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The present study deals mainly with the stratigraphy, structural geology and environment of deposition of the strata of the Arctic Platform, comprising mainly a structurally concordant succession of lower Paleozoic strata in the western three quarters of the island. The Paleozoic strata comprise, for the most part, a westerly dipping homocline. The greater part of the sedimentary column, in terms of age span and volume of sediments, is made up of Lower Cambrian to Lower Devonian strata. However, strata of Proterozoic, Mesozoic and Cenozoic ages are represented also. The column is divisible into three structurally conformable successions that are separated from one another by regional unconformities, and a fourth succession that includes two unnamed formations in the Haughton impact crater: 1. The Proterozoic is represer1ted by a single formation consisting mainly of sandstone and siltstone. Outcrops are limited to a small area on the south coast where the formation lies nonconformably on Precambrian crystalline rocks, and is overlain unconformably by Cambrian strata. 2. The Paleozoic sediments consist mainly of shelf-type carbonate strata. They are divisible into fifteen formations with a total exposed thickness of about 3700 m. Most formations maintain relatively uniform charac1 eristics throughout the report area. However, the three youngest formations, which outcrop in extreme western parts of the island, exhibit noteworthy facies relationships, with two shelf-type carbonate formations in southern parts of the island giving place laterally to graptolitic rocks in the north. Unconformities occur within the Paleozoic succession: between Lower and Middle Cambrian rocks; and probably between rocks of Late Ordovician and Early Silurian ages. 3. Three easily weathered formations are preserved in a series of grabens developed in the Paleozoic terrane of western Devon Island. They are: 1. the Hassel Formation, nonmarine sandstone, Albian to Cenomanian; 2. the Kanguk Formation, marine shale, Turonian to Campanian; 3. the Eureka Sound Formation, mainly neomarine sandstone, Maastrichtian. 4. The older of two formatior1s within the limits of the Haughton crater consists of impact breccia. The younger consists of lake sediments. Devon Island is cut by numerous, steeply-dipping, normal faults. Key words: Stratigraphy, structurC!l geology, environment of deposition, Phanerozoic rocks, Devon Island, Arctic Canada.

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Haughton Astrobleme is a nearly circular impact crater with a diameter of about 16 km and a central uplift in Devon Island. Bedrock exposed in the crater comprised the following mainly carbonate Lower Ordovician to, Upper Silurian formations in order upward: Eleanor River, Bay Fiord, Thumb Mountain, Irene Bay and Allen Bay. The Eleanor River Formation in the centre of the crater is raised about 480 m above its normal stratigraphic position outside the crater. The much shattered and faulted lower Paleozoic rocks within the crater contrast markedly with the subhorizontal surrounding strata. The Allen Bay Formation constitutes surface exposure around all but the easternmost part of the crater's border where the Thumb Mountain and Irene Bay Formations are exposed. Also exposed in the crater are two newly recognized, and as yet unnamed, formations: a polymict impact breccia that overlies the lower Paleozoic rocks, with marked angular unconformity and crops out over about a quarter of the area of the crater; and a unit of lake sediments near the western border of the crater that lies disconformably on the impact breccia and with angular'unconformity on the lower Paleozoic rocks. The impact breccia is composed chiefly of carbonate rocks, but locally contains clasts of Precambrian crystalline basement from a depth estimated to be at least 1700 m. The basement clasts show varying degrees of shock metamorphism, the highest being that displayed by rocks with vesicular, flow-banded feldspar or quartz glass. Coesite has been identified in a sample of gneiss. The lake sediments are interpreted as an infilling of the crater that occurred shortly after impact. On the basis of fossils, these sediments are dated as Miocene or, possibly, Pliocene. From this and other evidence, it is concluded that the impact took place in the Miocene or Pliocene. RESUME. "Haughton Astrobleme" est un cratere quasi-circulaire, causé par un impact; il a un diamètre d'environ 16 km avec un mamelon central et se situe dans 1'Ile de Devon: Les affleurements du cratère sont datés de l'Ordovicien au Silurien supérieur: les formations carbonatées représentées sont dans l'ordre "Eleanor River, Bay Fiord, Thumb Mountain, Irene Bay et Allen Bay." La formation Eleanor River au centre du cratère est montée d'environ 480 mètres au-dessus de sa position stratigraphique normale, en dehors du cratère. Les roches les plus brisées et faillées du Paléozoique inférieur, à l'intérieur du cratère, font un contraste marquant avec les bancs sub-horizontaux qui les entourent. La formation Allen Bay représente les afflueurements entourant l'ensemble mais ce sont des affleurements des formations "Thumb Mountain" et "Irene Bay" que l'on observe sur la bordure la plus orientale du cratère. De plus, deux formations nouvelles et pas encore "baptisées" ont été du Paléozoique inférieur en discordance angulaire accusée, dans environ un quart de la reconnues dans le cratère: une brèche d'impact polygénique qui repose sur les roches surface du cratèreun meurement de sédiments lacustres...