In Ellesmere Island, the Canadian Shield and Arctic Platform are flanked on the northwest by the lower Paleozoic Franklinian mobile belt, which comprises an unstable shelf (miogeocline) and a deep-water basin, divisible into an inner sedimentary belt and an outer sedimentary–volcanic belt. Both are tied to the shelf by interlocking facies changes, but additional exotic units may be present in the outer belt.Pearya, bordering the deep-water basin on the northwest, is divisible into four successions. Succession I comprises sedimentary and(?) volcanic rocks, deformed, metamorphosed to amphibolite grade, and intruded by granitic plutons at 1.0–1.1 Ga. Succession II consists mainly of platformal sediments (carbonates, quartzite, mudrock), with smaller proportions of mafic and siliceous volcanics, diamictite, and chert ranging in age from Late Proterozoic (Hadrynian) to latest Cambrian or Early Ordovician. Its concealed contact with succession I is tentatively interpreted as an angular unconformity. Succession III (Lower to Middle Ordovician?) includes arc-type and ocean-floor volcanics, chert, mudrock, and carbonates and is associated with fault slices of Lower Ordovician (Arenig) ultramafic–mafic complexes–possibly dismembered ophiolites. The faulted contact of succession III and the ultramafics with succession II is unconformably overlapped by succession IV, 7–8 km of volcanic and sedimentary rocks ranging in age from late Middle Ordovician (Blackriverian = early Caradoc) to Late Silurian (late Ludlow?). The angular unconformity at the base of succession IV represents the early Middle Ordovician (Llandeilo–Llanvirn) M'Clintock Orogeny, which was accompanied by metamorphism up to amphibolite grade and granitic plutonism. Pearya is related to the Appalachian–Caledonian mobile belt by the Grenville age of its basement, the age of its ultramafic–mafic complexes, and evidence for a Middle Ordovician orogeny, comparable in age and character to the Taconic. By contrast, the Franklinian mobile belt has a Lower Proterozoic (Aphebian) – Archean basement and was not deformed in the Ordovician. Stratigraphic–structural evidence suggests that Pearya was transported by sinistral strike slip as three or more slices and accreted to the Franklinian deep-water basin in the Late Silurian under intense deformation. The inferred sinistral motion is compatible with derivation from the northern Caledonides.

In the Yelverton Bay region of northwestern Ellesmere Island, bimodal intrusive and volcanic rocks are associated with a major fault in the Proterozoic–Cambrian rocks of the Pearya Terrane. The Wootton intrusion consists mainly of gabbro with lesser amounts of granitic and hybrid rocks; the Hansen Point volcanics are composed of felsic rocks and basalt. Plutonic zircons are very slightly discordant, but volcanic zircons have unusually high degrees of inheritance. Interpreted U/Pb zircon ages of 92.0 ± 1.0 Ma for the Wootton intrusion (assuming a wide range of inheritance ages) and of [Formula: see text] for the Hansen Point volcanics are close to the 93 Ma average of hornblende K/Ar dates obtained earlier for a small quartz diorite pluton in central northernmost Ellesmere Island. All fall into the early Late Cretaceous and indicate correlation with mafic volcanics of the Cenomanian–Turonian Strand Fiord Formation of eastern Axel Heiberg Island. The upper intercept age for the Hansen Point volcanics ([Formula: see text]) suggests that the felsic component in the bimodal suites was in part derived from the upper Middle Proterozoic (Neohelikian) basement gneiss. Limited field observations on the Wootton intrusion also are compatible with the hypothesis that the granitic component represents sialic basement, melted by mafic intrusion at depth during an extensional tectonic regime.

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.

This paper presents age determinations on six units of the Franklinian deep-water basin and the Pearya Terrane of northern Ellmere Island and discusses their tectonic implications.Four different fractions of detrital zircon from the Lower Cambrian Grant Land Formation of the deep-water basin all have average 207Pb/206Pb ages of 2.2–2.4 Ga, suggesting that the sediments were derived mainly from Aphebian–Archean parts of the Canadian Shield rather than from the Neohelikian crystalline basement of Pearya, as assumed earlier. The first evidence for Ordovician arc-type volcanism in the northern part of the deep-water basin is provided by a Llandeilo(?) zircon age of [Formula: see text] but the fault-bounded volcanic unit could be exotic.Four major stratigraphic successions are recognized in Pearya. Present zircon studies confirm that succession I has been affected by a 1.0–1.1 Ga orogeny, as inferred earlier by Sinha and Frisch from a Rb–Sr isochron. A zircon age of [Formula: see text] on a rhyolite demonstrates that succession II extended into the Late Cambrian or Early Ordovician.Granitic intrusions in the Pearya Terrane, at Cape Richards and Cape Woods, are, respectively, Middle Ordovician (463 ± 5 Ma) and Devonian (382 ± 18 Ma or, more likely, 390 ± 10 Ma) in age on the basis of combined zircon and sphene determinations. They are post-tectonic with regard to major deformations in the Middle Ordovician and Late Silurian. Both have a significant component of xenocrystic zircon, which appears to have been derived from succession I of Pearya on the basis of upper intercept ages.

The Canadian Arctic Archipelago, perched on the northern rim of the continent, is about 1.3 million km2 in area, including intervening waters (Fig. 1; Plate 9, index). Parry Channel, a seaway connecting Baffin Bay with the western Arctic Ocean, separates the Queen Elizebeth Islands to the north from another group of islands to the south. Rugged mountain ranges with extensive ice caps in the eastern part of the archipelago, and plateaus, lowlands, and a coastal plain in the western part, are all dissected by numerous channels and fiords (Dawes and Christie, Ch. 3).1 Outlines of the geography and rudiments of the geology were established during the last century and the first half of this century. This work was done by ship, with sledges, or on foot, under hardship and often tragic circumstances (Christie and Dawes, Ch. 2). A coherent stratigraphic-structural framework has emerged from subsequent systematic surface studies, which have been supported by helicopters since 1955. Paleontology, always at the forefront of Arctic earth science, has provided the basis for both regional correlations and reconstructions of the geologic history. Petroleum exploration has been active in the islands since the early 1960s, and by 1987, 176 wells had been drilled and more than 65,000 km of seismic reflection lines had been shot. The well data have been absorbed into the stratigraphic framework, and a few instructive seismic interpretations have been released (e.g., Harrison and Bally, 1988), but the bulk of the seismic work remains unpublished. Gravity surveys (Sobczak, Ch. 5A) and deep seismic refraction surveys, both carried out from the late 1950s onward, have permitted construction of crustal cross sections in the western parts of the islands (Sweeney and others, 1986; Sobczak and others, Ch. 5B), while aeromagnetic surveys (Coles, Ch. 5D), electrical conductivity studies (Niblett and Kurtz, Ch. 5E), and analyses of seismicity (Forsyth and others, Ch. 5C) have elucidated other aspects of crustal structure and tectonics.