Glacial Landscape Zones

Glaciated landscapes are systematically ordered in a north to south progression, from simple to complex in terms of landscape alteration. The 'complex' southern landscape is the one that will be most familiar to geologists working south of the permafrost limit. In the far north, lateral meltwater channels cut into terrain that either lacks other forms of glacial modification or is weakly glacially scoured and bears a thin till cover with sparse, faint flutings. Moraines are rare but include small end moraines (e.g. Craig Lake moraine; Smith, 1999), minor lateral moraines along fjords, and glacially tectonized bedrock masses (Dyke et al., 1992; Dyke, 1999; 2000; Fig. 7.2). Ice-contact deltas are limited mainly to fjord heads. Along with prodelta muds and more complex accumulations of glacimarine sediment (morainal banks; Evans 1990a, b; O Cofaigh et al., 1999),

Ice Thrust Ridges
Figure 7.2 Glacially tectonized bedrock (ice-thrust moraine) on Devon Island. Morainal ridges are indicated, but the ice-thrust material extends throughout the rough terrain studded with small lakes. This material is exceedingly coarse, blocks being typically metres across. (NAPL AI6762-I8.)

they constitute the only thick glacigenic sediments in this vast region. This terrain was covered during the last glaciation by a coalescent complex of alpine glaciers and plateau ice caps, collectively referred to as the Innuitian Ice Sheet (Blake, 1970). South of Parry Channel, alpine and plateau glaciers were coalescent with the northeast margin of the Laurentide Ice Sheet but remained dynamically distinct from it (Fig. 7.1).

Within the limits of the Late Wisconsinan Laurentide Ice Sheet, there are terrains of limited extent that are similar to those described above (e.g. south-central Melville Peninsula; Sim, 1960; Dredge, 2000, 2002), north-central Boothia Peninsula (Dyke, 1984), northeast Prince of Wales Island (Dyke et al., 1992) and parts of northwest Victoria Island (D.A. Hodgson, pers. comm.). Elsewhere, northern Laurentide terrain exhibits a further three-part, north—south (or outer—inner) zonation, which may be briefly described as follows (Fig. 7.3):

1. The outer Laurentide zone contains belts of ridged and hummocky moraine (Fig. 7.4) fronting well-fluted or drumlinized till. The streamlined till bordering the morainal belts is

Basal Sliding

Figure 7.3 Schematic sketch of major glacial landscape zones described in the text. Sinuous arrows are proglacial meltwater channels; arrows with single barbs are lateral meltwater channels; lines with rectangular ornaments are ice-thrust moraines; lines with multiple dots are end moraines; closed depressions represent kettles; lines of 'Vs' are eskers; lines with single dots are drumlins and flutings; and attenuated 'Ss' are Rogen moraines.

Figure 7.3 Schematic sketch of major glacial landscape zones described in the text. Sinuous arrows are proglacial meltwater channels; arrows with single barbs are lateral meltwater channels; lines with rectangular ornaments are ice-thrust moraines; lines with multiple dots are end moraines; closed depressions represent kettles; lines of 'Vs' are eskers; lines with single dots are drumlins and flutings; and attenuated 'Ss' are Rogen moraines.

inset by sparse, minor eskers or subglacial meltwater channels. Lateral meltwater channels tend to dominate patches of terrain where moraines have not formed, but also occur within the moraine belts, where they are cut into moraine ridges, till surfaces or bedrock. The largest Laurentide lateral meltwater channels occur within this zone (e.g. wrapping around the northern and eastern flanks of the Melville Hills; Klassen, 1971; Dyke et al., in press; Fig. 7.5). Inwash kame deltas formed in and filled small ice-marginal lakes (Fig. 7.5B). Proglacial

Figure 7.4 Part of ridged and hummocky end-moraine belt on Wollaston Peninsula, Victoria Island. The light-toned areas along the moraine crests (lines with dots) are sand and gravel kames. Note the proglacial meltwater channels (arrows with cross ticks) trending northward from each moraine. (NAPL AI6335-I67.)

