Recent collaborative field, petrological, and geochronological studies have provided important new data that aid in the definition of Caledonian lithotectonic terranes in Svalbard. Several lower–middle Paleozoic tectonothermal events have been outlined in north-central (Biskayer Peninsula) and west-central (Motalafjella area) Spitsbergen. Although a younger (Middle Silurian) event was approximately synchronous in both areas, older events were different in character and timing. In the Biskayer Peninsula a tectonothermal event occurred during the Middle to Late Cambrian and resulted in formation of eclogite in tectonically thickened continental crust. In contrast, in the Motalafjella area, Early to Middle Ordovician subduction of oceanic crust resulted in development of an accretionary wedge and formation of a blueschist-eclogite complex. The polyphase Caledonian evolution of Spitsbergen is generally similar to that of the Pearyan terrane in northernmost Ellesmere Island where pre– and post–Upper Ordovician island-arc volcanic sequences suggest several regionally significant orogenic events. The western, northwestern, and north-central tectonic elements of Spitsbergen, therefore, are considered to have been initiated at a similar time as the Pearyan terrane and are termed the “West Svalbard terrane.” There is no record, so far known, of Middle to Late Cambrian tectonic activity in northeastern Svalbard (including Ny Friesland and Nordaustlandet). However, Early to Middle Ordovician tectonic instability is reflected by initiation of an extensive depositional hiatus. Northeastern Svalbard tectonic elements appear to represent a coherent terrane (East Svalbard terrane), which amalgamated with the West Svalbard terrane in Middle Ordovician time. Although the West and East Svalbard terranes were palinspastically separated prior to Middle Ordovician amalgamation, they share, in part, similar Precambrian elements, including constituents of Grenville-age basement and upper Proterozoic (Vendian?) tillites with possibly time-correlative magmatic rocks. These Precambrian elements appear to be common along the entire western margin of Iapetus, and suggest that the two Svalbard terranes originated proximal to East Greenland.

Abstract Generation of oceanic crust at the boundary between the Greenland/North American and the northwestern part of the Eurasian plates has created the Norwegian-Greenland Sea. This relatively young ocean comprises a number of separate basins, plateaus, and ridges revealing that the break-up and separation of the two major plates have not, in geological terms, been a simple process. In this context we define the Norwegian-Greenland Sea as the deep ocean between Europe and Greenland, bounded in the south by the Greenland-Iceland-Faeroe shallow transverse and in the north by the Spitsbergen Fracture Zone (Fig. 1). Geographically, the term Greenland Sea has been used for the ocean between Svalbard and northeast Greenland, but here we have adopted the geologically accepted usage in which it relates to the deep ocean between the Greenland-Senja and Spitsbergen fracture zones. Passive continental margins consisting of well-developed shelves and slopes separate the Norwegian-Greenland Sea from the adjacent continental masses of Greenland, Svalbard and Fennoscandia. The two adjacent shallow seas, the North Sea and the Barents Sea were, prior to the formation of the deep ocean in early Cenozoic time, part of a much larger contiguous epicontinental sea between the continental masses. The scientific exploration of the deep ocean, which started late in the last century, was until the 1950s focused on physical oceanography and marine biology. It was not before the mid-1960s that systematic research programs in marine geology and geophysics were initiated. These investigations were pioneered by regional surveys carried out by Lamont-Doherty Geological Observatory

Abstract In order to reconstruct successively earlier configurations of lithosphère plates and their constituent parts, as related to the Barents shelf, a brief investigation of some possible past relations between Spitsbergen and the northwestern Eurasian plates, Greenland, the Canadian Arctic Islands, and the intervening seas and ocean basins is necessary. Working backward in time, I have “reversed” the late Phanerozoic spreading of the Norwegian and Greenland Sea basins of the Atlantic Ocean and the Eurasia basin of the Arctic Ocean. The results are familiar reconstructions of Triassic-Permian paleogeology that show Spitsbergen adjacent to North Greenland and Ellesmere Island. The restoration of Paleozoic displacements depends mainly on different interpretations of the Caledonian orogeny (especially the amount of closing and the amount of sinistral transcurrent movement involved). Relations between these structures, the North Greenland and Innuitian fold belts, the Lomonosov Ridge, and the Uralides, for instance, are critical. Precambrian movements and the development of the North Atlantic geosyncline are related both to alternative models for a proto-Atlantic ocean basin and to late Precambrian diastrophism as variously inferred.