A Glacial History of Roberts Massif, Central Transantarctic Mountains, Antarctica, Using Cosmogenic 3He, 10Be, and 21Ne Surface Exposure Ages
Ice-free areas at high elevation in the central Transantarctic Mountains preserve moraines and drift deposits that delineate the former thickness and extent of the East Antarctic Ice Sheet (EAIS); cosmogenic exposure ages on these features indicate when the ice sheet was as or more extensive than to...
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ftmaineuniv:oai:digitalcommons.library.umaine.edu:etd-3951 2023-06-11T04:06:12+02:00 A Glacial History of Roberts Massif, Central Transantarctic Mountains, Antarctica, Using Cosmogenic 3He, 10Be, and 21Ne Surface Exposure Ages Balter, Alexandra M 2018-08-01T07:00:00Z application/pdf https://digitalcommons.library.umaine.edu/etd/2941 https://digitalcommons.library.umaine.edu/context/etd/article/3951/viewcontent/Balter__Alexandra_Final_1.11.19.pdf unknown DigitalCommons@UMaine https://digitalcommons.library.umaine.edu/etd/2941 https://digitalcommons.library.umaine.edu/context/etd/article/3951/viewcontent/Balter__Alexandra_Final_1.11.19.pdf Electronic Theses and Dissertations Antarctica exposure ages East Antarctic Ice Sheet glacial history Geochemistry Geomorphology text 2018 ftmaineuniv 2023-05-04T18:03:00Z Ice-free areas at high elevation in the central Transantarctic Mountains preserve moraines and drift deposits that delineate the former thickness and extent of the East Antarctic Ice Sheet (EAIS); cosmogenic exposure ages on these features indicate when the ice sheet was as or more extensive than today. Approximately 30 existing cosmogenic-nuclide exposure ages from scattered locations within these deposits suggest that some moraines and drift sheets are at least 5 Ma old. Those ages imply that the age range of these deposits may span warm periods during the Miocene and Pliocene, during which the EAIS is hypothesized to have been much smaller than present and which constitute potentially important geologic analogues for future warm climates. Therefore, to evaluate the long-term stability of the ice sheet, I have obtained 3He, 10Be, and 21Ne exposure ages from 150 glacially-transported clasts on distinct ice-marginal landforms at Roberts Massif at the head of Shackleton Glacier. The majority of these data comprise 3He measurements on pyroxene extracted from Ferrar dolerite clasts and prepared using a refined HF etching method that improves both measurement throughput and reproducibility. I address the common problem of scatter in exposure ages due to cosmogenic-nuclide inheritance by (i) measuring large numbers of exposure ages, including ~7 from each landform, and (ii) resampling and averaging approaches based on both statistical criteria and field observations of boulder characteristics and geomorphic context. Moraines at Roberts Massif are openwork boulder belts characteristic of deposition by cold-based ice, which is consistent with present climate and glaciological conditions. Additionally, the lack of glaciofluvial deposits at Roberts Massif suggests that temperatures have not been sufficiently warm to induce surface melting of the ice at this location since at least the beginning of my glacial record. Apparent exposure ages at this site range from ~400 ka to 13 Ma, with individual moraine ages as old as ~8 ... Text Antarc* Antarctic Antarctica Ice Sheet Shackleton Glacier The University of Maine: DigitalCommons@UMaine Antarctic East Antarctic Ice Sheet Roberts massif ENVELOPE(-177.083,-177.083,-85.533,-85.533) Shackleton Shackleton Glacier ENVELOPE(-37.200,-37.200,-54.133,-54.133) Transantarctic Mountains |
institution |
Open Polar |
collection |
The University of Maine: DigitalCommons@UMaine |
op_collection_id |
ftmaineuniv |
language |
unknown |
topic |
Antarctica exposure ages East Antarctic Ice Sheet glacial history Geochemistry Geomorphology |
spellingShingle |
Antarctica exposure ages East Antarctic Ice Sheet glacial history Geochemistry Geomorphology Balter, Alexandra M A Glacial History of Roberts Massif, Central Transantarctic Mountains, Antarctica, Using Cosmogenic 3He, 10Be, and 21Ne Surface Exposure Ages |
topic_facet |
