The Maximum Extent of the Laurentide Ice Sheet along the East Coast of North America during the Last Glaciation

The margin of a former Laurentide ice sheet is traced through southern and central Alberta, from the Saskatchewan border southeast of Medicine Hat to beyond Rocky Mountain House, southwest of Edmonton. This margin, which marks the limit of a significant glacier advance or readvance, is thought to represent the maximum extent of Laurentide ice on the Canadian prairies during Classical Wisconsin time. In the south this margin follows a well-developed hummocky moraine; in the north it is indicated mainly by a discordance in trend of ice-flow markings, a disruption of drainage, and a change in maturity of topography on either side.

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Glacial and Sea Level History of Lowther and Griffith Islands, Northwest Territories: A Hint of Tectonics

Géographie physique et Quaternaire ◽

10.7202/032944ar ◽

2007 ◽

Vol 47 (2) ◽

pp. 133-145 ◽

Cited By ~ 11

Author(s):

Arthur S. Dyke

Keyword(s):

Northwest Territories ◽

Sea Level ◽

Ice Sheet ◽

Canadian Arctic ◽

Laurentide Ice Sheet ◽

Structural Elements ◽

Ice Flow ◽

Ice Load ◽

Last Glaciation ◽

History Of

ABSTRACT Lowther and Griffith islands, in the centre of Parry Channel, were overrun by the Laurentide Ice Sheet early in the last glaciation. Northeastward Laurentide ice flow persisted across at least Lowther Island until early Holocene déglaciation. Well constrained postglacial emergence curves for the islands confirm a southward dip of raised shorelines, contrary to the dip expected from the ice load configuration. This and previously reported incongruities may indicate regionally extensive tectonic complications of postglacial rebound aligned with major structural elements in the central Canadian Arctic Islands.

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A NEW SUBSPECIES, NEPHROTOMA LUNDBECKI ALEXANDERI, DESCRIBED FROM SOUTH OF THE MAXIMUM EXTENT OF THE LAURENTIDE ICE AND NEW DISTRIBUTION RECORDS FOR OTHER NEARCTIC NEPHROTOMA (DIPTERA: TIPULIDAE)

The Canadian Entomologist ◽

10.4039/ent11949-1 ◽

1987 ◽

Vol 119 (1) ◽

pp. 49-53 ◽

Cited By ~ 1

Author(s):

Pjotr Oosterbroek ◽

Ida R.M. Tangelder

Keyword(s):

Ice Sheet ◽

Laurentide Ice Sheet ◽

Palaearctic Species ◽

New Subspecies ◽

Maximum Extent ◽

New Distribution

AbstractSubspeciation in the circumpolar Nephrotoma lundbecki is discussed for a population from south of the Laurentide Ice Sheet, described here as N.l. alexanderi. For 18 nearctic Nephrotoma species new distribution records are presented, mainly from the northern Nearctic, adding considerably to our knowledge of the distribution of these species. Included is the second nearctic record of the palaearctic species Nephrotoma cornicina (L.).

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Late Wisconsin Advance and Retreat Pattern in the Miami Sublobe, Laurentide Ice Sheet

Annals of Glaciology ◽

10.1017/s026030550000851x ◽

1990 ◽

Vol 14 ◽

pp. 172-175 ◽

Cited By ~ 1

Author(s):

Thomas V. Lowell ◽

Robert Stuckenrath

Keyword(s):

Climatic Change ◽

Ice Sheet ◽

Laurentide Ice Sheet ◽

Maximum Extent ◽

Southern Margin ◽

Radiometric Ages ◽

A Site ◽

Age Estimates

Ice-sheet advance and retreat chronologies reflect climatic change in a manner that is difficult to decipher. Especially difficult is the placement of records into a chronologic sequence. Multiple age estimates obtained from three stratigraphic positions at a site in Ohio show that organics within deposits of the Miami sublobe, along the southern margin of the Laurentide ice sheet, may be up to 3000 years older than the age of the maximum Late Wisconsin extension of that sublobe. In addition, recent studies on organic accumulations above glacial drift provide bracketing ages for ice recession. When the existing radiometric ages for the Miami sublobe are interpreted with these new radiometric constraints, several fluctuations suggested by prior workers are unsupported. A simpler chronology for the Miami sublobe suggests that in late Wisconsin time the southern margin of the Laurentide ice sheet advanced through Ohio about 22 ka to its maximum extent at 19.7 and remained near there until 15 ka. This is in agreement with newly-refined stratigraphic histories of other Laurentide lobes.

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The Effects of the Laurentide Ice Sheet on North American Climate during the Last Glacial Maximum

Géographie physique et Quaternaire ◽

10.7202/032684ar ◽

2008 ◽

Vol 41 (2) ◽

pp. 291-299 ◽

Cited By ~ 22

Author(s):

A. J. Broccoli ◽

S. Manabe

Keyword(s):

North America ◽

Last Glacial Maximum ◽

North American ◽

Ice Sheet ◽

Glacial Maximum ◽

Laurentide Ice Sheet ◽

Last Glacial ◽

North American Climate ◽

The Last Glacial Maximum ◽

The Last Glacial

ABSTRACT A climate model, consisting of an atmospheric general circulation model coupled with a simple model of the oceanic mixed layer, is used to investigate the effects of the continental ice distribution of the last glacial maximum (LGM) on North American climate. This model has previously been used to simulate the LGM climate, producing temperature changes reasonably in agreement with paleoclimatic data. The LGM distribution of continental ice according to the maximum reconstruction of HUGHES et al. (1981) is used as input to the model. In response to the incorporation of the expanded continental ice of the LGM, the model produces major changes in the climate of North America. The ice sheet exerts an orographic effect on the tropospheric flow, resulting in a splitting of the midlatitude westerlies in all seasons but summer. Winter temperatures are greatly reduced over a wide region south of the Laurentide ice sheet, although summer cooling is less extensive. An area of reduced soil moisture develops in the interior of North America just south of the ice margin. At the same time, precipitation increases in a belt extending from the extreme southeastern portion of the ice sheet eastward into the North Atlantic. Some of these findings are similar to paleoclimatic inferences based on geological evidence.

