Age and origin of blockfields on Scottish mountains
Numerous researchers have proposed that blockfields on mid-latitude plateaux are frost-modified relicts formed initially by chemical weathering under warm, humid pre-Quaternary (Neogene) conditions. Others contend that they formed mainly by frost action during the Quaternary. We test these competing...
Published in: | Scottish Geographical Journal |
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Online Access: | https://risweb.st-andrews.ac.uk/portal/en/researchoutput/age-and-origin-of-blockfields-on-scottish-mountains(027ab8fb-b9f7-4ad7-86d5-2e320e9b3aef).html https://doi.org/10.1080/14702541.2013.855808 |
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ftunstandrewcris:oai:risweb.st-andrews.ac.uk:publications/027ab8fb-b9f7-4ad7-86d5-2e320e9b3aef 2023-05-15T15:55:50+02:00 Age and origin of blockfields on Scottish mountains Hopkinson, Charles Ballantyne, Colin 2014 https://risweb.st-andrews.ac.uk/portal/en/researchoutput/age-and-origin-of-blockfields-on-scottish-mountains(027ab8fb-b9f7-4ad7-86d5-2e320e9b3aef).html https://doi.org/10.1080/14702541.2013.855808 eng eng info:eu-repo/semantics/restrictedAccess Hopkinson , C & Ballantyne , C 2014 , ' Age and origin of blockfields on Scottish mountains ' , Scottish Geographical Journal , vol. 130 , no. 2 , pp. 116–141 . https://doi.org/10.1080/14702541.2013.855808 Blockfields Regolith Clay minerals Frost weathering Quaternary Neogene article 2014 ftunstandrewcris https://doi.org/10.1080/14702541.2013.855808 2021-12-26T14:23:15Z Numerous researchers have proposed that blockfields on mid-latitude plateaux are frost-modified relicts formed initially by chemical weathering under warm, humid pre-Quaternary (Neogene) conditions. Others contend that they formed mainly by frost action during the Quaternary. We test these competing hypotheses for blockfields on three mountains in NW Scotland: a matrix-supported diamict blockfield (sandstone), clast-supported diamict blockfield (quartzite) and an openwork blockfield (schist). Clay concentrations in the fine fraction are low (0–6.8%) and both clay:silt ratios and secondary clay minerals (illite, kaolinite and gibbsite) are consistent with prolonged chemical weathering under periglacial conditions. There is negligible depletion of labile elements in the fine fraction relative to the parent rock. Conversely, evidence for surface and near-surface granular disaggregation, an increase in clast angularity with depth, dominantly angular sand grains, in situ detached clasts and fractured clasts above rockhead favour formation by frost weathering under Pleistocene stadial conditions. There is no convincing evidence for blockfield inheritance from Neogene regolith. As the blockfields were buried under cold-based glacier ice during the last glacial maximum, they pre-date ice-sheet build-up at ∼35–30 ka. Measured rates of plateau surface lowering suggest that present blockfield regolith is probably of Late Pleistocene (<135 ka) age. Article in Journal/Newspaper Cold-based glacier Ice Sheet University of St Andrews: Research Portal Scottish Geographical Journal 130 2 116 141 |
institution |
Open Polar |
collection |
University of St Andrews: Research Portal |
op_collection_id |
ftunstandrewcris |
language |
English |
topic |
Blockfields Regolith Clay minerals Frost weathering Quaternary Neogene |
spellingShingle |
Blockfields Regolith Clay minerals Frost weathering Quaternary Neogene Hopkinson, Charles Ballantyne, Colin Age and origin of blockfields on Scottish mountains |
topic_facet |
Blockfields Regolith Clay minerals Frost weathering Quaternary Neogene |
description |
Numerous researchers have proposed that blockfields on mid-latitude plateaux are frost-modified relicts formed initially by chemical weathering under warm, humid pre-Quaternary (Neogene) conditions. Others contend that they formed mainly by frost action during the Quaternary. We test these competing hypotheses for blockfields on three mountains in NW Scotland: a matrix-supported diamict blockfield (sandstone), clast-supported diamict blockfield (quartzite) and an openwork blockfield (schist). Clay concentrations in the fine fraction are low (0–6.8%) and both clay:silt ratios and secondary clay minerals (illite, kaolinite and gibbsite) are consistent with prolonged chemical weathering under periglacial conditions. There is negligible depletion of labile elements in the fine fraction relative to the parent rock. Conversely, evidence for surface and near-surface granular disaggregation, an increase in clast angularity with depth, dominantly angular sand grains, in situ detached clasts and fractured clasts above rockhead favour formation by frost weathering under Pleistocene stadial conditions. There is no convincing evidence for blockfield inheritance from Neogene regolith. As the blockfields were buried under cold-based glacier ice during the last glacial maximum, they pre-date ice-sheet build-up at ∼35–30 ka. Measured rates of plateau surface lowering suggest that present blockfield regolith is probably of Late Pleistocene (<135 ka) age. |
format |
Article in Journal/Newspaper |
author |
Hopkinson, Charles Ballantyne, Colin |
author_facet |
Hopkinson, Charles Ballantyne, Colin |
author_sort |
Hopkinson, Charles |
title |
Age and origin of blockfields on Scottish mountains |
title_short |
Age and origin of blockfields on Scottish mountains |
title_full |
Age and origin of blockfields on Scottish mountains |
title_fullStr |
Age and origin of blockfields on Scottish mountains |
title_full_unstemmed |
Age and origin of blockfields on Scottish mountains |
title_sort |
age and origin of blockfields on scottish mountains |
publishDate |
2014 |
url |
https://risweb.st-andrews.ac.uk/portal/en/researchoutput/age-and-origin-of-blockfields-on-scottish-mountains(027ab8fb-b9f7-4ad7-86d5-2e320e9b3aef).html https://doi.org/10.1080/14702541.2013.855808 |
genre |
Cold-based glacier Ice Sheet |
genre_facet |
Cold-based glacier Ice Sheet |
op_source |
Hopkinson , C & Ballantyne , C 2014 , ' Age and origin of blockfields on Scottish mountains ' , Scottish Geographical Journal , vol. 130 , no. 2 , pp. 116–141 . https://doi.org/10.1080/14702541.2013.855808 |
op_rights |
info:eu-repo/semantics/restrictedAccess |
op_doi |
https://doi.org/10.1080/14702541.2013.855808 |
container_title |
Scottish Geographical Journal |
container_volume |
130 |
container_issue |
2 |
container_start_page |
116 |
op_container_end_page |
141 |
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1766391325345710080 |