modelling

English Abstract:

We present new palaeosecular variation master records for New Zealand on both archaeological and Holocene timescales. These have been compiled using continuous data from the detrital remanent magnetization of lake sediment cores with high-resolution C-14 based chronology, and are constrained and calibrated using directions and absolute palaeointensities obtained from the thermoremanent magnetizations of archaeological materials and volcanic rocks. All data has been “migrated” to a standard geographical location (40°S, 175°E) using a virtual geomagnetic pole (VGP) transformation. By a reciprocal VGP process, the master records can be used to calculate accurate palaeosecular variation records for all locations within the New Zealand region. The new record improves upon and extends by a factor of five the existing 20 year-old record. The geomagnetic field alternates between active periods of high amplitude swings from 12000 to 8000 BP and over the past 4000 years, and a relatively inactive period from 8000 to 4000 BP. The current field (Dec = 21.5° E, Inc = - 65.4°, F = 55.4 mT at 40°S, 175°E) represents a rare steep and easterly extreme in direction, but is close to average in intensity. The palaeointensity record mirrors to some extent the variation of the virtual axial geomagnetic moment seen in the global dataset, but shows some notable differences. We investigate the use of the archaeomagnetic master record as a dating tool, and the effect of including the Holocene record in global spherical harmonic-based field models.