50thKaikoura05 -1- Kaikoura 2005 CHARACTERISATION OF NEW ...
50thKaikoura05 -1- Kaikoura 2005 CHARACTERISATION OF NEW ...
50thKaikoura05 -1- Kaikoura 2005 CHARACTERISATION OF NEW ...
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present. The most important deficiency to date is<br />
the general lack of high-quality seismic data.<br />
Recently, Crown Minerals, the New Zealand<br />
government group charged with promoting and<br />
regulating oil and gas exploration, commissioned a<br />
high specification regional 2D survey intended to<br />
address some of the main data gaps in the East<br />
Coast Basin. A broad grid was planned to be<br />
acquired with a 12,000 metre streamer. It was<br />
expected that the long streamer would increase<br />
resolution of Paleogene and Cretaceous units. Infill<br />
lines were to be acquired with a streamer 8000<br />
metres long. The resulting 2,800 km data set<br />
consists of a series of northwest-southeast lines<br />
approximately orthogonal to the coast at a spacing<br />
of approximately 10 km as well as several long<br />
strike lines.<br />
The new data set has confirmed the existence of a<br />
large, little-deformed basin to the north of North<br />
Island and the Bay of Plenty, it has elucidated the<br />
complex structure of a large part of the East Coast<br />
Basin and has enabled generation of a general<br />
sequence stratigraphic model which assists in<br />
delineating reservoir targets.<br />
ORAL<br />
PALEOCEANOGRAPHIC RESULTS FROM<br />
A MARINE SEDIMENT CORE NEAR LORD<br />
HOWE ISLAND, TASMAN SEA.<br />
C. Waikari 1 ,D.M.Kennedy 1 &H.L.Neil 2<br />
1 School of Earth Sciences, Victoria University of<br />
Wellington, PO Box 600, Wgtn.<br />
2 National Institute of Water and Atmosphere,<br />
Wellington, New Zealand.<br />
(waikarcael*student.vuw.ac.nz)<br />
Lord Howe Island (33°S, 159°E) is the eroded<br />
remnant of a basaltic shield volcano, approximately<br />
500 km east of Australia and is situated in the path<br />
of an ocean boundary called the Tasman Front.<br />
This boundary marks the southern limit of the<br />
warm East Australian Current which flows from the<br />
Coral Sea down the east coast of Australia and<br />
across to New Zealand (between 30° and 35°S).<br />
The purpose of the study is to examine the<br />
influence of the shifting Tasman Front on the<br />
palaeoenvironment near an island setting.<br />
A 2.8 m piston core was collected from 780 m<br />
water depth in a trough between Lord Howe Island<br />
and Balls Pyramid (a smaller island 25 km SSE of<br />
Lord Howe Island). Oxygen and carbon isotope<br />
analyses were conducted using the planktonic<br />
foraminifera Globigerina bulloides and<br />
Globigerinoides ruber and the benthic foraminifer<br />
Uvigerina. In combination with standard and AMS<br />
radiocarbon ages these analyses provide a<br />
temperature and productivity proxy for<br />
oceanographic conditions around the island for the<br />
Holocene and back to oxygen isotope stage 3.<br />
Component analysis was undertaken to assess the<br />
species composition and shifts in floral and faunal<br />
composition across this oceanographic boundary.<br />
Preliminary analysis of the planktonic foraminifer<br />
data show three distinct changes related to different<br />
water masses coming in through the core.<br />
Compositional analysis of the whole core indicates<br />
that 2 distinct phases of deposition have occurred at<br />
the top (50 mm) and in the middle (1200 mm) of<br />
the core shown by a large decrease in abundance of<br />
the major components (foraminifera, corals,<br />
carbonate gastropods and ostracods) possibly<br />
relating to glacial periods and lowered sea level.<br />
One of the AMS dates places the top of the core at<br />
oxygen isotope stage 3. A complicating factor for<br />
the study is whether material eroded off the island<br />
and transported to the core site alters the preserved<br />
climatic signal. Another factor to consider is<br />
whether the presence of intermediate water masses<br />
has modified the sea surface temperature record<br />
found in the sediment around Lord Howe Island.<br />
ORAL<br />
BALANCING THE PLATE MOTION<br />
BUDGET IN THE SOUTH ISLAND, <strong>NEW</strong><br />
ZEALAND USING GPS, GEOLOGICAL AND<br />
SEISMOLOGICAL DATA<br />
Laura M. Wallace 1 , John Beavan 1 ,<br />
Rob McCaffrey 2 & Kelvin Berryman 1<br />
1 Institute of Geological and Nuclear Sciences, P.O.<br />
Box 30368, Lower Hutt.<br />
2 Dept. of Earth and Env. Science, Rensselaer<br />
Polytechnic Inst, Troy, NY, USA.<br />
(l.wallace*gns.cri.nz)<br />
The landmass of New Zealand exists as a<br />
consequence of transpressional collision between<br />
the Australian and Pacific plates, providing an<br />
excellent opportunity to quantify the kinematics of<br />
deformation at this type of tectonic boundary. We<br />
implement an elastic, rotating block approach in the<br />
interpretation of GPS, geologic (fault slip rate and<br />
azimuth) and seismological (earthquake slip<br />
vectors) data to describe the active deformation in<br />
the South Island, New Zealand. This method<br />
concomitantly allows us to “balance” the<br />
Pacific/Australia relative plate motion budget in the<br />
South Island. Using this approach, we<br />
simultaneously invert the data for angular velocity<br />
vectors of rotating tectonic blocks and the degree of<br />
interseismic coupling on faults bounding the<br />
blocks. The data are fit to within error, indicating<br />
that the “elastic block” method is plausible for<br />
interpretation of geodetic data within this plate<br />
boundary zone.<br />
50 th <strong>Kaikoura</strong>05 -92- <strong>Kaikoura</strong> <strong>2005</strong>