Western Canada Sedimentary Basin

The Western Canada Sedimentary Basin (WCSB) underlies 1.4 million square kilometres (540,000 sq mi) of Western Canada including southwestern Manitoba, southern Saskatchewan, Alberta, northeastern British Columbia and the southwest corner of the Northwest Territories. This vast sedimentary basin consists of a massive wedge of sedimentary rock extending from the Rocky Mountains in the west to the Canadian Shield in the east.

Source: Wikipedia — Western Canada Sedimentary Basin (CC BY-SA 4.0)