Browsing by Author "King, DN"

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    New Zealand's most easterly palaeotsunami deposit confirms evidence for major trans-Pacific event
    (Elsevier, 2018-11-01) Goff, JR; Goto, K; Chagué, C; Watanabe, M; Gadd, PS; King, DN
    Sedimentary, geochemical, geomorphological, radiocarbon and numerical modelling data were used to examine the nature, extent and age of a boulder scatter at Okawa Point, Chatham Island, New Zealand. Boulders up to 98 t were traced around 800 m inland and comprised both a landward and seaward grouping on either side of a mid-Holocene high-stand storm ridge dated to around 4840–4810 cal BP. The landward boulder scatter was linked with an enigmatic coarse sand/gravel layer that extends up to 1100 m inland and has been dated to around 3500–4500 cal BP. Numerical modelling indicated that while the seaward boulders that mainly rest upon the Chatham Island Schist shore platform could have been emplaced by either storm or tsunami waves, those landward of the mid-Holocene storm ridge were most probably transported by a tsunami. There are several near-contemporaneous palaeotsunami deposits reported from mainland New Zealand, Australia, SW Pacific and the wider Pacific region. If some or all of these are associated with the same basin-wide palaeotsunami then it appears likely to have been one of the largest Holocene Pacific palaeotsunamis. An analysis of historical and numerically modelled data suggests that the most likely candidate is from within the northern Chile seismic gap, with early evidence suggesting that a large palaeoseismic and palaeotsunami event may have occurred around 4000 yr BP. If correct, this has important implications for assessing the largest possible magnitude earthquakes in the northern Chile seismic gap and the size of the tsunamis they generate. © 2018 Elsevier B.V.
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    Reciting 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, M
    Sedimentary, 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.