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 Laurentide Ice-Flow Patterns: A Historical Review, and Implications of the Dispersal of Belcher Islands Erratics

2007 ◽  
Vol 44 (2) ◽  
pp. 113-136 ◽  
Author(s):  
Victor K. Prest
Keyword(s):  
Ice Sheet ◽  
Historical Review ◽  
Flow Patterns ◽  
The Arctic ◽  
Laurentide Ice Sheet ◽  
Complex Nature ◽  
Hudson Bay ◽  
Ice Flow ◽  
Flow Models ◽  
The North

ABSTRACTThis paper deals with the evolution of ideas concerning the configuration of flow patterns of the great inland ice sheets east of the Cordillera. The interpretations of overall extent of Laurentide ice have changed little in a century (except in the Arctic) but the manner of growth, centres of outflow, and ice-flow patterns, remain somewhat controversial. Present geological data however, clearly favour the notion of multiple centres of ice flow. The first map of the extent of the North American ice cover was published in 1881. A multi-domed concept of the ice sheet was illustrated in an 1894 sketch-map of radial flow from dispersal areas east and west of Hudson Bay. The first large format glacial map of North America was published in 1913. The binary concept of the ice sheet was in vogue until 1943 when a single centre in Hudson Bay was proposed, based on the westward growth of ice from Labrador/Québec. This Hudson dome concept persisted but was not illustrated until 1977. By this time it was evident from dispersal studies that the single dome concept was not viable. Dispersal studies clearly indicate long-continued westward ice flow from Québec into and across southern Hudson Bay, as well as eastward flow from Keewatin into the northern part of the bay. Computer-type modelling of the Laurentide ice sheet(s) further indicates their complex nature. The distribution of two indicator erratics from the Proterozoicage Belcher Island Fold Belt Group help constrain ice flow models. These erratics have been dispersed widely to the west, southwest and south by the Labrador Sector of more than one Laurentide ice sheet. They are abundant across the Paleozoic terrain of the Hudson-James Bay lowland, but decrease in abundance across the adjoining Archean upland. Similar erratics are common in northern Manitoba in the zone of confluence between Labrador and Keewatin Sector ice. Scattered occurences across the Prairies occur within the realm of south-flowing Keewatin ice. As these erratics are not known, and presumably not present, in Keewatin, they indicate redirection and deposition by Keewatin ice following one or more older advances of Labrador ice. The distribution of indicator erratics thus test our concepts of ice sheet growth.

Landform assemblages produced by the Laurentide Ice Sheet in northeastern British Columbia and adjacent Northwest Territories — constraints on glacial lakes and patterns of ice retreatThis article is one of a selection of papers published in this Special Issue on the theme Geology of northeastern British Columbia and northwestern Alberta: diamonds, shallow gas, gravel, and glaciers.

2008 ◽  
Vol 45 (5) ◽  
pp. 593-610 ◽  
Author(s):  
Jan M. Bednarski
Keyword(s):  
British Columbia ◽  
Northwest Territories ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Ice Flow ◽  
The North ◽  
Relative Chronology ◽  
Mountain Front ◽  
Ice Retreat ◽  
Cordilleran Ice Sheet

The Laurentide Ice Sheet reached the Canadian Cordillera during the last glacial maximum in northeastern British Columbia and adjacent Northwest Territories and all regional drainage to unglaciated areas in the north was dammed by the ice. Converging ice-flow patterns near the mountain front suggest that the Laurentide Ice Sheet likely coalesced with the Cordilleran Ice Sheet during the last glaciation. With deglaciation, the ice masses separated, but earlier ice retreat in the south meant that meltwater pooled between the mountain front and the Laurentide margin. The level of the flooding was controlled by persistent ice cover on the southern Franklin Mountains. Glacial Lake Liard formed when the Laurentide Ice Sheet retreated east of the southern Liard Range and, at its maximum extent, may have impounded water at least as far south as the Fort Nelson River. Deglaciation of the plains was marked by local variations in ice flow caused by a thin ice sheet becoming more affected by the topography and forming lobes in places. These lobes caused diversions in local drainage readily traced by abandoned meltwater channels. Radiocarbon ages from adjacent areas suggest the relative chronology of deglaciation presented here occurred between 13 and 11 ka BP.

