Open File Report 1964-01

Open File Report 1964-01

OFR 1964-01

Geology of the Maligne Valley Jasper National Park Area

Author(s) Research Council of AlbertaRoed, M.A. Date 1964-10-01

Nowhere in Jasper Park is the array of geological features so vividly displayed as in Maligne Lake Valley and in the lower part of the Maligne River Valley (the two together are referred to as Maligne Valley in this report). The Maligne Valley is over 36 miles long, is 1 to 4 miles wide in places and heads in the largest ice field in the Front Ranges of the Canadian Rockies, in the Brazeau Icefield. The entire valley has been heavily glaciated by valley glaciers in the not too distant past and is, in fact, a classical example of a glaciated U-shaped valley. As will be explained, the shape of the valley is largely due to the work of the glaciers in the Pleistocene Period or the Ice Age.

Maligne Lake is the largest lake in Jasper Park, being about 14 miles long and 1 mile wide. It is reported to be very deep near the south end of the valley, but no official records of soundings are available. The valley in which the lake lies was carved and excavated by valley glaciers, and the lake has been dammed at its northern end by an end moraine deposited by the last glacier, which flowed down the valley towards the Athabasca River. The glacial deposits and landforms forming the end moraine are excellent examples of glacial deposition and will be discussed and illustrated more fully in another part of this report.

The highest peak in the area is Mount Brazeau (11,386 feet), which stands southeast of Maligne Lake at the head of the Brazeau Ice field. It is barely visible behind the towering massif of Monkhead (10,535 feet). In general, the highest mountains are at the south end of the lake and are composed of strata that are of Cambrian, Ordovician and Devonian ages-rocks that were deposited between 600 million and 350 million years ago.

Northward from the high peaks at the south end of the lake, the valley sides are different in form and composition. The east side of the valley is made of steeply dipping limestone beds of Devonian to Mississippian age that form the spectacular range of sawtooth mountains called the Colin Range, which is part of the Queen Elizabeth Ranges. On the west side of the valley, and in sharp contrast to the east side, is the Maligne Range composed of Cambrian and Precambrian quartzite and shales. These mountains owe their more subdued outline to the glaciers, which moved over them and rounded them to their present form.

The Maligne River, arising at Maligne Pass (6,800 feet), flows into the northern part of Maligne Lake. At the northern end of the lake, the river flows out of the lake in a narrow channel to Medicine Lake. There is no visible northern outlet from Medicine Lake because the Maligne River flows underground (except during flood) for 9 miles before reappearing in its remarkable canyon, which is about 180 feet in depth. The water flowing in the riverbed between Medicine Lake and Maligne Canyon is derived from the adjacent mountainsides.

Not only is the Maligne Valley a U-shaped valley, but it is also a hanging tributary valley as a result of deepening or widening of the Athabasca Valley by glacial erosion at a faster rate than the tributary Maligne Valley. This process leaves the tributary at its junction with the main valley hanging above the main valley.