The Region And Its General Glacial Landscapes

The region is physiographically varied, ranging from the upland and lowland tundra on the Barren Grounds of the Arctic mainland west of Hudson Bay to the channels and islands of the Canadian Arctic Archipelago. Most of the region comprises undulatory plateaux and intervening wide valleys or lowlands, but extensively glaciated fretted mountains extend along the eastern margin of the region from Axel Heiberg and Ellesmere islands south to the Torngat Mountains of Labrador (Bird, 1967; Bostock, 1970; Dyke and Dredge, 1989; Hodgson, 1989; Fig. 1.7).

The larger of the alpine glacier complexes in these mountains persisted throughout the Holocene from Pleistocene precursors, whereas the smaller systems reformed during the Neoglacial. High parts of the plateau adjacent to the mountain rim also support ice caps, the largest of these, the

Figure 7.1 Map of northern Canada showing physiography, ice sheet limits and major place names. Region A is the mountainous eastern rim of Arctic Canada, heavily glaciated today (glaciers in black). Region B consists of medium-to-low elevation plateaux and lowlands. 1 = Penny Ice Cap, 2 = Barnes Ice Cap, 3 = Devon Ice Cap. (After Dyke et al., 2002).

Figure 7.1 Map of northern Canada showing physiography, ice sheet limits and major place names. Region A is the mountainous eastern rim of Arctic Canada, heavily glaciated today (glaciers in black). Region B consists of medium-to-low elevation plateaux and lowlands. 1 = Penny Ice Cap, 2 = Barnes Ice Cap, 3 = Devon Ice Cap. (After Dyke et al., 2002).

Barnes, Penny and Devon ice caps, also having persisted throughout the Holocene. The Barnes Ice Cap (c. 6000 km2 and 600 m thick) on Baffin Island is a remnant of the Laurentide Ice Sheet, consisting in part of Pleistocene ice, and has fluctuated in size during the Holocene (Ives and Andrews, 1963; Dyke, 1974; Dyke and Hooper, 2001). The similarly sized Penny Ice Cap is also a remnant of the Laurentide Ice Sheet with Pleistocene ice at its base (Fisher et al., 1998) but it probably functioned under its own ice divide even at the last glacial maximum (Dyke, 1979; Dyke et al., 1982). The plateau-based Devon Ice Cap and the large alpine ice complexes on Ellesmere and Axel Heiberg islands are remnants of the Innuitian Ice Sheet and have re-expanded substantially in the late Holocene (Blake, 1981, 1989; Koerner, 1989). Thus ice-marginal features in this region range from those currently forming, through a multitude of Neoglacial forms, to those that formed close to the last glacial maximum.

The islands of the Canadian Arctic Archipelago are separated by 50—100 km wide channels and dissected by marine re-entrants ranging from large fjords to drowned lowlands. The striking continuity of some pre-Quaternary erosion surfaces from island to island has prompted suggestions that they developed on a once contiguous landscape that was fractured by regional faulting (Bird, 1967; Kerr, 1980). The extent of glacial dissection of the archipelago remains an open question (Dyke et al., 1992), but it is inappropriate at present to apply a dominantly tectonic, fluvial, or glacial interpretation to physiographic evolution of the region.

During the Late Wisconsinan, the northern margin of the Laurentide Ice Sheet coalesced with local ice caps on northern Baffin Island and Somerset Island (Dyke, 1993; Dyke and Hooper, 2001) and with the Innuitian Ice Sheet in Parry Channel (Blake, 1970; Dyke, 1999). The northwest Laurentide ice margin abutted Banks and Melville islands where it was partly afloat as extensive areas of ice shelf (Vincent, 1982; Hodgson and Vincent, 1984; Hodgson et al., 1984; Dyke, 1987; Dyke and Prest, 1987; Hodgson, 1994). In the far west the ice sheet terminated on the lowlands adjacent to the Mackenzie River, its margins occupying the Tuktoyaktuk and Yukon coastal plains, Mackenzie Bay, and the then dry Beaufort continental shelf (Dyke and Prest, 1987; Dyke et al., 2002; Rampton, 1988; Vincent, 1989; Fig. 7.1).

The impact of Laurentide glaciation is manifest by up to 100 m thick drift and landforms such as flutings, drumlins, eskers and a variety of transverse ridges and belts of hummocky to ridged moraine, recording a strong radial flow of ice from former ice sheet dispersal centres in Keewatin (Sharpe, 1988; Dyke and Dredge, 1989) and Foxe Basin (Blackadar, 1958; Ives and Andrews, 1963, 1989; Andrews and Sim, 1964; Dredge 1995; 2000). Vigorous ice-stream flow is recorded in sets of subglacial streamlined landforms, which in places crosscut each other, and thereby document highly mobile dispersal centres and ice divides throughout the last glacial cycle (Dyke and Morris, 1988; Dyke and Dredge, 1989; Dyke et al., 1992; Hodgson, 1994; Clark and Stokes, 2001). The cross-cutting flow sets indicate that ice streams continued to actively channel glacier ice to the ice sheet margin during its recession, thereby providing considerable volumes of sediment for deposition in glacimarine basins and for moraine formation.

In contrast to the Laurentide Ice Sheet, the flow imprint of the Innuitian Ice Sheet and of plateau ice caps is much less distinct, a fact that encouraged the protracted debate about the very existence of this ice sheet (Dyke, 1999). Innuitian ice streams and associated debris dispersal trains are now being recognized as having flowed along the marine channels (Blake, 1992; Bednarski, 1998; Dyke, 1999; England, 1999; O Cofaigh et al., 2000). The large fjord systems (e.g. Nansen Sound, Eureka Sound, Greely Fjord, Baumann Fjord) extending back to the dispersal centres of the Innuitian Ice Sheet were probably the chief conduits for ice evacuation from its eastern, alpine sector. Early bathymetric work identified a large, hummocky drift belt on the polar continental margin that may represent the Late Wisconsinan Innuitian terminal moraine (Pelletier, 1966). In contrast, many upland plateaux appear to have escaped glacial scouring altogether, attesting to the persistence of cold-based ice beneath local ice divides

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