Abstract The depositional environments existing at the end of the Cretaceous Period continued into the Paleocene Epoch as the Laramide Orogeny continued to affect the western margin of the basin. Thick sequences of sediments derived from the Cordilleran Orogen were deposited in the Beaufort Sea in the north, while continental Paleocene beds were widely distributed in the south, spreading eastward from the rising Rocky Mountains across the Interior Platform. The thickest Tertiary sediments in the southern part of Western Canada Basin are preserved along the eastern side of the Rocky Mountain Foothills and within the adjacent Alberta Syncline (Fig. 4J.1). These strata originally extended much more widely across the Interior Plains, but occur now only as erosional remnants, the largest being the Cypress Hills of southern Alberta and Saskatchewan (Fig. 4J.2) and their eastern extension along the Saskatchewan-United States border from Wood Mountain to Turtle Mountain in Manitoba. Tertiary sediments of the eastern Canadian Cordillera and Interior Plains are almost wholly continental, contrasting with the thick marine and nonmarine section encountered in the region of Mackenzie Delta and Beaufort Sea. Tertiary sediments are extensively developed in Mackenzie Delta, Arctic Coastal Plain, and on the Arctic Continental Shelf. Limited exposures are found in the Caribou Hills on the eastern side of Mackenzie Delta (Fig. 4J.3), along the western margin of the delta, in the Richardson Mountains, and in a small area near Babbage River on Yukon Coastal Plain. Other occurrences are found in Bonnet Plume Basin, Brackett Basin near Norman Wells, and