scholarly journals Late Pleistocene and Holocene glaciation and deglaciation of Melville Peninsula, Northern Laurentide Ice Sheet

2004 ◽  
Vol 55 (2) ◽  
pp. 159-170 ◽  
Author(s):  
Lynda A. Dredge
Keyword(s):  
Sea Level ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
North Coast ◽  
Baffin Island ◽  
Ice Flow ◽  
Ice Caps ◽  
The North ◽  
Northern Areas ◽  
Controlled Flow

Abstract Melville Peninsula lies within the Foxe/Baffin Sector of the Laurentide Ice Sheet. Pre-Foxe/Pre-Wisconsin ice may have covered the entire peninsula. Preserved regolith in uplands indicates a subsequent weathering interval. Striations and till types indicate that, during the last (Foxe) glaciation, a local ice sheet (Melville Ice) initially developed on plateaus, but was later subsumed by the regional Foxe ice sheet. Ice from the central Foxe dome flowed across northern areas and Rae Isthmus, while ice from a subsidiary divide controlled flow on southern uplands. Ice remained cold-based and non-erosive on some plateaus, but changed from cold- to warm-based under other parts of the subsidiary ice divide, and was warm-based elsewhere. Ice streaming, generating carbonate till plumes, was prevalent during deglaciation. A late, quartzite-bearing southwestward ice flow from Baffin Island crossed onto the north coast. A marine incursion began in Committee Bay about 14 ka and advanced southwards to Wales Island by 8.6 ka. The marine-based ice centre in Foxe Basin broke up about 6.9 ka. Northern Melville Peninsula and Rae Isthmus were deglaciated rapidly, but remnant ice caps remained active and advanced into some areas. The ice caps began to retreat from coastal areas ~6.4 to 6.1 ka, by which time sea level had fallen from 150-180 m to 100 m.

Glacial Erosion by the Laurentide Ice Sheet

1978 ◽  
Vol 20 (83) ◽  
pp. 367-391 ◽  
Author(s):  
D. E. Sugden
Keyword(s):  
Thermal Regime ◽  
Basal Layer ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Lake Basin ◽  
List Type ◽  
Glacial Erosion ◽  
Ice Flow ◽  
Landscape Type ◽  
The North

AbstractThe aim of the paper is to analyse landscapes of glacial erosion associated with the Laurentide ice sheet at its maximum and to relate them lo the three main variables affecting glacial erosion, namely former basal thermal regime of the ice sheet, the topography of the bed, and the geology of the bed. The key to the analysis is the comparison of the distribution of landscape types with the simulated pattern of the basal thermal regime of the former ice sheet.Landscapes of areal scouring are found to be associated with zones of basal melting and occur beneath much of the former ice-sheet centre and in those places where the topography favoured converging ice flow. The landscape type may also have formed beneath cold-based ice when it was carrying debris inherited from an up-stream zone of regelation. Areas with little or no sign of glacial erosion occur primarily in the north in the Queen Elizabeth Islands but they also occur on uplands associated with diverging ice flow; they coincide with areas calculated to have been covered by cold-based ice devoid of debris. Landscapes of selective linear erosion are common on uplands near the eastern periphery of the ice sheet. In these situations, pre-existing valleys channelled ice flow and created a situation where there was warm-based ice over the valleys and cold-based protective ice over the intervening plateaux. Variations in the permeability of the bedrock base have modified the landscape pattern, mainly in those areas where there was a change from one basal thermal regime to another. In general, permeable rocks tend to have experienced less erosion than impermeable rocks.Using lake-basin density as an indication of the intensity of glacial erosion, a zone of maximum erosion is identified and this forms a ring between the centre of the former ice sheet and its periphery. This ring coincides with a zone where melt water from the ice-sheet centre is calculated to have frozen on to the bottom of the ice sheet. This regelation incorporated basal debris into the ice, forming a basal layer 20-50 m thick and afforded an efficient means of debris evacuation.A conceptual model is developed and hangs round the following postulates: (1)Landscapes of glacial erosion are related primarily to the basal thermal regime of the ice sheet.(2)Landscapes of glacial erosion are equilibrium forms related to maximum glacial conditions. This implies that at some stage in the Pleistocene the Laurentide ice sheet was in a stable maximum condition for a long period of time.(3)Mechanisms allowing evacuation of debris rather than those of abrasion or fracture may be the most important in influencing the amount of erosion achieved by an ice sheet.(4)Cold-based ice may accomplish erosion if it contains debris.

