New Zealand Journal of Geology and Geophysics abstracts
A radiometric age constraint from a tephra bed at the Miocene-Pliocene boundary
in New Zealand
PHIL SHANE
Department of Geology
The University of Auckland, Tamaki Campus
Private Bag 92 019
Auckland, New Zealand
Abstract A new isothermal plateau fission-track age (5.74 +/-
0.34 Ma) for a tephra bed c. 6 m below the Miocene-Pliocene
unconformity at Mangapoike River, Gisborne region, along with microfauna above
the unconformity, constrains the enclosing reversed magnetic polarity interval
to Chron 3r (c. 5.2-5.9 Ma). This is equivalent to the
Messinian-Zanclean Stage boundary position in the Mediterranean region. The new
magnetic polarity interpretation indicates that the unconformity at Mangapoike
River is of shorter duration than previously stated (c. 0.9 Ma) and
could represent the younger of the two terminal Miocene global glacial events.
There is a need to utilise tephra beds in New Zealand biostratigraphic
sequences to obtain radiometric ages for global correlation.
Keywords Miocene; Pliocene; tephra; fission-track;
geochronology; Mangapoike River
New Zealand Journal of Geology and Geophysics, 1998, Vol. 41: 111-114
0028-8306/98/4101-0111 $7.00/0 (c) The Royal Society of New Zealand
1998
Short communication
PDF file of entire paper: medium quality (327K); (scanned from paper original: notes about this process)
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