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Boulder emplacement and remobilisation by cyclone and submarine landslide tsunami waves near Suva City, Fiji

Lau, A.Y.A. and Terry, James P. and Ziegler, Alan and Pratap, Arti and Harris, Daniel (2018) Boulder emplacement and remobilisation by cyclone and submarine landslide tsunami waves near Suva City, Fiji. Sedimentary Geology, 364 . pp. 242-257. ISSN 0037-0738

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    Abstract

    The characteristics of a reef-top boulder field created by a local submarine landslide tsunami are presented for the first time. Our examination of large reef-derived boulders deposited by the 1953 tsunami near Suva City, Fiji, revealed that shorter-than-normal-period tsunami waves generated by submarine landslides can create a boulder field resembling a storm boulder field due to relatively short boulder transport distances. The boulder-inferred 1953 tsunami flow velocity is estimated at over 9 m s− 1 at the reef edge. Subsequent events, for example Cyclone Kina (1993), appear to have remobilised some large boulders. While prior research has demonstrated headward retreat of Suva Canyon in response to the repeated occurrence of earthquakes over the past few millennia, our results highlight the lingering vulnerability of the Fijian coastlines to high-energy waves generated both in the presence (tsunami) and absence (storm) of submarine failures and/or earthquakes. To explain the age discrepancies of U-Th dated coral comprising the deposited boulders, we introduce a conceptual model showing the role of repeated episodes of tsunamigenic submarine landslides in removing reef front sections through collapse. Subsequent high-energy wave events transport boulders from exposed older sections of the reef front onto the reef where they are deposited as ‘new’ boulders, alongside freshly detached sections of the living reef. In similar situations where anachronistic deposits complicate the deposition signal, age-dating of the coral boulders should not be used as a proxy for determining the timing of the submarine landslides or the tsunamis that generated them.

    Item Type: Journal Article
    Subjects: G Geography. Anthropology. Recreation > GB Physical geography
    G Geography. Anthropology. Recreation > GE Environmental Sciences
    L Education > L Education (General)
    Q Science > QE Geology
    Divisions: Faculty of Science, Technology and Environment (FSTE) > School of Geography, Earth Science and Environment
    Depositing User: Arti Pratap
    Date Deposited: 05 Oct 2018 15:51
    Last Modified: 05 Oct 2018 15:51
    URI: http://repository.usp.ac.fj/id/eprint/11078
    UNSPECIFIED

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