Glacial Erosion by the Laurentide Ice Sheet

1978 ◽  
Vol 20 (83) ◽  
pp. 367-391 ◽  
Author(s):  
D. E. Sugden
Keyword(s):  
Thermal Regime ◽  
Basal Layer ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Lake Basin ◽  
List Type ◽  
Glacial Erosion ◽  
Ice Flow ◽  
Landscape Type ◽  
The North

Abstract The aim of the paper is to analyse landscapes of glacial erosion associated with the Laurentide ice sheet at its maximum and to relate them lo the three main variables affecting glacial erosion, namely former basal thermal regime of the ice sheet, the topography of the bed, and the geology of the bed. The key to the analysis is the comparison of the distribution of landscape types with the simulated pattern of the basal thermal regime of the former ice sheet. Landscapes of area scouring are found to be associated with zones of basal melting and occur beneath much of the former ice-sheet centre and in those places where the topography favoured converging ice flow. The landscape type may also have formed beneath cold-based ice when it was carrying debris inherited from an up-stream zone of regelation. Areas with little or no sign of glacial erosion occur primarily in the north in the Queen Elizabeth Islands but they also occur on uplands associated with diverging ice flow; they coincide with areas calculated to have been covered by cold-based ice devoid of debris. Landscapes of selective linear erosion are common on uplands near the eastern periphery of the ice sheet. In these situations, pre-existing valleys channelled ice flow and created a situation where there was warm-based ice over the valleys and cold-based protective ice over the intervening plateaux. Variations in the permeability of the bedrock base have modified the landscape pattern, mainly in those areas where there was a change from one basal thermal regime to another. In general, permeable rocks tend to have experienced less erosion than impermeable rocks. Using lake-basin density as an indication of the intensity of glacial erosion, a zone of maximum erosion is identified and this forms a ring between the centre of the former ice sheet and its periphery. This ring coincides with a zone where melt water from the ice-sheet centre is calculated to have frozen on to the bottom of the ice sheet. This regelation incorporated basal debris into the ice, forming a basal layer 20-50 m thick and afforded an efficient means of debris evacuation. A conceptual model is developed and hangs round the following postulates: (1) Landscapes of glacial erosion are related primarily to the basal thermal regime of the ice sheet. (2) Landscapes of glacial erosion are equilibrium forms related to maximum glacial conditions. This implies that at some stage in the Pleistocene the Laurentide ice sheet was in a stable maximum condition for a long period of time. (3) Mechanisms allowing evacuation of debris rather than those of abrasion or fracture may be the most important in influencing the amount of erosion achieved by an ice sheet. (4) Cold-based ice may accomplish erosion if it contains debris.

scholarly journals Objective Reconstructions of the Late Wisconsinan Laurentide Ice Sheet and the Significance of Deformable Beds

