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.
Devon Island north of 76° comprises Grinnell Peninsula and a land area to the east, which is connected to the main part of Devon Island farther south. The study area is the geographic centre of the Canadian Arctic Islands and is also a geological centre in the sense that a number of different stratigraphic and tectonic trends converge and interact there. It straddles the Paleozoic platform-basin boundary and the southern margin of the younger Sverdrup Basin. The northerly fold trends of the Boothia Uplift-Cornwallis Fold Belt and the westerly trends of the Central Ellesmere Bold Belt intersect on Grinnell Peninsula. The total exposed succession on northern Devon Island is more than 9000 m thick and contains two major unconformities that correspond to the Cornwallis Disturbance and the Ellesmerian Orogeny. The Cambrian to Lower Devonian formations, affected by the Cornwallis Disturbance, consist of shelf carbonates and evaporites that grade westward and northwestward to pe(itic basinal sediments. The facies transition is marked by the development of large reefs at various stratigraphic levels The Middle and Upper Devonian succession was deposited during the interval between the Cornwallis Disturbance and the Ellesmeriun Orogeny. It consists of a lower carbonate unit that onlaps the Cornwallis Fold Belt, and grades up into nonmarine sandstones, which are the fill of the southeastward-advancing Ellesmerian foreland basin. The formations of the post-Ellesmerian Sverdrup Basin constitute a thin, mixed carbonate- clastic, basin-margin succession that ranges in age from EarIy Carboniferous to Early Triassic. Upper Cretaceous to Miocene, poorly consolidated shale and sandstone lie unconformably on lower Paleozoic rocks and are preserved in several small grabens. The Eurekan Orogeny produced a northwest-trending thrust belt and large, southeast-trending strike-slip zones that may still be active. Grinnell Peninsula lies north of and on structural strike with the Little Cornwallis lead- zinc district, but there are no known economic mineral occurrences on the peninsula.
The Kennedy Channel and Ella Bay formations are the two oldest stratigraphic units exposed in the Franklinian margin sedimentary sequence in the Canadian Arctic Islands. An Early Cambrian age had previously been accepted by the occurrence of trilobites and small shelly fossils in the type section of the Kennedy Channel Formation. Reinvestigation of the area around the type section shows that several large strike-slip faults cut the succession and that the olenelloid trilobites are from an infaulted slice of a younger unit, the Lower Cambrian Kane Basin Formation. Thus, there is no unambiguous paleontological evidence for the age of either the Kennedy Channel or Ella Bay formations. However, the abundance of stromatolites, absence of trace fossils, and separation from overlying Lower Cambrian clastics by a regional angular unconformity indicate a probable late Neoproterozoic age for these two formations. The Ella Bay Formation likely correlates with the Portfjeld Formation in North Greenland, the Spiral Creek Formation in East Greenland, and the Risky Formation of the Mackenzie Mountains in northwestern Canada. The passive margin that existed in northern Laurentia during the early Paleozoic was, therefore, established in the late Neoproterozoic, and the onset of rifting must have preceded this, rather than occurring in the Early Cambrian as some authors have suggested.
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