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 t
Trang 1Scandinavian Caledonides (with Greenland)
D G Gee, Universityof 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
depos-ition 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,
sep-arating the low-lying old cratons of eastern Europe
and Greenland
The Caledonian Orogeny, referred to as the
Scan-dian Orogeny in these northern regions, resulted from
the collision of two continents, Baltica and Laurentia
The former was much smaller than the latter and,
dur-ing 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
sedi-mentation, 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 presen-tation of each of the three major regions of develop-ment – 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 trans-ported from west-north-west to east-south-east onto the Palaeozoic platform successions of the Baltoscan-dian 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 1 The North Atlantic Caledonides, from eastern Canada
to the high Arctic Barents Shelf, in the Late Mesozoic.
64 EUROPE/Scandinavian Caledonides (with Greenland)