CHANGES TO PORIRUA HARBOR IN ABOUT 1855 - HISTORICAL TRADITION AND GEOLOGICAL EVIDENCE

There is a widely-believed tradition that tectonic uplift accompanying the West Wairarapa earthquake of 1855 reduced the navigability of the Pauatahanui arm of Porirua harbour and created new land at its head. This tradition arose some time before 1902, and was apparently confirmed by Adkin's (1921) report of elevated wave-cut rock platforms. I have reviewed the evidence for this idea, and found none. All young platforms lying east of the Ohariu Fault are now covered by high water spring tides. The elevation of the platforms to the west can be explained by movements of the fault, and shoreline changes at the head of the inlet by silting. The reminiscences of McKillop (1849) and the Admiralty chart of Stokes (1858, but surveyed in 1850) establish that before the earthquake sea-going vessels could use only the outer part of the Harbour, and that the Pauatahanui Inlet was accessible only to small boats. I have compiled an appendix to clarify the numerous confusions of spelling and location in the historical material. © 1990 Journal of the Royal Society of New Zealand.