New Zealand Journal of Geology and Geophysics abstracts
Late Holocene uplift of beach ridges at Turakirae Head, south Wellington coast, New Zealand
Maurice J. McSaveney1
Ian J. Graham1*
John G. Begg1
Alan G. Beu1
Alan G. Hull2
Kyeong Kim3
Albert Zondervan1
1GNS Science
PO Box 30368
Lower Hutt, New Zealand
2Golder Associates
230 Commerce, Suite 200
Irvine, CA 92602, USA
3NSF Arizona AMS Laboratory, Physics Building
University of Arizona
1118 East Forth Street
Tucson, Arizona 85721–0081
USA
*Author for correspondence.
With an appendix:
Macrofauna
of raised beaches at Turakirae Head
Alan G. Beu
Abstract Holocene
terraces at Turakirae Head on the south coast of the North Island, New
Zealand, record four recent earthquakes from simultaneous rupture of
the Wairarapa Fault and flexure of the Rimutaka Anticline. The lowest
tread and riser is the modern marine platform and storm beach that
began forming when the area was raised during the Mw
8.2 Wairarapa earthquake of AD 1855 January. The remaining chronology
is established by radiocarbon dating, in situ 10Be
surface-exposure dating, and slip-predictable uplift estimation. Prior
to AD 1855, uplifts occurred at 110–430 BC (max.
9.1 m), 2164–3468 BC (6.8 m), and
4660–4970 BC (7.3 m). Earlier uplift of unknown
magnitude occurred at c. 7000 BC but went unrecorded because
of rapidly rising sea level. Sea level was still rising when the two
oldest surviving beach ridges were raised.
Uplift at Turakirae Head in AD 1855 varied from 1.5 m at the
Wainuiomata River to 6.4 m at the crest of the Rimutaka Anticline.
Older beaches also are tilted, with the amount of tilt increasing with
age. Coastal uplift at the anticline crest has averaged 3.32
± 0.17 mm/yr over the past 9000 yr, and has changed little
over the past 0.5 m.y. Uplift fits a slip-predictable model of
earthquake occurrence, and is log-normally distributed with a mean of
7.3 ± 0.7 m. The most frequently occurring uplift is 7.1
± 0.9 m. Uplift in AD 1855 was not significantly smaller
than mean or mode, suggesting that the Turakirae Head sequence records
four great earthquakes of at least similar magnitude to that of AD
1855. The mean earthquake recurrence interval is 2194 ±
117 yr; the modal interval is 2122 ± 193 yr.
At the crest of the anticline, the coastal platform was cut
entirely during the postglacial rise of sea level until shortly before
4660–4970 BC. Away from the crest, however, it may have been
partially cut during low sea level of the penultimate glaciation. The
open-ocean radiocarbon reservoir correction (δR) for 10 14C dates of
coastal marine shells that died in AD 1855 at Turakirae Head is 3
± 14 cal. yr BP (and not –31 ± 13 cal. yr
BP, the currently accepted δR for central New Zealand coastal
waters).
Keywords Wairarapa; Turakirae; Rimutaka Range; AD 1855 earthquake; paleoseismology; coastal uplift; radiocarbon dating; 10Be surface exposure dating; Mollusca
G05031; Received 8 July 2005; accepted 19 June 2006; Online publication date 26 July 2006
New Zealand Journal of Geology & Geophysics, 2006, Vol. 49: 337–358
0028–8306/06/4903–0337 © The Royal Society of New Zealand 2006
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