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

ange of lower resolution or fragmentary records of
climatic events, based on glacial landforms and
deposits (central Southern Alps, South Island), river
terraces and deposits, loess deposits (eastern North
and South Islands), and aeolian quartz silt in nonquartzose,
loess-like, andesitic tephric deposits of
western North Island.
The poster reflects work-in-progress and aims to
assist comparison of the New Zealand
paleoclimatic records with those from the wider
Australasian region and elsewhere. The immediate
goal is the establishment of an Australasian-
INTIMATE climate event stratigraphy by the New
Zealand and Australian paleoclimate communities,
for presentation at the 2007 INQUA Cairns
Symposium.
POSTER
LATE QUATERNARY DISPLACEMENTS ON
THE WAITANGI FAULT, AVIEMORE DAM,
SOUTH ISLAND, NEW ZEALAND
D.J.A. Barrell 1 ,R.J.VanDissen 2 ,K.R.
Berryman 2 & S.A.L. Read 2
1 GNS Science, Private Bag 1930, Dunedin.
2 GNS Science, P.O. Box 30-368, Lower Hutt.
(d.barrell*gns.cri.nz)
Aviemore Dam was constructed across the Waitaki
River valley in the mid-1960s. The dam straddles
the steeply WSW-dipping Waitangi Fault. At the
time of construction, no evidence of late
Quaternary movement was documented on the
fault. However, in the mid-1990s, dam safety
review investigations unearthed evidence of late
Quaternary deformation, and this led to the detailed
paleoseismological investigations that provided
data for displacement characterisation of the fault
and subsequent evaluations of dam safety under
direct fault rupture loadings.
The primary paleoseismology investigation method
was the excavation of 10 trenches, the largest of
which was up to 10 m deep and 180 m long, across
faults and folds within 1 km of the dam,
accompanied by geological mapping of surface
exposures and landforms. Detailed logging of the
trench walls (typically 1:20 scale) documented the
geometry of Late Quaternary deposits and the
locations, amount and sense of slip of the most
recent fault displacements. Over 30 samples were
dated to constrain the timing of past fault
movements, using, where possible, at least two
duplicate methods of luminescence, and
complemented in a few instances by radiocarbon.
The investigations documented two, and possibly
three, surface rupture fault movements on the
Waitangi Fault in the last c. 23,000 years, with the
most recent movement between 13,100 and 14,100
years ago. These ruptures were located on, or up to
6 m west of, the bedrock fault that juxtaposes
Mesozoic- and Tertiary-age rocks (respectively east
and west of the fault). Relative upthrow has been to
the west in the late Quaternary. This represents a
reversal from a net westerly downthrow that
accumulated during the late Tertiary as shown by
the Mesozoic versus Tertiary rock relationships
across the fault.
The two most recent surface ruptures had singleevent,
west-side-up, vertical separations of c. 0.5 m
(penultimate) and c. 1.5 m (most recent).
Slickenside-lineations, and other slip indicators,
show an oblique right-lateral – reverse sense of late
Quaternary rupture, with a horizontal (H)
component greater than the vertical (V) component
(ratios of displacement in the range of 1H:3V to
1H:1V). In addition, a zone of “small-scale” late
Quaternary faults and folds, with single-event
vertical separations of up to 0.7 m, extends up to at
least 150 m west of the Waitangi Fault.
The fault displacement characteristics documented
from the field investigations were subsequently
used to derive earthquake performance assessments
for the dam, and to evaluate dam safety under direct
fault rupture loadings.
ORAL
THE DEVELOPMENT OF ANTARCTIC
GLACIAL HISTORY OVER THE LAST
FIFTY YEARS
P. J. Barrett
Antarctic Research Centre, Victoria University of
Wellington, P O Box 600, Wellington.
(peter.barrett*vuw.ac.nz)
Fifty years ago it was thought that the Northern
Hemisphere had experienced 4 glacial episodes
over the last two million years, and no-one
supposed the Southern Hemisphere would be much
different. That view was changed radically in 1973
with the first Antarctic offshore drilling by the
Glomar Challenger in the Ross Sea. The cruise,
which was led by Denny Hayes and Larry Frakes
and included three New Zealanders, Derek Burns,
Peter Webb and me, cored through glacial
sediments that dated back 25 million years. The
cruise that followed, Leg 29, led by Jim Kennett
and Bob Houtz, cored a series of deep ocean sites to
the north that covered the Cenozoic Era. This
yielded the first oxygen isotope curve, from which
they concluded there was Antarctic cooling and sea
ice in the latest Eocene, and the formation of an ice
sheet like today’s in the middle Miocene.
The Leg 29 results could not, however, resolve the
relative contributions of ice volume and
temperature to the isotope signal, and gave no
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