New Zealand Journal of Geology and Geophysics abstracts

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Towards a record of Holocene tsunami and storms for northern Hawke’s Bay, New Zealand

U. A. Cochran¹
K. R. Berryman¹
D. C. Mildenhall¹
B. W. Hayward²
K. Southall²
C. J. Hollis¹

¹Institute of Geological & Nuclear Sciences
P.O. Box 30 368
Lower Hutt, New Zealand
u.cochran@gns.cri.nz

²Geomarine Research
49 Swainston Road
St Johns, Auckland, New Zealand

Abstract  Eleven sand layers occur within Holocene low-energy estuarine and marginal marine sequences of blue-grey silty clay at two sites on the coastal plain between Wairoa and Mahia Peninsula, northern Hawke’s Bay, New Zealand. The sedimentology and fossil assemblages of these layers are consistent with deposition by high-energy influxes to the sites. Three influxes are terrestrial in nature and are thought to represent alluvial flood events. All other sand layers are marine derived and are likely to be the result of storm surges or tsunami. Tsunami inundation is favoured for two sand layers that occur in association with evidence for sudden subsidence at c. 6300 and c. 4800 yr BP. The c. 6300 yr inundation also coincides with previously identified evidence for a tsunami at a site 10 km westwards along the coast. Further investigation is required to distinguish between tsunami and storm surge deposition for the remaining six layers.

Keywords  Holocene; Wairoa; Mahia Peninsula; Hawke’s Bay; coastal hazards; floods; microfossils; sedimentology; storm surges; tsunami

G04033; Received 11 August 2004; accepted 31 March; Online publication date 22 August 2005
New Zealand Journal of Geology & Geophysics, 2005, Vol. 48: 507–515
0028–8306/05/4803–0507© The Royal Society of New Zealand 2005

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