Figure 7.4 Part of ridged and hummocky end-moraine belt on Wollaston Peninsula, Victoria Island. The light-toned areas along the moraine crests (lines with dots) are sand and gravel kames. Note the proglacial meltwater channels (arrows with cross ticks) trending northward from each moraine. (NAPL AI6335-I67.)

meltwater channels and associated outwash deposits are fairly common. Where the ice front contacted the sea or a glacial lake, moraines typically consist of coarse, crudely bedded glacimarine or glacilacustrine sediment. Ice-contact deltas are locally significant as are DeGeer moraines. A significant ice-marginal assemblage, the Winter Harbour moraine (till) and associated marginal drainage features, formed at the grounded distal edge of a large ice shelf during a readvance (Hodgson and Vincent, 1984). 2. In the middle Laurentide zone, there are some regionally significant end moraines of various compositions. Prominent among these are the Melville moraine (Sim, 1960; Dredge, 1990; Dyke and Prest, 1987), the Chantrey moraine (Dyke, 1984; Dyke and Prest, 1987), and the MacAlpine moraine (Blake, 1963; Falconer et al., 1965; Aylsworth and Shilts, 1989; Dyke and Prest, 1987). They are tens to hundreds of kilometres long with minor gaps and tend to form single ridges or tightly spaced parallel ridge sets (Fig. 7.6). These moraines front strongly developed fluting and drumlin fields that are inset, particularly in Keewatin, by impressively developed esker systems and associated subglacial channels and meltwater scour zones.

Figure 7.5 A) Large lateral channels cut into the thick drift of the Bluenose Lake end-moraine complex. The deepest channels are about 100 m deep (northwest corner). Note 'inwash' kame deltas built at the mouths of three channels where small ice-marginal lakes were filled with glacifluvial materials. (NAPL AI9428-7I). B) Large lateral channels cut into the lower flank of the Bluenose Lake end-moraine complex and adjacent drumlin field. The moraine is to the west, overlain in places by wind-eroded (white) glacial lake silts. Drumlins trend SSE-NNW in the northeast part of the photograph. The lateral channels bend abruptly in places into sub-marginal chutes. Kame deltas were deposited at these bends in small ice-marginal lakes occupying thermally eroded notches at these locations. Descending ice margins and lake levels are well marked by the succession of delta pads along a chute in the southeast quadrant. (NAPL A238I3-50). Reproduced with the permission of Natural Resources Canada 2010, courtesy of the National Air Photo Library.

Figure 7.5 A) Large lateral channels cut into the thick drift of the Bluenose Lake end-moraine complex. The deepest channels are about 100 m deep (northwest corner). Note 'inwash' kame deltas built at the mouths of three channels where small ice-marginal lakes were filled with glacifluvial materials. (NAPL AI9428-7I). B) Large lateral channels cut into the lower flank of the Bluenose Lake end-moraine complex and adjacent drumlin field. The moraine is to the west, overlain in places by wind-eroded (white) glacial lake silts. Drumlins trend SSE-NNW in the northeast part of the photograph. The lateral channels bend abruptly in places into sub-marginal chutes. Kame deltas were deposited at these bends in small ice-marginal lakes occupying thermally eroded notches at these locations. Descending ice margins and lake levels are well marked by the succession of delta pads along a chute in the southeast quadrant. (NAPL A238I3-50). Reproduced with the permission of Natural Resources Canada 2010, courtesy of the National Air Photo Library.

Collectively these are the giant radiating systems illustrated on the Glacial Map of Canada (Prest et al., 1968) and in later larger scale maps (Aylsworth and Shilts, 1989). Proglacial outwash and associated deltas are important here and DeGeer moraines are more common in formerly submerged areas than in the distal zone. Esker beads (or nodes, ranging up to esker deltas) mark debouchments ofchannelized subglacial meltwater into standing water. Regionally thick glacimarine deposits attest to abundant sediment delivery to the ice front. Lateral meltwater channels are not known in this zone. 3. The innermost Laurentide landscape is devoid of end moraines and is dominated instead by fields of Rogen moraine, commonly superimposed by flutings and eskers (Lee, 1959; Aylsworth and Shilts, 1989). However, subglacial meltwater features are far less prominent here than in the neighbouring middle zone.

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