50thKaikoura05 -1- Kaikoura 2005 CHARACTERISATION OF NEW ...

survived through in low numbers in geographicallyrestricted
refugia. One complete family
(Stilostomellidae – 21 species), characterised by an
unusual tooth structure in its necked aperture,
became extinct at this time; and a second family
(Pleurostomellidae – 24 species), also characterised
by unusual elliptical or hooded apertures, was
killed off except for two species that appear to have
just survived through. A further 30 species in the
large Nodosariidae family also died out and most of
these too, had unusual cribrate or narrow,
constricted apertures.
Prior to the MPT, many of the extinct species had
cosmopolitan distributions at middle bathyal to
upper abyssal depths (600-3000 m), although a
minority had geographically-limited distributions.
Our studies indicate that ~20% of the global
diversity of benthic foraminifera at these depths
(excluding the diverse unilocular taxa) became
extinct during the MPT. This was an extinction rate
of ~30% of the middle bathyal-upper abyssal
fauna/myrs, which is an order of magnitude greater
than the background extinction rate for deep-sea
benthic foraminifera of ~2-3%/ myrs.
ORAL
“CM/YR” IS NOW AVAILABLE – WHAT OF
THE NEXT 50 YEARS?
David Kear
34 West End, Whakatane
(kear*xtra.co.nz)
In its first 50 years, our Society exceeded all
expectations and world geology underwent its
greatest revolution. Belief in the Alpine Fault led to
that in Continental Drift, which sparked off a new
era of Plate Tectonics with a new unit for its
movements of “cm/yr”. There seems general
acceptance of these concepts in NZ, regarding other
parts of the world. Let us hope that the next 50
years will bring comparable acceptance regarding
NZ itself. Conclusions involving “plate tectoniclike”
movements by many authors have been
commonly ignored in appropriate diagrams and
papers – by various means ranging from denying all
discussion, to preferring a belief in zero-movement.
Plate tectonic conclusions, many dating back over
decades rather than years, that seem not to be fully
accepted in general papers (or need more
convincing reporting?), include:
�Northland Allochthon it took half those 50 years,
for even discussion to be acceptable.
�Central Volcanic Region (CVR) was created from
nothing since 2.5 Ma, along with the Havre
Trough. Stern’s diagram illustrating that situation
is nearly 20 years old.
�Alpine Fault was active in both North and South
Islands up to ca 5 Ma (major North Island faulting
has long been widely noted and joined commonly
to the Alpine Fault); its trace is now precisely
located as the CVR’s boundary, & could become
widely adopted.
� Offshore Northland has been shown to have
moved southeast between 15 & 5 Ma to become the
East Coast - in many publications dating back
between 10 and 38 years.
�Whakatane was moved southeast at 2�cm/year
for 400 k.yr (evidence 10+ years old).
�Clockwise North Island Rotation since 15 Ma – a
30 year-old average of 65 o has been supported
recently, but the effects of rotation are seldom
considered in general papers.
� Three North Island “Tectonic Events” (ca 10
m.yr apart since 25 Ma) have been named, but
ignored, for ca 10 years; they allow changes in
compression & tension to be dated accurately and
linked to (e.g.) important changes in the local class
of volcanism.
� A Single Subduction System, initially off
Northland, moved & rotated progressively via
Coromandel offshore, to become the Hikurangi
Subduction System with only one change in the
rotation rate at a tectonic event. No new data are
necessarily needed to reach such conclusions as
these. A 1963 diagram, based solely on then
published (pre- radiometric) data, nevertheless
illustrated the creation of the CVR from nothing.
The North Island predominates in these examples,
but the 2005 fieldtrip programme emphasises an
accelerating interest in Marlborough’s plate
tectonic history - reflected in several recent
convincing papers. Compatibility of evidence from
the two islands, at specific points backwards in
time, will be a key objective for the second 50 years
– Alpine Fault movement, large rotation, tectonic
events, subsurface termination of subduction,
effects on non-geologic factors etc. However the
overwhelming need will be to promote a greater
acceptance of the reality of NZ Plate Tectonics, in
both thinking and writing. Should that be achieved,
the next 50 years will be as exciting and rewarding
scientifically for the next generation as the last 50
years have been for us, and NZ will once again
stimulate world thinking about the revolutionary
science of plate tectonics.
ORAL
50 th Kaikoura05 -41- Kaikoura 2005