Browsing by Author "McFadgen, BG"
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- ItemHolocene record of long- and short-term environmental changes in a coastal wetland, New Zealand(Geological Society of Australia, 2014-07-07) Chagué-Goff, C; Cope, J; Goff, JR; Mooney, SD; Kilroy, C; Wong, HKY; McFadgen, BGLong- and short-term environmental changes in Moawhitu Wetland, D’Urville Island, New Zealand, were reconstructed using a multi-proxy approach. A local Māori oral tradition describes a giant wave destroying a community in the 15th century, however, except for a study in 1962, little geological work had been carried out to investigate this event or to establish a record of paleoenvironmental changes in the area. Three sedimentary sequences sampled across the wetland over a distance of 2 km were analysed for grain size, organic content, geochemistry (ICP-AES, ICP-MS and ITRAX), diatom assemblages and mineralogy, while the chronology was obtained using 14C and 210Pb dating, corroborated with pollen biostratigraphy. Results of this study indicate that the sand dune barrier at Moawhitu formed ca 7400–7200 years BP at the time when sea levels stabilised following the last deglaciation. This led to the establishment of a freshwater lake in the southern area, which gradually infilled to form a wetland with subsequent peat accumulation. In the central part of Moawhitu, lake and peatland sequences alternated. By ca 1200 years BP, with the exception of the existing lagoon at the northern end of the study area, conditions favourable to peatland formation were found throughout Moawhitu and continued into the 20th century when they were disrupted by drainage activities. Evidence for a tsunami 3300–3000 years BP was found in the northern part of Moawhitu wetland (based on sedimentological, geochemical and microfossil data). Geochemical signatures and marine diatom assemblages provide a record of tsunami inundation in the middle part of the wetland, beyond the extent of any sand deposit. No geochemical evidence could be found at the site further inland in the southern part of the wetland. Evidence for a contemporaneous tsunami deposit has also been reported ~100 km N, on Kapiti Island, on the west coast of the North Island of New Zealand, and the event has been attributed to a local fault rupture. So far, no sedimentological, geochemical or micropaleontological evidence for a giant wave in the 15th century has been found in the sedimentary sequence of Moawhitu wetland. However, pebble layers extending across large areas of the dunes have been recorded and these have also been associated with Maori occupation, thus inferring that the sand dune may indeed have acted as an effect barrier to any 15th century tsunami. This study indicates that more than one tsunami has affected Moawhitu, and further work is planned to document environmental changes in the area. Copyright Geological Society of Australia Inc.
- ItemPalaeotsunamis and their influence on Polynesian settlement(Sage Publications Ltd, 2012-09-01) Goff, JR; McFadgen, BG; Chagué-Goff, C; Nichol, SLThe 11 March 2011 TAhoku-oki tsunami caused widespread devastation to coastal communities in Japan. This event however was merely the latest, yet largest, of several similar occurrences in the Pacific that include the 2007 Solomon Islands, 2009 South Pacific and 2010 Chilean tsunamis. All have had their predecessors, and a growing data base of palaeotsunamis in the Pacific suggests recurrent events comparable with, and of larger magnitude than their recent historical counterparts. Here we show that evidence for regional palaeotsunamis provides an opportunity to re-evaluate hypotheses used to explain the punctuated history of human settlement patterns across the Pacific. In particular, the almost two millennia 'long pause' in eastward migration, and the abandonment of long distance sea-voyaging in the 15th century, may be related to palaeotsunamis, with potential sources including the tectonically active Tonga-Kermadec trench, the Kuwae caldera collapse, and the more distant Pacific-wide Ring of Fire. © 2012, SAGE Publications.
- ItemReciting the layers: evidence for past tsunamis at Mataora-Wairau Lagoon, Aotearoa-New Zealand(Elsevier B.V., 2017-07-01) King, DN; Goff, JR; Chagué-Goff, C; McFadgen, BG; Jacobsen, GE; Gadd, PS; Horrocks, MSedimentary, geochemical, microfossil and geochronological analyses were carried out on 10 sediment cores across the south-eastern corner of Mataora-Wairau Lagoon (M-WL), South Island, Aotearoa-New Zealand. This multi-proxy approach provides strong evidence for three late Holocene palaeotsunamis (two previously unreported) and a historical tsunami generated by rupture of the Wairarapa Fault in 1855 CE. The main scientific evidence for these events consists of anomalous, high-energy marine sediment layers that overlie material of contrasting composition. These layers coincide with peaks in planktonic and benthic marine to brackish-marine diatoms and geochemical signatures indicative of sudden changes in environmental conditions. Palaeotsunami I (maximum date 2095 cal. BP) and Palaeotsunami II (maximum date 915 cal. BP - previously identified by Clark et al., 2015) appear to represent large events contemporaneous with major earthquakes inducing tectonic uplift and coseismic subsidence around the Cook Strait region. Palaeotsunami II is close to the date of the earliest settlement of the M-WL area by Māori, and a traditional narrative that references loss of life following waves over-washing the Wairau boulder bank. Given the boulder bank was likely to have been seaward of its current position during events I and II, we surmise that the inundation distances would have been greater than the most landward extent (340 m) inferred from the deposits found in this study. Palaeotsunami III (maximum date 525 cal. BP) was associated with tectonic subsidence across the study site, most likely associated with rupture of the southern Hikurangi subduction zone. We expect the ongoing refinement of the methods used in this study, and the results from future studies of analogue sites and offshore fault systems, will improve our understanding of the significant tsunami hazard facing this region. © 2017 Elsevier B.V.
- ItemReturn of the Sea Monster – a tale from D’Urville Island, New Zealand(International Union for Quaternary Research, 2012-09-04) Chagué-Goff, C; Cope, J; McFadgen, BG; Mooney, SD; Kilroy, C; Zawadzki, A; Wong, HKY; Jacobsen, GENot available.