Using 36Cl exposure dating to date mass movement and assess land stability on the Nicholas Range, Tasmania

Adrian J. Slee*, Peter D. McIntosh, Timothy T. Barrows

*Corresponding author for this work

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    Abstract

    Detailed mapping of dolerite slope deposits overlying sedimentary Triassic rocks on the northern slopes of the Nicholas Range in northeastern Tasmania has revealed an extensive mass movement complex. Landforms north of the summit plateau of the Nicholas Range include the following: (1) a cliff of dolerite columns with associated scree slopes at its base; (2) a topple landscape consisting of several topples that have fallen in a north-easterly direction; (3) a “ripple” landscape consisting of a series of long boulder ridges aligned approximately east-west. Exposure dates were obtained for three large boulders (collapsed dolerite columns) from a ridge within the ripple landscape. The two youngest dates gave a mean age of 52.1 ± 1.9 ka using 36Cl. This is the estimated age for collapse of the dated columns from the cliff face c. 750 m to the south. Boulder ages and landscape morphology indicate that the ripple landscape developed by physical and chemical degradation and concurrent northern displacement of topples over a slip plane formed at the contact between dolerite colluvium and underlying Triassic sedimentary rocks. There is no evidence of movement today, other than localised debris flows associated with knickpoints in streams, and it is deduced that movement on the slip plane occurred under a cooler climate than that prevailing today, possibly under the influence of melting of winter snow during the last glacial cycle. As there is no evidence of significant recent mass movement and forests in the area are likely to have experienced many stand-destroying forest fires in the Holocene, forest harvest is not considered to pose a risk to landscape stability.

    Original languageEnglish
    Pages (from-to)2147-2154
    Number of pages8
    JournalLandslides
    Volume14
    Issue number6
    Early online date4 Aug 2017
    DOIs
    Publication statusPublished - 1 Dec 2017

    Keywords

    • Dolerite terrain
    • Exposure dating
    • Landslides
    • Last glacial
    • Mass movement
    • Topples

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