New Zealand Journal of Geology and Geophysics abstracts
Tidal range of marsh foraminifera for determining former sea-level heights in
New Zealand
BRUCE W. HAYWARD
HUGH R. GRENFELL
Department of Geology
University of Auckland
Private Bag 92 019
Auckland, New Zealand
DAVID B. SCOTT
Centre for Marine Geology
Dalhousie University
Halifax
Nova Scotia, B3H 3J5, Canada
Abstract Quantitative study of live and total foraminiferal
faunas in samples from six transects through marsh environments at Kaipara
Harbour, Miranda, and Pauatahanui Inlet, New Zealand (two transects each), show
the presence of a distinctive high tidal species association that has potential
for the recognition of former sea-level heights from late Quaternary deposits.
Seven species associations are recognised by R-mode cluster analysis of total
(live plus dead) foraminiferal faunal data. Mangrove forest and salt meadow
below MHWS (mean high water spring level), in near normal salinity marshes
(Kaipara, Miranda), are dominated by an Ammonia association with
subsidiary Elphidium excavatum, Haplophragmoides-Miliammina fusca, and
Helenina associations. In less saline marshes (Pauatahanui), the salt
meadow and rush marsh below MHWS, are dominated by a
Haplophragmoides-Miliammina fusca association. In all transects, the
narrow zone between MHWS and EHWS (extreme high water spring level) is
dominated (>90% relative abundance) by a Trochammina association
(T. inflata, T. macrescens, Miliammina obliqua). A palimpsest,
Ammonia-dominated, exposed beach fauna on the penultimate chenier
interferes with the recognition of this high tidal Trochammina zone in
one Miranda transect. Dependent upon their proximity to exposed sea conditions
and fast-flowing tidal channels, there are variable numbers of introduced
foraminiferal tests (Cornuspira association) in the marshes at all
levels. At Pauatahanui, a monospecific fauna of T. macrescens is present
just at EHWS (upper 0.1 m of tidal range). This has been recognised previously
only in northeast America and may provide the most accurate paleo-sea level
marker known.
There appear to be no significant tide-related trends in diversity, but in all
transects there is a marked abundance peak between MHWS and EHWS levels, which
if recognised in fossil faunas could also be useful in determining previous
sea-level heights.
Keywords New Zealand; Kaipara Harbour; Miranda; Pauatahanui
Inlet; marsh foraminifera; former sea levels; tidal range
New Zealand Journal of Geology & Geophysics, 1999, Vol. 42:
395-413
0028-8306/99/4203-0395 $7.00/0 (c) The Royal Society of New Zealand
1999
PDF file of entire paper: medium quality (3258K); (scanned from paper original: notes about this process)
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