Glacial dispersal of rock debris in central Gaspésie, Quebec, Canada

1993 ◽  
Vol 30 (8) ◽  
pp. 1697-1707 ◽  
Author(s):  
Rémi Charbonneau ◽  
Peter P. David
Keyword(s):  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Glacial History ◽  
Dispersal Pattern ◽  
Glacial Erosion ◽  
Ice Flow ◽  
Granite Pluton ◽  
Alpine Glacier ◽  
History Of ◽  
Late Wisconsinan

The lithological content of tills in central Gaspésie is evaluated by pebble counting of 231 samples collected in excavation pits and containing 200 pebbles each. The results are used here to establish the pattern of debris dispersal and to infer the glacial history of the area. The dispersal pattern is characterized by well-defined southeasterly (160–170°) and northeasterly (40–60°) trending trains. Half-distance values of glacial transport along the trains range from 5 to 9 km for both directions, suggesting ice flow events of considerable magnitude. The volume of material in the trains represents 1–6 m of glacial erosion of the bedrock. Glacial cirques and short U-shaped valleys, about 100–200 m deep, are incised into the McGerrigle Mountains granite pluton as well as the adjacent metabasalt. The corresponding trains are aligned with these erosional features, indicating that their clast content was derived from those features during an early Alpine Glacier Phase. The southeasterly trending dispersal trains are associated with an invasion of central Gaspésie by the Laurentide Ice Sheet during the Early Wisconsinan, whereas the northeasterly trending trains are associated with a local centre of outflow over Gaspésie during the Late Wisconsinan.

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).

Late Pleistocene depositional systems of Metropolitan Toronto and their engineering and glacial geological significance

1987 ◽  
Vol 24 (5) ◽  
pp. 1009-1021 ◽  
Author(s):  
N. Eyles
Keyword(s):  
Late Pleistocene ◽  
Cross Sections ◽  
Laurentide Ice Sheet ◽  
Drainage Network ◽  
Glacial History ◽  
Late Tertiary ◽  
History Of ◽  
Depositional Systems ◽  
Late Wisconsinan ◽  
Glacial Complex

The municipality of Metropolitan Toronto (area 480 km2, population 2.15 million) is centrally located on the Late Pleistocene sedimentary infill of the Laurentian Channel, a broad bedrock low up to 115 km wide connecting the Huron and Ontario basins. This channel forms part of a relict (late Tertiary?) drainage network (the Laurentian River) modified by Pleistocene glacial erosion and infilled by over 100 m of glacial and interglacial sediments. The subsurface stratigraphy of the channel fill below Metropolitan Toronto has been established from many different data sources and is depicted, in this paper, as a series of cross sections with a total length of nearly 105 km.The subsurface stratigraphy has been divided, provisionally, into five depositional complexes, which have been mapped in the subsurface along several transects. These are (1) a glacial complex of Illinoian (?) age, (2) a lacustrine complex of Sangamon Interglacial and earliest Wisconsinan sediments (120 000 – 75 000 BP?), (3) a glaciolacustrine – lacustrine complex spanning the Early and Mid-Wisconsinan (75 000 – 30 000 BP?), (4) a Late Wisconsinan (> 30 000 BP) glacial complex, and (5) a postglacial lacustrine complex (ca. 12 000 BP).The data presented in this paper are significant for applied geological investigations in the heavily urbanized Toronto area and provide new insights into the glacial history of the Ontario Basin, in particular the regional extent of the Laurentide Ice Sheet margin prior to the Late Wisconsinan.

Drift carbonate on the Canadian Shield. II: Carbonate dispersal and ice-flow patterns in northern Manitoba

1988 ◽  
Vol 25 (5) ◽  
pp. 783-787 ◽  
Author(s):  
L. A. Dredge
Keyword(s):  
Acid Rain ◽  
Ice Sheet ◽  
Flow Patterns ◽  
Canadian Shield ◽  
Lake Acidification ◽  
Laurentide Ice Sheet ◽  
Ice Streams ◽  
Dispersal Pattern ◽  
Ice Flow ◽  
Natural Lake

In northern Manitoba, carbonates were glacially dispersed westwards for distances up to 260 km beyond the limit of carbonate bedrock. The dispersal pattern in the surface till reflects the interaction of Keewatin and Hudson – Labrador ice in the region during the Wisconsin glaciation and suggests the presence of ice streams within the Laurentide Ice Sheet. Pre-Wisconsinan tills show different dispersal and ice-flow patterns. In unfrozen terrain, carbonate till sheets on the Shield buffer the effects of natural lake acidification and acid rain; however, their ability to buffer appears to be severely limited in permafrost terrain.

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

2007 ◽  
Vol 47 (2) ◽  
pp. 133-145 ◽  
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.

Ice-flow patterns and glacial transport in the eastern Hudson Bay region: implications for the late Quaternary dynamics of the Laurentide Ice Sheet

1995 ◽  
Vol 32 (12) ◽  
pp. 2057-2070 ◽  
Author(s):  
Michel Parent ◽  
Serge J. Paradis ◽  
Éric Boisvert
Keyword(s):  
Compositional Data ◽  
Late Quaternary ◽  
Regional Distribution ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Laurentide Ice Sheet ◽  
Hudson Bay ◽  
Ice Flow ◽  
Flow Phase ◽  
Late Wisconsinan

Recent field surveys in the eastern Hudson Bay region have led to the discovery of regional ice-flow sequences that require a significant reassessment of the late Quaternary dynamics of the Laurentide Ice Sheet. Two regional ice-flow phases can be recognized from till compositional data and from crosscutting relationships observed on striated bedrock surfaces: the oldest is directed toward the northwest and north-northwest, while the youngest is directed toward the west and includes a late-glacial deflection toward the southwest. The wide regional distribution of striae formed during the early northwestward glacial movement together with the recognition of palimpsest glacial dispersal trains associated with this phase suggest that it was a long-lived, time-transgressive regional event. The ensuing glacial movement is a regionally dominant westward ice-flow phase during which several large glacial dispersal trains were formed downglacier from distinctive bedrock sources. The largest of these trains extends westward over a distance of 120 km from Lac à l'Eau Claire to Hudson Bay. Regional glacial transport data as well as glacial and deglacial landforms indicate that this was a long-lived glacial phase, likely lasting throughout the Late Wisconsinan glacial maximum and until déglaciation about 8000 BP. The erosional and depositional record of the northwestward ice-flow event is quite comparable to that of the ensuing glacial phase, and it is thus thought to represent the Early Wisconsinan glacial maximum. In view of the large regional extent of the northwestward ice-flow phase, it must postdate the early buildup of the ice sheet. Along the southeastern Hudson Bay coast, the Late Wisconsinan westward glacial movement was followed by a southwestward deflection that was likely caused by glacial streaming prior to 8000 BP in James Bay, in response to calving and surging into Glacial Lake Ojibway.

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.

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