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The Shuswap Metamorphic Complex consists of three parts, each with unique stratigraphy and orogenic evolution, separated by major faults of diverse nature and having in common only a post-late Mesozoic tectonic history. The first part, the Monashee Complex, is a possible extension of the Precambrian Shield that contains limited evidence of Mesozoic orogenesis and that was rapidly uplifted during the Cretaceous to Paleogene. The Monashee Décollement, a warped mylonite zone interpreted as a regional thrust fault active through the Middle Jurassic, separates this complex from the second part, which contains rocks correlative with Hadrynian to late Paleozoic strata of the pericratonic prism. The third part, the Okanagan Complex, straddling the 49th Parallel from the Okanagan Valley to Kootenay Lake, contains the probable exhumed roots of a Mesozoic magmatic arc built upon possible North American continental and transitional crust and includes late Paleozoic and early Mesozoic suspect terranes.The Columbian Orogen formed during westward drift of the craton into a continent of accreted elements. Response of the craton, attenuated during at least two episodes of Proterozoic rifting, and its overlying sedimentary prism to underthrusting from the east and simultaneous collision with an accreting collage from the west took place in two stages. First, attenuated crust was telescoped and thickened to its approximate original configuration while westernmost parts of the bordering prism were deformed and metamorphosed (the Jura-Cretaceous Columbian Orogeny that affected the Okanagan Complex and strata above the Monashee Décollement). Second, the thickened crust, the deformed prism, and platformal strata were thrust eastward (the Late Cretaceous – Paleocene Laramide Orogeny that formed the Rocky Mountains Thrust Belt). Waning convergent tectonism led to ascendancy of crustal extension (primarily in the Okanagan Complex) and final uplift of cratonic massifs.

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A new seismic model of Canada's northeasternmost margin indicates a complex continent to ocean transition with similarities to both volcanic and nonvolcanic margins. The crustal structure beneath the Lincoln Sea includes: (i) a continental shelf with a uniform 3 km thick cover (velocity = 1.8-3.6 h i s ) overlying at least 6 km of synrift(?) basinal strata (velocity = 4.3-4.9 M s ) that terminate near the base of the slope; (ii) a thick unit of oceanic layer 2-type. velocity (5.4-5.8 h i s ) overlying a velocity structure resembling a volcanic margin; (iii) a high-velocity lower crust (> 7.4 kmls) resembling North Atlantic volcanic margins or the Alpha Ridge but different from the Lomonosov Ridge near the North Pole; (iv) a change in velocity structure 15-25 km seaward of the shelf-slope break that coincides with a distinct short-wavelength, highamplitude magnetic anomaly and the centre of a steep gravity gradient; and (v) a suggested Moho depth of 23 km beneath the Lincoln Sea margin along 63 O W .The velocity structure beneath the Lincoln Sea is transitional from thinned continental crust beneath the shelf to a structure with oceanic affinities to the north. Typical, 10 km thick oceanic crust is not apparent beneath the northern Lincoln Sea. The upper crustal structure resembles a rifted, nonvolcanic margin such as the Goban Spur, while the high lower crustal velocity resembles a volcanic margin like the Hatton Bank or an oceanic complex like the Alpha Ridge. North of the seismic survey, the enigmatic Lincoln Sea plateau may be an intruded Lomonosov Ridge segment or a volcanic complex similar to the Alpha Ridge or the Morris Jesup Plateau.Un modtle sismique nouvellement dabor6 pour la marge de 11extr6mit6 nord-est du Canada indique une transition continentale 21 ochnique complexe, prtsentant des traits cornrnuns aux marges volcaniques et non volcaniques. La structure crustale sous la mer de Lincoln inclut : (i) une plate-forme continentale avec une couverture uniforme d'une 6paisseur de 3 km (vitesse = 1,8-3,6 M s ) , qui recouvre au moins 6 km de strates d6pos6es dans un bassin en distension(?) (vitesse = 4,3 -4,9 h i s ) disparaissant p r b de la base du talus; (ii) une unit6 form6e d'une puissante couche oc6anique de vitesses de type-2 (5,4-5,8 h i s ) , sus-jacente B une structure de vitesses ressemblant B une marge volcanique; (iii) une crofite inf6-rieure de vitesses 6lev6es (>7,4 kmls) semblable aux marges volcaniques de 1'Atlantique Nord ou B la crgte d'Alpha, mais qui differe de la crgte de Lomonosov prts du p61e Nord; (iv) un changement dans la structure de vitesses B 15 -25 km vers le large de la discontinuit6 entre la plate-forme et le talus, coincidant avec une anomalie magnCtique de forte amplitude et de longueur d'onde courte distincte et avec le centre d'un gradient gravitaire abrupt; et (v) une profondeur sugg6r6e de 23 krn pour le Moho sous la marge de la mer de Lincoln, le long du 63" de longitude ouest.La structure de vitessses sous la mer de Lincoln indique le passage graduel d'une crofite ...

