The Innuitian Tectonic Province contains the record of a Phanerozoic mobile belt in northern Greenland and the Canadian Arctic Archipelago. Two fundamentally different phases in its development were separated by the Devonian–Carboniferous Ellesmerian Orogeny. The first contribution focuses on the early Paleozoic history of a key area, the second summarizes the Carboniferous to Cenozoic history of most of the Canadian part of the province.(1) The early Paleozoic architecture of the mobile belt is apparent only in Ellesmere Island, where exposures extend from the Canadian Shield through Arctic Platform and Franklinian basin into the Pearya orogenic welt. The Franklinian basin comprised the deep but ensulic Hazen Trough and two unstable shelves bordering it on the northwest and southeast. The northwestern shelf was a site of felsic to intermediate volcanism, mainly in the Ordovician Period. Pearya, a site of granitic plutonism in the Devonian Period, supplied much of the clastic basin fill. Its core consisted of a metamorphic complex, about 1.0 Ga old, exposed in basement uplifts in nor thernmost Ellesmere Island. Both basin and welt essentially formed part of the North American Plate, although rifting, evident from mafic and ultramafic intrusions, probably occurred in Early Devonian (or latest Silurian) time. The history of this part of the province is tentatively interpreted as response to the opening and closure of an ocean, connected with lapetus, that separated northern Ellesmere Island and Greenland from the sialic crust of the present Lomonosov Ridge and Barents Shelf. The Lomonosov Ridge still seems to be attached to the shelf off northeasternmost Ellesmere Island.(2) Deep subsidence and filling of Sverdrup Basin dominated the Innuitian region from Early Carboniferous through Late Cretaceous time. Large halokinetic diapirs and mafic dikes and sills intruded axial parts of the basin succession through Mesozoic time. Steep faults along the northwestern margin of the basin are Middle Cretaceous and older. Part of the northwestern rim of Sverdrup Basin sagged in latest Cretaceous time, becomingpart of the Arctic continental terrace. In the Late Cretaceous and early Tertiary a system of large grabens developed through the southern part of the Innuitian region, linking Canada Basin with Baffin Bay; about the same time, uplift formed some large arches in the northeastern part of the region. Middle Eocene and older rocks were laterally compressed by a phase of pre-Miocene folding and faulting. Some uplift took place in Oligocene or Miocene time on Axel Heiberg Island. The distribution of recent earth quakes does not indicate the presence of modern active plate margins.
Amund Ringnes, Cornwall, and Haig-Thomas islands are in the south-central part of the Sverdrup Basin, a large pericratonic depression in the Canadian Arctic Archipelago containing upper Paleozoic, Mesozoic, and Cenozoic marine and nonmarine sedimentary rocks. Strata exposed on those islands, and penetrated by drillholes, consist of alternating thick successions of sandstone, siltstone, and shale, ranging from possibly Middle Triassic to Upper Cretaceous; the exposed succession is about 5000 m thick. Sediments forming those terrigenous clastic rocks were transported to the basin mainly from source terrains south and east of the basin margin. Gabbro dykes and sills have intruded Mesozoic rocks on both Amund Ringnes and Cornwall islands; radiometric ages for the intrusions range from about 144 Ma to about 117 Ma. The intrusive rocks reach progressively higher in the stratigraphic succession toward the basin depocentre; this and other considerations lead to the suggestion that phases of mafic intrusion accompanied accelerated rates of crustal subsidence and sedimentation. Isolated remnants of upper Paleocene to middle Eocene sandstones lie with angular unconformity on Mesozoic strata on central Cornwall Island and south-central Amund Ringnes Island, demonstrating Late Cretaceous and early Tertiary uplift and erosion of at least 3600 m of strata along the crest of a northwestward-plunging regional element called Cornwall Arch. A huge piercement complex composed mainly of Mississippian and Pennsylvanian evaporitic rocks, has intruded M-ozoic strata on northern Amund Ringnes Island. The complex is part of a regional array of structures that were generated by halokinetic processes, perhaps beginning as early as Triassic. No active oil or gas seeps were observed on Amund Ringnes, Cornwall, or Haig-Thomas islands. Small sulphurous deposits on Amund Ringnes Island may have been generated partly by emanations of natural gas. Four exploratory wells were drilled on, or adjacent to, Amund Ringnes Island; all of the wells were dry. One well has been drilled on Cornwall Island. The lower part of the Mesozoic and upper part of the Paleozoic succession in parts of the region have been buried deeply, intruded widely by mafic dykes and sills (which have caused local alteration of the sedimentary rocks), uplifted by Tertiary tectonism, and breached deeply by erosion, thus diminishing the probabilities of large hydrocarbon pools.
Sedimentary structures and palyno-assemblages indicate that the sandstones of the lower part of the Hassel Formation of eastern Ellef Ringnes Island were deposited in an upper shore-face marine environment; sandstone, siltstone, shale and coal, comprising the middle and upper parts of the formation, have structures and features indicative of fluvial deposition. Thin, lenticular carbonaceous shale beds at Hoodoo Dome and Cape Cairo were analysed for their spore and pollen content. The microfloras indicate a late Albian and/or early Cenomanian age, which is consistent with regional paleontological and structural evidence. Humid, warm temperate conditions during Hassel deposition are suggested by the microflora.
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