New Zealand Journal of abstracts
Paleomagnetism of c. AD 1314 Kaharoa rhyolite and
the New Zealand
paleosecular variation master curve
NZPSV2007
D. J. Robertson
Physics Department
The University
of Auckland
Private Bag 92019
Auckland
1142,
New Zealand
Abstract Rhyolite domes were
extruded on Mt
Tarawera
summit during the Kaharoa eruption episode radiocarbon dated at AD 1314
± 12 yr.
Interiors of the domes are well exposed in deep craters formed during
the AD
1886 Tarawera eruption. Paleomagnetic studies have been carried out on
41
oriented cores obtained from 5 sites within Wahanga and Crater Domes.
The fresh
rhyolite rock is consistently strongly magnetised with NRM of 1–12 A/m.
Progressive thermal demagnetisation was applied to every sample.
Consistently
unicomponent Zijderveld trajectories were obtained, giving a mean
paleofield
direction of declination 354.6°,
inclination –61.2°, a95 4.3° during emplacement
of the rhyolite. These results impose a strong constraint on the
paleosecular
variation master curve for New Zealand,
which is accordingly revised. The similarity of paleofield directions
for
Crater Dome (extruded early in the Kaharoa eruption sequence) and
Wahanga Dome
(extruded late in the sequence) is consistent with little time having
separated
extrusion of these two domes.
:
39–50
0028–8306/07/5001–0039 © The Royal Society
of New Zealand
2007
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