The southern Laurentide Ice Sheet

Mickelson, David M.; Colgan, Patrick M.

doi:10.1016/s1571-0866(03)01001-7

Cited by 60 publications

(61 citation statements)

References 150 publications

(115 reference statements)

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“…Indeed, there is a general trend of fewer tunnel valleys in the more southerly ice lobes (James, Des Moines, Lake Michigan and Huron-Erie), where permafrost was reconstructed as less extensive (e.g. Johnson, 1990;Mickelson and Colgan, 2003). Regionally, we observe large inter-cluster variation in tunnel valley spacing and morphology (form and size), and their association with other glacial landforms (e.g.…”

Section: Implications For the Formation Of Tunnel Valleysmentioning

confidence: 64%

“…The valley cross-cutting it can be traced several tens of kilometres further to the west and therefore must have formed during an earlier phase when ice was more extensive. Mickelson and Colgan, 2003). Moreover, the very low icesurface slopes (∼ 0.001 m km −1 ; Clark, 1992) reconstructed for the James and Des Moines ice lobes would have resulted in low subglacial hydraulic gradients not conducive to channel formation (e.g.…”

Section: Southern Sector Of the Former Laurentide Ice Sheetmentioning

confidence: 99%

“…The locations of ice lobes along the southern sector of the Laurentide Ice Sheet are topographically controlled, mostly by upstream basins, and ice producing these lobes has been inferred to have surged or have been fast-flowing for at least part of their history (e.g. Mickelson and Colgan, 2003; Mar- (Leopold and Maddock, 1953;Leopold et al, 1964) and single flood event (e.g. Lamb and Fonstad, 2010).…”

Section: Southern Sector Of the Former Laurentide Ice Sheetmentioning

confidence: 99%

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Morphological properties of tunnel valleys of the southern sector of the Laurentide Ice Sheet and implications for their formation

Livingstone

Clark

2016

Earth Surf. Dynam.

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Abstract. 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.

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Section: Implications For the Formation Of Tunnel Valleysmentioning

confidence: 64%

Section: Southern Sector Of the Former Laurentide Ice Sheetmentioning

confidence: 99%

Section: Southern Sector Of the Former Laurentide Ice Sheetmentioning

confidence: 99%

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Morphological properties of tunnel valleys of the southern sector of the Laurentide Ice Sheet and implications for their formation

Livingstone

Clark

2016

Earth Surf. Dynam.

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“…During the last glacial maximum the entire field area was covered by the Laurentide Ice Sheet. Other than pockets of remnant paleosols and organic material mixed with tills, soil inception in the study area occurred no earlier than 15,600 14 C-yr BP, the approximate time of glacial retreat (Mickelson and Colgan, 2004).…”

Section: Geologic Setting Of the Hudson-mohawk Watershedmentioning

confidence: 91%

Linking lithology and land use to sources of dissolved and particulate organic matter in headwaters of a temperate, passive-margin river system

Longworth

Petsch

Raymond

et al. 2007

Geochimica et Cosmochimica Acta

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A number of rivers have been found to transport highly aged organic matter [OM]; however, the sources of this aged material remain a matter of debate. One potential source may be erosion and weathering of headwater lithologies rich in ancient sedimentary OM. In this study, waters, suspended particulates, streambed sediments, rocks and soils from fourteen small headwater watersheds of a mid-size, temperate, passive margin river were sampled and characterized by D 14 C, d 13 C, and POC/TPN ratios to identify sources of particulate and dissolved OM delivered to the river mainstem. These headwater sites encompass a range in lithology (OM-rich shales, OM-lean carbonate/mudstone facies, and OM-free crystalline rocks) and land use types (forested and agricultural), and allow investigation of the influence of agriculture and bedrock types on stream OM characteristics. Streams draining large areas of both agricultural land use and OM-rich lithology contain particulate OM [POM] that is more 14 C-depleted than streams draining forested, shale-free watersheds. However, this is not sufficient to account for the significantly lower D 14 C-POC measured in the river mainstem. Dissolved OM [DOM] D 14 C are in all cases enriched compared to POM from the same stream, but are otherwise highly variable and unrelated to either land use or lithology. POC/TPN ratios were likewise highly variable. POC and DOC d 13 C signatures were similar across all watersheds. Based on isotope mass balance, 14 C-free fossil OM sources contribute 0-12% of total stream POM. Although these results do not unequivocally separate the influences of land use and lithology, watershed coverage by shale and agriculture are both important controls on stream D 14 C-POC. Thus export of aged, particle-associated OM may be a feature of river systems along both passive and active continental margins.

