New Zealand Journal of Geology and Geophysics abstracts
Local stages to be used for the Wanganui Series (Pliocene-Pleistocene), and
their means of definition
A. G. BEU
Institute of Geological & Nuclear Sciences
P.O. Box 30 368
Lower Hutt, New Zealand
email: a.beu@gns.cri.nz
Abstract Suggestions to abandon New Zealand local stages, or
to redefine their boundaries solely at physically defined horizons, confuse the
two very distinct aims of a stage classification. These are objectively to
order New Zealand rocks on the basis of New Zealand biostratigraphic or other
chronostratigraphic criteria, and to allow correlation of the New Zealand
time-scale with the international one. For rapid, cost-effective identification
of stages in geological mapping and other frontier situations, their boundaries
must be characterised by biostratigraphic criteria, supplemented where
appropriate by physical stratigraphic horizons (magnetic polarity reversals,
sedimentary cycle boundaries, and, in particular, tephras).
Carter & Naish resurrected all Wanganui Series substages, but the original
reasons for their proposal are outdated. Fleming's choice of subdivisions was
governed by the "four glaciations" paradigm of the time, rather than the
current Milankovitch time-scale paradigm. New Zealand Pliocene-Pleistocene
stages need to be redefined at new stage-base boundaries (standard section and
point, or SSP), at horizons that allow them to be characterised by the criteria
of greatest utility in New Zealand.
Recommended stages and their SSPs (all sited in Wanganui Basin) are: Haweran
Stage, base of Rangitawa Tephra (0.35 Ma), Rangitawa Stream, Rangitikei valley;
Castlecliffian Stage, base of Ototoka tephra, Ototoka Beach, Wanganui;
Nukumaruan Stage, base of Hautawa Shellbed, Hautawa Road, Rangitikei valley;
Mangapanian Stage, base of Mangapani Shellbed, Mangapunipuni Stream, Waitotara
valley. The SSPs for the Waipipian and Opoitian Stages need to be redefined
using integrated molluscan, foraminiferal, and physical stratigraphic horizons
in a continuous section in Wanganui Basin, preferably the Wanganui River
section.
Keywords stages; biostratigraphy; Pliocene; Pleistocene;
Wanganui Basin; magnetic polarity stratigraphy; cyclostratigraphy;
tephrochronology; Mollusca
New Zealand Journal of Geology & Geophysics, 2001, Vol. 44:
113-125
0028-8306/01/4401-0113 $7.00/0 (c) The Royal Society of New Zealand
2001
PDF file of entire paper: medium quality (1973K); (scanned from paper original: notes about this process)
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