A Relict Pronival (Protalus) Rampart in the Tararua Range, North Island, New Zealand
ABSTRACT Debris ridges in New Zealand are routinely assumed to be ‘moraines’ and used as key Southern Hemisphere paleoclimatic sites without detailed evaluation of ridge origin. Here we assess the origin of a debris ridge adjacent to Dundas Ridge in the Tararua Range, North Island, New Zealand, thro...
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crwiley:10.1002/ppp.1759 2024-06-02T08:13:09+00:00 A Relict Pronival (Protalus) Rampart in the Tararua Range, North Island, New Zealand Brook, Martin S. Williams, Jacob 2012 http://dx.doi.org/10.1002/ppp.1759 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fppp.1759 https://onlinelibrary.wiley.com/doi/pdf/10.1002/ppp.1759 en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor Permafrost and Periglacial Processes volume 24, issue 1, page 67-74 ISSN 1045-6740 1099-1530 journal-article 2012 crwiley https://doi.org/10.1002/ppp.1759 2024-05-03T11:28:55Z ABSTRACT Debris ridges in New Zealand are routinely assumed to be ‘moraines’ and used as key Southern Hemisphere paleoclimatic sites without detailed evaluation of ridge origin. Here we assess the origin of a debris ridge adjacent to Dundas Ridge in the Tararua Range, North Island, New Zealand, through measurements of ridge morphology and sedimentary properties. The ridge has a steep c. 35° distal slope (height 18 m), compared with the c. 19° proximal slope (height 6 m), and on all transects the distal slopes contain the coarsest material (median b ‐axis clast widths of 0.18‐0.25 m), compared to distal samples (0.34‐0.37 m). Clast shape (C 40 range 40‐60%) and angularity (RA>65%) indicate typically angular and ‘slabby’ clasts, and along with the lack of fines, and the ca. 40‐m‐distance between the ridge crest and the foot of the backwall, lead us to reject a glacial (moraine) origin for the ridge. The single ridge morphology precludes a protalus rock glacier origin, while the lack of a broad hillslope scar and debris apron beyond the ridge excludes a landslide origin. Instead, we interpret the ridge as a pronival (protalus) rampart formed by supranival debris supply–from the ca. 200 m‐high southeastern slopes of Dundas Ridge–across a snowbed. Re‐distribution of snow by prevailing westerlies from Mt Dundas Ridge into the basin would have nourished the snowbed, which is likely to have formed during the interval 24‐18 ka BP, when a minor alpine‐style glaciation affected sectors of the Tararua Range. This is the first pronival rampart detailed in New Zealand, raising the possibility that debris ridges of pronival origin may also be present elsewhere in New Zealand's mountains. Copyright © 2012 John Wiley & Sons, Ltd. Article in Journal/Newspaper Permafrost and Periglacial Processes Wiley Online Library New Zealand Permafrost and Periglacial Processes 24 1 67 74 |
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Open Polar |
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Wiley Online Library |
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crwiley |
language |
English |
description |
ABSTRACT Debris ridges in New Zealand are routinely assumed to be ‘moraines’ and used as key Southern Hemisphere paleoclimatic sites without detailed evaluation of ridge origin. Here we assess the origin of a debris ridge adjacent to Dundas Ridge in the Tararua Range, North Island, New Zealand, through measurements of ridge morphology and sedimentary properties. The ridge has a steep c. 35° distal slope (height 18 m), compared with the c. 19° proximal slope (height 6 m), and on all transects the distal slopes contain the coarsest material (median b ‐axis clast widths of 0.18‐0.25 m), compared to distal samples (0.34‐0.37 m). Clast shape (C 40 range 40‐60%) and angularity (RA>65%) indicate typically angular and ‘slabby’ clasts, and along with the lack of fines, and the ca. 40‐m‐distance between the ridge crest and the foot of the backwall, lead us to reject a glacial (moraine) origin for the ridge. The single ridge morphology precludes a protalus rock glacier origin, while the lack of a broad hillslope scar and debris apron beyond the ridge excludes a landslide origin. Instead, we interpret the ridge as a pronival (protalus) rampart formed by supranival debris supply–from the ca. 200 m‐high southeastern slopes of Dundas Ridge–across a snowbed. Re‐distribution of snow by prevailing westerlies from Mt Dundas Ridge into the basin would have nourished the snowbed, which is likely to have formed during the interval 24‐18 ka BP, when a minor alpine‐style glaciation affected sectors of the Tararua Range. This is the first pronival rampart detailed in New Zealand, raising the possibility that debris ridges of pronival origin may also be present elsewhere in New Zealand's mountains. Copyright © 2012 John Wiley & Sons, Ltd. |
format |
Article in Journal/Newspaper |
author |
Brook, Martin S. Williams, Jacob |
spellingShingle |
Brook, Martin S. Williams, Jacob A Relict Pronival (Protalus) Rampart in the Tararua Range, North Island, New Zealand |
author_facet |
Brook, Martin S. Williams, Jacob |
author_sort |
Brook, Martin S. |
title |
A Relict Pronival (Protalus) Rampart in the Tararua Range, North Island, New Zealand |
title_short |
A Relict Pronival (Protalus) Rampart in the Tararua Range, North Island, New Zealand |
title_full |
A Relict Pronival (Protalus) Rampart in the Tararua Range, North Island, New Zealand |
title_fullStr |
A Relict Pronival (Protalus) Rampart in the Tararua Range, North Island, New Zealand |
title_full_unstemmed |
A Relict Pronival (Protalus) Rampart in the Tararua Range, North Island, New Zealand |
title_sort |
relict pronival (protalus) rampart in the tararua range, north island, new zealand |
publisher |
Wiley |
publishDate |
2012 |
url |
http://dx.doi.org/10.1002/ppp.1759 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fppp.1759 https://onlinelibrary.wiley.com/doi/pdf/10.1002/ppp.1759 |
geographic |
New Zealand |
geographic_facet |
New Zealand |
genre |
Permafrost and Periglacial Processes |
genre_facet |
Permafrost and Periglacial Processes |
op_source |
Permafrost and Periglacial Processes volume 24, issue 1, page 67-74 ISSN 1045-6740 1099-1530 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1002/ppp.1759 |
container_title |
Permafrost and Periglacial Processes |
container_volume |
24 |
container_issue |
1 |
container_start_page |
67 |
op_container_end_page |
74 |
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1800759827514785792 |