2007 ◽  
Vol 39 (3) ◽  
pp. 229-238 ◽  
Author(s):  
D. A. Fisher ◽  
N. Reeh ◽  
K. Langley
Keyword(s):  
Yield Stress ◽  
Flow Direction ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Hudson Bay ◽  
Ice Streams ◽  
Ice Flow ◽  
Surface Slopes ◽  
Late Wisconsinan

ABSTRACT A three dimensional steady state plastic ice model; the present surface topography (on a 50 km grid); a recent concensus of the Late Wisconsinan maximum margin (PREST, 1984); and a simple map of ice yield stress are used to model the Laurentide Ice Sheet. A multi-domed, asymmetric reconstruction is computed without prior assumptions about flow lines. The effects of possible deforming beds are modelled by using the very low yield stress values suggested by MATHEWS (1974). Because of low yield stress (deforming beds) the model generates thin ice on the Prairies, Great Lakes area and, in one case, over Hudson Bay. Introduction of low yield stress (deformabie) regions also produces low surface slopes and abrupt ice flow direction changes. In certain circumstances large ice streams are generated along the boundaries between normal yield stress (non-deformable beds) and low yield stress ice (deformabie beds). Computer models are discussed in reference to the geologically-based reconstructions of SHILTS (1980) and DYKE ef al. (1982).

Genesis of carbonate till in the lee sides of Precambrian Shield uplands, Hemlo area, Ontario

1987 ◽  
Vol 24 (10) ◽  
pp. 2004-2015 ◽  
Author(s):  
Stephen R. Hicock
Keyword(s):  
Ice Sheet ◽  
Glacial Maximum ◽  
Laurentide Ice Sheet ◽  
The South ◽  
Precambrian Shield ◽  
Basal Zone ◽  
Compressive Flow ◽  
Late Wisconsinan ◽  
Basal Till

Near Hemlo, Ontario, highly calcareous till is confined to areas located downglacier from Precambrian uplands, at least 150 km from the Paleozoic–Precambrian boundary. It comprises subglacial meltout till between lodgment tills, and the calcareous package overlies noncalcareous basal till (not studied) and underlies noncalcareous supraglacial meltout till. The tills can be distinguished by textural, carbonate, and clast compositions. Glaciotectonic deformations, stone fabrics and striae, and stone provenance from the tills, as well as erosional and depositional landforms, indicate that ice advanced to the south–southwest across bedrock contacts and over Precambrian uplands.Deposition of all five tills can be explained with one glacial event. As the Late Wisconsinan margin of the Laurentide ice sheet advanced against uplands about 20 km northeast of Hemlo it experienced compressive flow while depositing the non calcareous basal till. Upshearing of stoss-side local debris high into the ice also occurred as englacial ice overrode the slowed basal zone. Once over the upland, englacial ice assumed extending flow, and downshearing of distal debris, which was deposited as calcareous lodgment till on the lee sides of uplands. After the glacial maximum, the glacier ceased internal movement and subglacial meltout till was laid down. A late reactivation of the ice deposited the upper lodgment till and final stagnation formed the supraglacial meltout till.

scholarly journals Simulating the Early Holocene demise of the Laurentide Ice Sheet with BISICLES (public trunk revision 3298)

2020 ◽  
Vol 13 (9) ◽  
pp. 4555-4577
Author(s):  
Ilkka S. O. Matero ◽  
Lauren J. Gregoire ◽  
Ruza F. Ivanovic
Keyword(s):  
Mass Balance ◽  
General Circulation ◽  
Ice Sheet ◽  
Circulation Model ◽  
Early Holocene ◽  
Laurentide Ice Sheet ◽  
Hudson Bay ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
The North

