Abstract Triassic rocks of the Interior Platform and eastern Cordillera of Canada have long been recognized as an interesting and variable sequence of marine strata occupying an elongate belt that extends from the United States border on the south to 69°N latitude and Beaufort Sea on the north (Fig. 4G.1, 4G.2). Triassic deposits are best developed in Western Canada Basin of British Columbia and Alberta, where they occupy three main physiographic provinces, Rocky Mountains on the west, Rocky Mountain Foothills, and Interior Plains to the east. Triassic rocks also occur in Liard River area of southern Yukon Territory and within northern Yukon Territory and District of Mackenzie in the British, Barn, Richardson, Selwyn, Wernecke, and northwestern Ogilvie Mountains. However, because much more published information on Triassic rocks in Western Canada Basin is available, and because of the greater development and economic importance of the system there, most of this report will be directed toward the region south of latitude 60°N. Triassic rocks of the Rocky Mountains, Foothills, and Interior Plains comprise over 1200 m (Fig. 4G.1) of westward-thickening, siliciclastic and carbonate rocks and lesser amounts of evaporites. Contained marine faunas range in age from Griesbachian to Norian. The Triassic rocks of northern Yukon Territory display similar lithofacies but lack evaporites. The strata form a marine wedge deposited along a topographically low, tectonically stable continental shelf and shoreline, a continuation of Permian conditions at the passive western margin of the North American Craton. They form part of what is referred to as

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