The million-year evolution of the glacial trimline in the southernmost Ellsworth Mountains, Antarctica

David Sugden; Andrew Hein; John Woodward; Shasta Marrero; Angel Rodes; Stuart Dunning; Stewart Freeman; Kate Winter; Matthew  Westoby

doi:10.1016/j.epsl.2017.04.006

The million-year evolution of the glacial trimline in the southernmost Ellsworth Mountains, Antarctica

David Sugden, Andrew Hein, John Woodward, Shasta Marrero, Angel Rodes, Stuart Dunning, Stewart Freeman, Kate Winter, Matthew Westoby

School of Geosciences

Research output: Contribution to journal › Article › peer-review

Abstract / Description of output

An elevated erosional trimline in the heart of West Antarctica in the Ellsworth Mountains tells of thicker ice in the past and represents an important yet ambiguous stage in the evolution of the Antarctic Ice Sheet. Here we analyse the geomorphology of massifs in the southernmost Heritage Range where the surfaces associated with the trimline are overlain by surficial deposits that have the potential to be dated through cosmogenic nuclide analysis. Analysis of 100 rock samples reveals that some clasts have been exposed on glacially moulded surfaces
for 1.4 Ma and perhaps more than 3.5 Ma, while others reflect fluctuations in thickness during Quaternary glacial cycles. Modelling the age of the glacially moulded bedrock surface based on cosmogenic 10Be, 26Al and 21Ne concentrations from a depth-profile indicates a minimum exposure age of 2.1-2.6 Ma. We conclude that the glacially eroded surfaces adjacent to the trimline predate the Last Glacial Maximum and
indeed the Quaternary. Since erosion was by warm-based ice near an icesheet upper margin, we suggest it first occurred during the early
glaciations of Antarctica before the stepped cooling of the mid-Miocene at ~14 Ma. This was a time when the interior Antarctic continent had
summers warm enough for tundra vegetation to grow and for mountain glaciers to consist of ice at the pressure melting point. During these
milder conditions, and subsequently, erosion of glacial troughs is likely to have lowered the ice-sheet surface in relation to the mountains. This
means that the range of orbitally induced cyclic fluctuations in ice thickness have progressively been confined to lower elevations.

Original language	English
Pages (from-to)	42-52
Journal	Earth and Planetary Science Letters
Volume	469
Early online date	24 Apr 2017
DOIs	https://doi.org/10.1016/j.epsl.2017.04.006
Publication status	Published - 1 Jul 2017

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10.1016/j.epsl.2017.04.006Licence: Creative Commons: Attribution (CC-BY)

34116652. PFV. Sugden. Hein.
© 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license
Final published version, 4.42 MBLicence: CC BY

http://www.sciencedirect.com/science/article/pii/S0012821X17301851Licence: Creative Commons: Attribution (CC-BY)

Airborne Geophysical Investigations targets basal boundary conditions for the institute mollar ice streams, west antartica
Siegert, M.
NERC
1/04/10 → 31/08/13
Project: Research

Cite this

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title = "The million-year evolution of the glacial trimline in the southernmost Ellsworth Mountains, Antarctica",

abstract = "An elevated erosional trimline in the heart of West Antarctica in the Ellsworth Mountains tells of thicker ice in the past and represents an important yet ambiguous stage in the evolution of the Antarctic Ice Sheet. Here we analyse the geomorphology of massifs in the southernmost Heritage Range where the surfaces associated with the trimline are overlain by surficial deposits that have the potential to be dated through cosmogenic nuclide analysis. Analysis of 100 rock samples reveals that some clasts have been exposed on glacially moulded surfacesfor 1.4 Ma and perhaps more than 3.5 Ma, while others reflect fluctuations in thickness during Quaternary glacial cycles. Modelling the age of the glacially moulded bedrock surface based on cosmogenic 10Be, 26Al and 21Ne concentrations from a depth-profile indicates a minimum exposure age of 2.1-2.6 Ma. We conclude that the glacially eroded surfaces adjacent to the trimline predate the Last Glacial Maximum andindeed the Quaternary. Since erosion was by warm-based ice near an icesheet upper margin, we suggest it first occurred during the earlyglaciations of Antarctica before the stepped cooling of the mid-Miocene at ~14 Ma. This was a time when the interior Antarctic continent hadsummers warm enough for tundra vegetation to grow and for mountain glaciers to consist of ice at the pressure melting point. During thesemilder conditions, and subsequently, erosion of glacial troughs is likely to have lowered the ice-sheet surface in relation to the mountains. Thismeans that the range of orbitally induced cyclic fluctuations in ice thickness have progressively been confined to lower elevations.",

author = "David Sugden and Andrew Hein and John Woodward and Shasta Marrero and Angel Rodes and Stuart Dunning and Stewart Freeman and Kate Winter and Matthew Westoby",

note = "The research was supported by the UK Natural Environment Research Council: Grant numbers NE/1025840/1, NE/1034194/1 and NE/G013071/1. Likely to have open access fee paid so final version can be attached and made open upon publication but if not, set a 12 month embargo.",

