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

present. The most important deficiency to date is
the general lack of high-quality seismic data.
Recently, Crown Minerals, the New Zealand
government group charged with promoting and
regulating oil and gas exploration, commissioned a
high specification regional 2D survey intended to
address some of the main data gaps in the East
Coast Basin. A broad grid was planned to be
acquired with a 12,000 metre streamer. It was
expected that the long streamer would increase
resolution of Paleogene and Cretaceous units. Infill
lines were to be acquired with a streamer 8000
metres long. The resulting 2,800 km data set
consists of a series of northwest-southeast lines
approximately orthogonal to the coast at a spacing
of approximately 10 km as well as several long
strike lines.
The new data set has confirmed the existence of a
large, little-deformed basin to the north of North
Island and the Bay of Plenty, it has elucidated the
complex structure of a large part of the East Coast
Basin and has enabled generation of a general
sequence stratigraphic model which assists in
delineating reservoir targets.
ORAL
PALEOCEANOGRAPHIC RESULTS FROM
A MARINE SEDIMENT CORE NEAR LORD
HOWE ISLAND, TASMAN SEA.
C. Waikari 1 ,D.M.Kennedy 1 &H.L.Neil 2
1 School of Earth Sciences, Victoria University of
Wellington, PO Box 600, Wgtn.
2 National Institute of Water and Atmosphere,
Wellington, New Zealand.
(waikarcael*student.vuw.ac.nz)
Lord Howe Island (33°S, 159°E) is the eroded
remnant of a basaltic shield volcano, approximately
500 km east of Australia and is situated in the path
of an ocean boundary called the Tasman Front.
This boundary marks the southern limit of the
warm East Australian Current which flows from the
Coral Sea down the east coast of Australia and
across to New Zealand (between 30° and 35°S).
The purpose of the study is to examine the
influence of the shifting Tasman Front on the
palaeoenvironment near an island setting.
A 2.8 m piston core was collected from 780 m
water depth in a trough between Lord Howe Island
and Balls Pyramid (a smaller island 25 km SSE of
Lord Howe Island). Oxygen and carbon isotope
analyses were conducted using the planktonic
foraminifera Globigerina bulloides and
Globigerinoides ruber and the benthic foraminifer
Uvigerina. In combination with standard and AMS
radiocarbon ages these analyses provide a
temperature and productivity proxy for
oceanographic conditions around the island for the
Holocene and back to oxygen isotope stage 3.
Component analysis was undertaken to assess the
species composition and shifts in floral and faunal
composition across this oceanographic boundary.
Preliminary analysis of the planktonic foraminifer
data show three distinct changes related to different
water masses coming in through the core.
Compositional analysis of the whole core indicates
that 2 distinct phases of deposition have occurred at
the top (50 mm) and in the middle (1200 mm) of
the core shown by a large decrease in abundance of
the major components (foraminifera, corals,
carbonate gastropods and ostracods) possibly
relating to glacial periods and lowered sea level.
One of the AMS dates places the top of the core at
oxygen isotope stage 3. A complicating factor for
the study is whether material eroded off the island
and transported to the core site alters the preserved
climatic signal. Another factor to consider is
whether the presence of intermediate water masses
has modified the sea surface temperature record
found in the sediment around Lord Howe Island.
ORAL
BALANCING THE PLATE MOTION
BUDGET IN THE SOUTH ISLAND, NEW
ZEALAND USING GPS, GEOLOGICAL AND
SEISMOLOGICAL DATA
Laura M. Wallace 1 , John Beavan 1 ,
Rob McCaffrey 2 & Kelvin Berryman 1
1 Institute of Geological and Nuclear Sciences, P.O.
Box 30368, Lower Hutt.
2 Dept. of Earth and Env. Science, Rensselaer
Polytechnic Inst, Troy, NY, USA.
(l.wallace*gns.cri.nz)
The landmass of New Zealand exists as a
consequence of transpressional collision between
the Australian and Pacific plates, providing an
excellent opportunity to quantify the kinematics of
deformation at this type of tectonic boundary. We
implement an elastic, rotating block approach in the
interpretation of GPS, geologic (fault slip rate and
azimuth) and seismological (earthquake slip
vectors) data to describe the active deformation in
the South Island, New Zealand. This method
concomitantly allows us to “balance” the
Pacific/Australia relative plate motion budget in the
South Island. Using this approach, we
simultaneously invert the data for angular velocity
vectors of rotating tectonic blocks and the degree of
interseismic coupling on faults bounding the
blocks. The data are fit to within error, indicating
that the “elastic block” method is plausible for
interpretation of geodetic data within this plate
boundary zone.
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