Quaternary geology of northeastern Alberta

The Kazan upland, the only surface exposure of Precambrian shield in Alberta, was extensively scoured by the Laurentide Ice Sheet during the last glaciation and is now sparsely covered by glacial deposits. In contrast, areas underlain by Paleozoic sedimentary rocks west of the Slave River are covered by widespread glacial, deltaic, and lacustrine sediments. The ice sheet flowed southwestward over the area during the last glacial maximum, but the pattern of ice flow changed during deglaciation when two distinct lobes developed. A westward-flowing ice lobe, occupying the Lake Athabasca basin, converged with southwesterly flowing ice north of it. The lateral contact between the two lobes is marked by converging striae and a broad east-west band of glacial outwash and lake sediments. As the ice sheet retreated eastward, the Slave River lowland and Lake Athabasca basin were flooded from the north by glacial Lake McConnell. The ice sheet formed an extensive ice dam along the western edge of the Kazan upland and glacial Lake McConnell reached about 305 m a.s.l. near present-day Lake Athabasca. The Slave moraine marks the position of this ice front and is correlative with the 10 ka BP Cree Lake moraine of northeastern Saskatchewan. As glacial Lake McConnell drained, a large delta formed in the Slave River lowland depositing sand over the glaciolacustrine mud. The delta was at its largest when Lake Athabasca separated from glacial Lake McConnell between 9 and 8 ka BP. Later, in the Holocene, the Peace and Slave rivers incised the older deltaic sediments, forming the modern Peace River-Athabasca River delta.