Abstract Geologically, the East Greenland Shelf remained virtually unexplored for many years while the onshore East Greenland Mesozoic basin stratigraphy was intensely studied and served as a reference for the interpretation of the offshore East Greenland and northwest European margins. This development was a natural consequence of the excellent onshore basin exposure while polar pack ice is found almost year-around on the East Greenland shelf. The first geophysical information from the East Greenland shelf was published by Vogt (1970), Eldholm and Windisch (1974), Johnson and others (1975a, b), B. Larsen (1975), H. C. Larsen (1975, 1978), Henderson (1976), and Featherstone and others (1977). Results of the first multichannel reflection seismic surveying on the shelf were reported by Hinz and Schlüter (1978, 1980). On the basis of this information and initial results from an aeromagnetic survey (H. C. Larsen and Thorning, 1979, 1980), a regional geological model for the East Greenland Shelf was proposed by H. C. Larsen (1980). This model involved early Tertiary oceanic crust thought to be present below parts of the outer shelf off central East Greenland and subsided continental crust thought to be present up to approximately 100 km seaward of the shelf break off southeastern Greenland. The actual position of the shelf edge was found to be controlled mainly by post-rift sedimentation rather than deep crustal features (H. C. Larsen, 1980). It was further suggested that Cenozoic basins might dominate the southern half of the shelf while Mesozoic and Paleozoic basins were likely to be present beneath the northern shelf.

Abstract Late Proterozoic through Early Permian evaporite deposits are widespread in northern Canada, Greenland, and northern Eurasia. All of these evaporites are found today on the Atlantic Ocean, Eurasia, and Canada sides of the Lomonosov Ridge and its extensions into northern Siberia and northern Canada. No evaporites are known to be present on the Pacific side of the Lomonosov Ridge or north of its extensions into Siberia and Canada. This fact alone suggests that the Atlantic Ocean has been open into the Arctic since middle to late Proterozoic time; it further suggests that the Lomonosov Ridge and its continental extensions were in existence by late Proterozoic time. Hence, the distribution pattern indicates that the evaporites were brought in by, and precipitated from, marine waters entering via the present location of the Atlantic Ocean and the Lena Trough. Geologic data from Iceland, new geophysical data from the North Atlantic Ocean, and physical continuity of the Proterozoic Lomono-sovides around the Canadian basin of the Arctic Ocean lend strong support to the interpretation given here. Post-Devonian evaporite deposits in the Arctic are scarce, and their depocenters generally are farther south than those of Devonian and pre-Devonian times. The locations of the post-Devonian evaporite depocenters appear to be related to the formation of two sills across the present North Atlantic: the Franz Josef sill between Novaya Zemlya and Spitsbergen, separating the Arctic from the North Atlantic, and the Faeroe-Greenland sill extending from Scotland to southeastern Greenland. Because the known evaporite-distribution patterns show such close relations among the present North Atlantic and Arctic Oceans; the present continental positions; and the existing sites of the Lomonosov Ridge, the Franz Josef sill, and the Faeroe-Greenland sill, postulation of plate-tectonic models for the formation of the North Atlantic and Arctic is unnecessary. In fact, no plate-tectonic or polar-wandering mechanism yet proposed explains the orderly geometric relations between the evaporite deposits and the observed geographic-topographic features. Hence, sea-floor spreading, plate motions, and polar wandering—if they ever took place in the North Atlantic-Arctic region—were pre-late Proterozoic events.

