The Paleozoic sedimentary record in the Plains and Rocky Mountains (Eastern Cordillera) regions of western Canada is fairly complete, but it is characterized by five major unconformities and at least four lesser discontinuities. The five interregional breaks form the boundaries of four distinct depositional sequences which are, in general, equivalent to the Sauk, Tippecanoe, Kaskaskia, and Absaroka (lower part) of Sloss (1963). With minor exceptions, these sediments are all of miogeosynclinal and shallow shelf types. In the Western Cordillera west of the Rocky Mountain trench, Devonian and Mississippian rocks are almost totally lacking except in northwestern British Columbia where

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thick eugeosynclinal deposition occurred. It is probable that Pennsylvanian eugeosynclinal conditions prevailed in southern and central British Columbia, and the Permian is represented by widely distributed thick eugeosynclinal deposits in this region. There is some evidence of pre-Middle Devonian orogeny in the Western Cordillera, correlative with the Caledonian interval of Europe and the Arctic Islands, and, in a restricted sense, equivalent to the Cariboo orogeny of White (1959). In the interior cratonic region and the Rocky Mountains, the evidence indicates that the emergences of Late Proterozoic (Precambrian), Early Ordovician, Early Devonian, Late Pennsylvanian, and Late Permian were epeirogenic in character. Intracratonic features such as the Williston basin, Sweetgrass arch, W stern Alberta arch, Peace River arch, and Keewatin-Wisconsin arch in part had early development in Ordovician-Silurian time, but were emphasized during the post-Silurian to pre-Middle Devonian interval of uplift and deep erosion. The Paleozoic ended with the widespread post-Permian emergence and erosion, herein regarded as a discontinuity of interregional type.

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