Mississippian sedimentary rocks in Western Canada contain abundant microfossil material which can be effectively used to correlate and interpret the geology in this area. Three of these zones characterized by the key ostracode genera Richterina, Cribroconcha, and Paraparchites, are selected to demonstrate their practical application in solving structural and stratigraphic problems. The lowermost zone of the sequence Richterina sp. has restricted distribution within northwestern Alberta and illustrates some of the facies changes within these zones. The middle zone Cribroconcha sp. has been found in the basal Rundle or its equivalents in northwestern, central, and southern Alberta and also in the Mission Canyon of Saskatchewan, Manitoba, and North Dakota. This zone represents one of the first regionally distributed Mississippian faunas and is associated with varying lithologies dependent on basin position. The uppermost Paraparchites carbonarius zone has wide regional distribution and has been subdivided into a lower Glyptopleurina sp. and an upper Bythocypris marginifera zone. The zones are present in normal marine fades throughout the basin, except within southern Saskatchewan and the Williston basin where they occur in the restricted and evaporitic fades of the Charles formation.
The zones have practical application in discovering or verifying the presence of Rundle overlap in northwestern Alberta. The behavior of these zones over shelf areas and the changes within the zones are of use in determining facies changes and the depositional environments of these sediments. Widespread geographic distribution of the upper zones and subzones provide a means of correlating the Mississippian beds of the entire Western Canada basin.