Mesozoic and Cenozoic Depositional History of the Northern Interior Plains of Canada

Abstract Sedimentary rocks ranging in age from Early Cretaceous to Late Tertiary were deposited in the Anderson Basin, Peel Trough and Great Bear Basin and across intervening positive areas of the Carnwath Platform, Keele Arch and Eskimo Lakes Arch. Deposition was initiated during the Late Jurassic in the Anderson Basin. The main transgression onto the craton began in the Aptian with deposition of nonmarine sands on the Carnwath Platform, marine mudstones in the Anderson Basin, and marine sandstones in the Peel Trough. Transgression continued into the Albian. The seas encroached onto the Carnwath Platform and Keele Arch by expansion southward of the Anderson Basin and eastward of the Peel Trough, which resulted in the entire region, with the exception of the Keele Arch, being submerged by Middle Albian time. Subsidence of the Great Bear Basin primarily occurred in Middle Albian time. The Peel Trough and Great Bear Basin continued to expand onto the Keele Arch so that the two basins were linked across the southern part of the arch in the Late Albian and the arch was completely inundated by Turonian time. The Anderson Basin to the north, conversely, was uplifted and eroded so that no record exists of Late Albian, Cenomanian, Turonian and probably most of Coniacian time. Deposition was re-initiated there during the Late Coniacian and continued into the Maastrichtian. Similarly, the Great Bear Basin appears to have been uplifted and eroded in pre-Campanian time so that Upper Albian to Santonian rocks are missing. Conversely, the Peel Trough appears to have received continuous deposition from Albian to Paleocene time. Sandstone wedges within the Peel Trough sequence were derived from the Cordillera to the south and west. Deposition changed from marine to nonmarine in Late Maastrichtian time. Nonmarine deposition continued into the Paleocene with deposition of coarse conglomerates. Similarly, in the western Great Bear Basin, deposition appears to have changed from marine to nonmarine in Late Maastrichtian time. In the Anderson Basin, an unconformity separates Maastrichtian marine strata and nonmarine gravels and sands interpreted to be Late Miocene to Pliocene in age.