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Possible tsunami deposits from the 1855 earthquake, North Island, New Zealand

1999; Geological Society of London; Volume: 146; Issue: 1 Linguagem: Inglês

10.1144/gsl.sp.1999.146.01.21

2041-4927

James Goff, Michael Crozier, Venus Sutherland, Ursula Cochran, Phil Shane,

Geological and Geochemical Analysis

Abstract A series of three fining-upward sequences from deposits in the Okourewa Stream bank on the south coast of the North Island, New Zealand, investigated by grain-size, diatom, radiocarbon, geochemical and macrofaunal analyses have been tentatively interpreted as the products of a tsunami. The proposed event consisted of three separate waves (the second being the largest) generated by a surface rupture of a local fault. Changes in diatom assemblages and the presence of marine shells, pumice, and beach pebbles may represent a tsunami advancing inshore over beach, freshwater channel, and coastal wetland environments. Deposition occurred between ad 500 and 1890. The event in question may have currently the ad 1855 rupture of the West Wairarapa fault.