Abstract. Simulating the demise of the Laurentide Ice Sheet covering Hudson Bay in the Early Holocene (10–7 ka) is important for understanding the role of accelerated changes in ice sheet topography and melt in the 8.2 ka event, a century long cooling of the Northern Hemisphere by several degrees. Freshwater released from the ice sheet through a surface mass balance instability (known as the saddle collapse) has been suggested as a major forcing for the 8.2 ka event, but the temporal evolution of this pulse has not been constrained. Dynamical ice loss and marine interactions could have significantly accelerated the ice sheet demise, but simulating such processes requires computationally expensive models that are difficult to configure and are often impractical for simulating past ice sheets. Here, we developed an ice sheet model setup for studying the Laurentide Ice Sheet's Hudson Bay saddle collapse and the associated meltwater pulse in unprecedented detail using the BISICLES ice sheet model, an efficient marine ice sheet model of the latest generation which is capable of refinement to kilometre-scale resolutions and higher-order ice flow physics. The setup draws on previous efforts to model the deglaciation of the North American Ice Sheet for initialising the ice sheet temperature, recent ice sheet reconstructions for developing the topography of the region and ice sheet, and output from a general circulation model for a representation of the climatic forcing. The modelled deglaciation is in agreement with the reconstructed extent of the ice sheet, and the associated meltwater pulse has realistic timing. Furthermore, the peak magnitude of the modelled meltwater equivalent (0.07–0.13 Sv) is compatible with geological estimates of freshwater discharge through the Hudson Strait. The results demonstrate that while improved representations of the glacial dynamics and marine interactions are key for correctly simulating the pattern of Early Holocene ice sheet retreat, surface mass balance introduces by far the most uncertainty. The new model configuration presented here provides future opportunities to quantify the range of plausible amplitudes and durations of a Hudson Bay ice saddle collapse meltwater pulse and its role in forcing the 8.2 ka event.

I.—The Glacial Controversy in New Zealand

1917 ◽  
Vol 4 (6) ◽  
pp. 241-245 ◽  
Author(s):  
C. T. Trechmann
Keyword(s):  
New Zealand ◽  
Ice Sheet ◽  
Pleistocene Glaciation ◽  
The South ◽  
The North

The controversy which has arisen in recent years in New Zealand regarding the problem of the Pleistocene glaciation of that country resolves itself into the two following main questions:—1. Was there any glaciation in the North Island?2. Was there an ice-sheet covering the South Island?

Laurentide and montane glaciation along the Rocky Mountain Foothills of northeastern British Columbia

2007 ◽  
Vol 44 (4) ◽  
pp. 445-457 ◽  
Author(s):  
Jan M Bednarski ◽  
I Rod Smith
Keyword(s):  
British Columbia ◽  
Ice Sheet ◽  
Rocky Mountain ◽  
Laurentide Ice Sheet ◽  
Cosmogenic Dating ◽  
Surficial Geology ◽  
Continental Divide ◽  
Mountain Front ◽  
Late Wisconsinan ◽  
Cordilleran Ice Sheet

Mapping the surficial geology of the Trutch map area (NTS 94G) provides new data on the timing of continental and montane glaciations along the Foothills of northeastern British Columbia. Striated surfaces on mountain crests were dated to the Late Wisconsinan substage by cosmogenic dating. The striations were produced by eastward-flowing ice emanating from the region of the Continental Divide. This ice was thick enough to cross the main ranges and overtop the Rocky Mountain Foothill summits at 2000 m above sea level (asl). It is argued here that such a flow, unhindered by topography, could only have been produced by the Cordilleran Ice Sheet and not by local cirque glaciation. During this time, the Cordilleran Ice Sheet dispersed limestone and schist erratics of western provenance onto the plains beyond the mountain front. Conversely, the Laurentide Ice Sheet did not reach its western limit in the Foothills until after Cordilleran ice retreated from the area. During its maximum, the Laurentide ice penetrated the mountain valleys up to 17 km west of the mountain front, and deposited crystalline erratics from the Canadian Shield as high as 1588 m asl along the Foothills. In some valleys a smaller montane advance followed the retreat of the Laurentide Ice Sheet.

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