At five localities investigated in south-central British Columbia, Upper Triassic rocks are observed or inferred to unconformably overlie upper Paleozoic and older rocks. Paleozoic rocks beneath the unconformity show polyphase deformation and low-grade regional metamorphism which are absent in overlying rocks. Data from these and other localities define a regional angular unconformity of Late Permian or Early Triassic age on the western and southern margins of the Shuswap Metamorphic Complex. Permian and Triassic rocks preserve evidence of structural, sedimentary, and metamorphic events which permits separation of Triassic rocks into three fault-bounded tectonostratigraphic belts. The Eastern Belt contains the transition from miogeoclinal sedimentation throughout Triassic time in the Canadian Rockies to island arc volcanism in the Late Triassic to the west. Basal beds of the Triassic sequence become younger southwestward from the axis of the Early to Middle Triassic depocentre lying west of the Rockies. Rocks preserving Early Triassic deformation and metamorphism are restricted to the southwest comer of the belt and are truncated by the Pasayten Fault. The Central Belt, dominated by the products of Late, Triassic volcanism in northern and central British Columbia, consists mainly of Middle (?) and Upper Triassic sediments in the south. Meagre evidence indicates that widespread deformation and low-grade regional metamorphism occurred just prior to the Late Triassic. Evidence for these events is not found beyond the faulted margins of the Central Belt. In the Western Belt, an Upper Triassic sequence of tholeiitic basalt and overlying calcareous sediments disconformably overlies Permian rocks. In the western Cordillera, low-grade regional metamorphism and minor plutonism characterize Triassic orogenies. Early Triassic orogenesis in the southwestern comer of the Eastern Belt is coeval with the Sonoma Orogeny and the Middle-Late Triassic orogenesis of the Central Belt represents the Tahltanian Orogeny.Dane cinq l a l i t k s itudites dans le centre sud de la Colomhie-Britannique. on observe ou on i n h e que les roches du Trias sup6rieur recouvrent en discordance les roches du PaliazoIque superieusou des mches plus anciennes. Les mches du hleozoique sous la d~scordance exhibent une dPformation i multiples phases et un mitamorphisme kgional de faible intensit6 qui son1 absents dans les roches qui les recouvrent. Les ohscrvations dans ces localitis et en d'autres endmils defmissent une discordance anguEaire datant de la fin du Permien ou du dibut du Triav sur les bordures ouest et sud du complexe metamorphique de Shuswap. Les roches permiennes et triassiaues conservent la maraue de processus structuraux, sedimentaires et metamorphiques qui *errnettent de distinguer dansies roches du Trias trois zones tectonostratigraphiques limitees par des failles. La zone est contient la transition de sedimentation miogtosynclinale au cours du Trias dans les montagnes Rocheuses Bun volcanisme d'arc insulaire a I'ouest a la fin du Tr...

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The Geo-mapping Frontiers project was initiated to improve geoscience knowledge in the least understood parts of Canada's north. This publication presents a compilation and interpretation of geologic structures derived from both high and low resolution enhanced magnetic data (available from the GSC), enhanced LANDSAT imagery and topographic (DEM) data. The data sets included in this OPEN FILE include low resolution airborne magnetic data, a CDED DEM, legacy geological data (IPY map) and structural data compiled by the Yukon and NWT Geological Surveys as well as a newly interpreted dataset of geologic structures for the entire area of Canada's Arctic north of 60°. This is the second of a series of reports for the Geo-mapping Frontiers project, and is intended to provide structural information for mapping and exploration in Canada's Arctic.