Exshaw Formation

The Exshaw Formation is a marine stratigraphic unit of the Western Canada Sedimentary Basin, first described in 1937 from Jura Creek near Exshaw in the Canadian Rockies. Deposited from the Late Devonian into the Early Mississippian during the Hangenberg anoxic event, it records a shift from oxygen-poor offshore conditions to a more oxygenated marine setting nearer the paleocoastline. Its lower dark, organic-rich shales and upper calcareous and dolomitic siltstones preserve that environmental change. Widely distributed from the Canadian Rockies into the subsurface far to the north and south, the formation is especially important because its black shales are major petroleum source rocks and correlate southward with parts of the Bakken Formation.

Alberta · Canada