Recent investigations of the 0-5 geomagnetic field recorded by lava flows
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Date
2015-06-12
Authors
Johnson, Catherine L.
Constable, Catherine G.
Tauxe, Lisa
Barendregt, René W.
Brown, Laurie L.
Coe, Rob
Gans, Phil
Layer, Paul
Mejia, Vicky
Opdyke, Neil D.
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Abstract
We present a synthesis of paleomagnetic directional data collected from 873 lava flows at 17 different
locations under the collaborative Time Averaged geomagnetic Field Initiative (TAFI). The data range from
05
Ma in age, and provide new high quality data with improved spatial coverage. Data quality at each site
is measured using k, the best estimate of the Fisherian precision parameter, and its influence on inclination
anomaly and VGP dispersion is evaluated by systematically excluding data with successively higher values
of k. When combined with regional compilations from NW USA, SW USA, Japan, New Zealand, Hawaii,
Mexico, S. Pacific and the Indian Ocean, a data set of 2283 pairs of declination and inclination data, with
k>100, and VGP latitudes greater than 45 is obtained. This is a more than 7fold
increase over similar
quality data in the existing Global Paleomagnetic Database (GPMDB). The new data set spans 78 S to
53 N, and has sufficient temporal and spatial sampling to allow characterization of latitudinal variations in
the timeaveraged
field (TAF) and paleosecular variation (PSV) for the Brunhes and Matuyama epochs, and
for the 0–5 Myr interval combined. PSV, as measured by dispersion of virtual geomagnetic poles, shows
less latitudinal variation than predicted by current statistical PSV models. Variation of inclination anomaly
with latitude is assessed using 2parameter
zonal TAF models – these have axial quadrupole contributions
of 2% – 4% of the axial dipole term, and axial octupole contributions of 3% – 5%. Approximately 2%
of the octupole signature is likely the result of bias incurred by averaging unit vectors. The new data set
provides significant improvement over previous compilations, and can contribute to a new generation of
global paleomagnetic field models.
Description
Sherpa Romeo green journal (pre or post print only)
Keywords
Paleomagnetic directional data , Lava flows , Time-Averaged Field Investigations (TAFI) , Geomagnetic field , 0-5 Ma