Abstract This concluding chapter provides a brief, interpretative overview of the geological history of Innuitian Orogen and Arctic Platform with emphasis on unsolved major problems, and a summary of their resources. References quoted in previous chapters will not be repeated; for geographic names, see Figure 1 (in pocket). The northern part of the Canadian Shield (including Greenland) consists of a number of relatively small continental plates of Archean age that were welded together into a single supercontinent in a series of Early Proterozoic orogenies. The outlines of the Archean cratons and intervening Early Proterozoic orogenic belts have not yet been established for the High Arctic, but an orogen 1.91.95 Ga old is recognized in southeastern Ellesmere Island and adjacent parts of Greenland (Chapter 6). An extensive late Middle Proterozoic rifting event is indicated by mafic volcanic and intrusive rocks and associated coarse clastic sediments exposed on Melville Peninsula (Fury and Hecla Basin), northern Baffin Island and Bylot Island (Borden Basin), southeastern Ellesmere Island and adjacent parts of West Greenland (Thule Basin), and northeastern Greenland (Chapter 6). Radiometric ages suggest correlation with the extensive Mackenzie dyke swarm of the eastern Cordillera, dated at about 1.2 Ga. The rift deposits are succeeded by shallow marine clastic and carbonate sediments that also are represented on Victoria Island (Shaler Group). Age and correlation of the sedimentary units are problematic. Lithological relationships suggest that the sedimentary units in the Borden and Thule basins are correlative, but the former have yielded late Middle Proterozoic paleomagnetic ages, whereas

ABSTRACT The original location and tectonic setting of the prominent Paleocene dike swarm in the British Isles are reconstructed for a “tight fit” of the North Atlantic region prior to any Cenozoic opening of the ocean basin between Greenland and Europe. The present-day northwest-southeast–oriented swarm originally trended toward southern Greenland and the locations of magmatic rocks of comparable age along the eastern and western margins of Greenland and approximately the position of the Iceland hotspot at 70–60 Ma in a “fixed hotspot” model. This raises the possibility that the northeast-southwest–oriented extensional stress field in which the dikes and associated central igneous complexes were emplaced may have been generated by impingement on the base of the lithosphere by a rising plume beneath present-day West Greenland. It is speculated, on the basis of seismic tomography and three-dimensional modeling, that the Paleocene igneous activity in the British Isles may have resulted from flow of a hot “finger” of upper mantle outward from the plume, perhaps controlled by preexisting lithospheric structures and the distant location of a second Paleocene volcanic province in central Europe.

Caledonian (435–425 Ma) and “Grenvillian” (950–900 Ma) S-type leucogranites and augen gneisses are prominent in the thrust units that form the southern half of the East Greenland Caledonian orogen, south of 76°N. Such rocks do not occur further north (76°N–81°N), where the bedrock is dominated by Paleoproterozoic orthogneisses and metagranitoid rocks (2000–1750 Ma). More mafic Caledonian granitoid rocks (quartz diorites, granodiorites, quartz monzonites, syenites, etc.) are found only in the southernmost parts of the orogen (∼71°N), side by side with S-type leucogranites. The S-type granites were formed by partial fusion of “fertile” lithologies within the late Mesoproterozoic Krummedal supracrustal sequence prior to or during emplacement of the thrust units and subsequent collapse of the orogen. The lack of similar granites north of 76°N is probably related to the absence of major units of metasedimentary rocks in that area. Among the granitoid rocks in the southernmost area, an early quartzdioritic to granodioritic intrusion was dated at 466 ± 9 Ma; this is ∼35 m.y. older than most Caledonian S-type granites. Quartzmonzonitic, granitic, and syenitic intrusions have yielded ages of 444–432 Ma. These rocks are geochemically similar to Caledonian granites in Scotland and may be related to subduction of oceanic lithosphere underneath East Greenland. The north-south variation in the occurrence of granites in the East Greenland Caledonides is the expression of an original (pre-thrusting) west-east zonation. It is envisaged that the orogen consists of a number of parallel belts, now telescoped by thrusting: a southeastern belt containing supracrustal rocks (Krummedal sequence) with leucogranites, with more mafic granitoids in the southeast, and a northwestern belt where these rocks do not occur. These belts are envisaged to run from Scotland over the southern parts of the East Greenland Caledonides and, obliquely to the Greenland coast, over the North-East Greenland shelf to Svalbard and Norway, where similar rock units also occur.

