In the sedimentary basins of the Great Plains province of the United States and western Canada, large amounts of rock, broadly described as evaporitic, are either themselves petroleum-bearing or so situated in their geological association with petroleum that evaporite geology bears directly on the petroleum occurrence.

Two general evaporite facies suites can be distinguished: (1) coastal shoal/salt-flat suite, and (2) reef/salt-basin suite.

1. Desert-zone coastal salt-flats, now widely called sabkhas (sebkas), have the outstanding peculiarity of a geochemical regime which transforms carbonate mud and carbonate sand to microdolomite, and simultaneously generates sheets of nodular anhydrite above high tide level. The permeability changes thus effected make stratigraphic traps for oil. Fossil sabkhas among Mississippian strata of the Williston basin and the Late Devonian of the Western Canada basin hold large reserves of petroleum and sulfur.

2. Salt deposits are extensive in the Devonian, some in shallow-shelf ("megasabkha") positions and others in salt basins where the evaporites overlie a reef-bearing formation. The evaporites surround the reef masses though they are not in stratigraphic-facies relation with them. Large petroleum reserves exist in the reefs of one basin, though not in the largest one. The Devonian salt basin deposits have analogs in the Delaware and Zechstein basins.

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