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“…1), whilst those along the southern margin tend to have a more smudged record which is often difficult to unravel. This may reflect the more dynamic nature of the southern margin, which is thought to be characterised by episodic advance and retreat (Mickelson and Colgan, 2003), leaving a geomorphic and sedimentary record which is a composite of multiple events. In concert with Jennings (2006) we contend that ice streaming played a dominant role in controlling the southern margin fluctuations, and anticipate that further paleo-ice streams will be identified here.…”

Section: Inventaire Des Courants Paléoglaciaires Examinés Dans Cet Armentioning

confidence: 99%

Ice Streams of the Laurentide Ice Sheet

Winsborrow

Clark

Stokes

2006

gpq

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Ice streams had a major influence on the configuration and the stability of the Laurentide Ice Sheet. Their identification is crucial for an understanding of ice sheet behaviour and their importance is reflected by the recent increase in paleo-ice stream research. This paper provides a synopsis of Laurentide paleo-ice streams, compiled from published sources and our mapping from satellite imagery and aerial photography. In total, 49 hypothesised ice streams are reviewed, and categorised according to the strength of evidence for streaming and knowledge of their extent. A map of Laurentide paleo-ice streams is presented, along with tables documenting the nature of evidence on which streaming behaviour has been invoked. The distribution of ice streams demonstrates the spatial organisation of fast ice flow, and overlapping imprints document major changes in ice flow during retreat. We note that Laurentide paleo-ice streams exhibit a much greater range in size than those currently operating in Antarctica.Les courants glaciaires ont eu une influence déterminante sur la configuration et la stabilité de l’Inlandsis Laurentidien. Leur identification est cruciale pour la compréhension du comportement de la calotte glaciaire et l’intensification récente de la recherche sur les courants paléoglaciaires témoigne de leur importance. Dans cet article, nous présentons une vue d’ensemble des courants paléoglaciaires de l’Inlandsis Laurentidien, compilée à partir de la revue des sources publiées et de notre cartographie établie à l’aide d’imagerie satellite et de photographies aériennes. En tout, nous avons étudié 49 hypothèses de courants glaciaires. Nous les avons classées selon l’importance du témoignage de leur écoulement et la connaissance que nous avons de leur extension. Nous proposons une carte des courants paléoglaciaires laurentidiens ainsi que des tableaux décrivant la nature de la preuve permettant d’établir le comportement de l’écoulement. La répartition des courants glaciaires montre l’organisation spatiale d’un écoulement glaciaire rapide et le chevauchement des empreintes traduit les changements de l’écoulement durant son retrait. Nous notons que la taille des courants paléoglaciaires laurentidiens est plus importante que celle des courants glaciaires actuels de l’Antarctique

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The southern Laurentide Ice Sheet

Cited by 60 publications

References 150 publications

Morphological properties of tunnel valleys of the southern sector of the Laurentide Ice Sheet and implications for their formation

Morphological properties of tunnel valleys of the southern sector of the Laurentide Ice Sheet and implications for their formation

Linking lithology and land use to sources of dissolved and particulate organic matter in headwaters of a temperate, passive-margin river system

Ice Streams of the Laurentide Ice Sheet

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