Timothy G. Fisher

Glacial Lake Agassiz: The northwestern outlet and paleoflood

Valley morphology and sediment in the Fort McMurray region of Alberta indicate that a catastrophic flood discharged down the lower Clearwater and Athabasca river valleys 9900 yr B.P. Geomorphic and chronologic evidence suggests that glacial Lake Agassiz (Emerson phase) was the probable water source. As the flood incised a drainage divide located near the Alberta-Saskatchewan border, the level of glacial Lake Agassiz decreased by 46 m, discharged 2.4 x 106 m3/s for at least 78 days, and stabilized at 438 m above sea level in the Lake Wasekamio area. At that time water entered the Arctic Ocean via glacial Lake McConnell and the Mackenzie River, rather than the Gulf of Mexico via the Mississippi River, as previously thought. Such a large influx of fresh water (8.6 km3/h) into the Arctic at the close of the last glaciation may have had an abrupt, major influence on northern climate.

Subglacial meltwater origin and subaerial meltwater modifications of drumlins near Morley, Alberta, Canada

Abstract Drumlins in the Bow valley west of Calgary, Alberta, are interpreted as the product of subglacial and subaerial meltwater erosion. On the sides of the Bow valley highly elongated, streamlined, first-generation drumlins are aligned in an en-echelon fashion and are not significantly modified by post-glacial processes. In the valley bottom, scalloped, stubby, irregularly spaced second-generation drumlins are found in close association with valley fill. The drumlins are composed of bedrock and diamicton, and some are overlain by a thin gravel veneer. Stratified gravel is found on the leeward flanks of some second-generation drumlins. Meltwater erosional forms (s-forms) found on the limestone bedrock up-flow of the drumlins, and crescentic furrows around their proximal ends, indicate that subglacial meltwater beneath the Bow valley ice was probably the main erosive agent responsible for the shaping of the drumlins. The second-generation drumlins are believed to be the remnants of the first-generation drumlins that were dissected and reworked by postglacial, subaerial meltwater flow(s). Meltwater drainage from ice-dammed glacial Lake Kananaskis and possibly other glacially dammed tributary valley lakes, resulted in the deposition of megaripples (3.5 m high, 40 m wavelength) 8 km down-flow from the drumlins and reverse eddy deposits on the flanks of the drumlins. Post-glacial Bow River incision and terrace development has continued to further sculpt these forms.

Exploration for Pleistocene aggregate resources using process-depositional models in the Fort Mcmurray region, Ne Alberta, Canada

Abstract At present, the Fort McMurray region of Alberta, Canada, is experiencing an aggregate supply shortage. Both Syncrude and Suncor oil sand mines have exploited most of their local reserves, and haul costs are rapidly increasing from distant new sources. Previous aggregate studies in this region have focused on mapping known deposits rather than explaining the distribution of gravel by using process-depositional models as exploration tools and exploring for sources closer to the aggregate users. Aggregate deposits in the McMurray region are associated with two major Pleistocene geomorphic events: (1) glacial Lake McMurray; and (2) a catastrophic flood from glacial Lake Agassiz. Aggregate resources associated with Late Pleistocene glacial Lake McMurray are subaqueous fan deposits, beaches and deltas. Several large aggregate deposits are found along the benchlands of the lower Clearwater and Athabasca valleys. These valleys are a former spillway system eroded by a catastrophic flood from glacial Lake Agassiz 9900 years before present (BP). Discovery of other aggregate resources in the McMurray region will be best accomplished by understanding the flood soillway depositional patterns and regional deglacial history.