New Zealand Journal of Geology and Geophysics abstracts
A tectonically uplifted marine shoreline deposit, Knights Point, Westland, New Zealand
Alan F. Cooper
Fabian Kostro
Geology Department
University of Otago
P.O. Box 56
Dunedin, New Zealand
alan.cooper@stonebow.otago.ac.nz
Abstract An 11 m thick subhorizontal beach
deposit rests on steeply dipping Cretaceous bedrock. Sediments, ranging
from a basal boulder bed to upper sands, are poorly sorted and
negatively skewed, indicating pronounced winnowing of fine material.
Impact features on quartz grain surfaces attest to high-energy
turbulent environments, and are similar to those found on clasts from
modern nearby beaches. The Haast River was source to some of the sand
and gravel. Heavy minerals from the Dun Mountain Ophiolite Belt were
transported 85 km by fluvial/glacial and longshore drift
processes, necessitating caution when using apparent lateral separation
of source material for estimating strike-slip displacement rates on the
Alpine Fault. An optical luminescence age estimate of 123 ±
7 ka for Knights Point beach sands dates to the last interglacial
(MIS 5e). A shore-platform altitude of 113 m a.s.l. requires
tectonic uplift of the Australian plate of 0.86 mm/yr, an order of
magnitude less than the nearby Pacific plate.
Keywords Knights Point; beach sediments; marine terrace; last interglacial; OSL dating; heavy mineral compositions
G05036; Online publication date 12 May 2006; Received 25 July 2005; accepted 12 December 2005
New Zealand Journal of Geology & Geophysics, 2006, Vol. 49: 203–216
0028–8306/06/4902–0203 © The Royal Society of New Zealand 2006
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