Formation of patterned ground and sublimation till over Miocene glacier ice in Beacon Valley, southern Victoria Land, Antarctica
A thin glacial diamicton, informally termed Granite drift, occupies the floor of central Beacon Valley in southern Victoria Land, Antarctica. This drift is <1.0 m thick and rests with sharp planar contacts on stagnant glacier ice reportedly of Miocene age, older than 8.1 Ma. The age of the ice is...
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ftunivbruxelles:oai:dipot.ulb.ac.be:2013/173065 2023-05-15T13:42:08+02:00 Formation of patterned ground and sublimation till over Miocene glacier ice in Beacon Valley, southern Victoria Land, Antarctica Marchant, David D.R. Lewis, Adam R. Phillips, William M. Moore, E. J. Souchez, Roland Denton, George H. Sugden, David Potter Jr. Noel Landis, Gary P. 2002-06 No full-text files http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/173065 en eng uri/info:doi/10.1130/0016-7606(2002)114<0718:FOPGAS>2.0.CO;2 http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/173065 Geological Society of America bulletin, 114 (6 Glaciologie Géologie et minéralogie Antarctica cosmogenic-nuclide exposure dating Dry Valleys periglacial features polygons info:eu-repo/semantics/article info:ulb-repo/semantics/articlePeerReview info:ulb-repo/semantics/openurl/article 2002 ftunivbruxelles 2022-06-12T20:35:13Z A thin glacial diamicton, informally termed Granite drift, occupies the floor of central Beacon Valley in southern Victoria Land, Antarctica. This drift is <1.0 m thick and rests with sharp planar contacts on stagnant glacier ice reportedly of Miocene age, older than 8.1 Ma. The age of the ice is based on 40Ar/39Ar analyses of presumed in situ ash-fall deposits that occur within Granite drift. At odds with the great age of this ice are high-centered polygons that cut Granite drift. If polygon development has reworked and retransported ash-fall deposits, then they are untenable as chronostratigraphic markers and cannot be used to place a minimum age on the underlying glacier ice.Our results show that the surface of Granite drift is stable at polygon centers and that enclosed ash-fall deposits can be used to define the age of underlying glacier ice. In our model for patterned-ground development, active regions lie only above polygon troughs, where enhanced sublimation of underlying ice outlines high-centered polygons. The rate of sublimation is influenced by the development of porous gravel-and-cobble lag deposits that form above thermal-contraction cracks in the underlying ice. A negative feedback associated with the development of secondary-ice lenses at the base of polygon troughs prevents runaway ice loss. Secondary-ice lenses contrast markedly with glacial ice by lying on a δD versus δ18O slope of 5 rather than a precipitation slope of 8 and by possessing a strongly negative deuterium excess. The latter indicates that secondary-ice lenses likely formed by melting, downward percolation, and subsequent refreezing of snow trapped preferentially in deep polygon troughs.The internal stratigraphy of Granite drift is related to the formation of surface polygons and surrounding troughs. The drift is composed of two facies: A nonweathered, matrix-supported diamicton that contains >25% striated clasts in the >16 mm fraction and a weathered, clast-supported diamicton with varnished and wind-faceted gravels and ... Article in Journal/Newspaper Antarc* Antarctica Victoria Land DI-fusion : dépôt institutionnel de l'Université libre de Bruxelles (ULB) Beacon Valley ENVELOPE(160.650,160.650,-77.817,-77.817) Stagnant Glacier ENVELOPE(68.550,68.550,-70.500,-70.500) Victoria Land |
institution |
Open Polar |
collection |
DI-fusion : dépôt institutionnel de l'Université libre de Bruxelles (ULB) |
op_collection_id |
ftunivbruxelles |
language |
English |
topic |
Glaciologie Géologie et minéralogie Antarctica cosmogenic-nuclide exposure dating Dry Valleys periglacial features polygons |
spellingShingle |
Glaciologie Géologie et minéralogie Antarctica cosmogenic-nuclide exposure dating Dry Valleys periglacial features polygons Marchant, David D.R. Lewis, Adam R. Phillips, William M. Moore, E. J. Souchez, Roland Denton, George H. Sugden, David Potter Jr. Noel Landis, Gary P. Formation of patterned ground and sublimation till over Miocene glacier ice in Beacon Valley, southern Victoria Land, Antarctica |
