ABSTRACT: The glacial geology of the Archer Fiord/Lady Franklin Bay area, northeastern Ellesmere Island, N.W.T., Canada

CGRG Bibliography of Canadian Geomorphology
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Abstract

Along the southern margin of the Hazen Plateau and in inner Archer Fiord, a discontinuous system of lateral and terminal moraines form a major, morpho-stratigraphic boundary. The moraines are collectively termed the Hazen Moraines. Thirty-four radiocarbon dates from material in raised marine deposits have been obtained. The majority of dates indicate that postglacial uplift began along the margin of the Hazen Moraines at ca. 8100 B.P. Deglaciation inland of the Hazen Moraines occurred as early as 7000-7300 B.P. The entire outer south shore of Archer Fiord/Lady Franklin Bay (>100 km), and southward to Cape Defosse, Kennedy Channel, shows synchronous postglacial emergence around 7500 B.P. This synchronous emergence (7500 B.P.) is considered to represent glacio-isostatic unloading caused by deglaciation along northwestern Greenland and from the Hazen Moraines fifty kilometers inland. The maximum ice margin during the last glaciation wasattained at, or prior to, 8100 B.P. with regional deglaciation underway by 7500 B.P. The Hazen Moraines, therefore, are radiometrically equivalent to the Cockburn Phase of eastern Baffin Island. A more extensive, older till occurs above and beyond the Hazen Moraines and represents one or more periods of glacierization out Archer Fiord/Lady Franklin Bay to Robeson and Kennedy Channels. This till extends up to 670 and 840 m a.s.l. at the heads of the inland fiords. A lateral moraine, near Cape Defosse, Kennedy Channel, is the coastal equivalent of this older till. A radio-carbon date associated with this moraine dated 27,950±5400 B.P. (St 4325) and may be broadly contemporaneous with the ice advance. This date, along with the weathering of an associated ice-contact terrace, suggests that this maximum ice advance is a pre-late Wisconsin event. This older, most extensive till also falls below the summits of inter-fiord highlands and hence geologic evidenceexists for Wisconsin refugia (Brassard, 1971) over sections of northern Ellesmere Island. Large land areas, above and beyond the Hazen Moraines, were ice-free during the last glaciation. Local postglacial isobases over northeastern Ellesmere Island and Polaris Promontory, Greenland, show a strong upward tilt toward the margin of the Greenland Ice Sheet. This substantiates the conclusion of a restricted ice advance over northeastern Ellesmere Island during the last glaciation and consequently the resulting glacio-isostatic dominance of the Greenland ice load over the field area. Regional isobases, constructed over northern Greenland and the Queen Elizabeth Islands, show a major ridge extending northeastward from the Eureka Sound area towards Greenland. The ice load from the last glaciation over the Queen Elizabeth Islands therefore appears to have produced a regional, westward extension of the northwestern Greenland isobases. Postglacial uplift curvesconstructed in the Archer Fiord/Lady Franklin Bay area indicate a general exponential curve similar to others in Arctic Canada. These uplift curves indicate that the present rate of postglacial rebound and the eustatic sea level rise are nearing equilibrium. Palaeo-eskimo tent rings (ca. 1000 years old) are being overridden by present day, ice-pushed ridges along the outer fiord and may indicate the onset of coastal submergence.

Bibliography of Canadian Geomorphology