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Four unconformity-bounded quartzose fluvial sequences filled the Athabasca Basin between about 1760 Ma and 1500 Ma, each with distinct subbasin architecture, grain-size distribution, and paleocurrent directions. Maximum thickness of the Athabasca Group at any one place is about 1500 m, although much has been eroded and the aggregate stratotype thickness is 3800 m. Sequence 1 is Fair Point Formation (conglomeratic Lobstick and pebbly quartz arenite Beartooth members). Sequence 2 begins with conglomeratic Read Formation in the east and sandy Smart Formation in the west, overlain by Manitou Falls Formation (conglomeratic Bird, sandy Collins, and clay-intraclast-rich Dunlop members in the east and centre; sandy Warnes Member to the southeast and pebbly sandy Raibl Member to the northeast). Sequence 3 includes the Lazenby Lake Formation (conglomeratic Hodge, sandy-muddy Clampitt, pebbly Shiels, and sandy Larter members), and the Wolverine Point Formation (mudstone-rich Brule and sandy Claussen members). Sequence 4 comprises Locker Lake Formation (pebbly Snare, conglomeratic Brudell, and pebbly Marsin members), Otherside Formation (pebbly Archibald and sandy Birkbeck members), Douglas Formation quartz arenite and carbonaceous mudstone, and Carswell Formation stromatolite and oolite with minor basal siliciclastic interbeds.

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