topic_facet |
Glaciologie Géologie et minéralogie Antarctica cosmogenic-nuclide exposure dating Dry Valleys periglacial features polygons |
description |
A thin glacial diamicton, informally termed Granite drift, occupies the floor of central Beacon Valley in southern Victoria Land, Antarctica. This drift is <1.0 m thick and rests with sharp planar contacts on stagnant glacier ice reportedly of Miocene age, older than 8.1 Ma. The age of the ice is based on 40Ar/39Ar analyses of presumed in situ ash-fall deposits that occur within Granite drift. At odds with the great age of this ice are high-centered polygons that cut Granite drift. If polygon development has reworked and retransported ash-fall deposits, then they are untenable as chronostratigraphic markers and cannot be used to place a minimum age on the underlying glacier ice.Our results show that the surface of Granite drift is stable at polygon centers and that enclosed ash-fall deposits can be used to define the age of underlying glacier ice. In our model for patterned-ground development, active regions lie only above polygon troughs, where enhanced sublimation of underlying ice outlines high-centered polygons. The rate of sublimation is influenced by the development of porous gravel-and-cobble lag deposits that form above thermal-contraction cracks in the underlying ice. A negative feedback associated with the development of secondary-ice lenses at the base of polygon troughs prevents runaway ice loss. Secondary-ice lenses contrast markedly with glacial ice by lying on a δD versus δ18O slope of 5 rather than a precipitation slope of 8 and by possessing a strongly negative deuterium excess. The latter indicates that secondary-ice lenses likely formed by melting, downward percolation, and subsequent refreezing of snow trapped preferentially in deep polygon troughs.The internal stratigraphy of Granite drift is related to the formation of surface polygons and surrounding troughs. The drift is composed of two facies: A nonweathered, matrix-supported diamicton that contains >25% striated clasts in the >16 mm fraction and a weathered, clast-supported diamicton with varnished and wind-faceted gravels and ... |
format |
Article in Journal/Newspaper |
author |
Marchant, David D.R. Lewis, Adam R. Phillips, William M. Moore, E. J. Souchez, Roland Denton, George H. Sugden, David Potter Jr. Noel Landis, Gary P. |
author_facet |
Marchant, David D.R. Lewis, Adam R. Phillips, William M. Moore, E. J. Souchez, Roland Denton, George H. Sugden, David Potter Jr. Noel Landis, Gary P. |
author_sort |
Marchant, David D.R. |
title |
Formation of patterned ground and sublimation till over Miocene glacier ice in Beacon Valley, southern Victoria Land, Antarctica |
title_short |
Formation of patterned ground and sublimation till over Miocene glacier ice in Beacon Valley, southern Victoria Land, Antarctica |
title_full |
Formation of patterned ground and sublimation till over Miocene glacier ice in Beacon Valley, southern Victoria Land, Antarctica |
title_fullStr |
Formation of patterned ground and sublimation till over Miocene glacier ice in Beacon Valley, southern Victoria Land, Antarctica |
title_full_unstemmed |
Formation of patterned ground and sublimation till over Miocene glacier ice in Beacon Valley, southern Victoria Land, Antarctica |
title_sort |
formation of patterned ground and sublimation till over miocene glacier ice in beacon valley, southern victoria land, antarctica |
publishDate |
2002 |
url |
http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/173065 |
long_lat |
ENVELOPE(160.650,160.650,-77.817,-77.817) ENVELOPE(68.550,68.550,-70.500,-70.500) |
geographic |
Beacon Valley Stagnant Glacier Victoria Land |
geographic_facet |
Beacon Valley Stagnant Glacier Victoria Land |
genre |
Antarc* Antarctica Victoria Land |
genre_facet |
Antarc* Antarctica Victoria Land |
op_source |
Geological Society of America bulletin, 114 (6 |
op_relation |
uri/info:doi/10.1130/0016-7606(2002)114<0718:FOPGAS>2.0.CO;2 http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/173065 |
_version_ |
1766162971275296768 |