Abstract

The Cambrian of the Plains has been divided into Upper and Middle Cambrian. Correlations leading to this subdivision, which incorporates all conclusive paleontological evidence available to the author, are presented in three profiles, two of which extend into western Saskatchewan where the Middle Cambrian is widespread Middle Cambrian nomenclature typical of the Banff-Yoho Parks area is extended to the Plains. Maps and profiles emphasize two main lithologic types: carbonates, characteristic of the Rocky Mountains outcrops, in the west; and coarse, mainly rounded elastics, a diachronous eastern facies component that has its source on the Precambrian Shield.

A structure map, and an isopach map with superimposed elementary facies outlines in Plains and Mountains, further illustrate some aspects of the Middle Cambrian. Facies and thicknesses are closely related. Thicknesses increase from east to west. Four facies provinces governed by depth of deposition and distance from the clastic source area of the Pre-cambrian Shield are arranged in belts with roughly northwest-southeast trending boundaries. From east to west these are: (a) Coarse Basal Clastic Belt; (b) Glauconitic Silt-Shale Belt; (c) Submerging Shelf Carbonate Belt, culminating in a section of approximately 4,000 feet containing reefoid rocks in the Rocky Mountains; (d) Western Deeper Water Shale Belt, west of a line from Field, British Columbia to Blairmore, Alberta and farther southwest through Cranbrook, British Columbia where it attains a thickness of over 5,000 feet.

In the Plains a number of positive and negative depositional trends are observed. The negative trends are associated with carbonate deposition, the positive trends are devoid of carbonates.

Oil shows are summarized. Attention is given to the possibility that petroliferous reef-type carbonates, as found in the Eldon formation of the Mountains may extend into the Foothills and Plains.