Taconite Inlet Project

6. Physiography and geomorphology

This section continues the Geographic setting discussion of section 1, here focusing specifically on the watershed of the principal stream entering Lake C2. The intent is to provide background on the topographic relief, drainage net and geomorphology of the catchment. (Colored DEM of the watershed)

The Lake C2 inlet stream drainage is the largest on the west side of a small peninsula defined by Taconite and M'Clintock Inlets, on the west and east sides respectively. To the south, Egingwah Creek extends through a broad east-west valley nearly to the Taconite River (Map of northern Ellesmere Island). The high point of the watershed, White Mountain, is the highest elevation on the peninsula, at ca. 1200 m. Glaciers are currently least extensive in the quadrant of White Mountain encompassed by the watershed (Watershed Oblique). It is not known whether this reflects uneven distribution of accumulation, due for example to regional airflow, or is due to advection of clouds and moisture off the Arctic Ocean basin.

The two largest glaciers within the watershed, both ca. 0.5 km^2 in area, were visited on two occasions. Several other glaciers are visible on the oblique air photo, although some of what appear to be glaciers may in fact be areas of permanent snow. The two visited glaciers coalesce to form one very steep terminus (ca. 45). The terminus elevation on the 1:50,000 scale map is 380 m (1:50,000 watershed map), based on 1959 aerial photographs. The measured elevation in 1991 was 400 +/-10 m; if both elevations were correct, little position change has occurred in 30 years.

Four ablation stakes were installed to a depth of about one meter, at elevations between 500 and 550 m on the coalescing glaciers, prior to most of the 1991 ablation. These were revisited at the end of the 1992 ablation season, in hopes of documenting two seasons of ablation. However, only one stake was located (at 545 m), which recorded 52 cm of ice ablation. Conditions were not ideal for locating the other stakes, due to blowing snow and 20-40 cm of new snow covering the glacier. Nonetheless, assuming the 5 cm diameter aluminum stakes ablated out rather than broke off, ablation at the other three stakes over two years was at least one meter of ice.

Observations at the margin of the glacier indicated that the bed was frozen. Temperatures in the ablation stake holes immediately after drilling ranged from -4.2 to -7.2C (July 8) at about one meter. No evidence was observed for the current or former presence of englacial or subglacial meltwater.

The drainage net of the watershed is well developed (1:50,000 watershed map). The pattern is in part structurally controlled (see Geology section), and in part dendritic. At least one case of stream piracy is apparent, visible on the map (ca. 2.5 km ESE of the Lake C2 delta). The main channel gradient above the lake averages 3.7 and 3.2, from the coalescing glaciers and southern glaciers, respectively. The gradient steepens slightly over the lowest 2 km (4.3), where the stream becomes incised.

At Lake C2, the inlet stream has built an immense fan-foreset delta (Lake C2 delta). In his delta classification scheme, Smith (1991) indicates that such deltas are typical of streams in Canada draining small mountainous watersheds into deep lakes. Measurements to ca. 25 m water depth revealed a very linear delta front, sloping at 32. The immense volume of sediment comprising the delta, and the large median diameter, both suggest that fluvial processes have been more intense in the past.

As the oblique view of the watershed suggests (Watershed Oblique), very little of the watershed is either at sea level or at the highest elevation. The 1:250,000 scale topographic map was used to determine an area-elevation relationship for the watershed. (Area-elevation curve) Most of the area (76 percent) is between 300 and 750 m above mean sea level (a.s.l.), with a median elevation of ca. 460 m (50 percent of area above and below). In terms of source areas for snowmelt runoff, melting which takes place at the elevation zone where the greatest area is located (i.e. 300-750 m) will be the most probable source area for the annual nival flood.

Despite the extensive glacierization of the landscape around Taconite Inlet, fluvial erosion appears to be the dominant force of landscape development. Stream valleys throughout the watershed are sharply V-shaped, with straight, steep valley sides. Valley bottoms are seldom wider than the stream channel. One exception is a broad area of outwash which extends ca. 1000 m, from below the confluence of the two main stream segments downstream to a constriction in the valley where resistant strata outcrop. No evidence of lateral or streambank erosion was observed; slopes continue directly to the channel or valley train.

Outcrops are few in the watershed, as weathered rock fragments cover virtually all slopes. This material has probably formed by frost shattering, the effects of which were illustrated by entire boulders which appeared to have shattered in situ. Ten 500 m long slope sections, more-or-less randomly selected on the 1:50000 scale topographic map, averaged 30 and ranged between 22 and 39. These steep gradients result in rapid runoff routing to the stream channels.

As a result of the steep valley slopes, much of the regolith (or scree) appears to be in transit by slow mass movement. No relict or recent sites of rapid mass movements such as landslides were observed, although localized areas of rock fall were not uncommon. In 1992, snow avalanches were widespread. These probably occurred in early May, and resulted in extensive redistribution of snow into the stream valleys (Avalanche deposition in stream valley). Rock fragments from the slopes were often incorporated into the avalanches, although not to a great extent.

Frost-shattered rocks in flatter sites have developed extensive lichen cover. In very isolated areas where vegetation has developed, solifluction appears to be quite active. Pattern ground features, typical of periglacial environments, are primarily evident in the watershed in areas below the marine limit. These most commonly are in the form of stone stripes.

Glacial features are very limited in the watershed, despite current glacierization. Erosional forms were primarily found on a bench with abundant outcrops just above (east) of the delta (ca. 110 m a.s.l.). Here, observed features were interpreted to be roches moutonnees, meltwater channels and striae. Depositional glacial features, if any have been preserved, were exceedingly difficult to recognize, as others have found in the northern islands (cf. Rudberg, 1963). Till may in fact mantle the landscape, and erratics are certainly present, but neither were recognized as such due to weathering and the ubiquitous residuum of varying lithology. No moraines of any type were observed below or in the vicinity of the coalescing glaciers. Nor was there any distinction in lichen cover suggestive of recent glacier retreat (i.e. lichen kill).

More comprehensive geomorphological investigations around the watershed would have been valuable. In addition to time limitations, however, steep slopes, loose footing and narrow stream-filled valleys made exploration difficult. The observations discussed above, however, illustrate the importance of fluvial processes to landscape evolution at this high latitude site. Very few point sources for fluvial sediment were identified, in contrast to glacierized or arctic watersheds elsewhere, where such processes as subglacial erosion, lateral stream channel erosion through morainic deposits (cf. Rudberg, 1963), and active layer detachment slides (cf. Lewkowicz and Wolff, 1994) provide sediment to streams. Nonetheless, abundant weathering products and steep slopes have provided abundant material for fluvial transport in the past, as confirmed by the immensity of the Lake C2 delta.

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