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AU - Sugden, David

AU - Hein, Andrew

AU - Woodward, John

AU - Marrero, Shasta

AU - Rodes, Angel

AU - Dunning, Stuart

AU - Freeman, Stewart

AU - Winter, Kate

AU - Westoby, Matthew

N1 - The research was supported by the UK Natural Environment Research Council: Grant numbers NE/1025840/1, NE/1034194/1 and NE/G013071/1. Likely to have open access fee paid so final version can be attached and made open upon publication but if not, set a 12 month embargo.

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N2 - An elevated erosional trimline in the heart of West Antarctica in the Ellsworth Mountains tells of thicker ice in the past and represents an important yet ambiguous stage in the evolution of the Antarctic Ice Sheet. Here we analyse the geomorphology of massifs in the southernmost Heritage Range where the surfaces associated with the trimline are overlain by surficial deposits that have the potential to be dated through cosmogenic nuclide analysis. Analysis of 100 rock samples reveals that some clasts have been exposed on glacially moulded surfacesfor 1.4 Ma and perhaps more than 3.5 Ma, while others reflect fluctuations in thickness during Quaternary glacial cycles. Modelling the age of the glacially moulded bedrock surface based on cosmogenic 10Be, 26Al and 21Ne concentrations from a depth-profile indicates a minimum exposure age of 2.1-2.6 Ma. We conclude that the glacially eroded surfaces adjacent to the trimline predate the Last Glacial Maximum andindeed the Quaternary. Since erosion was by warm-based ice near an icesheet upper margin, we suggest it first occurred during the earlyglaciations of Antarctica before the stepped cooling of the mid-Miocene at ~14 Ma. This was a time when the interior Antarctic continent hadsummers warm enough for tundra vegetation to grow and for mountain glaciers to consist of ice at the pressure melting point. During thesemilder conditions, and subsequently, erosion of glacial troughs is likely to have lowered the ice-sheet surface in relation to the mountains. Thismeans that the range of orbitally induced cyclic fluctuations in ice thickness have progressively been confined to lower elevations.

AB - An elevated erosional trimline in the heart of West Antarctica in the Ellsworth Mountains tells of thicker ice in the past and represents an important yet ambiguous stage in the evolution of the Antarctic Ice Sheet. Here we analyse the geomorphology of massifs in the southernmost Heritage Range where the surfaces associated with the trimline are overlain by surficial deposits that have the potential to be dated through cosmogenic nuclide analysis. Analysis of 100 rock samples reveals that some clasts have been exposed on glacially moulded surfacesfor 1.4 Ma and perhaps more than 3.5 Ma, while others reflect fluctuations in thickness during Quaternary glacial cycles. Modelling the age of the glacially moulded bedrock surface based on cosmogenic 10Be, 26Al and 21Ne concentrations from a depth-profile indicates a minimum exposure age of 2.1-2.6 Ma. We conclude that the glacially eroded surfaces adjacent to the trimline predate the Last Glacial Maximum andindeed the Quaternary. Since erosion was by warm-based ice near an icesheet upper margin, we suggest it first occurred during the earlyglaciations of Antarctica before the stepped cooling of the mid-Miocene at ~14 Ma. This was a time when the interior Antarctic continent hadsummers warm enough for tundra vegetation to grow and for mountain glaciers to consist of ice at the pressure melting point. During thesemilder conditions, and subsequently, erosion of glacial troughs is likely to have lowered the ice-sheet surface in relation to the mountains. Thismeans that the range of orbitally induced cyclic fluctuations in ice thickness have progressively been confined to lower elevations.

U2 - 10.1016/j.epsl.2017.04.006

DO - 10.1016/j.epsl.2017.04.006

M3 - Article

SN - 0012-821X

VL - 469

SP - 42

EP - 52

JO - Earth and Planetary Science Letters

JF - Earth and Planetary Science Letters

ER -

The million-year evolution of the glacial trimline in the southernmost Ellsworth Mountains, Antarctica

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Airborne Geophysical Investigations targets basal boundary conditions for the institute mollar ice streams, west antartica

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