Abstract Two first-order depositional provinces are distinguished — a southeastern shelf, which encompasses nearly all of the Arctic Platform and a large part of the Franklinian mobile belt, and a northwestern deep water basin. The latter, in turn, is divisible into a southeastern sedimentary subprovince, and a northwestern sedimentary and volcanic subprovince. The unstable boundary between deep water basin and shelf migrated cratonward from late Early Cambrian to Early Devonian time. In the preceding chapter, the Cambrian to Silurian depositional history of North Greenland has been divided into seven evolutionary phases that are applicable to both shelf and deep water basin as they are based, to some extent, on shifts of their mutual boundary. This organization was feasible because in Greenland only northern parts of the shelf province, which have been affected markedly by the cratonward expansion of the basin, are exposed. Separate schemes for shelf and basin, however, are required in the Arctic Islands where both provinces are more extensive and more complex stratigraphically. It is most convenient to discuss the stratigraphy of Franklinian Shelf and Arctic Platform in terms of informal time-rock slices, and that of the deep water basin in terms of unrelated, variably diachronous, informal rock units. The basic differences in the stratigraphic record of the two provinces reflects the fact that different geological processes are important in them. Eustatic fluctuations in sea level, for example, affect primarily the shelf; tectonic events in “outboard” orogenic belts affect primarily the basin. The different classifications chosen in Chapters 7

Abstract This volume describes and interprets the geology of the northern margin of the North American continent in the Canadian Arctic Archipelago and North Greenland 1 . The northwestern part of this region is underlain by the Innuitian Tectonic Province, which comprises strata of the Late Proterozoic to Late Devonian Franklinian mobile belt, the Carboniferous to Paleogene Sverdrup Basin, and the Cretaceous-Cenozoic Arctic Continental Terrace Wedge (Fig. 4.1). The Franklinian mobile belt, deformed in Late Silurian to Early Carboniferous time, and the Sverdrup Basin, deformed in Paleogene time, together constitute the Innuitian Orogen. The junction of the Franklinian mobile belt with the Caledonides is concealed by the Wandel Sea off northeastern Greenland, and also by the upper Paleozoic and younger strata of the Wandel Sea Basin, the junction with the Cordillera and the Arctic Alaska Plate is covered by the Beaufort Sea. The southeastern part of the region discussed in this volume is underlain by the Arctic Platform, characterized by Cambrian to Paleogene strata that are contiguous with those in the Innuitian Orogen but relatively undisturbed. The Arctic Platform is a part of the sedimentary cover of the North American craton that is separated from other parts, such as the Interior and Hudson platforms, by Recent seaways or erosional gaps. Until World War II, explorers moved freely between the archipelago and Greenland, but in the post-war period the international boundary has become increasingly effective, and geological investigations have been carried out separately in the two areas. As a result, somewhat different stratigraphic and

Abstract The late Caledonian megatectonic framework of the Arctic-North Atlantic area and its borderlands is summarized in Plate 1. The Caledonian orogenic cycle spanned Late Cambrian to earliest Devonian times. It embraced the Late Cambrian to Early Ordovician Grampian/Finnmarkian, the mid- to Late Ordovician Taconic, and the Late Silurian to early Gedinnian Main Scandinavian or late Caledonian orogenies (Gee and Sturt, 1986; Fig. 1). The late Caledonian evolution of the Arctic-North Atlantic domain involved the convergence of four plates. The Late Ordovician and Silurian sinistral oblique collision of the continental Laurentia-Greenland and Fennosarmatian plates was preceded by the progressive subduction of the oceanic Iapetus plate and culminated in their Late Silurian-Early Devonian suturing along the Arctic-North Atlantic Caledonides. With this the Laurussian Megacontinent, also referred to as the North Continent, was formed (Wilson, 1966; Phillips et al., 1976; Roberts and Gale 1978; Soper and Hutton, 1984). At the same time, the oceanic Proto-Tethys plate converged northward with the colliding Laurentia-Greenland and Fennosarmatian plates (Fig. 2). Northward subduction of the Proto-Tethys plate at an arc-trench system marking the southeastern margin of Laurentia and the southwestern margin of Fennosarmatia was accompanied by the northward rafting of a number of continental fragments that were rifted off the northern margin of Gondwana during the Cambro-Ordovician and Early Silurian. Some of these micro-continents (allochthonous terranes) became accreted during the Caledonian orogenic cycle to the southern margin of the newly forming North Continent (Laurussia). These continental fragments are enclosed by the North German-Polish, Mid-European, and Ligerian-Moldanubian Caledonian