Morphological properties of tunnel valleys of the southern sector of the Laurentide Ice Sheet and implications for their formation
Tunnel valleys have been widely reported on the bed of former ice sheets and are considered an important expression of subglacial meltwater drainage. Although known to have been cut by erosive meltwater flow, the water source and development of channels has been widely debated; ranging between outbu...
| Main Authors: | , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-07-01
|
| Series: | Earth Surface Dynamics |
| Online Access: | http://www.earth-surf-dynam.net/4/567/2016/esurf-4-567-2016.pdf |
| _version_ | 1818536941570752512 |
|---|---|
| author | S. J. Livingstone C. D. Clark |
| author_facet | S. J. Livingstone C. D. Clark |
| author_sort | S. J. Livingstone |
| collection | DOAJ |
| description | Tunnel valleys have been widely reported on the bed of former ice
sheets and are considered an important expression of subglacial meltwater
drainage. Although known to have been cut by erosive meltwater flow, the
water source and development of channels has been widely debated; ranging
between outburst flood events through to gradually occurring channel
propagation. We have mapped and analysed the spatial pattern and morphometry
of tunnel valleys and associated glacial landforms along the southern sector
of the former Laurentide Ice Sheet from high-resolution digital elevation
models. Around 2000 tunnel valleys have been mapped, revealing an organised
pattern of sub-parallel, semi-regularly spaced valleys that form in
distinctive clusters. The tunnel valleys are typically < 20 km long,
and 0.5–3 km wide, although their width varies considerably down-valley.
They preferentially terminate at moraines, which suggests that formation is
time dependent; while we also observe some tunnel valleys that have grown
headwards out of hill-hole pairs. Analysis of cross-cutting relationships
between tunnel valleys, moraines and outwash fans permits reconstruction of
channel development in relation to the retreating ice margin. This
palaeo-drainage reconstruction demonstrates incremental growth of most
valleys, with some used repeatedly or for long periods, during deglaciation,
while others were abandoned shortly after their formation. Our data and
interpretation support gradual (rather than a single-event) formation of
most tunnel valleys with secondary contributions from flood drainage of
subglacial and or supraglacially stored water down individual tunnel
valleys. The distribution and morphology of tunnel valleys is shown to be
sensitive to regional factors such as basal thermal regime, ice and bed
topography, timing and climate. |
| first_indexed | 2024-12-11T18:44:24Z |
| format | Article |
| id | doaj.art-b53e2afca784468fb53c218b219be1cd |
| institution | Directory Open Access Journal |
| issn | 2196-6311 2196-632X |
| language | English |
| last_indexed | 2024-12-11T18:44:24Z |
| publishDate | 2016-07-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Earth Surface Dynamics |
| spelling | doaj.art-b53e2afca784468fb53c218b219be1cd2022-12-22T00:54:31ZengCopernicus PublicationsEarth Surface Dynamics2196-63112196-632X2016-07-014356758910.5194/esurf-4-567-2016Morphological properties of tunnel valleys of the southern sector of the Laurentide Ice Sheet and implications for their formationS. J. Livingstone0C. D. Clark1Department of Geography, University of Sheffield, Sheffield, S10 2TN, UKDepartment of Geography, University of Sheffield, Sheffield, S10 2TN, UKTunnel valleys have been widely reported on the bed of former ice sheets and are considered an important expression of subglacial meltwater drainage. Although known to have been cut by erosive meltwater flow, the water source and development of channels has been widely debated; ranging between outburst flood events through to gradually occurring channel propagation. We have mapped and analysed the spatial pattern and morphometry of tunnel valleys and associated glacial landforms along the southern sector of the former Laurentide Ice Sheet from high-resolution digital elevation models. Around 2000 tunnel valleys have been mapped, revealing an organised pattern of sub-parallel, semi-regularly spaced valleys that form in distinctive clusters. The tunnel valleys are typically < 20 km long, and 0.5–3 km wide, although their width varies considerably down-valley. They preferentially terminate at moraines, which suggests that formation is time dependent; while we also observe some tunnel valleys that have grown headwards out of hill-hole pairs. Analysis of cross-cutting relationships between tunnel valleys, moraines and outwash fans permits reconstruction of channel development in relation to the retreating ice margin. This palaeo-drainage reconstruction demonstrates incremental growth of most valleys, with some used repeatedly or for long periods, during deglaciation, while others were abandoned shortly after their formation. Our data and interpretation support gradual (rather than a single-event) formation of most tunnel valleys with secondary contributions from flood drainage of subglacial and or supraglacially stored water down individual tunnel valleys. The distribution and morphology of tunnel valleys is shown to be sensitive to regional factors such as basal thermal regime, ice and bed topography, timing and climate.http://www.earth-surf-dynam.net/4/567/2016/esurf-4-567-2016.pdf |
| spellingShingle | S. J. Livingstone C. D. Clark Morphological properties of tunnel valleys of the southern sector of the Laurentide Ice Sheet and implications for their formation Earth Surface Dynamics |
| title | Morphological properties of tunnel valleys of the southern sector of the
Laurentide Ice Sheet and implications for their formation |
| title_full | Morphological properties of tunnel valleys of the southern sector of the
Laurentide Ice Sheet and implications for their formation |
| title_fullStr | Morphological properties of tunnel valleys of the southern sector of the
Laurentide Ice Sheet and implications for their formation |
| title_full_unstemmed | Morphological properties of tunnel valleys of the southern sector of the
Laurentide Ice Sheet and implications for their formation |
| title_short | Morphological properties of tunnel valleys of the southern sector of the
Laurentide Ice Sheet and implications for their formation |
| title_sort | morphological properties of tunnel valleys of the southern sector of the laurentide ice sheet and implications for their formation |
| url | http://www.earth-surf-dynam.net/4/567/2016/esurf-4-567-2016.pdf |
| work_keys_str_mv | AT sjlivingstone morphologicalpropertiesoftunnelvalleysofthesouthernsectorofthelaurentideicesheetandimplicationsfortheirformation AT cdclark morphologicalpropertiesoftunnelvalleysofthesouthernsectorofthelaurentideicesheetandimplicationsfortheirformation |