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)

1987 ◽  
Vol 119 (1) ◽  
pp. 49-53 ◽  
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.).

The probable extent of Classical Wisconsin ice in southern and central Alberta

1977 ◽  
Vol 14 (11) ◽  
pp. 2614-2619 ◽  
Author(s):  
A. MacS. Stalker
Keyword(s):  
Ice Sheet ◽  
Rocky Mountain ◽  
Laurentide Ice Sheet ◽  
The South ◽  
Ice Flow ◽  
Canadian Prairies ◽  
Maximum Extent ◽  
The North ◽  
Glacier Advance

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.

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

1990 ◽  
Vol 14 ◽  
pp. 172-175 ◽  
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.

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

1990 ◽  
Vol 14 ◽  
pp. 172-175 ◽  
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.

scholarly journals Defining the maximum extent of the Laurentide Ice Sheet in Home Bay (eastern Arctic Canada) during the Last Glacial episode

Boreas ◽  
2019 ◽  
Vol 49 (1) ◽  
pp. 52-70 ◽  
Author(s):  
Yan Lévesque ◽  
Guillaume St‐Onge ◽  
Patrick Lajeunesse ◽  
Pierre‐Arnaud Desiage ◽  
Etienne Brouard
Keyword(s):  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Arctic Canada ◽  
Maximum Extent ◽  
Last Glacial ◽  
The Last Glacial

EARLY DEGLACIAL THINNING OF THE LAURENTIDE ICE SHEET FOLLOWED BY RAPID REGIONAL DEGLACIATION

2017 ◽  
Author(s):  
Aaron M. Barth ◽  
◽  
Shaun A. Marcott ◽  
Alex Horvath ◽  
Jeremy D. Shakun ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Laurentide Ice Sheet
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