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Possible Causes of the Variability of Postglacial Uplift in North America

Quaternary Research ◽

10.1016/0033-5894(71)90062-7 ◽

1971 ◽

Vol 1 (4) ◽

pp. 522-531 ◽

Cited By ~ 4

Author(s):

Richard H. Fillon

Keyword(s):

North America ◽

Ice Sheet ◽

Tectonic Activity ◽

Laurentide Ice Sheet ◽

Uplift Rate ◽

Geophysical Research ◽

Northeastern North America ◽

Isostatic Uplift ◽

Uplift Rates ◽

Consistent Manner

Postglacial uplift data from 33 sites in northeastern North America reveal that during the period from 11,000 years B.P. to 7000 years B.P., glacio-isostatic uplift rates varied in a consistent manner with distance from the former margin of the Laurentide Ice Sheet. The consistent trends of these uplift rate variations with distance from the former ice sheet margin suggest that they were not the result of changes in the rate of ice sheet retreat or local tectonic activity. They instead may have resulted from rebound affected significantly by the earth's viscosity at a depth approximately equal to the wavelength of isostatic deformation [McConnell, R.K., Jr., Journal of Geophysical Research70, 5171 (1965)]. Extremely high viscosities below 600 km, however, probably provide the lower limit for this relationship.

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Late Wisconsin Advance and Retreat Pattern in the Miami Sublobe, Laurentide Ice Sheet

Annals of Glaciology ◽

10.3189/s026030550000851x ◽

1990 ◽

Vol 14 ◽

pp. 172-175 ◽

Cited By ~ 1

Author(s):

Thomas V. Lowell ◽

Robert Stuckenrath

Keyword(s):

Climatic Change ◽

Ice Sheet ◽

Laurentide Ice Sheet ◽

Maximum Extent ◽

Southern Margin ◽

Radiometric Ages ◽

A Site ◽

Age Estimates

Ice-sheet advance and retreat chronologies reflect climatic change in a manner that is difficult to decipher. Especially difficult is the placement of records into a chronologic sequence. Multiple age estimates obtained from three stratigraphic positions at a site in Ohio show that organics within deposits of the Miami sublobe, along the southern margin of the Laurentide ice sheet, may be up to 3000 years older than the age of the maximum Late Wisconsin extension of that sublobe. In addition, recent studies on organic accumulations above glacial drift provide bracketing ages for ice recession. When the existing radiometric ages for the Miami sublobe are interpreted with these new radiometric constraints, several fluctuations suggested by prior workers are unsupported. A simpler chronology for the Miami sublobe suggests that in late Wisconsin time the southern margin of the Laurentide ice sheet advanced through Ohio about 22 ka to its maximum extent at 19.7 and remained near there until 15 ka. This is in agreement with newly-refined stratigraphic histories of other Laurentide lobes.

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Palimpsest tunnel valleys: evidence for relative timing of advances in an interlobate area of the Laurentide ice sheet

Annals of Glaciology ◽

10.3189/172756499781821940 ◽

1999 ◽

Vol 28 ◽

pp. 47-52 ◽

Cited By ~ 20

Author(s):

Alan E. Kehew ◽

Linda P. Nicks ◽

W. Thomas Straw

Keyword(s):

North America ◽

Lake Michigan ◽

Ice Sheet ◽

Laurentide Ice Sheet ◽

Great Lakes Region ◽

Relative Timing ◽

Outburst Flood ◽

Flow Lines ◽

Lake Michigan Lobe ◽

East West

AbstractDuring retreat from the lateWisconsinan maximum advance in the Great Lakes region of North America, the Laurentide ice sheet margin became distinctly lobate. The Lake Michigan, Saginaw, and Huron—Erie lobes converged in southern Michigan and Indiana, U.S.A. to form a complex interlobate region. Some time after the glacial maximum, the Lake Michigan lobe advanced over landscapes previously formed by the Saginaw lobe. This can be explained by an asynchronous advance of the Lake Michigan lobe during a Saginaw lobe retreat or by an increase in size of the Lake Michigan lobe relative to the Saginaw lobe during a synchronous readvance.Cross-cutting relationships in southwestern Michigan, including palimpsest tunnel valleys, document the overriding of Saginaw lobe terrain. Deep, generally straight trenches parallel to glacial flow lines with hummocky, irregular sides and bottoms are interpreted as tunnel valleys. Saginaw lobe tunnel valleys trend northeast—southwest and Lake Michigan lobe tunnel valleys generally trend east—west.At some time after a Saginaw lobe retreat in southern Michigan, the drumlinized landscape was overridden by an advance of the Lake Michigan lobe to an ice-marginal position at the Tekonsha moraine. Saginaw lobe tunnel valleys in the overridden area were completely filled with ice and debris from the Saginaw lobe retreat at the time of the Lake Michigan lobe advance. Supraglacial and proglacial sediments were deposited over the buried valleys by the Lake Michigan lobe, sometimes by meltwater streams that flowed at high angles to the trends of the valleys. After entrenchment of the Kalamazoo River valley, probably by a subglacial outburst flood, short tributaries were cut nearly at right angles across and through the debris and ice within several buried Saginaw lobe tunnel valleys. After the retreat of the Lake Michigan lobe, subsequent melting of ice in the palimpsest tunnel valleys exhumed the valleys, creating the cross-cutting relationships with the Lake Michigan lobe deposits.

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