Antarctica exposure ages East Antarctic Ice Sheet glacial history Geochemistry Geomorphology |
description |
Ice-free areas at high elevation in the central Transantarctic Mountains preserve moraines and drift deposits that delineate the former thickness and extent of the East Antarctic Ice Sheet (EAIS); cosmogenic exposure ages on these features indicate when the ice sheet was as or more extensive than today. Approximately 30 existing cosmogenic-nuclide exposure ages from scattered locations within these deposits suggest that some moraines and drift sheets are at least 5 Ma old. Those ages imply that the age range of these deposits may span warm periods during the Miocene and Pliocene, during which the EAIS is hypothesized to have been much smaller than present and which constitute potentially important geologic analogues for future warm climates. Therefore, to evaluate the long-term stability of the ice sheet, I have obtained 3He, 10Be, and 21Ne exposure ages from 150 glacially-transported clasts on distinct ice-marginal landforms at Roberts Massif at the head of Shackleton Glacier. The majority of these data comprise 3He measurements on pyroxene extracted from Ferrar dolerite clasts and prepared using a refined HF etching method that improves both measurement throughput and reproducibility. I address the common problem of scatter in exposure ages due to cosmogenic-nuclide inheritance by (i) measuring large numbers of exposure ages, including ~7 from each landform, and (ii) resampling and averaging approaches based on both statistical criteria and field observations of boulder characteristics and geomorphic context. Moraines at Roberts Massif are openwork boulder belts characteristic of deposition by cold-based ice, which is consistent with present climate and glaciological conditions. Additionally, the lack of glaciofluvial deposits at Roberts Massif suggests that temperatures have not been sufficiently warm to induce surface melting of the ice at this location since at least the beginning of my glacial record. Apparent exposure ages at this site range from ~400 ka to 13 Ma, with individual moraine ages as old as ~8 ... |
format |
Text |
author |
Balter, Alexandra M |
author_facet |
Balter, Alexandra M |
author_sort |
Balter, Alexandra M |
title |
A Glacial History of Roberts Massif, Central Transantarctic Mountains, Antarctica, Using Cosmogenic 3He, 10Be, and 21Ne Surface Exposure Ages |
title_short |
A Glacial History of Roberts Massif, Central Transantarctic Mountains, Antarctica, Using Cosmogenic 3He, 10Be, and 21Ne Surface Exposure Ages |
title_full |
A Glacial History of Roberts Massif, Central Transantarctic Mountains, Antarctica, Using Cosmogenic 3He, 10Be, and 21Ne Surface Exposure Ages |
title_fullStr |
A Glacial History of Roberts Massif, Central Transantarctic Mountains, Antarctica, Using Cosmogenic 3He, 10Be, and 21Ne Surface Exposure Ages |
title_full_unstemmed |
A Glacial History of Roberts Massif, Central Transantarctic Mountains, Antarctica, Using Cosmogenic 3He, 10Be, and 21Ne Surface Exposure Ages |
title_sort |
glacial history of roberts massif, central transantarctic mountains, antarctica, using cosmogenic 3he, 10be, and 21ne surface exposure ages |
publisher |
DigitalCommons@UMaine |
publishDate |
2018 |
url |
https://digitalcommons.library.umaine.edu/etd/2941 https://digitalcommons.library.umaine.edu/context/etd/article/3951/viewcontent/Balter__Alexandra_Final_1.11.19.pdf |
long_lat |
ENVELOPE(-177.083,-177.083,-85.533,-85.533) ENVELOPE(-37.200,-37.200,-54.133,-54.133) |
geographic |
Antarctic East Antarctic Ice Sheet Roberts massif Shackleton Shackleton Glacier Transantarctic Mountains |
geographic_facet |
Antarctic East Antarctic Ice Sheet Roberts massif Shackleton Shackleton Glacier Transantarctic Mountains |
genre |
Antarc* Antarctic Antarctica Ice Sheet Shackleton Glacier |
genre_facet |
Antarc* Antarctic Antarctica Ice Sheet Shackleton Glacier |
op_source |
Electronic Theses and Dissertations |
op_relation |
https://digitalcommons.library.umaine.edu/etd/2941 https://digitalcommons.library.umaine.edu/context/etd/article/3951/viewcontent/Balter__Alexandra_Final_1.11.19.pdf |
_version_ |
1768378026442096640 |