NORTH AMERICA/Northern Cordillera 45 (5) latest Jurassic to Palaeogene marine to nonmarine clastics deposited in foreland basins concomitantly with folding and thrusting towards and over the continental platform Rocky Mountains and (in part) Tintina Trenches Internal part Some major physiographical units: Columbia, Cassiar, and southern Brooks Range Bedrock: (1) local Palaeoproterozoic continental basement; (2) Neoproterozoic rift-related clastic and volcanic rocks; (3) Palaeozoic, mainly deep-water, clastic rock, rift- and arc-related volcanic and plutonic rocks; (4) local Late Palaeozoic to Early Jurassic magmatic and sedimentary rocks formed in island arcs and marginal basins; (5) Middle Jurassic to Paleocene plutonic rocks; and (6) local Palaeogene magmatic and sedimentary rocks; rocks typically metamorphosed up to high grades and complexly deformed (mainly) during Middle Jurassic to earliest Tertiary compression, and also (in the south) by Palaeogene extension and (in the north) dextral strike-slip faulting Intermontane Plateau System Some major physiographical units: northernmost Columbia Plateau, Interior Plateaus, Skeena Mountains, Yukon Plateaus, Yukon–Tanana Upland, Kuskowim Mountains, Coastal Lowlands, Seward Peninsula Bedrock: (1) variably metamorphosed Neoproterozoic and Palaeozoic continental margin deposits in Alaska and Yukon; elsewhere (2) Devonian to Early Jurassic sedimentary and magmatic rocks formed in island arcs, accretionary complexes, and back-arc basins; (3a) Middle Jurassic to Palaeogene continental magmatic arc rocks, and (3b) marine and non-marine clastic deposits eroded from tectonically uplifted regions; (4) local Neogene flood basalt; rocks deformed by compression mainly in the Mesozoic and extension–transtension in the Early Tertiary Pacific Mountains System Internal part Some major physiographical units: North Cascade Ranges (in Washington) and Cascade Mountains (in British Columbia), Coast Mountains, northern Alaska Range Bedrock: (1) dominant ($80%) Middle Jurassic to Palaeogene plutonic rocks (called the Coast Plutonic Complex); (2) Palaeozoic to Holocene volcanic and sedimentary rocks formed mainly in magmatic arcs, but locally in accretionary complexes; most rocks metamorphosed up to high grades and complexly deformed mainly in mid-Cretaceous to Palaeogene time Coastal depressions External part Some major physiographical units: Olympic Mountains, Insular Mountains, Saint Elias Mountains, Alaska Ranges, Aleutian Range, Aleutian Islands, continental shelf and slope Bedrock: (1) latest Proterozoic to mid-Cretaceous volcanic and sedimentary rock formed mainly in island arc and (in Triassic) oceanic plateau settings; (2) mid-Cretaceous and younger clastics eroded mainly from Coast and Cascade Mountains region; (3) Early Palaeozoic to Palaeogene plutons; (4) Early Jurassic to Holocene clastic-rich accretionary complexes in part underlying continental shelf and slope; most rocks folded and thrust oceanwards in Cretaceous to Holocene time Features west and south of the Northern Cordillera: Pacific Ocean here underlain by Juan de Fuca and Pacific oceanic plates Appendix B: Summary Descriptions of Northern Cordilleran Terranes The abbreviations in parentheses are used in Figure 3; most palaeogeographical references are made with respect to the North American continental interior Continental Margin Terranes Displaced Neoproterozoic, Palaeozoic, and, locally, Early Mesozoic sedimentary rocks Arctic Alaska (AA): former North American continental margin deposits, locally with Devonian plutons, possibly rifted away by counterclockwise rotation of $70 from its former position near the Canadian Arctic Islands in Early Cretaceous time ( 130 Ma) Cassiar (CA): former North American continental margin deposits, sliced off and translated northwards by 425–2000 km on right-lateral strike-slip faults Coldfoot (CO), Kootenay (KO), Ruby (RB), Seward (SD), and Yukon-Tanana (YT): derived mainly from Neoproterozoic and Early Palaeozoic rift and lower slope deposits, and Middle Devonian to Early Carboniferous continental margin arcs; metamorphosed