Abstract The Jurassic System in western Canada is of interest particularly for the evidence it brings to bear on the early history of the mid-Jurassic to mid-Cretaceous Columbian orogeny, and for its economic significance. Its sediments contain the record of eustatic and epeirogenic events related partly to the early stages of the opening of the North Atlantic Ocean in the east, and the history of collision of allochthonous terranes in the west with the westerly drifting continent. Superimposition of the effects of the early phases of the Columbian Orogeny and the related foredeep on the older pre-orogenic sediments of Western Canada Basin, and the demise of Williston Basin as a depocentre are seen in the Jurassic succession of the western Plains and Rocky Mountains. Late events of the Ellesmerian tectonic phase in Brooks-Mackenzie Basin are recorded in northern Yukon Territory and adjacent Northwest Territories. Jurassic sedimentary rocks form significant hydrocarbon reservoirs and source rocks in western Canada. The immense coal reserves of the southern Canadian Rocky Mountains occur in an Upper Jurassic-Lower Cretaceous succession; the Jurassic of southern Manitoba hosts two of Canada’s major gypsum mines; and some of the phosphate deposits, currently subeconomic, in southeastern British Columbia are Jurassic in age.

Abstract The pre-Late Devonian Cordilleran miogeocline consisted of extensive shallow-water platforms upon which carbonate-clastic deposits accumulated. They were flanked to the west by deep-water environments where shale and carbonate accumulated (Rocky Mountains Assemblage). Clastic sediments were largely craton-derived. During the Late Devonian sedimentation patterns changed dramatically as turbiditic, chert-rich clastics, derived from the west and north, flooded the northern Cordillera (Earn and Imperial assemblages). Shale (Besa River Assemblage) was deposited far out onto the miogeocline and InteriorPlatform; the carbonate front of the Rundle Assemblage retreated far to the east and south of its Middle Devonian position. By mid-Mississippian time the clastic influx waned and normal marine shelf carbonate and clastic sedimentation resumed, once again with clastics derived from the craton. Devono-Mississippian plutonism occurred only in northernmost Yukon Territory, and volcanism was restricted to central Yukon and south-central British Columbia.Pre-Late Mississippian folding occurred in northern Yukon but elsewhere deformation is expressed only by local high-angle faults and disconformities. Devono-Mississippian tectonism in the northern Yukon involved uplift and granitic intrusion in Frasnian to Early Mississippian time, resulting in an upward shoaling and southward-prograding clastic wedge. The sequence consists of shale at the base, flyschoid sediments near the middle, and partly fluvial-deltaic strata at the top. Deformation migrated southward from the area of uplift until the clastics themselves were folded prior to the mid-Carboniferous. The source of Devono-Mississippian sediments in the central Cordillera was uppermost Precambrian quartzose clastics and lower Paleozoic chert from the western miogeocline. Western coarse clastics are typified