Journal
JOURNAL OF QUATERNARY SCIENCE
Volume 34, Issue 8, Pages 685-696Publisher
WILEY
DOI: 10.1002/jqs.3168
Keywords
kame; Lake Wakatipu; landform origin; paraglacial; rock avalanche
Funding
- Aberystwyth University Research Fund
- Massey University [RM17927]
- University of Dundee
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Ambiguous landscape histories can arise from equivocal or incomplete geomorphological, sedimentological or geochronological evidence. In this study, we apply quantitative analyses to robustly assess the origin and age of a field of rounded mounds, known as 'The Hillocks'. Using clast analysis, the sediment is shown to be consistent with a landslide origin but inconsistent with other glacial sediments in the region. Cosmogenic Be-10 exposure age dating suggests The Hillocks formed 8 ka. Ground-penetrating radar reveals that the deposit rests upon deltaic foreset beds; combined with topographical data, we calculate a deposit volume of 15-27 M m(3), consistent with the estimated volume of the proposed source area. Overall, our data support a rock avalanche origin, indicating that by 8 ka the valley was ice-free at The Hillocks' location, and the level of Lake Wakatipu was lower than 340 m asl by this time. The Dart River delta shoreline was situated somewhere between The Hillocks and the present day shoreline at that time, and has prograded at a maximum average rate of 1 m a(-1) since 8 ka. These findings are significant given the lack of landforms by which to constrain glacial or post-glacial landscape histories in this region of New Zealand. Copyright (c) 2019 John Wiley & Sons, Ltd.
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