64 EUROPE/Scandinavian Caledonides (with Greenland) Scandinavian Caledonides (with Greenland) D G Gee, University of Uppsala, Uppsala, Sweden ß 2005, Elsevier Ltd All Rights Reserved Introduction The Caledonide Orogen of the North Atlantic region reaches northwards from type areas in the British Isles, along the eastern edge of Greenland and western Scandinavia, to the Barents Shelf and the Svalbard Archipelago Prior to the opening of the Norwegian and Greenland seas and the Eurasian Basin in the Tertiary (Figure 1), this ca 3000 km long segment of the orogen was about 1000 km wide A substantial part of this width, perhaps as much as 30–40%, was the result of a long period of post-orogenic extension, lasting from the Late Palaeozoic into and through the Mesozoic, which was accompanied by the deposition of thick sedimentary successions; these now compose the continental shelves and host the main oil and gas resources of northern Europe Thus, at the time of orogeny in the mid-Palaeozoic, this northern part of the Caledonides was a long and relatively narrow (ca 600–700 km wide) mountain belt, similar in dimensions and majesty to today’s Himalayas, separating the low-lying old cratons of eastern Europe and Greenland The Caledonian Orogeny, referred to as the Scandian Orogeny in these northern regions, resulted from the collision of two continents, Baltica and Laurentia The former was much smaller than the latter and, during collision, played a similar role to that of India in the present-day Himalayan context The Scandian Orogeny began in the Silurian and extended into and through the Early Devonian; the name is derived from the Scandes, the mountains of Norway and western Sweden However, it is worth remembering that today’s mountains, along the coasts of Scandinavia and eastern Greenland, are the result of Tertiary uplift during the opening of the Greenland and Norwegian seas; they are not the relics of Palaeozoic mountains, although they are dominated by Caledonian rocks Before the collision of Baltica and Laurentia and the Scandian Orogeny, these two continents were separated by the Iapetus Ocean The closure of the Iapetus Ocean occurred over a period of about 80 Ma and involved the development of subduction systems along the margins of both Laurentia and Baltica and a wide range of tectonothermal activity This complex situation, involving magmatism and sedimentation, deformation and metamorphism, was an essential part of the Early Caledonian evolution, prior to the final collision of the continents and a Devonian change in global stress regimes: compression and lateral shortening gave way to regional extension The tectonic evolution of the northern part of the Caledonide Orogen is discussed below, after a presentation of each of the three major regions of development – western Scandinavia, eastern Greenland, and the Barents Shelf Western Scandinavia The Scandian mountains, with many peaks reaching a little over 2000 m, extend for nearly 2000 km along the length of Norway; they include substantial regions of western Sweden and the westernmost highest parts of Finland The Caledonide Orogen, on land, is up to 300 km wide and extends off the Norwegian coast for a further 200–300 km beneath the shallow shelf areas of the Norwegian Sea The orogen (Figure 2) is dominated by thrust sheets transported from west-north-west to east-south-east onto the Palaeozoic platform successions of the Baltoscandian margin of Baltica The front of the orogen is generally marked by a prominent thrust scarp, clearly indicating that these allochthonous (i.e transported) rocks originally, in the Devonian, extended much further eastwards, perhaps as far as 100 km, onto the platform Figure The North Atlantic Caledonides, from eastern Canada to the high Arctic Barents Shelf, in the Late Mesozoic